<PAGE>
                                                                   EXHIBIT 10.15

              CRYSTAL PRODUCTION AND TECHNOLOGY TRANSFER AGREEMENT


         This CRYSTAL PRODUCTION AND TECHNOLOGY TRANSFER AGREEMENT is made and
entered into as of the first day of April, 1999, by and between CTI, INC., a
Tennessee corporation, 810 Innovation Drive, Knoxville, Tennessee 37932, U.S.A.
(hereinafter referred to as "CTI"), and CRYSTAL PHOTONICS, INC., a Florida
corporation, 2729 N. Financial Court, Sanford, Florida 32773, U.S.A.
(hereinafter referred to as "CPI").

                                    RECITALS

CTI is engaged in research and development, manufacture and sale of positron
emission tomography (hereinafter referred to as "PET") technologies, and other
technologies including detector technologies. CTI is licensed by Schlumberger
Technology Corporation for the world wide exclusive right to manufacture and
sell Lu(2)SiO(5): Ce single crystals (hereinafter referred to as "LSO") which
can be used in such applications as gamma-ray detection for PET and other
detector technologies. CPI engages in research and development, production, and
sale of single crystals which can be used for various applications. CTI desires
to engage CPI to produce LSO for the use by CTI on the terms and conditions set
forth below.

                                   AGREEMENTS:

         IN CONSIDERATION OF the forgoing premises, and the mutual terms,
covenants and conditions contained herein, CTI and CPI mutually agree as
follows:

         1. Production Facility.

                  a. CPI agrees to dedicate at least fifteen (15) and up to
         twenty five (25) high temperature furnace systems for LSO crystal
         growth by * technique for CTI within the next 24 months starting July
         1999. Such furnaces must be sufficient for the growth of LSO crystals
         which meet the single crystal specifications set forth in Exhibit A
         attached hereto.

                  b. CTI agrees by initiating this contract commitment and by
         agreeing to enter into an annual purchase contract for LSO to assist
         CPI in financing construction of these new furnaces including power
         back-up systems and the necessary Iridium crucibles, rods and lids
         located at the CPI facility for growth of LSO crystals.

                  c. The CPI crystal production facility will include trained
         staff of engineers and technicians as necessary to keep all the
         furnaces in continuous operation and to produce LSO crystals meeting
         the specifications in Exhibit A.

                  d. CPI may use the furnaces described above dedicated to CTI
         for * purposes when they are not being utilized for CTI purposes. CPI
         agrees to immediately return the furnace systems to the dedicated use
         of CTI upon the request of CTI.


*Omitted information is the subject of a request for confidential treatment
pursuant to Rule 406 under the Securities Act of 1933 and has been filed
separately with the Securities and Exchange Commission.

<PAGE>

         2. Raw Materials; Production of Crystals:

                  a. CTI will supply to CPI all the 99.99% pure Lu(2)O(3) for
         LSO crystal growth by CPI for use by CTI. CPI will promptly utilize the
         furnaces dedicated to production for CTI to timely produce LSO crystals
         for CTI which meet the specifications set forth in Exhibit A, and
         promptly deliver such crystals to CTI.

                  b. CPI represents and warrants to CTI that LSO crystals
         supplied to CTI hereunder will be produced to the highest quality
         standard of its technology limit, and free from defect in material and
         workmanship. It will comply with the specifications set forth in
         Exhibit A.

                  c. CPI will produce LSO crystals continuously based on an
         open-end purchase order from CTI specifying the size, quantity and
         required delivery date. CTI shall supply the raw Lutetium material to
         CPI in a timely manner.

                  d. CPI will account for all the 99.99% Lu(2)O(3) supplied by
         CTI in terms of mass balance of Lu(2)O(3) by written record in form of
         Exhibit B attached hereto, or other mutually agreeable written record.

                  e. CPI will return to CTI upon request in a timely manner all
         LSO scrap for recovery of 99.99% Lu(2)O(3). CTT will allow reasonable
         amount of loss of Lu(2)O(3) due to loading, crucible cleaning, slab and
         block fabrication and finally accidental leakage or other unintentional
         loss such as massive power failure or other natural disasters.

                  f. CTI will provide to CPI the result of measurements and
         analyses of the crystal quality for CPI's quality control program.

                  g. CPI will assist CTI to improve the LSO crystal production
         at CTI's Knoxville, Tennessee facility and to provide suggestions to
         reduce the cost of manufacture of LSO crystals in accordance with the
         licensing agreement set forth in section 5.b.

                  h. CPI and CTI will work together for the duration of this
         contract to increase light yield and reduce the cost of growing LSO
         crystals. This technical cooperation will take place at CPI's facility
         and CTI's facility where personnel from CPI and CTI will be allowed to
         observe all the processes and equipment used for LSO production at both
         facilities. Within thirty (30) days after the execution of this
         contract, CPI will make its best effort to send technical personnel at
         CTI's expense to CTI's growth-facility to monitor and to modify the LSO
         growth process in order to increase both the crystal yield and light
         output of LSO crystals to a level comparable to that of CPI. CTI will
         make any necessary changes to the CTI crystal growth stations that will
         cause the CPI and CTI growth stations to be near identical.



