<PAGE>

                                                                    EXHIBIT 10.1

           STOCK PURCHASE, REORGANIZATION AND JOINT VENTURE AGREEMENT

                                      AMONG

                                CTI GROUP, INC.,
                             CTI PET SYSTEMS, INC.,
                             Dr. Terry D. Douglass,
                                Dr. Ronald Nutt,
                              Michael C. Crabtree,
                                 J. Kelly Milam,

                                       and

                            SIEMENS GAMMASONICS, INC.


<PAGE>

                                      INDEX
<TABLE>
<S>     <C>                         <C>                                                                      <C>
1.       Certain Definitions
         1.1                        Affiliate.............................................................    1
         1.2                        Assets................................................................    1
         1.3                        Beneficial Ownership..................................................    2
         1.4                        CPS Business..........................................................    2
         1.5                        CTI Common Stock......................................................    2
         1.6                        Cyclotron Common Stock................................................    2
         1.7                        Damages...............................................................    2
         1.8                        Encumbrance...........................................................    2
         1.9                        Exchange Act..........................................................    2
         1.10                       Financial Statements..................................................    2
         1.11                       Force Majeure.........................................................    3
         1.12                       Governmental Body.....................................................    3
         1.13                       Group Common Stock....................................................    3
         1.14                       Non-Siemens Group Shareholders........................................    3
         1.15                       Options to Acquire Group Common Stock.................................    3
         1.16                       Person................................................................    3
         1.17                       Phelps Agreement......................................................    3
         1.18                       SEC...................................................................    3
         1.19                       Securities Act........................................................    3
         1.20                       Taxes.................................................................    3

2.       Sale and Purchase of Group Shares................................................................    4

3.       Formation and Capitalization of CTI
         3.1                        Incorporation.........................................................    4
         3.2                        Exchange of Certain Group Shares for CTI Shares.......................    4
         3.3                        Acquisition of CTI Shares by Group....................................    4
         3.4                        Options to Acquire Group Shares.......................................    4
         3.5                        Distribution of CTI Common Stock by Group.............................    5
         3.6                        Shareholdings After Closing...........................................    5

4.       Closing
         4.1                        Management's Deliverables.............................................    5
         4.2                        Group's Deliverables..................................................    6
         4.3                        CPS's Deliverables....................................................    6
         4.4                        Siemens' Deliverables.................................................    6
         4.5                        Conditions to Siemens' Obligations at Closing.........................    7
         4.6                        Conditions to Obligations of Group, CPS and
                                           Management at Closing..........................................    9
         4.7                        Post-Closing Events...................................................   10
</TABLE>


                                      -i-
<PAGE>

<TABLE>
<S>     <C>                         <C>                                                                       <C>
5.       Representations and Warranties of Group
         5.1                        Organization and Good Standing........................................    10
         5.2                        Capitalization........................................................    10
         5.3                        Corporate Authority...................................................    11
         5.4                        Compliance with Laws; Governmental Authorities........................    11
         5.5                        Financial Statements..................................................    11
         5.6                        Tax Matters...........................................................    12
         5.7                        Absence of Undisclosed or Contingent Liabilities......................    12
         5.8                        Absence of Certain Changes and Events.................................    12
         5.9                        Title to Properties; Absence of Liens and Encumbrances................    13
         5.10                       Patents, Trademarks and Know-How......................................    13
         5.11                       Litigation............................................................    13
         5.12                       Contracts.............................................................    14
         5.13                       Officers and Employees................................................    14
         5.14                       Full Disclosure.......................................................    14
         5.15                       Fully Paid Nonassessable Common Stock.................................    14
         5.16                       Continuation of Business..............................................    14
         5.17                       No Brokerage Fees.....................................................    15
         5.18                       Insurance.............................................................    15
         5.19                       Energy Supplies, Raw Materials and Components.........................    15
         5.20                       FDA Matters; No Recalls...............................................    15
         5.21                       Employee Benefit Plans................................................    15
         5.22                       Consents..............................................................    15
         5.23                       Accounts Receivable...................................................    16
         5.24                       Inventory.............................................................    16
         5.25                       Books and Records.....................................................    16
         5.26                       Labor Relations.......................................................    16
         5.27                       Environmental Compliance..............................................    17
         5.28                       Employee Occupational Hazard and Other Claims.........................    17
         5.29                       Condition of Facilities/Sites and No Reportable Incidents.............    17

6.       Representations and Warranties of Management
         6.1                        Compliance with Laws; Governmental Authorities........................    17
         6.2                        Absence of Undisclosed or Contingent Liabilities......................    17
         6.3                        Absence of Certain Changes and Events.................................    18
         6.4                        Litigation............................................................    18
         6.5                        Officers and Employees................................................    19
         6.6                        FDA Matters; No Recall................................................    19
         6.7                        Environmental Compliance..............................................    19
         6.8                        Employee Occupational Hazard and Other Claims.........................    19
         6.9                        Condition of Facilities/Sites and No Reportable Incidents.............    19

7.       Relationship of the Parties......................................................................    20

8.       Representations and Warranties of Siemens
         8.1                        Organization and Good Standing........................................    20
         8.2                        Corporate Authority...................................................    20
         8.3                        No Brokerage Fees.....................................................    21
         8.4                        Intent................................................................    21
         8.5                        Receipt of Information................................................    21
         8.6                        Consents..............................................................    21
</TABLE>


                                      -ii-
<PAGE>

<TABLE>
<S>     <C>                         <C>                                                                       <C>
9.       Covenants of Group
         9.1                        Financial Statements..................................................    21

10.      Covenants of CPS
         10.1                       FDA Approval..........................................................    22
         10.2                       Components............................................................    22

11.      Covenants of Management
         11.1                       Voting................................................................    22
         11.2                       Management of CPS.....................................................    22
         11.3                       Non-Competition.......................................................    22
         11.4                       Non-Competition by CTI................................................    23
         11.5                       Conduct of Business...................................................    23

12.      Covenants of Siemens
         12.1                       Future Capitalization of CTI..........................................    23
         12.2                       Non-Competition.......................................................    24
         12.3                       Amendment of Stockholders' Agreement..................................    24

13.      Management of Group
         13.1                       Election of Directors.................................................    24
         13.2                       Voting Policy.........................................................    24
         13.3                       Research and Development..............................................    24
         13.4                       Officers of Group.....................................................    24
         13.5                       Stockholder Votes.....................................................    25
         13.6                       Material Board Decisions..............................................    25
         13.7                       Resolution of Impasse.................................................    26
         13.8                       CTI Board.............................................................    26
         13.9                       Additional Capital....................................................    27
         13.10                      Intercompany Transfers................................................    27
         13.11                      Business Plan.........................................................    27
         13.12                      Distribution Agreement................................................    27

14.      Additional Purchase and Sale Rights
         14.1                       Siemens' Additional Purchase Rights...................................    28
         14.2                       CTI's Additional Sale Rights..........................................    28
         14.3                       Purchase and Sale in Event of Default.................................    29

15.      Stock Transfer Restriction and Right of First Refusal............................................    30

16.      Sale of CTI Common Stock by Management...........................................................    31

17.      Specific Performance       ......................................................................    31

18.      Dispute Resolution         ......................................................................    31

19.      Product Liability          ......................................................................    32

20.      Pension and Employee Benefit Matters.............................................................    32
</TABLE>


                                      -iii-
<PAGE>

<TABLE>
<S>     <C>                         <C>                                                                       <C>
21.      Termination of this Agreement
         21.1                       Termination...........................................................    32
         21.2                       Effect of Termination.................................................    33

22.      Miscellaneous
         22.1                       Expenses..............................................................    33
         22.2                       Successors; Assignment................................................    33
         22.3                       Entire Agreement; Amendment...........................................    33
         22.4                       Survival of Representations, Warranties and Covenants;
                                         Indemnification..................................................    33
         22.5                       Notices...............................................................    35
         22.6                       Applicable Law........................................................    35
         22.7                       Counterparts; Headings................................................    35
         22.8                       Confidential Information..............................................    36
         22.9                       Publicity.............................................................    37
         22.10                      Invalidity............................................................    37
         22.11                      Waiver................................................................    37
</TABLE>


                                      -iv-
<PAGE>


                                LIST OF EXHIBITS

<TABLE>
<CAPTION>
      Exhibit No.                   Description
      -----------                   -----------
<S>                                 <C>
         1.2                        Assets of CPS and Group
         3.1                        Charter of CTI, Inc.
         3.3(a)                     CTI Administrative Personnel
         3.3(b)                     Amendment of Phelps Agreement
         3.4                        Basis of Exchange of Options
         3.6                        CTI Shareholder Agreement
         4.1(a)                     Stock Purchase Agreement
         4.1(c)                     Opinion of Counsel to Management
         4.2(b)                     Option Exchange Agreement
         4.2(c)                     Opinion of Counsel to Group
         4.4(d)                     Opinion of Counsel to Siemens
         4.5(i)(2)                  List of Consultants' Agreements Assignments
         4.5(i)(3)                  Background Rights to be Assigned by CCS to CPS
         4.5(i)(6)                  Amendment to Phelps Consulting Agreement
         4.5(j)                     Amendment of OEM Exclusive Distribution Rights Agreement
         4.5(m)(1)                  Technical Service Agreement
         4.5(m)(2)                  Administrative Service Agreement
         5.1(a)                     CTI Group, Inc. Charter and Bylaws
         5.1(b)                     CPS Charter and Bylaws
         5.2(a)                     List of Shareholders of CTI Group, Inc.
         5.2(b)                     Exceptions to CTI Representations Regarding Capitalization of Group and CPS
         5.3                        Exceptions to CTI Representations Regarding Corporation Authority of Group and CPS
         5.4                        Exceptions to CTI Representations Regarding Compliance
         5.8                        Exceptions to CTI Representations Regarding Absence of Changes
         5.9                        Exceptions to CTI Representations Regarding Title
         5.10                       Group and CPS Patents, Trademarks and Know-how
         5.12                       Group and CPS Contracts
         5.20                       Exceptions to CTI Representations Regarding FDA Matters
         5.21                       Group and CPS Benefit Plans and Arrangements
         5.29                       Material Documents Regarding Nuclear and Environment Incidents
         8.1                        Certificate of Incorporation and Bylaws of Siemens Gammasonics, Inc.
         11.2                       Management Function Descriptions and Employment Contracts
         12.3                       Amendment of Stock Purchase and Stockholders' Agreement
         13.4(b)                    Officers of Group
         13.4(c)                    Responsibilities of CFO
         13.4(d)                    Officers Positions Subject to Siemens Designation
         13.10                      Transfer Prices
         13.11                      CPS Five-Year Business Plan
         14.1                       Siemens Minima Plus 20% Plan
</TABLE>


                                      -v-
<PAGE>

           STOCK PURCHASE, REORGANIZATION AND JOINT VENTURE AGREEMENT

         This STOCK PURCHASE, REORGANIZATION AND JOINT VENTURE AGREEMENT (this
"Agreement") is made and entered into as of the 9th day of December, 1987, by
and among CTI GROUP, INC., a Tennessee corporation with its principal office in
Knoxville, Tennessee (hereinafter referred to as "Group"), CTI PET SYSTEMS,
INC., a Tennessee corporation with its principal office in Knoxville, Tennessee
(hereinafter referred to as "CPS"), DR. TERRY D. DOUGLASS, DR. RONALD NUTT,
MICHAEL C. CRABTREE and J. KELLY MILAM (hereinafter referred to collectively as
"Management" and individually as "Management Person"), and SIEMENS GAMMASONICS,
INC., a Delaware corporation with its principal office in Des Plaines, Illinois
(hereinafter referred to as "Siemens").

                                   WITNESSETH:

         WHEREAS, CPS is engaged in the CPS Business (as hereinafter defined)
and is a wholly-owned subsidiary of Group; and

         WHEREAS, Siemens wishes to purchase and acquire, and the Non-Siemens
Group Shareholders (as hereinafter defined) are willing to sell, sufficient
Group Common Stock to Siemens so that Siemens (and its Affiliate Siemens Capital
Corporation) holds 49.9% of total outstanding Group Common Stock and thereafter
to operate Group as a joint venture company upon the terms and conditions set
forth herein; and

         WHEREAS, it is the intention and desire of the parties hereto to
provide for certain rights and obligations pertaining to Siemens' purchase of
Group Common Stock.

         NOW, THEREFORE, in consideration of the premises and the mutual terms,
covenants and conditions set forth herein, the parties agree as follows:

1.       CERTAIN DEFINITIONS. The following terms whenever used in this
         Agreement, shall have the meanings ascribed below. Other terms defined
         in the body of this Agreement shall have the meanings assigned therein.

1.1      "Affiliate" shall mean, with respect to a specified Person, a Person
         that directly, or indirectly, through one or more intermediaries,
         controls, is controlled by, or is under common control with, the
         specified Person, but shall not include any Person less than fifty
         percent (50%) of the ordinary voting power of which is not directly or
         indirectly held by the specified Person and its other Affiliates unless
         such specified Person and its other Affiliates control a majority of
         the board of directors or other governing body thereof.

1.2      "Assets" shall mean the assets, properties and business of Group and
         CPS, whether tangible or intangible, wherever located, including,
         without limitation, all real estate and improvements thereon,
         buildings, storage facilities, loading and transshipment facilities,
         manufacturing and other production equipment, furniture, fixtures,
         trucks, automobiles and other vehicles normally used in connection
         therewith (either on or off the premises), instruments, research and
         development equipment, data processing equipment, communications
         equipment, construction in process, leasehold improvements, the


<PAGE>

         contracts (as defined below), all sales and promotional literature,
         files and data, intellectual property rights, processes, formulations,
         know-how, trade secrets and business as a going concern and good will.
         "Assets" includes without limitation all items listed in Exhibit 1.2
         attached hereto.

1.3      "Beneficial Ownership" or any derivative or variant thereof shall have
         the meaning ascribed to it in Rule 13d-3 promulgated under the Exchange
         Act.

1.4      "CPS Business" shall mean the business conducted by CPS in developing,
         acquiring, manufacturing, assembling, selling and distributing the
         following products:

         (a)      Cyclotrons and RDS products (as described in Exhibit 4.5(j)
                  hereto) for primary use in clinical positron emission
                  tomography systems, including gamma-emitter capability with
                  maximum energy of 20 MeV (or such higher levels as may be or
                  in the future become desirable in the positron emission
                  tomography business);

         (b)      Probes for the detection of positron emitters;

         (c)      Other generator systems producing positron emitters, including
                  infusion pumps;

         (d)      Planar cameras dedicated for coincidence detection of positron
                  emitters; and

         (e)      Ring tomographs (emission computerized axial tomograph image
                  devices) and other positron image devices.

1.5      "CTI Common Stock" shall mean the shares of voting common stock of CTI,
         Inc., a Tennessee corporation, par value $.01 per share. Where
         appropriate, all references to CTI Common Stock shall be deemed to
         include all subscription rights, options or warrants to purchase CTI
         Common Stock, all securities convertible into, or exchangeable for,
         such CTI Common Stock and all securities entitled to vote in the same
         manner and under the same circumstances as such CTI Common Stock.

