TREX MEDICAL CORPORATION

                           DIRECTORS STOCK OPTION PLAN

                    As amended and restated effective as of June 18, 1999

1.      Purpose

        The purpose of this Directors Stock Option Plan (the "Plan") of Trex
Medical Corporation (the "Company") is to encourage ownership in the Company by
outside directors of the Company whose services are considered essential to the
Company's growth and progress and to provide them with a further incentive to
become directors and to continue as directors of the Company. The Plan is
intended to be a nonstatutory stock option plan.

2.      Administration

        The Board of Directors, or a Committee (the "Committee") consisting of
one or more directors of the Company appointed by the Board of Directors, shall
supervise and administer the Plan. Grants of stock options under the Plan and
the amount and nature of the options to be granted shall be automatic in
accordance with Section 5. However, all questions of interpretation of the Plan
or of any stock options granted under it shall be determined by the Board of
Directors or the Committee and such determination shall be final and binding
upon all persons having an interest in the Plan.

3.      Participation in the Plan

        Directors of the Company who are not employees of the Company or any
subsidiary or parent of the Company shall be eligible to participate in the
Plan. Directors who receive grants of stock options in accordance with this Plan
are sometimes referred to herein as "Optionees."

4.      Stock Subject to the Plan

        The maximum number of shares that may be issued under the Plan shall be
200,000 shares of the Company's Common Stock (the "Common Stock"), subject to
adjustment as provided in Section 9. Shares to be issued upon the exercise of
options granted under the Plan may be either authorized but unissued shares or
shares held by the Company in its treasury. If any option expires or terminates
for any reason without having been exercised in full, the unpurchased shares
subject thereto shall again be available for options thereafter to be granted.

5.      Terms and Conditions

        A.     Annual Stock Option Grants

        Each Director of the Company who meets the requirements of Section 3 and
who is holding office immediately following the Annual Meeting of Stockholders
commencing with the Annual Meeting of Stockholders held in calendar year 2000,
shall be granted an option to purchase 1,000 shares of Common Stock at the close
of business on the date of such Annual Meeting.

        B.     General Terms and Conditions Applicable to All Grants.

               1. Options shall be immediately exercisable at any time from and
               after the grant date and prior to the date which is the earliest
               of:

                      (a) three years after the grant date for options granted
               under Section 5(A), (b) two years after the Optionee ceases to
               serve as a director of the Company, Thermo Electron or any
               subsidiary of Thermo Electron (one year in the event the Optionee
               ceases to meet the requirements of this Subsection by reason of
               his or her death), or (c) the date of dissolution or liquidation
               of the Company.

               2. The exercise price at which Options are granted hereunder
               shall be the average of the closing prices reported by the
               national securities exchange on which the Common Stock is
               principally traded for the five trading days immediately
               preceding and including the date the option is granted or, if
               such security is not traded on an exchange, the average last
               reported sale price for the five-day period on the NASDAQ
               National Market List, or the average of the closing bid prices
               for the five-day period last quoted by an established quotation
               service for over-the-counter securities, or if none of the above
               shall apply, the last price paid for shares of the Common Stock
               by independent investors in a private placement.

               3. All options shall be evidenced by a written agreement
               substantially in such form as shall be approved by the Board of
               Directors or Committee, containing terms and conditions
               consistent with the provisions of this Plan.

6.      Exercise of Options

        A.     Exercise/Consideration

        An option may be exercised in accordance with its terms by written
notice of intent to exercise the option, specifying the number of shares of
stock with respect to which the option is then being exercised. The notice shall
be accompanied by payment in the form of cash or shares of Common Stock of the
Company (the shares so tendered referred to herein as "Tendered Shares") with a
then current market value equal to the exercise price of the shares to be
purchased; provided, however, that such Tendered Shares shall have been acquired
by the Optionee more than six months prior to the date of exercise (unless such
requirement is waived in writing by the Company). Against such payment the
Company shall deliver or cause to be delivered to the Optionee a certificate for
the number of shares then being purchased, registered in the name of the
Optionee or other person exercising the option. If any law or applicable
regulation of the Securities and Exchange Commission or other body having
jurisdiction in the premises shall require the Company or the Director to take
any action in connection with shares being purchased upon exercise of the
option, exercise of the option and delivery of the certificate or certificates
for such shares shall be postponed until completion of the necessary action,
which shall be taken at the Company's expense.

        B.     Tax Withholding

        The Company shall have the right to deduct from payments of any kind
otherwise due to the Optionee any federal, state or local taxes of any kind
required by law to be withheld with respect to any shares issued upon exercise
of options under the Plan. Subject to the prior approval of the Company, which
may be withheld by the Company in its sole discretion, the Optionee may elect to
satisfy such obligations, in whole or in part, (i) by causing the Company to
withhold shares of Common Stock otherwise issuable pursuant to the exercise of
an option or (ii) by delivering to the Company shares of Common Stock already
owned by the Optionee. The shares so delivered or withheld shall have a fair
market value equal to such withholding obligation. The fair market value of the
shares used to satisfy such withholding obligation shall be determined by the
Company as of the date that the amount of tax to be withheld is to be
determined. Notwithstanding the foregoing, no election to use shares for the
payment of withholding taxes shall be effective unless made in compliance with
any applicable requirements of Rule 16b-3.