                                      -2-
<PAGE>

         3. Purchase Requirements.

                  a. Provided that CPI can meet the quality standard set forth
         on Exhibit A and that CPI's LSO manufacturing cost does not exceed
         CPI's LSO manufacturing cost by more than * (*) percent, CTI will
         during the term of this Agreement, purchase from CPI (*) or more of
         CTI's need for PET and other detectors production, up to a maximum
         required amount not to exceed the amount of crystals produced by a
         maximum of twenty-five (25) furnace systems at CPI's facility. In the
         case CPI's cost exceeds CTI's by more than * %, CPI's will have the
         right to audit CTI's cost.

                  b. As long as CPI can meet the contract requirement of crystal
         quality, delivery schedule and cost, and CTI has need for LSO, CTI
         shall not unilaterally reduce or terminate the purchase of LSO crystals
         from CPI without parallel reduction in production of LSO at CTI's
         Knoxville facility. CTI will have the right to accept any and all of
         the LSO crystals grown at the CPI facility exceeds the production set
         forth in 3.c. The production parity is defined as equal number of
         crystal pullers used at each facility. If CTI unilaterally reduces or
         terminates the purchase of LSO crystals from CPI without comparable
         reduction at CTI, CTI shall compensate CPI for the loss of net income
         based on the production capacity at CPI's facility for the balance of
         the contract term.

                  c. If CPI produces LSO crystals hereunder satisfactorily and
         increases the number of furnace systems beyond the maximum of
         twenty-five (25) provided for in Section 3.a. above, CTI will negotiate
         with CPI in good faith towards an agreement to increase the percentage
         of CTI's crystal requirements to be provided by CPI:

         4. Price; Payment.

                  a. CTI will pay to CPI for LSO crystals provided hereunder
         meeting the specifications set forth on Exhibit A an amount per unit
         volume equal to the actual manufacturing cost of LSO plus * ( * )
         percent excluding the Lu(2)O(3) raw material cost. The price for 1999
         is $ * /cc of the slab volume excluding the Lu(2)O(3) raw material and
         this price will be adjusted retroactively at the end of 1999 based on
         actual LSO manufacturing cost plus * ( * ) percent. The actual LSO
         manufacturing cost will be confirmed by a CTI audit at the end of each
         year. The price for HRRT block will be adjusted to accommodate the
         extra material loss and the cost of the block fabrication.

         For year 2000 and beyond the price of LSO will be the average of the
         LSO manufacturing cost plus *(*) percent for year 2000 and the LSO
         manufacturing cost plus *(*) percent for the previous year. This
         provides CPI with an incentive to improve the manufacturing cost and a
         mechanism for CTI to obtain improvements in the technology.

                  b. CPI will invoice CTI on a weekly basis for crystals
         delivered delivered to CTI.


*Omitted information is the subject of a request for confidential treatment
pursuant to Rule 406 under the Securities Act of 1933 and has been filed
separately with the Securities and Exchange Commission.


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<PAGE>

                  c. CTI shall pay CPI for crystals delivered and invoiced, at
         the prices set forth in Section 4.a. above, within thirty (30) days
         after receipt of invoice.

                  d. After the execution of this Agreement, CTI will allow CPI
         to continue production of LSO crystals using existing growth facility
         and existing price as defined in 4a during the loan application and
         construction period of the new crystal growth stations.