1.6      "Cyclotron Common Stock" shall mean the shares of no par value voting
         common stock of CTI Cyclotron Systems, Inc., a California corporation.
         Where appropriate, all references to Cyclotron Common Stock shall be
         deemed to include all subscription rights, options or warrants to
         purchase Cyclotron Common Stock, all securities convertible into, or
         exchangeable for, such Cyclotron Common Stock and all securities
         entitled to vote in the same manner and under the same circumstances as
         such Cyclotron Common Stock.

1.7      "Damages" shall mean any loss, liability, damages (excluding indirect,
         consequential and incidental damages) and expense (including, without
         limitation, costs of investigation and defense and reasonable
         attorneys' fees).

1.8      "Encumbrance" shall mean any security interest, mortgage, lien, pledge,
         charge or restriction of any kind with respect to any property,
         including, without limitation, any material restriction on the use,
         voting, transfer, receipt of income or other exercise of any attributes
         of ownership of such property.

1.9      "Exchange Act" shall mean the Securities Exchange Act of 1934, as
         amended.

1.10     "Financial Statements" shall have the meaning set forth in Section 5.5
         below.


                                      -2-
<PAGE>

1.11     "Force Majeure" shall mean any unforeseen event or condition, not
         existing as of the date of this Agreement and not reasonably within the
         control of the affected party or any of its Affiliates, which prevents,
         in whole or in part, the performance by the party of its material
         obligations hereunder, including, without limiting the generality of
         the foregoing, acts of state or governmental action, riots, war, acts
         of terrorism, sabotage, strikes, lockouts, prolonged shortage of energy
         supplies, fire, flood, hurricanes, earthquakes, lightning and
         explosion.

1.12     "Governmental Body" shall mean any United States or foreign national,
         state, municipal or other local government or multinational body
         (including, without limitation, the European Economic Community), any
         subdivision, agency, commission or authority thereof, or any
         quasi-governmental or private body exercising any regulatory, taxing,
         marketing, importing or other governmental or quasi-governmental
         authority.

1.13     "Group Common Stock" shall mean the shares of voting common stock of
         Group, par value $.01 per share. Where appropriate, all references to
         Group Common Stock shall be deemed to include all subscription rights,
         options or warrants to purchase Group Common Stock, all securities
         convertible into, or exchangeable for, such Group Common Stock and all
         securities entitled to vote in the same manner and under the same
         circumstances as such Group Common Stock.

1.14     "Non-Siemens Group Shareholders" shall mean all of the shareholders of
         Group other than Siemens Capital Corporation.

1.15     "Options to Acquire Group Common Stock" shall mean options to acquire
         shares of Group Common Stock granted to employees of CPS (formerly
         named Computer Technology and Imaging, Inc.) and Group pursuant to the
         Incentive Stock Option Plans and Optional Bonus Plans for Key Employees
         of those corporations.

1.16     "Person" shall mean an individual, a corporation, a partnership, an
         association, a joint company, a joint venture, an unincorporated
         organization, a trust or other entity, including, without limitation,
         any employee pension, profit sharing and other benefit plans and
         trusts.

1.17     "Phelps Agreement" shall mean the License Agreement between Dr. Michael
         E. Phelps and CPS dated January 1, 1985, regarding know-how (as defined
         therein) for the production of emission computerized axial tomograph
         systems. The rights of Phelps under the said License Agreement were
         assigned by Phelps to Group pursuant to that certain Stock Purchase and
         Technology Transfer Agreement between them dated April 7, 1987.

1.18     "SEC" shall mean the Securities and Exchange Commission.

1.19     "Securities Act" shall mean the Securities Act of 1933, as amended.

1.20     "Taxes" shall include all taxes, charges, levies, fees, interest,
         penalties, additions to tax or other assessments including, but not
         limited to, income, excise, property, sales, use, payroll, value added
         and franchise taxes and customs duties, imposed by any Governmental
         Body and any payments with respect thereto required under any tax
         sharing agreement.


                                      -3-
<PAGE>

2.       SALE AND PURCHASE OF GROUP SHARES. On the terms and subject to the
         conditions of this Agreement, and in reliance upon the representations,
         warranties, covenants and agreements herein set forth, Management shall
         cause the Non-Siemens Group Shareholders to sell to Siemens, and
         Siemens hereby agrees to purchase from the Non-Siemens Group
         Shareholders a sufficient number of the shares of Group Common Stock
         issued and outstanding as of the Closing (as hereinafter defined) to
         give Siemens, when combined with the shares of Group Common Stock held
         by Siemens' Affiliate Siemens Capital Corporation forty-nine and
         nine-tenths percent (49.9%) of the then issued and outstanding Group
         Common Stock, for an aggregate purchase price of $30 million (the
         "Purchase Price") plus interest thereon from the date hereof to the
         Closing Date at a rate equal to the one-month certificate of deposit
         rate published in the Wall Street Journal on the date hereof.

3.       FORMATION AND CAPITALIZATION OF CTI.

3.1      Incorporation. Prior to or contemporaneously with the Closing (as
         defined hereinbelow), Management shall cause to be formed a Tennessee
         corporation to be called CTI, Inc. ("CTI"). The authorized
         capitalization of CTI shall consist of ten million (10,000,000) shares
         of voting common stock having a par value of one cent ($.01) per share.
         The charter and bylaws of CTI shall be substantially in the form of
         Exhibit 3.1 attached hereto.

3.2      Exchange of Certain Group Shares for CTI Shares. At the Closing,
         Management shall cause the Non-Siemens Group Shareholders to exchange
         all of their remaining Group Common Stock, after the purchase and sale
         provided for in Section 2 above, for CTI Common Stock, on the basis of
         one share of CTI Common Stock for each share of Group Common Stock.

3.3      Acquisition of CTI Shares by Group. At the Closing, Group shall
         transfer, assign and set over to CTI all of its Cyclotron Common Stock
         and its right to payment pursuant to Section 3(a)(iii) of the Phelps
         Agreement in exchange for seven and seventy-one-hundredths percent
         (7.71%) of the CTI Common Stock under the terms of an agreement in
         substantially the same form as the Stock Purchase and Stockholders'
         Agreement among Computer Technology and Imaging, Inc., Dr. Terry Dean
         Douglass, Dr. Ronald Nutt, Michael Callann Crabtree, James Kelly Milam
         and Siemens Capital Corporation, dated April 22, 1985, under which
         agreement Group may transfer CTI Common Stock to Siemens with the
         rights under the agreement applying to Siemens and Group thereafter.
         Prior to or simultaneously with the Closing, Group will use its best
         efforts to cause the transfer of the personnel listed on Exhibit 3.3(a)
         to CTI. In connection with such assignments, Section 3(a)(iii) of the
         Phelps Agreement and the rights and duties of Group and CTI shall be
         amended to provide for a two percent (2%) Management and Technology Fee
         on CPS sales (net of returns and allowances) of ECAT and RDS systems
         payable through December 31, 1994 (excluding (a) any sales to CTI or
         its Affiliates and (b) any sales of services, parts or accessories) to
         CTI in lieu of the two and five-tenths percent (2.5%) payment presently
         being made by CPS to Group for ECAT scanner sales by CPS, as set forth
         on Exhibit 3.3(b) hereto.

3.4      Options to Acquire Group Shares. Upon the Closing, the formation of CTI
         and the exchange by the Non-Siemens Group Shareholders of Group Common
         Stock for CTI Common Stock, all of the outstanding Options to Acquire
         Group Common Stock shall be


                                      -4-
<PAGE>

         exchanged for options to acquire CTI Common Stock on the basis set
         forth on Exhibit 3.4 hereto.

3.5      Distribution of CTI Common Stock by Group. Upon the Closing and the
         acquisition of CTI Common Stock by Group provided for in Section 3.3
         above, Group shall distribute all of its CTI Common Stock to its
         shareholders on a pro rata basis. The CTI Common Stock distributed to
         CTI as part thereof shall be cancelled by CTI.

3.6      Shareholdings After Closing. After the Closing, as a result of the
         transactions described hereinabove, the issued and outstanding shares
         of Group and CTI shall be held as follows:

<TABLE>
<CAPTION>
                                                             Percentage
                                     Shareholder         of Outstanding Shares
                                     -----------         ---------------------
<S>                                  <C>                 <C>
         Group                       CTI                       50.1%
                                     Siemens                   49.9%
         CTI                         Non-Siemens                 96%
                                     Siemens                      4%
</TABLE>

         Neither Siemens nor any other shareholder of CTI other than Siemens
         shall have any special rights with respect to the purchase, sale or
         registration of their CTI Common Stock except as expressly set forth in
         this Agreement, the Charter of CTI, the stock purchase and
         shareholders' agreement referenced in Section 3.3 between Siemens and
         CTI or an agreement or agreements entered into hereafter. Each CTI
         Shareholder, including Management but excluding Group and Siemens,
         shall execute and deliver to CTI a Shareholder Agreement in
         substantially the form of Exhibit 3.6 hereto.

4.       CLOSING. The closing of the sale and purchase of shares of the Group
         Common Stock described herein (the "Closing") shall take place at the
         offices of Siemens Capital Corporation, 767 Fifth Avenue, New York, New
         York 10153 on January 5, 1988 or on a date thereafter (the "Closing
         Date") to be agreed to by the parties to occur within ten (10) days
         after the parties obtain the required approvals of the United States
         Department of Justice and Federal Trade Commission under the
         Hart-Scott-Rodino Antitrust Improvements Act and the Bundeskartellamt
         of the Federal Republic of Germany, which approvals the parties agree
         to pursue promptly and diligently.

4.1      Management's Deliverables. At the Closing, Management shall deliver to
         Siemens:

         (a)      Stock purchase agreements with the Non-Siemens Group
                  Shareholders, in substantially the form attached hereto as
                  Exhibit 4.1(a) providing for the sale to Siemens of Group
                  Common Stock as provided in Section 2 above.

         (b)      Certificates evidencing the Group Common Stock being sold and
                  purchased hereunder.

         (c)      The written opinion of counsel to Management in substantially
                  the form set forth in Exhibit 4.1(c) attached hereto.

         (d)      The representations and warranties of Management made
                  hereunder shall be true in all material respects as of the
                  Closing; Management shall have performed and


                                      -5-
<PAGE>

                  complied in all respects with all of their undertakings and
                  agreements required by this Agreement to be performed and
                  complied with by Management prior to the Closing; and Siemens
                  shall have been furnished with certificates of Management,
                  dated the Closing Date, certifying to that effect.

4.2      Group's Deliverables.  At the Closing, Group shall deliver to Siemens:

         (a)      A certified copy of resolutions duly adopted by the Board of
                  Directors of Group approving the execution, delivery and
                  performance of this Agreement and the issuance and delivery of
                  the Group Common Stock being sold hereunder and of all other
                  corporate action necessary or proper to enable Group to comply
                  with the terms hereof.

         (b)      Agreements by the holders of all of the outstanding Options to
                  Acquire Group Common Stock to exchange such Options for
                  options to acquire CTI Common Stock on the basis set forth on
                  Exhibit 4.2(b) hereto.

         (c)      The written opinion of Baker, Worthington, Crossley,
                  Stansberry & Woolf, counsel to Group, in substantially the
                  form set forth in Exhibit 4.2(c) hereto.

         (d)      The representations and warranties of Group made hereunder
                  shall be true in all material respects as of the Closing;
                  Group shall have performed and complied in all respects with
                  all of their undertakings and agreements required by this
                  Agreement to be performed and complied with by Group prior to
                  the Closing; and Siemens shall have been furnished with
                  certificates of Group, dated the Closing Date, certifying to
                  that effect.

4.3      CPS's Deliverables. At the Closing, CPS shall deliver to Siemens the
         amendment of the OEM Exclusive Distribution Rights Agreement between
         CPS and Siemens referred to in Section 13.12 hereof.

4.4      Siemens' Deliverables. At the Closing, Siemens shall deliver to CPS,
         Group or Management, as appropriate:

         (a)      The aggregate purchase price for the Group Common Stock being
                  purchased and sold hereunder, of thirty million dollars
                  ($30,000,000), plus interest thereon as provided in Section 2,
                  paid by wire transfer or cashier's or certified check.

         (b)      A certified copy of resolutions duly adopted by Siemens' Board
                  of Directors approving the execution, delivery and performance
                  of this Agreement and of all other corporate action necessary
                  or proper to enable Siemens to comply with the terms hereof.

         (c)      The amendment of the OEM Exclusive Distribution Rights
                  Agreement between CPS and Siemens referred to in Section 13.12
                  hereof.

         (d)      The written opinion of Walter G. Gans, counsel to Siemens, in
                  substantially the form set forth in Exhibit 4.4(d) hereto.

         (e)      The amendment of the Stock Purchase and Stockholders'
                  Agreement referred to in Section 12.3 hereof.


                                      -6-
<PAGE>

4.5      Conditions to Siemens' Obligations at Closing.

         (a)      The Group Common Stock. The legality of the sale of the Group
                  Common Stock to be sold at the Closing and the validity and
                  form of the certificate(s) representing such shares, all other
                  instruments relating to the sale and delivery of such Group
                  Common Stock and all corporate and other proceedings taken on
                  or prior to the Closing by CTI, Group, CPS and Management, in
                  connection with the performance of this Agreement, shall be
                  satisfactory to Siemens and its counsel, and Siemens and its
                  counsel shall have received from CTI, Group, CPS and
                  Management copies of all such documents or other evidence as
                  Siemens or said counsel may reasonably request in order to
                  establish the effective consummation of such transactions and
                  the taking of all corporate and governmental proceedings in
                  connection therewith, in form (as to certification and
                  otherwise) and substance satisfactory to Siemens and said
                  counsel.

         (b)      All Representations True. All representations and warranties
                  of Management and CTI contained in this Agreement shall be
                  true and correct on and as of the Closing Date.

         (c)      Action by Boards of Directors. Except as provided in this
                  Agreement, the Charters and the Bylaws of Group and CPS as in
                  effect on the date of this Agreement shall not have been
                  further amended, modified or supplemented in any respect; no
                  resolution shall have been adopted by the shareholders or the
                  Boards of Directors of Group or CPS which would have any
                  material effect upon the rights of Siemens; and Group and CPS
                  shall have delivered to Siemens such certificates of public
                  officials as Siemens and its counsel shall reasonably require
                  to confirm the fulfillment of this condition.

         (d)      Performance. CTI, Group, CPS and Management shall have
                  performed and complied with all agreements and conditions
                  contained in this Agreement required to be performed or
                  complied with on their parts prior to or on the Closing and
                  shall not be in default in the performance or observance of
                  any of the terms, covenants or conditions of this Agreement.

         (e)      Proceedings. All corporate and other proceedings to be taken
                  by CTI, Group, CPS and Management in connection with the
                  transactions contemplated by this Agreement, and all documents
                  incidental thereto shall be satisfactory in form and substance
                  to Siemens and its counsel; and Siemens and its counsel shall
                  have received all such counterpart originals or certified or
                  other copies of all documents as Siemens and its counsel may
                  reasonably request in connection with said transactions and
                  all proceedings taken in connection therewith.