7.      Transferability

        Except as may be authorized by the Board, in its sole discretion, no
Option may be transferred other than by will or the laws of descent and
distribution, and during an Optionee's lifetime an Option may be exercised only
by him or her (or in the event of incapacity, the person or persons properly
appointed to act on his or her behalf). The Board may, in its discretion,
determine the extent to which Options granted to an Optionee shall be
transferable, and such provisions permitting or acknowledging transfer shall be
set forth in the written agreement evidencing the Option executed and delivered
by or on behalf of the Company and the Optionee.

8.      Limitation of Rights to Continue as a Director

        Neither the Plan, nor the quantity of shares subject to options granted
under the Plan, nor any other action taken pursuant to the Plan, shall
constitute or be evidence of any agreement or understanding, express or implied,
that the Company will retain a Director for any period of time, or at any
particular rate of compensation.

9.      Adjustments in the Event of Certain Transactions

        (a) In the event of a stock dividend, stock split or combination of
shares, or other distribution with respect to holders of Common Stock other than
normal cash dividends, the Board will make (i) appropriate adjustments to the
maximum number of shares that may be delivered under the Plan under Section 4
above, and (ii) appropriate adjustments to the number and kind of shares of
stock or securities subject to Options then outstanding or subsequently granted,
any exercise prices relating to Options and any other provisions of Options
affected by such change.

        (b) In the event of any recapitalization, merger or consolidation
involving the Company, any transaction in which the Company becomes a subsidiary
of another entity, any sale or other disposition of all or a substantial portion
of the assets of the Company or any similar transaction, as determined by the
Board, the Board in its discretion may make appropriate adjustments to
outstanding Options to avoid distortion in the operation of the Plan.

10.     Limitation of Rights in Option Stock

        The Optionees shall have no rights as stockholders in respect of shares
as to which their options shall not have been exercised, certificates issued and
delivered and payment as herein provided made in full, and shall have no rights
with respect to such shares not expressly conferred by this Plan or the written
agreement evidencing options granted hereunder.

11.     Stock Reserved

        The Company shall at all times during the term of the options reserve
and keep available such number of shares of the Common Stock as will be
sufficient to permit the exercise in full of all options granted under this Plan
and shall pay all other fees and expenses necessarily incurred by the Company in
connection therewith.

12.     Securities Laws Restrictions

        A.     Investment Representations.

        The Company may require any person to whom an option is granted, as a
condition of exercising such option, to give written assurances in substance and
form satisfactory to the Company to the effect that such person is acquiring the
Common Stock subject to the option for his or her own account for investment and
not with any present intention of selling or otherwise distributing the same,
and to such other effects as the Company deems necessary or appropriate in order
to comply with federal and applicable state securities laws.

        B.     Compliance with Securities Laws.

        Each option shall be subject to the requirement that if, at any time,
counsel to the Company shall determine that the listing, registration or
qualification of the shares subject to such option upon any securities exchange
or under any state or federal law, or the consent or approval of any
governmental or regulatory body, or that the disclosure of non-public
information or the satisfaction of any other condition is necessary as a
condition of, or in connection with, the issuance or purchase of shares
thereunder, such option may not be exercised, in whole or in part, unless such
listing, registration, qualification, consent or approval, or satisfaction of
such condition shall have been effected or obtained on conditions acceptable to
the Board of Directors. Nothing herein shall be deemed to require the Company to
apply for or to obtain such listing, registration or qualification, or to
satisfy such condition.



13.     Change in Control

        A.     Impact of Event

        In the event of a "Change in Control" as defined in Section 13(A), the
following provisions shall apply, unless the agreement evidencing the Award
otherwise provides (by specific explicit reference to Section 13(B) below). If a
Change in Control occurs while any Options are outstanding, then, effective upon
the Change in Control, each outstanding Option under the Plan that was not
previously exercisable and vested shall become immediately exercisable in full
and will no longer be subject to a right of repurchase by the Company.