         5. Licenses.

                  a. CTI hereby grants to CPI a Limited royalty-free sublicense
         in and to all the technology, know-how and intellectual property rights
         related to the production of LSO granted to CTI under its Exclusive
         Patent and Technology License Agreement with Schlumberger Technology-
         Corporation dated February 1, 1995, as amended (the "Schlumberger
         License"), a copy of which is attached hereto as Exhibit C, to the
         extent necessary to, and for the sole purpose of, production of LSO for
         CTI hereunder. The term of this license shall be only for the term of
         this Agreement. Upon any termination of this Agreement, CPI shall
         return to CTI only such technology included in the Schlumberger
         License. CPI acknowledges and agrees that this Agreement, and the
         limited sublicense granted hereby, are subject to, and CPI agrees to be
         bound by, the terms of the Schlumberger License.

                  b. CPI hereby grants to CTI a limited royalty-free license in
         and to all the technology, know-how and intellectual property rights of
         CPI related to the production of LSO developed at CPI (the "CPI
         Technology"). The term of this license shall be only for the term of
         this Agreement.

                  c. CTI and CPI agree not to transfer nor hire employees from
         each other without mutual consent during the Agreement period and no
         less than three years after the expiration of the Agreement. If either
         party hires ex-employees of the other company, they will notify the
         company before the hiring occurs.

         6. Exclusivity. CPI agrees not to grow LSO for, or sell LSO to, any
entity other than CTI without the expressed written consent of CTI. CTI agrees
to sublicense the Schlumberger License exclusively to CPI during the entire
duration of this contract as long as CPI meets CTI's quality, delivery and cost
of LSO.

         7. CTI Production Facility. CPI acknowledges that CTI is developing at
its Knoxville, Tennessee facility and has the capability to produce LSO by the
CPI crystal growth process, both during and after the term of this Agreement,
and that nothing contained herein shall prohibit CTI from doing so. CPI
acknowledges and agrees that CTI shall be free to use without restriction any
and all information and know-how relating to the production of LSO obtained in
connection with this Agreement, whether obtained from CPI or elsewhere. CTI is
restricted from transferring to any of the LSO crystal growth technology to a
third party without a written consent from CPI during or after the Agreement.


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<PAGE>

         8. Term. The term of this Agreement shall begin on the date hereof and,
subject to the provisions of Section 9 hereof; continue for five (5) years
thereafter. By mutual agreement, this Agreement can be extended.

         9. Termination.

                  a. CTI and CPI may terminate this Agreement at anytime by
         mutual agreement. Such termination shall not relieve either party from
         liability for any breach of its obligation under this Agreement prior
         to termination.

                  b. In the event that either party hereto breaches this
         Agreement and has not cured such breach within thirty (30) days after
         written notice from the other describing such breach, then the
         non-breaching party shall be entitled to terminate this Agreement and
         pursue its legal remedies for such breach.

                  c. Upon termination of this Agreement for any reason, any
         remaining raw materials and supplies provided to CPI by CTI will be
         promptly returned to CTI. CTI agrees to purchase any finished and
         not-yet delivered LSO crystals at the price set forth prior to the
         termination.

         10. Confidentiality. The parties contemplate that, in the course of
performance under this Agreement, each party may furnish to the other
proprietary information confidential to the disclosing party. Each party agrees
not to disclose to others the proprietary confidential information of the other
party, and agrees to hold such information confidential in the same manner as it
holds its own confidential information. Provided, however, that in no event
shall either party be obliged to treat confidential any information that (i) can
be shown to have been known to or in the possession of either party prior to the
disclosure thereof by the other party; (ii) is or becomes known or generally
available to the public other than as a result of acts or omissions of such
party; or (iii) is made available to such party by the third party without
similar restriction or without violation by such third party of any Agreement
with the other party.

         11. Indemnification. Each party hereto will indemnify and hold harmless
the other from and against all liability, loss, cost or expense arising out of
or resulting from the indemnifying party's failure to comply with its
obligations hereunder, or any negligence or other wrongful conduct of the
indemnifying parry, its officers, employees or agents in their performance
hereunder. Provided, however, that notwithstanding the foregoing neither party
shall be liable to the other for consequential damages or lost profits.


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<PAGE>

         12. Resolution of Disputes.

                  a. All disputes and controversies between the parties hereto
         of every kind and nature arising out of or in connection with this
         Agreement as to the existence, construction, validity, interpretation
         or-meaning, performance, nonperformance, enforcement, operation,
         breach, continuation, or termination of this Agreement which cannot be
         settled promptly by agreement shall be submitted to a single arbitrator
         with experience in high technology, commercial matters to be chosen by
         the senior executive officers for each of the parties within thirty
         (30) days after demand for arbitration by either of the parties. If the
         parties cannot within such time agree on an arbitrator, the arbitrator
         shall be chosen under American Arbitration Association procedures from
         its panels of arbitrators with high technology commercial experience.