         (f)      Financial Statements. Siemens shall have received audited
                  financial statements of CPS dated as of December 31, 1986, and
                  unaudited financial statements of Group and CPS as of dates
                  after December 31, 1986 through the Closing Date, that are
                  produced in the ordinary course of business on a consistent
                  basis, but not less than once per quarter (but, with respect
                  to Group, after April 7, 1987 only); all certified by the
                  chief financial officers of Group and CPS, respectively. There
                  shall have been no material adverse change in the financial
                  condition or the business of CPS since December 31, 1986, or
                  Group since April 7, 1987.


                                      -7-
<PAGE>

         (g)      Officers' Certificates. Siemens shall have received Officers'
                  Certificates executed by officers of CPS and Group, dated the
                  Closing Date and satisfactory in form and substance to Siemens
                  and its counsel, confirming the representations and warranties
                  made by CPS and Group hereunder.

         (h)      Board Approval. As of the Closing, Management and the Boards
                  of Directors of CTI, CPS and Group shall have duly authorized
                  the execution, delivery and performance of this Agreement.

         (i)      Intellectual Property Matters.

                  (1)      CPS Assets in CCS. Siemens shall have received a copy
                           of an assignment from CTI Cyclotron Systems, Inc.
                           ("CCS") to CPS in form reasonably satisfactory to
                           Siemens of design and technology for the RDS 112,
                           dated at or prior to the Closing Date.

                  (2)      Consulting Agreements. CPS and CCS shall use best
                           efforts to obtain assignment agreements executed by
                           consultants to CTI and CPS and third parties,
                           including those listed on Exhibit 4.5(1)(2) attached
                           hereto, dated at or prior to the Closing Date and
                           satisfactory in form and substance to Siemens and its
                           counsel, assigning the results, including
                           intellectual property rights developed pursuant to
                           consulting, development and technology transfer
                           agreements or arrangements with CPS or CCS, as the
                           case may be, to CPS or CCS, respectively, and Siemens
                           shall be provided copies of such assignment
                           agreements.

                  (3)      Patent and Know-How License. Siemens shall have
                           received a patent and know-how license from CCS to
                           CPS with respect to the background rights of CCS used
                           or useful by CPS in the CPS Business, including those
                           identified more specifically in Exhibit 4.5(i)(3)
                           attached hereto, dated at or prior to the Closing
                           Date and satisfactory in form and substance to
                           Siemens and its counsel.

                  (4)      Software Licenses. Siemens shall have received copies
                           of properly executed licenses and/or sublicenses from
                           CPS' suppliers, including that from Gould, Inc.,
                           necessary for CPS to copy, distribute and/or transfer
                           all software and firmware contained in CPS's PET
                           scanners and RDS 112 products (including all such
                           software and firmware which has been modified and/or
                           embedded within the written code for such products),
                           dated at or prior to the Closing Date and
                           satisfactory in form and substance to Siemens and its
                           counsel, or proof satisfactory to Siemens that such
                           licenses or sublicenses are not necessary to the
                           continued operation of the CPS Business.

                  (5)      Phelps Assignment. Group shall have received a Final
                           Assignment and Bill of Sale transferring the RDS
                           Know-how and Consulting Results under consulting
                           agreements to Group executed by Michael E. Phelps
                           dated at or prior to the Closing Date and
                           satisfactory in form and substance to Siemens and its
                           counsel. "RDS Know-how" shall mean any and all
                           documents, models and design and technical
                           information, data,


                                      -8-
<PAGE>

                           drawings, plans, flow charts, specifications,
                           formulations and reports and, in addition, all other
                           general and specific knowledge, experience,
                           techniques and information, whether in written form
                           or not, necessary for the manufacture, assembly,
                           sale, application and operation of RDS systems,
                           excluding any such know-how with respect to which
                           Phelps does not have rights or ownership or control
                           or the right to grant a license. "Consulting Results"
                           shall mean all ideas, inventions, improvements,
                           know-how, creations, materials, works, writings,
                           reports, publications and information collected,
                           assembled, conceived, suggested, originated,
                           developed, constructed, rendered or provided by
                           Phelps under such consulting agreements, including
                           the intellectual property rights therein.

                  (6)      Phelps Consulting Agreement. Siemens shall have
                           received a properly executed amendment to the
                           Consulting Agreement between Michael E. Phelps and
                           Group, dated April 7, 1987, dated at or prior to the
                           Closing Date in substantially the same form as that
                           attached hereto as Exhibit 4.5(i)(6).

         (j)      Distribution Agreement Amendment. Siemens shall have received
                  a properly executed Amendment to the OEM Exclusive
                  Distribution Rights Agreement among Computer Technology and
                  Imaging, Inc., Siemens, Dr. Terry Dean Douglass, Dr. Ronald
                  Nutt, Michael Callann Crabtree and James Kelly Milam dated as
                  of May 20, 1986, dated at or prior to the Closing Date, in
                  substantially the same form as that attached hereto as Exhibit
                  4.5(j).

         (k)      Employment Agreements. Siemens shall have received copies of
                  properly executed employment agreements with each of the
                  Management Persons, in substantially the same form as that
                  attached hereto as Exhibit 11.2, dated at or prior to the
                  Closing Date.

         (l)      CTI Warranties. Management shall have caused CTI to execute
                  and Siemens shall have received certified copies of
                  resolutions of the Board of Directors of CTI undertaking to
                  assume (1) the representations and warranties contained in
                  Section 5 hereof and (2) the expenses referenced at Section
                  22.1 hereof, dated at or prior to the Closing Date, in form
                  and substance reasonably satisfactory to counsel for Siemens.

         (m)      Service Agreements. Siemens shall have received a properly
                  executed Technical Service Agreement among CTI, CTI Cyclotron
                  Systems, Inc., CPS and Siemens, and a properly executed
                  Administrative Service Agreement between CTI and CPS, both
                  dated at or prior to the Closing Date, in substantially the
                  form as that attached hereto as Exhibits 4.5(m)(1) and
                  4.5(m)(2).

4.6      Conditions to the Obligations of Group, CPS, Management and the
         Non-Siemens Shareholders at Closing.

         (a)      All Representations True. The representations and warranties
                  made by Siemens contained in this Agreement shall be true on
                  and as of the Closing Date.


                                      -9-
<PAGE>

         (b)      Performance. Siemens shall have performed and complied with
                  all agreements, obligations and conditions required by this
                  Agreement to be performed by it.

         (c)      Proceedings. All corporate and other proceedings of Siemens
                  required by law and otherwise in connection with the
                  performance of this Agreement, and all documents incident
                  thereto, shall have been performed or executed.

         (d)      Board Approval. As of the closing, the Board of Directors of
                  Siemens shall have duly authorized the execution, delivery and
                  performance of this Agreement and the purchase of the Group
                  Common Stock being sold hereunder.

4.7      Post-Closing Events. Management agrees to vote and to cause CTI at the
         Closing to enter into an agreement to vote in favor of a merger of
         Group and CPS at such time as Siemens deems it appropriate. Upon the
         occurrence of such merger, this Agreement shall continue in full force
         and effect and all agreements, covenants and other obligations of Group
         hereunder shall be agreements, covenants and obligations of CPS.

5.       REPRESENTATIONS AND WARRANTIES OF CTI. Management hereby covenants and
         agrees that it will cause CTI at the Closing to enter into an agreement
         representing and warranting to Siemens as follows:

5.1      Organization and Good Standing of Group and CPS. Group is a corporation
         duly organized, validly existing and in good standing under the laws of
         the State of Tennessee, and has all requisite corporate power and
         authority to carry on its business as it is now being conducted and to
         own the properties and assets it now owns. Copies of Group's Charter
         and all amendments thereto effected prior to the date hereof and the
         Bylaws of Group as amended to the date hereof, both certified to be
         correct by the Secretary of Group, are attached hereto as Exhibit
         5.1(a) and are complete and correct as at the date hereof. CPS is a
         corporation duly organized, validly existing and in good standing under
         the laws of the State of Tennessee, and has all requisite corporate
         power and authority to carry on its business as it is now being
         conducted and to own the properties and assets it now owns. Copies of
         CPS's Charter and all Amendments thereto effected prior to the date
         hereof and the Bylaws of CPS as amended to the date hereof, both
         certified to be correct by the Secretary of CPS, are attached hereto as
         Exhibit 5.1(b) and are complete and correct as at the date hereof.

5.2      Capitalization, Title to Group and CPS Common Stock. The authorized
         capital stock of Group consists of ten million (10,000,000) shares of
         Group Common Stock having a par value of One Cent ($.01) per share, of
         which as of October 1, 1987, six million six hundred fifty-nine
         thousand nine hundred ninety (6,659,990) shares were issued and
         outstanding. Attached hereto as Exhibit 5.2(a) is a list of the
         shareholders of Group and the number of shares held by each as of the
         date hereof. To the knowledge of CTI and according to the stock record
         of Group, each Non-Siemens Group Shareholder is the true and lawful
         owner of the amount of Group Common Stock set forth opposite his name
         in Exhibit 5.2(a), free of any Encumbrances and has the legal right,
         power and authority to sell such Group Common Stock to Siemens. Except
         as set forth in Exhibit 5.2(b) hereto, Group has no obligation to issue
         any additional shares of Group Common Stock or any other form of
         capital stock of Group or any securities convertible into or
         exchangeable for, or giving any person the right to acquire from Group
         and shares of Group Common Stock or any other form of capital stock of
         Group. There are no outstanding rights, options, warrants, calls,
         commitments, contracts or agreements for the purchase from or


                                      -10-
<PAGE>

         sale by Group of any shares of its capital stock, except as set forth
         in this Section 5.2 and in Exhibit 5.2(b). The authorized capital stock
         of CPS consists of ten million (10,000,000) shares of common stock
         having a par value of One Cent ($.01) per share, of which as of October
         1, 1987 one million four hundred eighty-three thousand fifty-eight
         (1,483,058) shares were issued and outstanding, all of which are held
         by Group. CPS has no obligation to issue any additional shares of its
         common stock or any other form of capital stock of CPS or any
         securities convertible into or exchangeable for, or giving any person
         the right to acquire from CPS any shares of CPS common stock or any
         other form of capital stock of CPS. There are no outstanding rights,
         options, warrants, calls, commitments, contracts or agreements for the
         purchase from or sale by CPS of any shares of its capital stock.

5.3      Corporate Authority. The Board of Directors of Group and CPS have duly
         authorized the execution, delivery and performance of this Agreement
         and have duly authorized the transfer and delivery of the Group Common
         Stock being sold by the Non-Siemens Group Shareholders hereunder and
         pursuant to the individual Stock Purchase Agreement as referred to in
         Section 4.1(a); no other corporate proceedings on the part of Group or
         CPS are necessary to authorize this Agreement and the issuance and
         delivery of the Group Common Stock being sold hereunder. Except as set
         forth in Exhibit 5.3 hereto, neither the execution, delivery or
         performance of this Agreement nor the issuance and delivery of the
         Group Common Stock being sold hereunder, nor compliance with, nor
         fulfillment of, the terms and provisions of this Agreement does or will
         (a) violate or conflict with, or result in, any breach of any of the
         terms, conditions or provisions of, or constitute a default (or an
         event which with notice or lapse of time, or both, would become a
         default) under the Charter or Bylaws of either Group or CPS, or any
         agreement, indenture, lease, mortgage or other instrument to which
         either it is a party or by which it is bound, (b) require any
         affirmative approval, consent, authorization or other order or action
         of any court, governmental authority or regulatory body or of any
         creditor of either Group or CPS, (c) result in any material violation
         of any provision of any law, rule, regulation or any court order,
         judgment, writ, injunction, decree or arbitration award or
         determination, or (d) give any party with rights under any such
         instrument, agreement, mortgage, judgment, order, award, decree or
         other restriction the right to terminate, modify or otherwise change
         the rights or obligations of either Group or CPS. Each of Group and CPS
         has full power and authority to do and perform all acts and things
         required to be done by it under this Agreement. This Agreement, when
         duly executed and delivered by Group or CPS, as the case may be,
         constitutes a legal, valid, binding and enforceable agreement of Group
         or CPS, respectively.

5.4      Compliance with Laws; Governmental Authorities. Except as set forth in
         Exhibit 5.4 attached hereto, each of Group and CPS has complied in all
         material respects with any and all applicable statutes, orders, rules
         and regulations promulgated by governmental authorities relating in any
         material respect to the financial conditions, business, operations or
         prospects of Group and CPS and neither Group nor CPS has received any
         notice of alleged violation of any such statute, order, rule or
         regulation. Except as set forth in Exhibit 5.4 hereto, neither Group
         nor CPS is required to submit any notice, report or other filing with
         any governmental authority in connection with the execution, delivery
         or performance by it of this Agreement or the issuance and delivery of
         the Group Common Stock being sold hereunder.

5.5      Financial Statements. Group has delivered and disclosed to Siemens
         audited consolidated financial statements dated December 31, 1986 and
         unaudited consolidated


                                      -11-
<PAGE>

         financial statements for the quarters ended March 31, 1987 for CPS,
         together with unaudited consolidated financial statements for the
         quarters ended June 30, 1987 and September 30, 1987 for each of Group
         and CPS (hereinafter referred to as the "Group Financial Statements"
         and the "CPS Financial Statements", respectively, and collectively
         hereinafter referred to as the "Financial Statements"). Such Financial
         Statements (a) are true, correct and complete, (b) fairly present the
         financial condition, assets and liabilities of Group and CPS, as the
         case may be, and their subsidiaries as of such date and the results of
         its operations for such periods, (c) have been prepared in accordance
         with generally accepted accounting principles applied on a consistent
         basis and (d) are certified by the Chief Financial Officer of Group and
         CPS, respectively.

5.6      Tax Matters. Each of Group and CPS has duly filed all United States,
         Tennessee and California returns with respect to Taxes which it has
         been and is by law required to file. The provisions made for taxes on
         the Financial Statements as of September 30, 1987, are sufficient for
         the payment of all federal, state, county, local and foreign taxes of
         Group and CPS accrued and unpaid at that date, whether or not disputed.
         Neither Group nor CPS is aware of any additional taxes, interest or
         penalties alleged to be due or owing.

5.7      Absence of Undisclosed or Contingent Liabilities. Except as and to the
         extent reflected or reserved against in the Financial Statements,
         neither Group nor CPS had at September 30, 1987, any material
         liabilities or obligations, secured or unsecured (whether accrued,
         absolute, contingent or otherwise), of a nature customarily reflected
         in a corporate balance sheet, or the notes thereto, prepared in
         accordance with generally accepted accounting principles consistently
         applied. Since such date neither Group nor CPS has incurred any
         material liabilities or obligations other than in the ordinary course
         of business.