        B.     Definition of "Change in Control"

        "Change in Control" means an event or occurrence set forth in any one or
more of subsections (a) through (d) below (including an event or occurrence that
constitutes a Change in Control under one of such subsections but is
specifically exempted from another such subsection):

        (a) the acquisition by an individual, entity or group (within the
meaning of Section 13(d)(3) or 14(d)(2) of the Exchange Act) (a "Person") of
beneficial ownership of any capital stock of Thermo Electron Corporation
("Thermo Electron") if, after such acquisition, such Person beneficially owns
(within the meaning of Rule 13d-3 promulgated under the Exchange Act) 40% or
more of either (i) the then-outstanding shares of common stock of Thermo
Electron (the "Outstanding TMO Common Stock") or (ii) the combined voting power
of the then-outstanding securities of Thermo Electron entitled to vote generally
in the election of directors (the "Outstanding TMO Voting Securities");
provided, however, that for purposes of this subsection (a), the following
acquisitions shall not constitute a Change in Control: (i) any acquisition by
Thermo Electron, (ii) any acquisition by any employee benefit plan (or related
trust) sponsored or maintained by Thermo Electron or any corporation controlled
by Thermo Electron, or (iii) any acquisition by any corporation pursuant to a
transaction which complies with clauses (i) and (ii) of subsection (c) of this
definition; or

        (b) such time as the Continuing Directors (as defined below) do not
constitute a majority of the Board of Directors of Thermo Electron (the "Thermo
Board") (or, if applicable, the Board of Directors of a successor corporation to
Thermo Electron), where the term "Continuing Director" means at any date a
member of the Thermo Board (i) who was a member of the Thermo Board as of July
1, 1999 or (ii) who was nominated or elected subsequent to such date by at least
a majority of the directors who were Continuing Directors at the time of such
nomination or election or whose election to the Thermo Board was recommended or
endorsed by at least a majority of the directors who were Continuing Directors
at the time of such nomination or election; provided, however, that there shall
be excluded from this clause (ii) any individual whose initial assumption of
office occurred as a result of an actual or threatened election contest with
respect to the election or removal of directors or other actual or threatened
solicitation of proxies or consents, by or on behalf of a person other than the
Thermo Board; or

        (c) the consummation of a merger, consolidation, reorganization,
recapitalization or statutory share exchange involving Thermo Electron or a sale
or other disposition of all or substantially all of the assets of Thermo
Electron in one or a series of transactions (a "Business Combination"), unless,
immediately following such Business Combination, each of the following two
conditions is satisfied: (i) all or substantially all of the individuals and
entities who were the beneficial owners of the Outstanding TMO Common Stock and
Outstanding TMO Voting Securities immediately prior to such Business Combination
beneficially own, directly or indirectly, more than 60% of the then-outstanding
shares of common stock and the combined voting power of the then-outstanding
securities entitled to vote generally in the election of directors,
respectively, of the resulting or acquiring corporation in such Business
Combination (which shall include, without limitation, a corporation which as a
result of such transaction owns Thermo Electron or substantially all of Thermo
Electron's assets either directly or through one or more subsidiaries) (such
resulting or acquiring corporation is referred to herein as the "Acquiring
Corporation") in substantially the same proportions as their ownership,
immediately prior to such Business Combination, of the Outstanding TMO Common
Stock and Outstanding TMO Voting Securities, respectively; and (ii) no Person
(excluding the Acquiring Corporation or any employee benefit plan (or related
trust) maintained or sponsored by Thermo Electron or by the Acquiring
Corporation) beneficially owns, directly or indirectly, 40% or more of the then
outstanding shares of common stock of the Acquiring Corporation, or of the
combined voting power of the then-outstanding securities of such corporation
entitled to vote generally in the election of directors; or

        (d) approval by the stockholders of Thermo Electron of a complete
liquidation or dissolution of Thermo Electron.

14.     Amendment of the Plan

        The provisions of Sections 3 and 5 of the Plan shall not be amended more
than once every six months, other than to comport with changes in the Code, the
Employee Retirement Income Security Act of 1974, or the rules thereunder.
Subject to the foregoing, the Board of Directors may at any time, and from time
to time, modify or amend the Plan in any respect, except that if at any time the
approval of the Stockholders of the Company is required as to such modification
or amendment under Rule 16b-3, the Board of Directors may not effect such
modification or amendment without such approval.

        The termination or any modification or amendment of the Plan shall not,
without the consent of an Optionee, affect his or her rights under an option
previously granted to him or her. With the consent of the Optionees affected,
the Board of Directors may amend outstanding option agreements in a manner not
inconsistent with the Plan. The Board of Directors shall have the right to amend
or modify the terms and provisions of the Plan and of any outstanding option to
the extent necessary to ensure the qualification of the Plan under Rule 16b-3.

15.     Effective Date of the Plan

        The Plan shall become effective when adopted by the Board of Directors,
but no option granted under the Plan shall become exercisable until six months
after the Plan is approved by the Stockholders of the Company.

16.     Notice

        Any written notice to the Company required by any of the provisions of
the Plan shall be addressed to the Secretary of the Company and shall become
effective when it is received.

17.     Governing Law

        The Plan and all determinations made and actions taken pursuant hereto
shall be governed by the laws of the State of Delaware.