                  b. The arbitration hearing shall be held in Knoxville,
         Tennessee, if CPI initiates arbitration and in Orlando, Florida, if CTI
         initiates arbitration, or at such other place as the parties and the
         arbitrator agree, within forty-five (45) days after the dispute is
         submitted to an arbitrator. The Commercial Arbitration Rules of the
         American Arbitration Association, or such other rules and procedures as
         the arbitrator may determine, shall be utilized in the arbitration
         proceedings. The arbitration hearing shall be concluded in not more
         than two (2) days unless otherwise ordered by the arbitrator. The
         award on the hearing shall be made within thirty (30) days after the
         close of the submission of evidence at or in connection with the
         hearing. An award rendered by the arbitrator appointed pursuant to this
         Agreement shall be final and binding on the parties to such proceeding.
         Judgment on such award may be entered by any of the disputing parties
         in any court having jurisdiction over the parties.

                  c. The provision of this Section 11 of this Agreement shall be
         a complete bar and defense to any suit, action or proceeding instituted
         in any court or before any administrative tribunal with respect to any
         dispute or controversy arising out of or in connection with this
         Agreement. The arbitration provisions of this Agreement shall, with
         respect to any such dispute or controversy, survive the termination or
         expiration of this Agreement.

                  d. The parties shall each bear all of their respective
         arbitration cost and expenses; provided, however, that the parties
         shall share equally the cost and expenses of the arbitrator.

         13. Miscellaneous.

                  a. Modification. This Agreement may not be modified without a
         mutual consent of the parties hereto.


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<PAGE>

                  b. Severability. In the event that any clause of this
         Agreement is held invalid or unenforceable, it is agreed between the
         parties that the remainder of the Agreement will remain in effect and
         enforceable.

                  c. Waiver. The failure of either party at any time to require
         strict performance by the other party of any provision hereof shall in
         no manner affect the right of such party thereafter to enforce the
         same. The right of either party hereto to require strict performance by
         the other party of any terms or obligations imposed upon such other
         party by this Agreement shall not in any way be affected by any
         previous waiver, forbearance or course of dealing.

                  d. Applicable Law. This Agreement shall be governed by an
         interpreted in accordance with the laws of the state of Tennessee.

                  e. Force Majeure. If the performance under this Agreement by
         either party is prevented, restricted, or interfered with by reason of
         fire or other casualty or accident, strikes or labor disputes,
         inability to procure raw materials, power or other supplies, war,
         invasion, civil commotion, or other violence, or other similar act or
         conditions beyond the control of either party hereto, the party so
         affected shall, upon giving prompt written notice to the other party,
         be excused from such performance to the extent of such prevention,
         restriction, or interference, provided that the party so affected shall
         use its best efforts to avoid or remove such causes of nonperformance
         and shall continue performance hereunder with the utmost dispatch
         whenever such causes are removed. In the event that such prevention,
         restriction, or interference exceeds two (2) months, the other party
         shall have the right to terminate this Agreement.

                  f. Notices. Any notice hereunder must be in writing and may be
         given by certified mail, and shall be deemed to have been given when
         such registered or certified letter, properly addressed, is mailed; if
         given otherwise than registered and certified letter, notice shall be
         deemed to have been given when delivered.

         If such notice to be given to CTI, it shall be addressed as follows:

                  CTI, Inc.
                  810 Innovation Drive
                  Knoxville, TN 37932
                  Attention: Ronald Nutt

         If such notice is to be given to CPI, it shall be addressed as follows:

                  Crystal Photonics, Inc.
                  2729 N. Financial Court
                  Sanford, FL 32773
                  Attention:  Bruce Chai

                  g. Benefit; Assignment. The rights and obligations of the
         parties hereto shall bind and inure to the benefit of the parties and
         their respective successors and



                                      -7-
<PAGE>

         assigns. This Agreement shall not be assigned or transferred by either
         party, in whole or in part, without the prior written consent of the
         other party, which consent shall not unreasonably be withheld.

                  h. Relationship of Parties. This Agreement shall not construed
         as constituting the parties as a partnership joint venture or any other
         form of association which would impose on either party liability for
         the actions or failure to act on the other party.

                  i. Exhibits. The parties agree to work diligently on the
         exhibits and to finish the exhibits within thirty (30) days after the
         date of this contract.

         IN WITNESS WHEREOF, the parties, by their duly authorized
representatives, do execute this Agreement, intending to be legally bound, as of
the day and year first written above.


CTI, Inc.



By:      /s/ Ronald Nutt
   --------------------------------------------------
         Ronald Nutt, Ph.D.
         Senior Vice President
         And Technology Director


Crystal Photonics, Inc.


