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                                                                  EXHIBIT 10.37

                              SHAREHOLDER AGREEMENT

                  This AGREEMENT is made and entered into by and between CTI,
Inc., a Tennessee corporation (the "Corporation"), and the undersigned
shareholder of the Corporation ("Shareholder"), effective as of the date set
forth hereinbelow.

                                  WITNESSETH:

                  WHEREAS, the Corporation is a corporation formed and organized
under the laws of the State of Tennessee for the purpose of engaging in, among
other activities, the business of developing, manufacturing, marketing and
selling instruments, systems and services to scientific, diagnostic, analytical
and industrial markets; and

                  WHEREAS, Shareholder is an employee of the Corporation or an
affiliate of the Corporation, and the Corporation has granted to Shareholder an
option or options or other rights to purchase, or otherwise acquire, or
Shareholder has heretofore acquired, certain capital stock of the Corporation,
subject to the terms and conditions set forth herein, to which terms and
conditions Shareholder has agreed;

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

                  1. Shareholder shall not sell or otherwise transfer or dispose
of any of Shareholder's shares of stock of the Corporation, or options to
acquire shares of stock of the Corporation, whenever or however acquired, to any
person, firm, or corporation without the consent of the Corporation unless
Shareholder shall have first made the offer to the Corporation hereinafter
described and such offer shall not have been accepted.

                           a. The offer shall be made in writing to the
Corporation and shall consist of an offer to sell all the shares of the
Corporation owned by Shareholder, to which shall be attached a statement of
Shareholder's intention to sell or otherwise transfer or dispose of some or all
of Shareholder's shares, the name and address of Shareholder's prospective bona
fide purchaser or other transferee, the number of shares involved in the
proposed sale or transfer, and the price and other terms of such sale or
transfer.

                           b. Within thirty (30) days after the receipt of such
offer, the Corporation may, at its option, elect to purchase all, but not less
than all, of the shares of the Corporation offered by Shareholder. The
Corporation shall exercise its election to purchase by giving notice thereof to
Shareholder. The notice shall specify a date for the closing of the purchase
which shall be not more than thirty (30) days after the date of the giving of
such notice. The purchase price for the shares of the Corporation owned by
Shareholder shall be the price therefor offered by the bona fide purchaser or
transferee named in the offer to the Corporation.

                  2. Shareholder shall not encumber any shares of stock of the
Corporation or options to acquire shares of stock of the Corporation to secure
any indebtedness or other obligation without the consent of the Corporation.



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                  3. In the event of any sale or other transfer or encumbrance
of any of Shareholder's shares of stock of the Corporation, whether as permitted
by this Agreement or otherwise, such shares of stock shall be and remain subject
to all of the terms and provision of this Agreement.

                  4. Notwithstanding the foregoing, Shareholder may from time to
time transfer Shareholder's shares of stock of the Corporation to and among
Shareholder's immediate family members, and trusts or by will solely for the
benefit of Shareholder or Shareholder's immediate family members, without
offering the Corporation the right to purchase the shares of the Corporation so
transferred. Provided, however, that in connection with any such transfer such
shares of stock of the Corporation shall be subject to the terms and provisions
of this Agreement and each transferee of such shares shall agree in writing in
advance to be bound by the terms and provisions of this Agreement.

                  5. Shareholder agrees that in the event of the termination of
Shareholder's employment by the Corporation or any affiliate of the Corporation
for any reason, the Corporation shall have the right and option to purchase
Shareholder's shares of stock of the Corporation. Such option may be exercised
within sixty (60) days after such termination of employment. The purchase price
for Shareholder's stock shall be its fair market value.

                  6. Shareholder acknowledges and agrees that the shares of
stock of the corporation subject to this Agreement have not been registered
under the Securities Act of 1933, as amended (The "Act") or the Tennessee
Securities Act of 1980, as amended (The "Tennessee Act"), and may not be sold,
transferred, or otherwise disposed of unless they are first registered under the
Act and The Tennessee Act and all rules and regulations relating to the sale,
transfer, or other disposition of securities thereunder have been complied with,
or until the holder of such shares provides information satisfactory to the
Corporation that such registration and compliance is not required.

                  7. Shareholder agrees that each certificate representing
shares of the Corporation owned by Shareholder, whether now owned or hereafter
acquired, whether pursuant to this Agreement or otherwise, shall have placed
thereon a legend deemed by the Corporation to be appropriate to restrict the
transfer of such shares in accordance with the provisions hereof.

                  8.       a. The terms, covenants and conditions of this
Agreement shall be binding upon and shall inure to the benefit of the parties
hereto and their respective heirs, executors, administrators and permitted
assigns.

                           b. This Agreement shall not be assignable by either
of the parties without the prior written consent of all of the other party.

                           c. This Agreement shall be construed in accordance
with and governed by the laws of the State of Tennessee.



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                           d. No change or modification of this Agreement shall
be valid unless the same be in writing and signed by both of the parties hereto.

                           IN WITNESS WHEREOF, the parties have executed this
Agreement this 20th day of December, 1996.

                                               CTI, INC.


                                               By: /s/ Ronald Nutt
                                                   -----------------------------

                                               Title: Vice President
                                                      --------------------------

Witness as to Shareholder:                     SHAREHOLDER:

/s/ Anne H. Sale                               /s/ Terry Douglass
-----------------------------                  -----------------------------


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