5.8      Absence of Certain Changes and Events. Except as set forth in Exhibit
         5.8 hereto, since December 31, 1986, each of CPS, and since April 7,
         1987, Group has conducted its business in the ordinary and usual
         course, and there has not been (i) any material adverse change in the
         business, financial condition or results of operations of either Group
         or CPS; (ii) any damage, destruction or other casualty loss (whether or
         not covered by insurance) affecting the properties, liabilities,
         prospects or business of either Group or CPS, including any damage or
         destruction of property by fire or other casualty, whether or not
         covered by insurance, (iii) any increase in the compensation payable or
         to become payable by either Group or CPS to any of its officers or
         employees or any increase in any bonus, insurance, pension or other
         employee benefit plan, payment or arrangement made by either Group or
         CPS for or with any such officers or employees, except for increases in
         the ordinary course of business, (iv) any labor dispute, other than
         routine matters; which will have an effect on the business, financial
         condition or results of operations of either Group or CPS, (v) any
         commitment or transaction (including, without limiting the generality
         of the foregoing, any borrowing or capital expenditure) entered into by
         either Group or CPS, other than in the ordinary and usual course of
         business, (vi) any change in the accounting principles, procedures,
         methods or practices of either Group or CPS, (vii) any removal or grant
         of permission to remove from any building, facility or real property
         controlled by either Group or CPS, any machinery, equipment, fixture,
         vehicles, or other personal property or parts thereof, except in the
         ordinary course of business as conducted by either Group on April 7,
         1987 or CPS on December 31, 1986, (viii) any change in credit policy of
         either Group or CPS as to sales of inventories or collection of
         receivables, (ix) any entry into any transaction of merger or
         consolidation, except as may be contemplated hereby, (x) any deferral
         of scheduled maintenance or repair of the Assets,


                                      -12-
<PAGE>

         (xi) any change in standard written warranties with regard to products
         of either Group or CPS, or (xii) any other event or condition of any
         character materially and adversely affecting the business, financial
         condition or results of operations of either Group or CPS.

5.9      Title to Properties; Absence of Liens and Encumbrances. Group and CPS
         have good and marketable title to all of its material Assets free and
         clear of Encumbrances that would adversely affect their availability
         for their intended use by Group and CPS except (a) as set forth in
         Exhibit 5.9 hereto; and (b) liens for current taxes not yet due and
         payable, which liens do not involve any danger of the sale, forfeiture
         or loss of any material amount of the Assets and do not interfere with
         the business of CPS as it was conducted at December 31, 1986, or Group
         as it was conducted at April 7, 1987. The Assets include all assets,
         tangible and intangible, real and personal (i) in which Group or CPS
         has ownership, leasehold, license or other rights on the date hereof,
         and (ii) which have been or are used in the conduct of the business of
         Group or CPS. All of the property, plant and equipment included in the
         Assets is in normal working order, except for ordinary wear and tear,
         retirements in the ordinary course of business, normal maintenance and
         repair, and breakdowns that do not affect the operation of any facility
         included in the Assets for more than a temporary period. The machinery
         and equipment included in the Assets are sufficient for the conduct of
         the business of Group and CPS in the manner in which it is being
         conducted as of this date, and as of December 31, 1986 as to CPS, and
         April 7, 1987, as to Group.

5.10     Patents, Trademarks and Know-how. All trademarks, trademark
         applications, trade names, copyrights, inventions, patents (including
         all reissues, division, continuations, and extensions thereof), patent
         applications, patent disclosures docketed, and any other statutory
         rights, used by Group or CPS are listed in Exhibit 5.10. Except as
         specifically set forth and described in Exhibit 5.10, the intellectual
         property rights listed therein are owned outright by Group or CPS,
         together with all processes, formulations, know-how and trade secrets
         used in its business, free and clear of all liens and encumbrances and
         no royalties are required to be paid to anyone under or with respect to
         any of them. Except as set forth in Exhibit 5.10, CTI has no knowledge
         of and has not received any notice of conflict with the asserted rights
         of others with respect to any intellectual property right used in, or
         useful to, the business of Group or CPS. Neither Group nor CPS has
         licensed anyone to use any patents, know-how or other proprietary
         rights of Group or CPS and, except as set forth in Exhibit 5.10, CTI
         has no knowledge of the infringing use by anyone of any such patents,
         know-how or other proprietary rights or the infringement by Group or
         CPS of any patents, know-how, or any other proprietary rights owned by
         any other person.

5.11     Litigation. There are no unsatisfied judgments, injunctions,
         stipulations, awards, orders or decrees against either Group or CPS
         with respect to any of the Assets or the business of Group or CPS.
         There is no action, lawsuit, claim, proceeding, arbitration or
         investigation pending as to which Group or CPS has received actual
         notice or, to the knowledge of CTI, threatened against or relating to
         Group or CPS, their properties or businesses which, if decided
         adversely against Group or CPS, as the case may be, would have a
         materially adverse effect upon the financial condition of Group or CPS,
         respectively. CTI has no knowledge that either of Group or CPS is in
         default with respect to any order, writ, injunction or decree of any
         court or any Governmental Body, affecting or relating to Group or CPS.
         To the best of CTI's knowledge, there is no basis for any such
         litigation, arbitration, other proceedings or investigations or for
         claims alleging or claiming violations with respect to the operations
         of Group and CPS of laws (including


                                      -13-
<PAGE>

         the common law) relating to U.S. or foreign antitrust, trade
         regulation, unfair competition, the infringement of patents,
         copyrights, trademarks, trade names or other intellectual property
         rights, the pollution of air, water or land, environmental, labor,
         safety, hazardous materials or conditions, pension, employee benefits
         or rights, breach of contract, torts (including product liability),
         breach of warranties (whether express or implied), discrimination,
         Taxes, technology or currency export or import controls, or the Foreign
         Corrupt Practices Act, where any such litigation, arbitration, other
         proceeding, investigation or claim may involve or result in Damages
         exceeding U.S. $50,000 or restrictions under equity or law in the
         operation of the business of Group or CPS in the manner in which the
         business of Group or CPS has been operated to date.

5.12     Contracts. Exhibit 5.12 hereto contains a list of each contract,
         agreement or understanding, whether written or oral (including any and
         all amendments thereto), to which Group or CPS is a party and which is
         material to the continued use of Assets, or the conduct of the business
         or financial condition of Group or CPS and all contracts and agreements
         entered into outside the ordinary course of business (collectively, the
         "Contracts"). True and correct copies of Contracts have been made
         available to Siemens. Each of Group and CPS has substantially complied
         with all the material provisions of the Contracts and is not in
         material default under any of the terms thereof. "Material" for
         purposes of this Section 5.12 shall mean contracts, agreements or
         understanding involving $50,000 or more.

5.13     Officers and Employees. So far as CTI is aware, no officer or employee
         of Group or CPS is obligated under any contract or other agreement or
         is subject to any judgment, decree or order of any court or
         administrative agency which would conflict with (a) his obligation to
         use his best efforts to promote the interests of Group or CPS, as the
         case may be, (b) the conduct of the business of Group or CPS, as the
         case may be, as presently conducted, or (c) the carrying on by an
         officer or employee of the business of Group or CPS, as the case may
         be, as an officer or employee.

5.14     Full Disclosure. The representations and warranties by CTI hereunder or
         any written statement or certificate furnished to Siemens by CTI
         pursuant hereto do not or does not and will not at the Closing contain
         any untrue statement of a material fact or omit to state a material
         fact required to be stated therein or necessary to make the
         representation or warranty herein or any written statement or
         certificate furnished to Siemens by CTI pursuant hereto, in light of
         the circumstances in which it is or they are made, not misleading. CTI
         has not failed to disclose any information nor misstated any
         information with respect to the business, assets, operation or
         financial condition of Group or CPS of which CTI had knowledge at the
         time and which would have reasonably been material to Siemens in
         connection with the purchase of the Group Common Stock or the
         transactions contemplated hereby.

5.15     Fully Paid Nonassessable Common Stock. The Group Common Stock being
         sold by the Non-Siemens Group Shareholders as contemplated by this
         Agreement has been duly and validly issued, and is fully paid and
         nonassessable.

5.16     Continuation of Business. Neither Group nor CPS has any knowledge of
         any factors or conditions which preclude Group or CPS from the
         continuation of its present business operations.


                                      -14-
<PAGE>

5.17     No Brokerage Fees. No person acting on CTI's, Group's, CPS's,
         Management's or the Non-Siemens Group Shareholders' behalf has any
         claim for a brokerage commission, finder's fee or other like payment in
         connection with this Agreement or the transactions contemplated hereby.

5.18     Insurance. Group maintains insurance on a basis deemed by Group to be
         adequate for its purposes and shall continue such insurance or
         comparable insurance.

5.19     Energy Supplies, Raw Materials and Components. Neither Group nor CPS
         has received any notice by any corporation or organization supplying
         natural gas, coal, oil or electrical power to it or raw materials or
         components used in the business and operations of Group or CPS, that
         supplies of such energy source, raw materials or components will become
         unavailable to the extent reasonably required for continued conduct of
         the business of Group or CPS.

5.20     FDA Matters; No Recalls. To the best of CTI's knowledge and except as
         set forth at Exhibit 5.20 attached hereto, the manufacturing operations
         of each of Group and CPS are conducted in accordance with Good
         Manufacturing Practices, as defined by the Federal Food and Drug
         Administration (the "FDA"), and are duly registered with the FDA; the
         products and labeling of each of Group and CPS have received all
         necessary approvals from the FDA and other regulatory authorities to
         permit the marketing of these products in the United States; the
         products of each of Group and CPS are not subject to any recall or
         retrofit action and neither Group nor CPS knows of any basis for any
         such recall or retrofit action; and each of Group and CPS fully
         complies in all material respects with applicable record keeping and
         reporting obligations prescribed by the FDA including, without
         limitation, incident reporting under the Medical Device Reporting
         Regulations.

5.21     Employee Benefit Plans. Exhibit 5.21 lists all benefit plans and
         benefit arrangements available to employees of each of Group and CPS
         (the "Benefit Plans and Arrangements"). To the best of CTI's knowledge,
         each Benefit Plan and Arrangement has been maintained and administered
         in all material respects in accordance with applicable law, and that
         the assets of each funded Benefit Plan or Arrangement is sufficient to
         cover the liabilities determined therefor on an actuarial basis, the
         latest of which determinations has been delivered by Management to
         Siemens. For purposes of this Section, the term "Benefit Plans" shall
         mean each and all "employee benefit plans" as defined in Section 3(3)
         of the Employee Retirement Income Security Act of 1974, as amended
         ("ERISA"), maintained or contributed to by Seller and covering
         employees of Group and CPS, including (a) any such plans that are
         "employee welfare benefit plans" as defined in Section 3(1) of ERISA
         and (b) any such plans that are "employee pension benefit plans" as
         defined in Section 3(2) of ERISA; and the term "Benefit Arrangements"
         shall mean life and health insurance, hospitalization, savings,
         holiday, vacation, severance pay, sick pay, sick leave, disability,
         tuition refund, service award, company car, scholarship, relocation,
         patent awards and other contracts (other than employment, consultancy
         or severance contracts), policies or practices of Group and CPS
         providing employee or executive benefits to employees of Group and CPS,
         other than the Benefit Plans.

5.22     Consents. Except for filings under the Hart-Scott-Rodino Antitrust
         Improvements Act of 1976, as amended (the "HSR Act") and with the
         Bundeskartellamt in the Federal Republic of Germany, no consent,
         approval or authorization of, or exemption by, or filing with, any
         governmental or regulatory authority is required in connection with the


                                      -15-
<PAGE>

         execution, delivery and performance by CTI, Group, CPS or Management of
         this Agreement or the taking of any other action contemplated hereby,
         excluding, however, consents, approvals, authorizations, exemptions and
         filings, if any, which Siemens is required to obtain or make.

5.23     Accounts Receivable. All accounts receivable reflected in the Financial
         Statements and those accruing since the date of the most recent
         Financial Statements represent bona fide transactions in the ordinary
         course of business which represent actual sales and require no further
         act on the part of Group or CPS to make such accounts receivable
         payable by the account debtors. CTI has no reason to believe that such
         accounts receivable, net of established reserves, are not collectible
         in the ordinary course of business in the book amounts thereof as shown
         on the Financial Statements.

5.24     Inventory. The inventories represented in the audited Financial
         Statement consist of inventories purchased for resale, raw materials
         and supplies, work in process and finished goods. The inventories are
         accounted for at December 31, 1986 as to CPS, and at April 7, 1987 as
         to Group, in accordance with U.S. GAAP, and are accounted for net of
         reserves established in accordance with U.S. GAAP. The inventories
         shown on the audited Financial Statement, or thereafter acquired by
         Group and CPS, consist of items, net of reserves, are consistent with
         reasonable quality standards and in amounts and mix consistent with
         past practices of Group and CPS; the values at which such inventories
         are carried on the audited Financial Statement reflect the normal
         inventory valuation policy of Group and CPS; the present inventories of
         Group and CPS are not excessive; and the value of all items not in
         saleable condition or of obsolete material or of materials of below
         standard quality have been written down to realizable market value or
         adequate reserves have been provided therefor consistent with U.S.
         GAAP.

5.25     Books and Records. The minute books and stock record books of Group and
         CPS are true, complete and correct in all material respects. Such
         minute books reflect accurately in all material respects all material
         actions approved or taken by their governing boards, any committees
         thereof and their stockholders in their capacities as such. All such
         minute books and stock record books have been made available to Siemens
         or its representatives. True, complete and correct copies of the
         certificate of incorporation and by-laws or other constituent documents
         of Group and CPS have been delivered to Siemens.

5.26     Labor Relations. The labor relations between Group and CPS, on the one
         hand, and their respective employees, on the other hand, are peaceful.
         Neither Group nor CPS is a party to, and the employees of neither Group
         nor CPS are covered by, any collective bargaining or other labor union
         contract. Neither Group nor CPS has breached or otherwise failed to
         comply in any material way with any provisions of any such agreement or
         contract and there are no material grievances outstanding against Group
         or CPS thereunder. CTI has not received notice of any unfair labor
         practice complaints or age, sex, racial or other discrimination
         complaints pending against Group or CPS before the National Labor
         Relations Board, the Equal Employment Opportunities Commission, any
         other Governmental Body or any court or arbitrators. Within the past 24
         months, there have been no activities or proceedings known to CTI of
         any labor union (or representatives thereof) to organize any
         unorganized employees of Group or CPS or any strikes, slowdowns, work
         stoppages, lockouts or threats thereof known to CTI by or with respect
         to employees employed by Group or CPS.


                                      -16-
<PAGE>

5.27     Environmental Compliance. Each of Group and CPS (1) has complied in all
         material respects with environmental laws and regulations, whether
         federal, state or local, whether domestic or foreign; and (2) has not
         made statements in any documents material to such matters submitted to
         Governmental Bodies containing untrue statements of material fact or
         omitting any statement of material fact necessary to make the
         statements therein not misleading.

5.28     Employee Occupational Hazard and Other Claims. Neither Group nor CPS
         has received any written claim or, to the knowledge of CTI, threat,
         other than workers' compensation claims, by any of its present or past
         employees for Damages arising out of alleged occupational hazards,
         unsafe conditions of employment or other similar claims related to the
         work environment.