By:      /s/ Bruce Chai
   -----------------------------------------
         Bruce Chai
         President

         constituting the parties as a partnership joint venture or any other
         form of association which would impose on either party liability for
         the actions or failure to act on the other party.

         IN WITNESS WHEREOF, the parties, by their duly authorized
representatives, do execute this Agreement, intending to be legally bound, as of
the day and year first written above.


                                      -8-

<PAGE>

CTI, Inc.



By:      /s/ Ronald Nutt
   --------------------------------------------------
         Ronald Nutt, Ph.D.
         Senior Vice President
         And Technology Director




Crystal Photonics, Inc.



By:      /s/ Bruce Chai
   --------------------------------------------------
         Bruce Chai Ph.D.
         President


EXHIBITS to
CRYSTAL PRODUCTION AND TECHNOLOGY TRANSFER AGREEMENT

A.       Specifications for LSO crystals

         Amendments to Exhibit A:

                  (1) Light yield and energy resolution is based on current
                      material standard which is * of BGO and energy resolution
                      of *

                  (2) Even though the CTI's exhibit shows a complete boule, the
                      actual delivery is in slab and block form. CTI acknowledge
                      that there are losses of material due to cracking during
                      slicing, even though the crystal is crack-free prior to
                      cutting.

                  (3) Crystal cost to be determined by the formula proposed in
                      section 4.a.

                  (4) The cost of HRRT blocks will be calculated separately.

A.       Mass balance sheet

         Amendments to Exhibit B:

                  Calculation should allow reasonable loss of materials during
         hot loading, crucible leakage, crucible residual charge removal and
         cutting and fabricating into slabs or blocks. CPI will provide material
         loss calculation based on current LSO production.

B.       Determination of CPI cost of production

                  The calculation is based on the actual cost of LSO crystal
         production at CPI during 1998. The calculation is based on "perfect
         growth" of 4 stations at CPI.

* Omitted information is the subject of a request for confidential
  treatment pursuant to Rule 406 under the Securities Act of 1933 and has been
  filed separately with the Securities and Exchange Commission.




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<PAGE>


         The actual growth yield is much less. The calculation provides the
         absolute minimum cost of LSO crystals based on current technology.

         (A) Production yield (perfect growth):

         Total number of crystals produced per month per station = 3.5
                                                     2
         Total volume per LSO slab = [pie] x (3.1 cm)  x 1.0 cm = 30.2 cc
         Total number of slabs per crystal = 13
         Total volume of slabs per crystal = 390 cc
         Total volume yield per station per month = 390 x 3.5 = 1,365 cc

         (B) Production cost (actual value)

                  (1)    Equipment depreciation:

                         Cost per growth station plus two Iridium crucibles = *
                         Linear depreciation for 5 years = $ *
                         Cost of water cooling system per growth station = $ *
                         Linear depreciation for 5 years = $ *
                         UPS power back up system per growth station = $ *
                         Linear depreciation for 5 years = $ *

                         Total depreciation per station per month = $ *

                  (2)    Direct Expenses per station per month:

                         Electricity = $ *
                         Liquid nitrogen (plus tank rental) = $ *
                         Slab cutting and shipping = $ *
                         Furnace glass tube, insulation materials = $ *
                         Plant repairs and RF generator maintenance = $ *
                         Iridium crucible repair = $ *
                         Iridium crucible re-fabrication = $ *
                         Iridium leasing during fabrication = $ *
                         Silica and cerium oxide = $ *
                         Total cost per station per month = $ *

                  (3)    Labor and Office expenses:

                         Wages + overhead per month average for 1998 = $ *
                         Total number of operating growth stations = 6
                         Cost per growth station = $ *

                         Estimated per station cost with 20 LSO stations = $ *

                  (4)    Summary:

                         Total operating cost per station per month = $ *

* Omitted information is the subject of a request for confidential
  treatment pursuant to Rule 406 under the Securities Act of 1933 and has been
  filed separately with the Securities and Exchange Commission.


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<PAGE>

                         Current cost based on 100% yield per cc of LSO = $ *
                         Current effective yield = *
                         Current effective cost of production per cc = $ *

                         Estimated operating cost based on 20 LSO stations = $ *
                         Estimated cost based on 100% yield per cc of LSO = $ *
                         Estimated effective yield = *
                         Estimated effective cost of production per cc = $ *
                         Estimated cost plus 25% profit = $ *

C.       Schlumberger License:

D.       CPI's patent petition:

* Omitted information is the subject of a request for confidential
  treatment pursuant to Rule 406 under the Securities Act of 1933 and has been
  filed separately with the Securities and Exchange Commission.



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