5.29     Condition of Facilities/Sites and No Reportable Incidents. The
         Knoxville, Tennessee plant site included in the Assets contains no
         condition which may result in recovery in excess of $50,000 by any
         Person of remedial or removal cost, natural resource damages or other
         cost, expenses or damages arising from any injury to public health,
         safety or the environment relating to such plant site, including any
         recovery under public nuisance liability or the Comprehensive
         Environmental Response, Compensation, and Liability Act, 42 U.S.C. ss.
         9601 et seq. (1982), as amended by the Superfund Amendments and
         Reauthorization Act of 1986, H.R. 2005, 99th Cong. 2d. Sess., 132 Cong.
         Rec. 9031 (enacted October 17, 1986); the Resource Conservation and
         Recovery Act of 1976, 42 U.S.C. ss. 6901 et seq. (1983) (Supp. 1986),
         as amended by the Hazardous and Solid Waste Amendments of 1984, 42
         U.S.C. ss. 6926 (g) (Supp. 1986); the Federal Water Pollution Control
         Act, 33 U.S.C. ss. 1257 et seq. (1982); the Safe Drinking Water Act, as
         amended, 42 U.S.C. ss. 300 et seq. (1982); the Clean Air Act, 42 U.S.C.
         ss. 7901 et seq. (1982); or any similar statute applicable in the
         State of Tennessee. Neither Group nor CPS has ever had an incident with
         respect to nuclear regulatory or other environmental matters which was
         required to be reported to a Governmental Body and which was not so
         reported; Exhibit 5.29 contains a list of all material documents
         submitted or received by Group or CPS with respect to such incidents.

6.       REPRESENTATIONS AND WARRANTIES OF MANAGEMENT. Management represents and
         warrants as follows:

6.1      Compliance with Laws; Governmental Authorities. Except as set forth in
         Exhibit 5.4 hereto, to the knowledge of Management, each of Group and
         CPS has complied in all material respects with any and all applicable
         statutes, orders, rules and regulations promulgated by governmental
         authorities relating in any material respect to the financial
         conditions, business, operations or prospects of Group and CPS and
         neither Group nor CPS has received any notice of alleged violation of
         any such statute, order, rule or regulation. To the knowledge of
         Management and, except as set forth in Exhibit 5.4 hereto, neither
         Group nor CPS is required to submit any notice, report or other filing
         with any governmental authority in connection with the execution,
         delivery or performance by it of this Agreement or the issuance and
         delivery of the Group Common Stock being sold hereunder.

6.2      Absence of Undisclosed or Contingent Liabilities. To the knowledge of
         Management and except as and to the extent reflected or reserved
         against in the Financial Statements, neither Group nor CPS had at
         September 30, 1987, any material liabilities or obligations, secured or
         unsecured (whether accrued, absolute, contingent or otherwise), of a
         nature


                                      -17-
<PAGE>

         customarily reflected in a corporate balance sheet, or the notes
         thereto, prepared in accordance with generally accepted accounting
         principles consistently applied. Since such date neither Group nor CPS
         has incurred any material liabilities or obligations other than in the
         ordinary course of business.

6.3      Absence of Certain Changes and Events. Except as set forth in Exhibit
         5.8 hereto, since December 31, 1986, each of CPS, and since April 7,
         1987, Group has conducted its business in the ordinary and usual
         course, and there has not been (i) any material adverse change in the
         business, financial condition or results of operations of either Group
         or CPS; (ii) any damage, destruction or other casualty loss (whether or
         not covered by insurance) affecting the properties, liabilities,
         prospects or business of either Group or CPS, including any damage or
         destruction of property by fire or other casualty, whether or not
         covered by insurance, (iii) any increase in the compensation payable or
         to become payable by either Group or CPS to any of its officers or
         employees or any increase in any bonus, insurance, pension or other
         employee benefit plan, payment or arrangement made by either Group or
         CPS for or with any such officers or employees, except for increases in
         the ordinary course of business, (iv) any labor dispute, other than
         routine matters; which will have an effect on the business, financial
         condition or results of operations of either Group or CPS, (v) any
         commitment or transaction (including, without limiting the generality
         of the foregoing, any borrowing or capital expenditure) entered into by
         either Group or CPS, other than in the ordinary and usual course of
         business, (vi) any change in the accounting principles, procedures,
         methods or practices of either Group or CPS, (vii) any removal or grant
         of permission to remove from any building, facility or real property
         controlled by either Group or CPS, any machinery, equipment, fixture,
         vehicles, or other personal property or parts thereof, except in the
         ordinary course of business as conducted by either Group on April 7,
         1987 or CPS on December 31, 1986, (viii) any change in credit policy of
         either Group or CPS as to sales of inventories or collection of
         receivables, (ix) any entry into any transaction of merger or
         consolidation, except as may be contemplated hereby, (x) any deferral
         of scheduled maintenance or repair of the Assets, (xi) any change in
         standard written warranties with regard to products of either Group or
         CPS, or (xii) any other event or condition of any character materially
         and adversely affecting the business, financial condition or results of
         operations of either Group or CPS.

6.4      Litigation. There are no unsatisfied judgments, injunctions,
         stipulations, awards, orders or decrees against either Group or CPS
         with respect to any of the Assets or the business of Group or CPS.
         There is no action, lawsuit, claim, proceeding, arbitration or
         investigation pending as to which Group or CPS has received actual
         notice or, to the knowledge of Management, threatened against or
         relating to Group or CPS, their properties or businesses which, if
         decided adversely against Group or CPS, as the case may be, would have
         a materially adverse effect upon the financial condition of Group or
         CPS, respectively. To the knowledge of Management, neither of Group or
         CPS is in default with respect to any order, writ, injunction or decree
         of any court or any Governmental Body, affecting or relating to Group
         or CPS. To the knowledge of Management, there is no basis for any such
         litigation, arbitration, other proceedings or investigations or for
         claims alleging or claiming violations with respect to the operations
         of Group and CPS of laws (including the common law) relating to U.S. or
         foreign antitrust, trade regulation, unfair competition, the
         infringement of patents, copyrights, trademarks or trade names or other
         intellectual property rights, the pollution of air, water or land,
         environmental, labor, safety, hazardous materials or conditions,
         pension, employee benefits or rights, breach of contract, torts
         (including product liability), breach of warranties (whether express or
         implied), discrimination, Taxes, technology or currency


                                      -18-
<PAGE>

         export or import controls, or the Foreign Corrupt Practices Act, where
         any such litigation, arbitration, other proceeding, investigation or
         claim may involve or result in Damages exceeding U.S. $50,000 or
         restrictions under equity or law in the operation of the business of
         Group or CPS in the manner in which the business of Group or CPS has
         been operated to date.

6.5      Officers and Employees. To the knowledge of Management, no officer or
         employee of Group or CPS is obligated under any contract or other
         agreement or is subject to any judgment, decree or order of any court
         or administrative agency which would conflict with (a) his obligation
         to use his best efforts to promote the interests of Group or CPS, as
         the case may be, (b) the conduct of the business of Group or CPS, as
         the case may be, as presently conducted, or (c) the carrying on by an
         officer or employee of the business of Group or CPS, as the case may
         be, as an officer or employee.

6.6      FDA Matters; No Recalls. To the knowledge of Management, the
         manufacturing operations of each of Group and CPS are conducted in
         accordance with Good Manufacturing Practices, as defined by the Federal
         Food and Drug Administration (the "FDA"), and are duly registered with
         the FDA; the products and labeling of the Division have received all
         necessary approvals from the FDA and other regulatory authorities to
         permit the marketing of these products in the United States; the
         products of each of Group and CPS are not subject to any recall or
         retrofit action and neither Group nor CPS knows of any basis for any
         such recall or retrofit action; and each of Group and CPS fully
         complies in all material respects with applicable record keeping and
         reporting obligations prescribed by the FDA including, without
         limitation, incident reporting under the Medical Device Reporting
         Regulations.

6.7      Environmental Compliance. To the knowledge of Management, each of Group
         and CPS (1) has complied in all material respects with environmental
         laws and regulations, whether federal, state or local, whether domestic
         or foreign; and (2) has not made statements in any documents material
         to such matters submitted to Governmental Bodies containing untrue
         statements of material fact or omitting any statement of material fact
         necessary to make the statements therein not misleading.

6.8      Employee Occupational Hazard and Other Claims. To the knowledge of
         Management, neither Group nor CPS has received any written claim or
         threat, other than workers' compensation claims, by any of its present
         or past employees for Damages arising out of alleged occupational
         hazards, unsafe conditions of employment or other similar claims
         related to the work environment.

6.9      Condition of Facilities/Sites and No Reportable Incidents. To the
         knowledge of Management, the Knoxville, Tennessee plant site included
         in the Assets contains no condition hereof which may result in recovery
         in excess of $50,000 by any Person of remedial or removal cost, natural
         resource damages or other cost, expenses or damages arising from any
         injury to public health, safety or the environment relating to such
         plant site, including any recovery under public nuisance liability or
         the Comprehensive Environmental Response, Compensation, and Liability
         Act, 42 U.S.C. ss. 9601 et seq. (1982), as amended by the Superfund
         Amendments and Reauthorization Act of 1986, H.R. 2005, 99th Cong. 2d.
         Sess., 132 Cong. Rec. 9031 (enacted October 17, 1986); the Resource
         Conservation and Recovery Act of 1976, 42 U.S.C. ss. 6901 et seq (1983)
         (Supp. 1986), as amended by the Hazardous and Solid Waste Amendments of
         1984, 42 U.S.C. ss. 6926(g) (Supp. 1986); the Federal Water Pollution
         Control Act, 33 U.S.C. ss. 1257 et


                                      -19-
<PAGE>

         seq. (1982); the Safe Drinking Water Act, as amended, 42 U.S.C. ss. 300
         et seq. (1982); the Clean Air Act, 42 U.S.C. ss. 7901 et seq. (1982);
         or any similar statute applicable in the State of Tennessee. To the
         knowledge of Management neither Group nor CPS has ever had an incident
         with respect to nuclear regulatory or other environmental matters which
         was required to be reported to a Governmental Body and which was not so
         reported; and further, to the knowledge of Management Exhibit 5.29
         contains a list of all material documents submitted or received by
         Group or CPS with respect to such incidents.

7.       RELATIONSHIP OF THE PARTIES. Siemens and CTI intend by their ownership
         of Group Common Stock to pursue the business and operations of Group
         and CPS through a joint venture company. They do not, however, intend
         to create a partnership for such purpose, or for any other purposes.
         Siemens and CTI acknowledge and agree that both intend to pursue
         business opportunities in related and non-related areas and that
         neither owes a duty to the other to offer to or allow the other to
         participate in or otherwise be a part of such business opportunities,
         or to refrain from competing with each other or with Group or CPS,
         except as specifically provided herein.

8.       REPRESENTATIONS AND WARRANTIES OF SIEMENS. Siemens represents and
         warrants to CTI, CPS, Group and Management as follows:

8.1      Organization and Good Standing. Siemens is a corporation duly
         organized, validly existing and in good standing under the laws of the
         State of Delaware, and has full corporate power and authority to carry
         on its business as it is now being conducted and to own the properties
         and assets it now owns. Copies of Siemens' Certificate of Incorporation
         as amended and restated through and including the date hereof and of
         Siemens' Bylaws as amended to the date hereof, both certified to be
         correct by Siemens' Secretary, are attached hereto as Exhibit 8.1 and
         are complete and correct as at the date hereof.

8.2      Corporate Authority. As of the Closing, the Board of Directors of
         Siemens will have duly authorized the execution, delivery and
         performance of this Agreement and the purchase of the Group Common
         Stock being sold hereunder. No other corporate proceedings on the part
         of Siemens will be necessary to authorize this Agreement and the
         purchase of the Group Common Stock being sold by the Non-Siemens Group
         Shareholders as contemplated by this Agreement. Neither the execution,
         the performance of this Agreement, the purchase of the Group Common
         Stock being sold hereunder, nor compliance with or fulfillment of the
         terms and provisions of this Agreement does or will (a) violate or
         conflict with, or result in, any breach of any of the terms, conditions
         or provisions of, or constitute a default (or an event which with
         notice or lapse of time, or both, would become a default) under the
         Certificate of Incorporation or Bylaws of Siemens or any agreement,
         indenture, lease, mortgage or other instrument to which it is a party
         or by which it is bound, (b) require any affirmative approval, consent,
         authorization or other order or action of any court, governmental
         authority or regulatory body or of any creditor of Siemens, (c) result
         in any material violation of any provision of any law, rule, regulation
         or any, court order, judgment, writ, injunction, decree or arbitration
         award or determination, or (d) give any party with rights under any
         such instrument, agreement, mortgage, judgment, order, award, decree or
         other restriction the right to terminate, modify or otherwise change
         the rights or obligations of Siemens. Siemens has full power and
         authority to do and perform all acts and things required to be done by
         it under this Agreement.


                                      -20-
<PAGE>

8.3      No Brokerage Fees. No person acting on behalf of Siemens has any claim
         for a brokerage commission, finder's fee or other like payment in
         connection with this Agreement or the purchase of the Group Common
         Stock being sold by the Non-Siemens Group Shareholders as contemplated
         by this Agreement.

8.4      Intent. Siemens is acquiring the Group Common Stock being sold by the
         Non-Siemens Group Shareholders and the CTI Common Stock as contemplated
         by this Agreement, and, upon exercise of its options and rights
         hereunder, will be acquiring additional securities, for its own account
         and not with a view to the distribution or resale thereof. Siemens
         understands that there is no present market in such securities or in
         any other securities of Group and CTI; that no assurance can be given
         that any such market will develop; and that Group has no present intent
         to register its securities under the Securities Act or the Exchange
         Act.

8.5      Receipt of Information. Siemens represents and warrants that by reason
         of its relationship with Group, including but not limited to its
         involvement in developing Group business plans, its representation on
         the Group Board of Directors and through other information made
         available to it, Siemens has been given access to all information,
         including but not limited to financial, product, market and operational
         information, that it has requested.

8.6      Consents. Except for filings under the HSR Act and with the
         Bundeskartellamt in the Federal Republic of Germany, no consent,
         approval or authorization of, or exemption by, or filing with, any
         governmental or regulatory authority is required in connection with the
         execution, delivery and performance by Siemens of this Agreement or the
         taking of any other action contemplated hereby, excluding, however,
         consents, approvals, authorizations, exemptions and filings, if any,
         which CTI, Group, CPS or Management is required to obtain or make.

9.       COVENANTS OF GROUP.

9.1      Financial Statements. As long as Siemens or its transferee Affiliate,
         if any (herein "Stockholder"), continues to hold any of the Group
         Common Stock, Group shall:

         (a)      Furnish Stockholder within thirty (30) days after the end of
                  each quarter of each fiscal year of Group a balance sheet of
                  Group as at the end of such period, and a statement of income,
                  expense and net earnings of Group for the period from the
                  beginning of the fiscal year to the date of such statement,
                  prepared in accordance with generally accepted accounting
                  principles applied on a consistent basis and in reasonable
                  detail. Each such balance sheet and statement shall set forth
                  in comparative form in corresponding figures as at the end of
                  and for the corresponding period one (1) year prior thereto,
                  and each shall be certified as true, complete and correct
                  (subject to adjustment upon year-end audit) by the chief
                  financial officer of Group.

         (b)      Furnish Stockholder as soon as practicable, but in any event
                  within one hundred twenty (120) days after the end of each
                  fiscal year, a copy of Group's annual audited financial
                  statements, which shall include among other things a balance
                  sheet as at the end of such fiscal year and a statement of
                  income, expense and net earnings for such year in reasonable
                  detail, which balance sheet and statement


                                      -21-
<PAGE>

                  shall set forth in each case in comparative form the
                  corresponding figures for the previous year and shall be
                  certified by Group's independent public accountants; and

         (c)      Deliver to Stockholder such financial statements, reports and
                  other information as Siemens shall reasonably request.

                  In the event Group owns subsidiaries with respect to which it
                  files consolidated tax returns, the financial statements
                  referred to in Sections 9.1(a) and 9.1(b) above may be
                  prepared on a consolidated basis with such subsidiaries.

         (d)      Group will permit representatives of Siemens, at Siemens'
                  expense, to visit and inspect any of the properties of Group
                  or its subsidiaries and to discuss the affairs, finances and
                  accounts of Group and its subsidiaries with their respective
                  officers, at such reasonable times and with such reasonable
                  frequency as Siemens may request.

10.      COVENANTS OF CPS.

10.1     FDA Approval. CPS agrees to pursue diligently all necessary United
         States Food and Drug Administration and other administrative approvals
         for the CPS Business.

10.2     Components. CPS will use its best efforts (within economic and
         functional parameters) to use the same components and systems solutions
         (i.e., conceptual designs) as Siemens uses within its medical
         technology business.

11.      COVENANTS OF MANAGEMENT.

11.1     Voting. Each Management Person agrees to vote his shares of Group
         Common Stock prior to the Closing, and thereafter his shares of CTI
         Common Stock, and to vote as a director of Group, CTI and CPS in a
         manner consistent with the terms of this Agreement.

11.2     Management of CPS. Each Management Person agrees to manage CPS (in
         management positions described in Exhibit 11.2 hereto) for a period of
         five (5) years from the Closing Date, pursuant to the terms of the
         Administrative Service Agreement in substantially the form attached
         hereto as Exhibit 4.5(m)(1) and employment contracts with CTI in
         substantially the form attached hereto as part of Exhibit 11.2. In
         managing CPS, each Management Person is and shall remain at all times
         (unless terminated by CTI) an employee of CTI and is not an employee of
         CPS or its subsidiaries. Such Management Person shall not be entitled
         to and are not qualified under any employee benefit plans, including
         but not limited to pension, health and insurance plans, provided by CPS
         for its employees.

11.3     Non-Competition. Until the expiration of three (3) years after the date
         of termination of his employment by CTI for any reason, each Management
         Person shall not participate in any business competitive with the CPS
         Business, as defined in Section 1.4 hereinabove, whether for its own
         account or as a partner, joint venturer, agent, stockholder of a
         corporation (other than a beneficial owner of less than one percent
         (1%) of the outstanding voting stock thereof), directly or indirectly,
         or otherwise, except for such peripheral and OEM equipment as may be
         mutually agreed by the parties hereto, such


                                      -22-
<PAGE>

         agreement not to be unreasonably withheld. The activities of CTI
         contemplated in Section 12.1 shall not be deemed to violate this
         Section 11.3.

11.4     Non-Competition by CTI. At or prior to the Closing, Management shall
         cause CTI to undertake that, until the expiration of three (3) years
         after the date of the sale by CTI of twenty-five percent (25%) or more
         of its direct or indirect equity ownership in CPS, CTI and its
         Affiliates shall not participate in any business competitive with the
         CPS Business, as defined in Section 1.4 herein above, whether for its
         own account or as a partner, joint venturer, agent, stockholder of a
         corporation (other than a beneficial owner of less than one percent
         (1%) of the outstanding voting stock thereof), directly or indirectly,
         or otherwise, except for such peripheral and OEM equipment as may be
         mutually agreed by the parties hereto, such agreement not to be
         unreasonably withheld. The activities of CTI contemplated in Section
         12.1 shall not be deemed to violate this Section 11.4.

11.5     Conduct of Business. Prior to the Closing, and except as otherwise
         contemplated by this Agreement or consented to or approved by Siemens
         in writing, Management covenants and agrees that:

         (a)      Business in Ordinary Course. Management shall cause each of
                  Group and CPS to operate its business diligently and in good
                  faith only in the ordinary and usual course in accordance with
                  Management's past practices, which shall include the
                  maintenance of all insurance policies covering Group and CPS.

         (b)      No Change in Accounting Practices. Except as may be consented
                  to by Siemens in writing or as required by U.S. GAAP,
                  Management shall not cause Group or CPS to make any changes in
                  accounting practices or in the method of recording sales
                  including, without limiting the foregoing, the accounting
                  methods used by Group and CPS in the recognition of income.

         (c)      Capital Stock. Management shall cause Group and CPS not to
                  issue or sell any Group Common Stock or CPS Common Stock,
                  respectively, except for any sale of Group Common Stock
                  pursuant to the exercise of existing stock options.

         (d)      No Redemption or Distributions. Management shall not allow
                  Group or CPS directly or indirectly to redeem, purchase or
                  otherwise acquire any of the Group Common Stock or the CPS
                  Common Stock, or make any distributions or pay any dividends
                  to the stockholders of Group or CPS.

12.      COVENANTS OF SIEMENS.

12.1     Future Capitalization of CTI. Siemens acknowledges that it is
         Management's intention that CTI expand into new businesses peripheral
         to Group. The businesses which Management intends to cause CTI to
         develop include F-18 Distribution Centers, Positron Emission Tomography
         ("PET") Diagnostic Centers, PET Detector Systems, PET Chemistry Systems
         and other related businesses, which businesses shall not be competitive
         with the CPS Business. The parties acknowledge that CTI will likely
         require new capital to develop these businesses, and that the
         shareholders of CTI may require further liquidity in the future.
         Siemens agrees that it will not oppose future CTI capitalization
         efforts.


                                      -23-
<PAGE>

12.2     Non-Competition. Until the expiration of three (3) years after the date
         of the sale by Siemens of twenty-five percent (25%) or more of its
         direct or indirect equity ownership in CPS, Siemens and its Affiliates
         shall not participate in any business competitive with the CPS
         Business, as defined in Section 1.4 hereinabove, whether for its own
         account or as a partner, joint venturer, agent, stockholder of a
         corporation (other than a beneficial owner of less than one percent
         (1%) of the outstanding voting stock thereof), directly or indirectly,
         or otherwise, except for such peripheral and OEM equipment as may be
         mutually agreed by the parties hereto, such agreement not to be
         unreasonably withheld.

12.3     Amendment of Stockholders' Agreement. Siemens shall prior to or
         simultaneously with the Closing cause its affiliate, Siemens Capital
         Corporation ("SCC"), to enter into the Amendment of the Stock Purchase
         and Stockholders' Agreement dated April 22, 1985 among CPS, Management
         and SCC attached hereto as Exhibit 12.3.

13.      MANAGEMENT OF GROUP. For so long as Siemens and any Affiliate of
         Siemens, in the aggregate, are the beneficial owners of at least
         forty-nine percent (49%) of the issued and outstanding Group Common
         Stock, and CTI and any affiliates of CTI, in the aggregate, are the
         beneficial owners of at least fifty and one-tenth (50.1%) of the issued
         and outstanding Group Common Stock:

13.1     Election of Directors. Siemens and CTI shall have equal representation
         on the Board of Directors of Group. Initially, from and after the
         Closing Date, the Board of Directors of Group shall be comprised of six
         (6) directors, three (3) designated by Siemens and three (3) designated
         by CTI. Upon any change in the ownership of Group Common Stock,
         representation on the Board of Directors of Group shall be proportional
         to each stockholder's stock ownership, rounded to the nearest whole
         number.

13.2     Voting Policy. The Board of Directors of Group shall vote in such a way
         as to maximize the growth potential of Group and CPS.

13.3     Research and Development. Total combined research and development
         expenses of Group and CPS shall be specified at a level of
         approximately ten to twelve percent (10% to 12%) of sales volume of CPS
         (net sales to Siemens) as set forth in the annual business plan
         approved by the Board of Directors of Group and CPS.

13.4     Officers of Group.

         (a)      If the Chairman of the Board of Directors of Group is a
                  representative of CTI, then the President of Group shall be a
                  representative of Siemens and, similarly, if the Chairman of
                  the Board of Directors of Group is a representative of
                  Siemens, then the President of Group shall be a representative
                  of CTI.

         (b)      Initially, upon the Closing, the officers of Group shall be as
                  reflected on Exhibit 13.4(b) hereto.

         (c)      Siemens shall have the right to designate the Controller/Vice
                  President, Finance and Chief Financial Officer of Group and
                  CPS; the Controller/Vice President, Finance and Chief
                  Financial Officer shall be the chief financial officer of
                  Group and CPS and shall have the duties set forth on Exhibit
                  13.4(c) hereto.


                                      -24-
<PAGE>

         (d)      After five (5) years from the Closing Date, Siemens shall have
                  the right to designate persons to fill two (2) management
                  positions in CPS, in addition to the Controller/Vice
                  President, Finance and Chief Financial Officer. Unless
                  mutually agreed otherwise, the management positions to which
                  this section applies shall be those positions listed in
                  Exhibit 13.4(d) attached hereto.

         (e)      Siemens shall have the right to assign up to six (6) people to
                  become employees of CPS, e.g., in the service, research and
                  development and marketing departments of CPS, and Group and
                  CPS agree that such persons will be hired by CPS and
                  integrated into CPS's operations, as such positions become
                  available through attrition of existing employees, or as new
                  positions are established through growth. Siemens may
                  designate such persons at any time, regardless of the
                  availability of openings for them, but at its own expense if
                  no such openings are available. Office space for Siemens
                  personnel who have not become CPS employees will be at
                  Siemens' expense, on a pro rata facility cost basis.

13.5     Stockholder Votes. To the maximum extent permitted by applicable law,
         all matters which would otherwise require action by the stockholders of
         Group shall be submitted to the Board of Directors of Group for action.
         All actions to be taken by vote of the stockholders of Group (except
         for those delegated to the Board of Directors pursuant to the preceding
         sentence) shall be made by two-thirds (2/3) majority vote of the
         stockholders, unless a greater majority is required by law, in which
         case the greater majority shall be required.

13.6     Material Board Decisions. The following matters, among others, shall be
         submitted to the Board of Directors of Group, which shall take action
         on them by majority vote of the entire Board of Directors:

         (a)      New product development calling for the expenditure of more
                  than Two Hundred Fifty Thousand Dollars ($250,000) per year.

         (b)      All single expenditures, or related expenditures in the
                  aggregate, exceeding Two Hundred Fifty Thousand Dollars
                  ($250,000) each.

         (c)      Election of officers of Group and determination of
                  compensation and benefits for officers.

         (d)      The offering or registration under state or federal securities
                  laws, of any shares of Group Common Stock or any other
                  securities of Group.

         (e)      Amendments of the Charter or bylaws of Group.

         (f)      The incurrence of indebtedness for borrowed funds in excess of
                  the maximum amount thereof set forth in the most recent annual
                  budget approved by the Board of Directors of Group, or which
                  would cause the debt/equity ratio of Group to exceed that
                  established in such budget.

         (g)      The incurrence of any guaranty obligations.

         (h)      The sale, lease, pledge or other disposition of more than ten
                  percent (10%) of the real estate, plant and equipment of
                  Group.


                                      -25-
<PAGE>

         (i)      The acquisition of any assets of or equity interest in, or the
                  making of loans to, any entity or person except in the
                  ordinary course of Group's business, or as specifically
                  authorized in the most recent annual budget approved by the
                  Board of Directors of Group.

         (j)      Adoption and revision of corporate plans, including short,
                  medium and long-range business plans, annual budgets, annual
                  operation plans, five-year business plans, research and
                  development budgets, and the like.

         (k)      Conclusion, termination or amendment of agreements with others
                  respecting patents, know-how and other proprietary rights.

         (l)      Declaration of dividends or other distributions of profits.

         (m)      Any other decisions or actions not in the ordinary course of
                  Group's business or which materially affect Group or its
                  assets.

13.7     Resolution of Impasse. An "Event of Impasse" shall be deemed to have
         occurred if and when any of the following shall have occurred:

         (a)      The most recent annual budget approved by the Board of
                  Directors of Group shall have less than three (3) months
                  remaining before its expiration, a new five-year business plan
                  has not been approved during the most recent year and has not
                  been extended until a new annual budget or five-year plan has
                  been approved, and either Siemens or CTI shall have given to
                  the other written notice that an Event of Impasse has
                  occurred; or

         (b)      CTI or Siemens proposes in good faith and in the exercise of
                  reasonable business judgment a Material Board Decision (as
                  defined hereinabove) on two (2) consecutive occasions after
                  the issue had been placed on the agenda for the second board
                  meeting and the proposal is rejected in bad faith on each such
                  occasion.

         If and when an Event of Impasse has occurred, the Board of Directors
         shall promptly appoint an Impasse Committee of three members. One
         member shall be selected by CTI, one by Siemens, and the third by the
         first two members; in the event that the members selected by CTI and
         Siemens cannot mutually agree upon a third member, such member shall be
         selected by counsel for CTI and Siemens. It shall be the responsibility
         of the Impasse Committee to arrive unanimously at a resolution of the
         Event of Impasse. The resolution recommended by the Impasse Committee
         shall be binding on the parties hereto (1) unless it is rejected by a
         majority of the members of the Board of Directors of Group, in which
         event the Board will then either (A) resolve the impasse, (B) appoint
         another Impasse Committee (provided, however, that no more than two (2)
         Impasse Committees may be appointed for any given Event of Impasse), or
         (c) recommend that CTI or Siemens buy out the other's Group Common
         Stock interest on mutually agreeable terms, and (2) provided that a
         recommendation by the Impasse Committee of a buyout by either Group or
         Siemens of the other shall not be binding on the parties.

13.8     CTI Board. For so long as CTI and any of its Affiliates, in the
         aggregate, and Siemens and any of its Affiliates, in the aggregate,
         each holds more than twenty percent (20%) of


                                      -26-
<PAGE>

         the outstanding Group Common Stock, Siemens shall be entitled to
         designate one of the Siemens designee board members of Group for
         election to the Board of Directors of CTI, and Management agrees to
         vote its shares of CTI for the election of such designee.

13.9     Additional Capital. In the event that additional capital investment is
         needed by Group in accordance with a business plan approved by its
         Board of Directors, then CTI and Siemens will each contribute such
         capital in proportion to their ownership of Group Common Stock, unless
         another option, e.g., borrowing, is mutually agreed by CTI and Siemens.
         If either is unable or refuses to make such capital contribution, then
         Group shall issue sufficient shares of Group Common Stock at fair
         market value, determined in the manner provided in Sections 14.1 and
         14.2 hereof to raise the necessary capital. The other Group shareholder
         which has contributed its share of the necessary capital shall have a
         right of first refusal to purchase such shares.

13.10    Intercompany Transfers. The parties acknowledge that it is the
         intention of Management that CTI develop businesses involving products
         and services related to the CPS Business, either directly itself, or
         through subsidiaries or other Affiliates. Siemens and CPS understand
         and agree that CTI and its Affiliates may use CPS products for the
         establishment of its own distribution centers for positron-emitting
         radioisotopes and compounds, for its own PET diagnostic centers, and
         for the other purposes contemplated in Section 12.1. The parties
         further agree that with respect to the development of Qualified
         Distribution Centers, CTI or its Affiliates may purchase RDS
         (radioisotope distribution systems) products, including any
         improvements and advances thereto, directly from CPS on the same terms
         and conditions on which Siemens purchases from CPS pursuant to the OEM
         Exclusive Distribution Rights Agreement among CPS, Management and
         Siemens, at prices equal to the transfer prices set forth on Exhibit
         13.10 hereto. For purposes of this Section, a "Qualified Distribution
         Center" shall be a location owned by CTI or its Affiliates, for which
         CTI can demonstrate a commitment, expressed in writing, by at least one
         unrelated third party, for the purchase of positron-emitting
         radioisotopes and compounds from such Distribution Center. CPS
         products, including RDS products, not purchased for Qualified
         Distribution Centers shall be purchased from Siemens or its Affiliates
         at prices to be negotiated on a case by case basis. For centers which
         they own and operate, CTI or its Affiliates may purchase ECAT systems
         directly from Siemens and its Affiliates at prices to be negotiated on
         a case by case basis. All CPS products sold pursuant to this Section
         13.10 shall not be resold by CTI in competition with CPS, Siemens or
         customers of Siemens or its Affiliates.

13.11    Business Plan. Attached hereto as Exhibit 13.11 is a copy of the
         current five-year business plan for CPS which states the expected
         sales, expenses and investment levels for CPS, including proportions of
         debt and equity, together with an expectation range. Exhibit 13.11 is
         for reference only, and has not been approved by CTI and Siemens. As
         soon as practicable following the Closing, an initial annual business
         plan shall be developed and adopted for Group and CPS.

13.12    Distribution Agreement. At the Closing, CPS, Management and Siemens
         will enter into and execute an amendment of the May 20, 1986 OEM
         Exclusive Distribution Rights Agreement among them to add thereto
         additional products of CPS. The form of the amendment shall be
         substantially as set forth in Exhibit 4.5(j) hereto.


                                      -27-
<PAGE>

14.      ADDITIONAL PURCHASE AND SALE RIGHTS.

14.1     Siemens' Additional Purchase Rights. Siemens shall have the right from
         and after the Closing Date to purchase from CTI additional shares of
         Group Common Stock up to the number of shares of Group Common Stock
         required to bring Siemens' ownership of Group Common Stock to eighty
         percent (80%) of the then issued and outstanding capital stock of Group
         at such time (or thereafter) as any of the following events shall
         occur:

         (a)      A change in control of CTI incident to which Management does
                  not continue to hold, in the aggregate, more shares of CTI
                  Common Stock than any other single shareholder other than
                  Siemens or any of its Affiliates, unless the prior written
                  consent of Siemens is obtained, which consent shall not be
                  unreasonably withheld; or

         (b)      From and after five (5) Years from the date hereof, at such
                  time as the dollar sales volume of CTI's business, other than
                  the CPS Business, is greater than the dollar sales volume of
                  CPS; or

         (c)      From and after seven (7) years from the date hereof,

         provided, however, (1) Siemens' additional purchase right described in
         this Section 14.1 shall be contingent upon CPS having exceeded the
         number of aggregate units required to be sold from the date hereof to
         the date of exercise of such purchase right as specified in the
         "Siemens minima plus 20% plan" attached hereto as Exhibit 14.1 in the
         year immediately preceding its election to exercise its purchase right,
         (2) CTI shall have a one-time right to defer the exercise of such right
         by Siemens for a period of one year after the initial notice of
         exercise, i.e., upon Siemens' initial notice of its intent to exercise
         its right to purchase additional shares of Group Common Stock
         hereunder, CTI shall have the right to decline to sell such shares to
         Siemens, and Siemens may not again undertake to exercise such right to
         purchase additional shares of Group Common Stock for one year after the
         initial notice of exercise which was so declined, and (3) Siemens'
         additional purchase right described in this Section 14.1 shall be
         contingent on approval from the Bundeskartellamt office in the Federal
         Republic of Germany, which approval shall be sought in good faith by
         Siemens. The price to be paid for the Group Common Stock pursuant to
         such purchase right shall be a price to be negotiated by Siemens and
         CTI, provided, however, that in the event that they cannot agree upon a
         price within sixty (60) days from the date of effective notice of
         exercise, the price shall be determined by the following appraisal
         procedure: Each party shall obtain a valuation of the Group Common
         Stock by an independent professional experienced in the valuation of
         closely-held corporations similar to Group. If the valuations thus
         obtained are within twenty percent (20%) of each other, the price to be
         paid for the Group Common Stock to be purchased from CTI by Siemens
         shall be the average of the two valuations. If the difference between
         the valuations is more than twenty percent (20%), the two parties
         making those valuations shall select a third independent professional
         experienced in the valuation of closely-held corporations similar to
         Group to make a valuation, and the price to be paid for the Group
         Common Stock to be purchased by Siemens from CTI shall be the average
         of the two of the three valuations which are the closest to each other.

14.2     CTI's Additional Rights. CTI shall have the right from and after the
         Closing to require Siemens to purchase from CTI additional shares of
         Group Common Stock up to the number of shares of Group Common Stock
         required to bring Siemens' ownership of


                                      -28-
<PAGE>

         Group Common Stock to eighty percent (80%) of the then issued and
         outstanding capital stock of Group at such time (or thereafter) as any
         of the following events shall occur:

         (a)      A change in control of CTI incident to which Management does
                  not continue to hold, in the aggregate, more shares of CTI
                  Common Stock than any other single Shareholder other than
                  Siemens or any of its Affiliates, unless the prior written
                  consent of Siemens is obtained, which consent shall not be
                  unreasonably withheld; or

         (b)      From and after five (5) years from the date hereof, at such
                  time as the dollar sales volume of CTI's business, other than
                  the CPS Business, is greater than the dollar sales volume of
                  CPS; or

         (c)      From and after seven (7) years from the date hereof,

         provided, however, (1) CTI's additional sale right described in this
         Section 14.2 shall be contingent upon CPS having exceeded the number of
         aggregate units required to be sold from the date hereof to the date of
         exercise of such sale right as specified in the "Siemens minima plus
         20% plan" attached hereto as Exhibit 14.1 in the year immediately
         preceding its election to exercise its sale right, (2) Siemens shall
         have a one-time right to defer the exercise of such sale right for a
         period of one year after the initial notice of exercise, i.e., upon
         CTI's initial notice of its intent to exercise its right to require
         Siemens to purchase additional shares of Group Common Stock, Siemens
         shall have the right to decline to purchase such shares, and CTI may
         not again undertake to exercise such right to require Siemens to
         purchase additional shares of Group Common Stock for one year after the
         initial notice of exercise which was so declined, and (3) CTI's
         additional purchase right described in this Section 14.2 shall be
         contingent on approval from the Bundeskartellamt office in the Federal
         Republic of Germany, which approval shall be sought in good faith by
         Siemens. The price to be paid for the Group Common Stock pursuant to
         such purchase right shall be a price to be negotiated by Siemens and
         CTI, provided, however, that in the event they cannot agree upon a
         price within sixty (60) days from the date of effective notice of
         exercise, the price shall be determined by the following appraisal
         procedure: Each party shall obtain a valuation of the Group Common
         Stock by an independent experienced in the valuation of closely-held
         corporations similar to Group. If the valuations thus obtained are
         within twenty percent (20%) of each other, the price to be paid for the
         Group Common Stock to be purchased by Siemens from CTI shall be the
         average of the two valuations. If the difference between the valuations
         is more than twenty percent (20%), the two parties making those
         valuations shall select a third independent professional experienced in
         the valuation of closely-held corporations similar to Group to make a
         valuation, and the price to be paid for the Group Common Stock to be
         purchased by Siemens from CTI shall be the average of the two of the
         three valuations which are the closest to each other.

14.3     Purchase and Sale in Event of Default. For purposes of this Section
         14.3, an "Event of Default" shall be deemed to have occurred if and
         when any of the following shall have occurred, and shall not have been
         cured within thirty (30) days after written notice thereof given to the
         defaulting party by the non-defaulting party:

         (a)      Any representation or warranty herein made by Siemens on the
                  one hand or CTI, Group, CPS or Management on the other proves
                  to have been false in any material respect when made;


                                      -29-
<PAGE>

         (b)      CTI or Siemens (or any Affiliate of Siemens holding Group
                  shares) files a bankruptcy petition, makes a general
                  assignment for the benefit of creditors or has an involuntary
                  bankruptcy petition filed against it; or

         (c)      CTI or Siemens is unwilling or unable to provide additional
                  capital to Group in accordance with a previously approved plan
                  or previously approved commitment to do so.

         Upon the occurrence of an Event of Default as defined hereinabove, the
         non-defaulting shareholder of Group shall have the right to (A) name
         its designees to any or all management positions of Group without
         liability to any displaced person under any management or employment
         contract, and (B) name an additional representative to the Board of
         Directors of Group. The non-defaulting party will immediately be
         relieved of any contractual requirements in any management or
         employment contracts and may administer a sale of additional Group
         Common Stock to provide previously committed funds, such sales to occur
         at fair market value in accordance with the procedure set forth at
         Sections 14.1 and 14.2 above. The non-defaulting shareholder shall have
         the right to purchase such additional Group Common Stock at its fair
         market value for sixty (60) days after determination of the price of
         the shares.

15.      STOCK TRANSFER RESTRICTION AND RIGHT OF FIRST REFUSAL. The provisions
         of this Section 15 shall apply at and after the Closing. Neither CTI
         nor Siemens may transfer its Group Common Stock for a period of five
         (5) years from the Closing Date; provided, however, that Siemens or CTI
         may during such time transfer such stock to any Affiliate of Siemens or
         CTI, so long as such transfer does not violate any applicable
         securities laws, subject to the provisions of Section 22.2 below. After
         five (5) years from the Closing Date, if CTI or Siemens contemplates a
         sale of its Group Common Stock, it shall notify the other stockholder,
         and they shall attempt to agree upon a price pursuant to which the
         other stockholder may purchase the Group Common Stock of the selling
         stockholder. If they cannot agree upon a price, then the selling
         stockholder's Group Common Stock shall be subject to a right of first
         refusal in favor of the other stockholder, as provided hereinbelow,
         which right of first refusal shall survive after any transfer to a
         third party. If Siemens or CTI or any of their permitted transferees
         (the "Selling Stockholder") desires to sell any of its Group Common
         Stock to any party other than (A) an Affiliate of Siemens or CTI, (B)
         any general or limited partnership in which Siemens or CTI, or an
         Affiliate of Siemens or CTI, is a partner, or (C) any Management
         Person, then:

15.1     The Selling Stockholder shall give notice to the other stockholder of
         any transactions covered by this Section 15. The notice shall include
         (A) the name, address and principal business activity of the
         prospective purchaser; (B) the number of shares of stock proposed to be
         sold; (C) the manner in which the sale is proposed to be made
         (including the proposed closing date); and (D) the price at which, or
         other consideration for which, and the material terms upon which, such
         sale is proposed to be made, and stating that such proposed sale is, to
         the best of the Selling Stockholder's knowledge, bona fide.

15.2     During the thirty (30) day period commencing on the date the other
         stockholder receives the Selling Stockholder's notice, the other
         stockholder shall have the right to acquire all but not less than all
         of the shares of Group Common Stock proposed to be sold by the Selling
         Stockholder in such transaction. Such right shall be exercised, if at
         all, by an


                                      -30-
<PAGE>

         irrevocable notice of exercise given by the other stockholder and
         received by the Selling Stockholder prior to the expiration of such
         period, accompanied by a statement that the other stockholder shall pay
         the Selling Stockholder in accordance with the terms provided for in
         the proposed transaction.

15.3     If the other stockholder exercises its rights under this Section 15,
         the Selling Stockholder shall deliver certificates duly endorsed for
         transfer representing the shares of Group Common Stock purchased by the
         other stockholder in accordance with the terms specified in such notice
         against receipt of payment therefor.

15.4     The closing shall occur on the date specified in the Selling
         Stockholder's notice.

15.5     If the conditions prescribed in this Section 15 have been met in
         connection with the proposed sale of Group Common Stock by the Selling
         Stockholder and the other stockholder has not elected to exercise its
         right of first refusal hereunder, then the Selling Stockholder shall be
         free to effect such sale for a period of one hundred eighty (180) days
         following the date of the notice given under Section 15.1 hereof, but
         only to the person or persons specified in such notice and at the price
         (or for the consideration) and on substantially the same terms
         specified therein, and if such sale does not occur within such 180 day
         period, Group Common Stock proposed to be sold will continue to be
         subject to this Agreement to the same extent as if such notice had not
         been given.

16.      SALE OF CTI COMMON STOCK BY MANAGEMENT. So long as Siemens owns one
         percent (1%) or more of the issued and outstanding CTI Common Stock,
         and provided that at such time there has been no public offering of CTI
         Common Stock, if at any time any Management Person wishes to sell any
         of his CTI Common Stock, he shall first notify both Siemens and CTI of
         his intention to do so, to enable them to offer competitive bids for
         his CTI Common Stock, provided, however, that this Section 16 shall not
         be construed as a right of first refusal or a requirement that the
         Management Person sell his shares to Siemens or CTI.

17.      SPECIFIC PERFORMANCE. The parties recognize that, because of the nature
         of the subject matter of this Agreement, it would be impracticable and
         extremely difficult to determine actual damages in the event of a
         breach of this Agreement. Accordingly, if any party commits a breach,
         or threatens to commit a breach, of any of the provisions of Sections
         2, 3, 4, 9, 10, 11, 12, 13, 14, 15 or 16 the other parties shall have
         the right to seek and receive a temporary restraining order, injunction
         or other equitable remedy, including, without limitation, the right to
         have the provisions of this Agreement specifically enforced by any
         court having equity jurisdiction, it being acknowledged and agreed that
         any such breach or threatened breach will cause irreparable injury and
         that money damages will not provide an adequate remedy.

18.      DISPUTE RESOLUTION. Except with respect to resolution of events of
         impasse, for which a separate procedure is set forth at Section 13.7
         above, the parties agree to resolve amicably and in good faith any
         disputes arising from the interpretation of any provisions of this
         Agreement. In the event of any disagreement among the parties
         concerning any provision hereof upon the request of any party the
         matter shall be immediately referred to the managements of Siemens and
         CTI. If within a period of 30 days after reference of the matter to
         them the respective managements are unable to agree upon a resolution,
         any party may within 30 days after the aforesaid 30-day period elect to
         utilize a non-binding resolution procedure whereby each party presents
         its case at a hearing held in Chicago,


                                      -31-
<PAGE>

         Illinois or Knoxville, Tennessee, on an alternating basis, with the
         first hearing to be held in Chicago, Illinois, before a panel
         consisting of the Chief Executive Officer of each of Siemens and CTI
         and a mutually acceptable neutral advisor, who shall be selected from
         the Center for Public Resources' Judicial Panel. Prior to the hearing,
         the parties and the neutral advisor shall agree on a set of ground
         rules for the hearing. At the conclusion of the hearing, the Chief
         Executive Officers of each of Siemens and CTI shall meet and attempt to
         resolve the matter. If the matter cannot be resolved at such meeting,
         the neutral advisor may be called upon to render his opinion as to how
         the matter would be resolved had the matter been on trial in a court of
         law. After the opinion is received, the executives shall meet again and
         try to resolve the matter. If the matter cannot be resolved at such
         meeting, any party may give to the other party notice of its intention
         to litigate. No litigation may be commenced concerning the matter in
         dispute until 60 days have elapsed from the sending of the notice to
         litigate; provided, however, that such litigation may be commenced
         prior to such date if the applicable statute of limitations would run
         prior thereto. The parties shall bear their respective costs incurred
         in connection with this procedure, including the fees and expenses of
         the neutral advisor. Only after the foregoing procedure has been
         exhausted shall either party resort to litigation as the final
         adjudication of the dispute.

19.      PRODUCT LIABILITY. Management shall cause CTI at the Closing to enter
         into an agreement to hold Siemens harmless against any and all product
         liability, including but not limited to, personal injuries and property
         damages, recovered by any claimant relating to products manufactured or
         sold by Group or CPS before the Closing Date, including but not limited
         to products in the inventories of Group and CPS at the Closing Date,
         plus any attorney's fees incurred by Siemens in connection with such a
         claim, provided that CTI shall not be responsible for liability on such
         products in the event that the damages or injuries which resulted in
         such liabilities shall be the result of alterations, repairs or service
         on products, shipment or installation of the products or other action
         relating to such products by or on behalf of Siemens after the Closing
         Date. The responsibility of CTI under this Section shall extend to
         products which Group or CPS did not manufacture but which were sold by
         or on behalf of Group or CPS prior to the Closing Date.

20.      PENSION AND EMPLOYEE BENEFIT MATTERS. Group, CPS and Siemens shall
         comply with the provisions of the benefits plans listed on Exhibit 5.21
         attached hereto and all the laws applicable thereto.

21.      TERMINATION OF THIS AGREEMENT.

21.1     Termination. This Agreement may be terminated before the Closing occurs
         only as follows:

         (a)      By written agreement of the parties at any time;

         (b)      By Siemens, by notice to other parties at any time, if
                  satisfaction of one or more of the conditions specified in
                  Section 4.5 is or becomes impossible;

         (c)      By Group or Management, by notice to Siemens at any time, if
                  satisfaction of one or more of the conditions specified in
                  Section 4.6 is or becomes impossible; or

         (d)      By any of the parties by notice to the others at any time
                  after March 15, 1988.


                                      -32-
<PAGE>

21.2     Effect of Termination. In the event that this Agreement is terminated
         pursuant to Section 21.1, such termination shall be without any
         liability or further obligation of any party to another and the
         obligations and agreements in this Agreement shall terminate and have
         no further effect, except for liabilities and obligations (a) under
         Sections 22.1 and 22.8 hereof, which shall survive such termination, or
         (b) based on any intentional failure to perform or comply with any
         covenant or agreement herein or for any intentional misrepresentation
         or breach of any warranty herein which causes Damages, and such
         termination shall not constitute a waiver of any claim with respect
         thereto.

22.      MISCELLANEOUS.

22.1     Expenses. Except as otherwise provided herein, Management shall cause
         CTI to pay, on the one hand, and Siemens shall pay, on the other hand,
         the expenses incurred in connection with this Agreement and the
         transactions contemplated hereby by CTI, Group, CPS, the Non-Siemens
         Group Shareholders and Management, in the first case, and Siemens, in
         the second case. The payment of all transfer taxes and documentary
         taxes (other than those imposed by jurisdictions outside the United
         States) which may be imposed upon each transaction shall be paid by CTI
         at each closing with respect to the securities transferred in
         proportion to their interest in the securities transferred.

22.2     Successors; Assignment. This Agreement shall be binding upon and shall
         inure to the benefit of and be enforceable by the successors of the
         parties hereto. Except as otherwise provided herein, this Agreement
         shall not be assignable. Each of Siemens and CTI shall have the right
         to transfer all or any of the Group Common Stock owned by it to any
         Affiliate of Siemens or CTI, respectively; provided, however, that such
         Affiliate of Siemens or CTI, as the case may be, shall agree in advance
         in writing to be bound by all the terms of this Agreement. In such
         case, the Affiliate of Siemens shall be entitled to enforce as against
         CTI, Group, CPS and Management all of the terms and conditions of this
         Agreement to the same extent as this Agreement could be enforced by
         Siemens, but Siemens shall remain bound by the terms of this Agreement,
         and the Affiliate of CTI shall be entitled to enforce as against
         Siemens all of the terms and conditions of this Agreement to the same
         extent as this Agreement could be enforced by CTI or Management, but
         CTI and Management shall remain bound by the terms of this Agreement.

22.3     Entire Agreement; Amendment. This Agreement and the exhibits hereto set
         forth the entire understanding between the parties with respect to
         their respective subject matters. They may not be modified, amended,
         altered or supplemented and no provision may be waived except by a
         written agreement signed by the parties thereto which shall be
         authorized by all necessary corporate action of each party.

22.4     Survival of Representations, Warranties and Covenants; Indemnification.

         (a)      All representations, warranties, covenants and agreements made
                  herein shall survive the execution and delivery of this
                  Agreement and the purchase and sale of the Group Common Stock
                  provided for hereunder.

         (b)      If the Closing occurs, each of CTI and Management, on the one
                  hand, and Siemens, on the other hand, shall indemnify and hold
                  the others and Group harmless from and against all Damages
                  arising from or in connection with:


                                      -33-
<PAGE>

                  (1)      any misrepresentation or breach of any warranty made
                           by it herein or in any Exhibit delivered by it at the
                           Closing pursuant hereto or attached hereto;

                  (2)      any breach or non-fulfillment of any covenant or
                           agreement required to be performed by it hereunder or
                           thereunder; and

                  (3)      any and all actions, suits, investigations,
                           proceedings, demands, assessments, judgments, costs
                           and legal and other expenses incidental to any of the
                           foregoing;

                  provided, however, that CTI and Management shall each be
                  obligated to indemnify and hold harmless Siemens in connection
                  with their own respective misrepresentations, breach or
                  non-fulfillment only; it is not intended that CTI or
                  Management be responsible for the other's misrepresentations,
                  breach or non-fulfillment. Notwithstanding anything to the
                  contrary herein, none of CTI, Management or Siemens shall be
                  required so to indemnify and hold harmless with respect to the
                  first U.S. $50,000 in Damages in the aggregate for which it is
                  liable under this section. In determining the amount of
                  Damages for purposes of this Section, (y) notwithstanding
                  anything to the contrary herein, neither Siemens nor
                  Management or the Non-Siemens Group Shareholders shall have
                  any liability for indemnification hereunder with respect to
                  any claim resulting from the events described in this section
                  of which the indemnifying party is unaware unless a notice of
                  claim, in reasonable detail, with respect thereto shall have
                  been given to the indemnifying party with sufficient
                  promptness after the indemnified party becomes aware of the
                  relevant facts pertaining to such claim that the indemnifying
                  party's ability to minimize or eliminate such Damages has not
                  been materially adversely affected by delay; and (z) no
                  Damages shall be deemed sustained to the extent that such
                  Damages are covered by insurance for the benefit of the
                  indemnified party.

         (c)      Procedure -- Each indemnified party shall give notice to the
                  indemnifying party of any claim hereunder with reasonable
                  promptness after obtaining knowledge thereof, including,
                  without limitation, any third party claim against the
                  indemnified party or Group which might give rise to a claim
                  against the indemnifying party hereunder, stating the nature
                  and basis of such claim and the amount thereof, in reasonable
                  detail, to the extent then known by the indemnified party. The
                  indemnified party shall keep the indemnifying party fully
                  informed, use all reasonable efforts to defend such claim or
                  litigation and present any defense reasonably suggested by the
                  indemnifying party or its counsel. The indemnifying party
                  shall have the right to participate in such third-party claim
                  or litigation by counsel and accountants, at its own expense,
                  and, upon notice to the indemnified party, to assume, at its
                  own expense, the defense or prosecution thereof, as the case
                  may be, with counsel approved by the indemnified party (which
                  approval shall not be unreasonably withheld). If the
                  indemnifying party assumes such defense or prosecution, it
                  shall have no liability for any legal or other expenses
                  subsequently incurred by the indemnified party in connection
                  with such proceeding other than the reasonable costs of
                  investigation and cooperation with the indemnifying party in
                  such defense or prosecution, but it shall thereafter indemnify
                  and hold the other, the other's Affiliates and Group


                                      -34-
<PAGE>

                  harmless from all Damages with respect to such claim or
                  litigation. The indemnified party shall not make, or offer to
                  make, any settlement of any claim or litigation which might
                  give rise to a right of indemnification from the indemnifying
                  party, without the consent of such indemnifying party, which
                  consent shall not be unreasonably withheld.

22.5     Notices. All notices, requests, claims, demands and other
         communications hereunder shall be in writing and shall be given by
         personal delivery, cable, telegram or telex, or by mail (registered or
         certified mail, postage prepaid, return receipt requested) to the
         respective parties as follows:

            If to Group:        CTI Group, Inc.
                                810 Innovation Drive
                                Knoxville, Tennessee 37932
                                Attention:  Terry D. Douglass

                                with a copy to:

                                Dennis R. McClane, Esq.
                                Baker, Worthington, Crossley, Stansberry & Woolf
                                            530 Gay Street, S.W.
                                            P.O. Box 1792
                                            Knoxville, Tennessee 37901

            If to Siemens, to:  Siemens Gammasonics, Inc.
                                2000 Nuclear Drive
                                Des Plaines, Illinois 60818
                                Attention:  President

                                with a copy to:

                                General Counsel
                                Siemens Capital Corporation
                                767 Fifth Avenue
                                New York, New York 10153

         or to such other address as either party may have furnished to the
         other in writing in accordance herewith.

22.6     Applicable Law. This Agreement shall be governed by and construed in
         accordance with the substantive law of the State of Tennessee.

22.7     Counterparts; Headings. This Agreement may be executed in several
         counterparts, each of which shall be an original, but all of which
         together shall constitute one and the same agreement. The headings
         contained in this Agreement are solely for the convenience of the
         parties, and are not intended to and do not limit, construe or modify
         any of the terms and conditions hereof.


                                      -35-
<PAGE>

22.8     Confidential Information.

         (a)      Subject to (b) below, whether or not the Closing occurs, (1)
                  CTI and Management shall, and shall cause Group and CPS to
                  keep confidential and not disclose to any Person (other than,
                  with appropriate undertakings of confidentiality, its
                  employees, attorneys, accountants and other advisers) or use
                  (except in connection with the transactions contemplated
                  hereby) all confidential information relating to the Siemens
                  Businesses, and (2) Siemens shall, and shall cause its
                  Affiliates to, keep confidential and not disclose to any
                  Person (other than, with appropriate undertakings of
                  confidentiality, its employees, attorneys, accountants and
                  other advisers) or use (except in connection with the
                  transactions contemplated hereby) all confidential information
                  relating to the Group Businesses, in either case obtained by
                  them from the other pursuant to or in preparation for this
                  Agreement.

         (b)      Section 22.8(a) shall not be violated by disclosure pursuant
                  to court order or as otherwise required by law or in
                  connection with a Governmental Body investigation, provided
                  that the CTI, Management or Siemens, as the case may be, gives
                  the other notice of such required disclosure of the other's
                  confidential information and cooperates as such other may
                  reasonably request in contesting such required disclosure. The
                  obligations imposed by Section 22.8(a) shall not apply, or
                  shall cease to apply, to any such confidential information
                  when, and to the extent that, such confidential information:

                  (1)      Was known (on a non-confidential basis) to the party
                           (or any Affiliate thereof) receiving the confidential
                           information at the time of such receipt; or

                  (2)      Was, or becomes through no breach of such recipient's
                           obligations hereunder, known to the public either
                           before or after such receipt; or

                  (3)      Becomes known (on a non-confidential basis) to the
                           recipient (or any Affiliate thereof) from sources
                           other than the party providing such confidential
                           information under circumstances not involving any
                           breach of any confidentiality obligation between such
                           source and the party providing such confidential
                           information; or

                  (4)      Is independently developed by the recipient (or any
                           Affiliate thereof).

         (c)      If the transactions contemplated by this Agreement are not
                  consummated, (1) upon the request of Siemens, Management
                  shall, and shall cause Group and any Affiliates of Group to,
                  return promptly any written materials that they have received
                  from Siemens, its Affiliates or their representatives in
                  connection with this Agreement or the transactions
                  contemplated hereby, together with any copies of such
                  materials made by them, and (2) upon the request of
                  Management, Siemens shall, and shall cause its Affiliates to,
                  return promptly any written materials that they have received
                  from Siemens, the Siemens Affiliates or their representatives
                  in connection with this Agreement or the transactions
                  contemplated hereby, together with any copies of such
                  materials made by them. Management and Siemens shall, and
                  shall cause their respective Affiliates to, use their best
                  efforts to cause their respective Affiliates, employees,
                  attorneys,


                                      -36-
<PAGE>

                  accountants and advisers to whom information is disclosed
                  pursuant to this Section 22.8(c) to comply with its
                  provisions.

         (d)      For purposes of this Section 22.8 only, the terms "Siemens
                  Businesses" and "Group Businesses" shall mean all business
                  activities of Siemens and its Affiliates and all business
                  activities of Group and its Affiliates, respectively, and the
                  business of CPS in each case.

22.9     Publicity. The parties agree that no publicity, release or other public
         announcement concerning the transactions contemplated by this Agreement
         shall be issued by any party without the advance approval of both the
         form and substance of the same by the other parties and their counsel,
         which approval, in the case of any publicity, release or other public
         announcement required by applicable law, shall not be. unreasonably
         withheld or delayed.

22.10    Invalidity. If any one or more of the provisions or any part thereof
         contained in this Agreement shall for any reason be held to be invalid,
         illegal or unenforceable in any respect, such invalidity, illegality or
         unenforceability shall not affect the remaining provisions or parts
         thereof of this Agreement and this Agreement shall be construed in such
         a way and to the extent permitted by law to give effect to the intent
         of such provision or part thereof.

22.11    Waiver. The failure of any party to exercise any of its rights
         hereunder or to enforce any of the terms or conditions of this
         Agreement on any occasion shall not constitute or be deemed a waiver of
         that party's rights thereafter to exercise any rights hereunder or to
         enforce each and every term and condition of this Agreement.

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.

ATTEST:                                     CTI GROUP, INC.


         /s/ Michael C. Crabtree            By:      /s/ Terry D. Douglass
-------------------------------------          ---------------------------------
Title:  Vice President                          Terry D. Douglass
                                                President

ATTEST:                                     CTI PET SYSTEMS, INC.


         /s/ Michael C. Crabtree            By:      /s/ Terry D. Douglass
-------------------------------------          ---------------------------------
Title:  Vice President                           Title:  President

Witness:

         /s/ Mary Lou Marks                          /s/ Terry D. Douglass
-------------------------------------          ---------------------------------
                                                  Dr. Terry D. Douglass
Witness:

         /s/ Mary Lou Marks                          /s/ Ronald Nutt
-------------------------------------          ---------------------------------
                                                     Dr. Ronald Nutt


                                      -37-
<PAGE>

Witness:

         /s/ Mary Lou Marks                          /s/ Michael C. Crabtree
-------------------------------------          ---------------------------------
                                                     Michael C. Crabtree
Witness:

         /s/ Mary Lou Marks                          /s/ J. Kelly Milam
-------------------------------------          ---------------------------------
                                                     J. Kelly Milam


ATTEST:                                     SIEMENS GAMMASONICS, INC.


                                            By:
-------------------------------------          ---------------------------------
Title:                                      Title:
      -------------------------------             ------------------------------


                                      -38-