MASTER CASH MANAGEMENT, GUARANTEE
                        REIMBURSEMENT AND LOAN AGREEMENT


      This  AGREEMENT  is  entered  into as of the 1st day of June,  1999 by and
between Thermo Electron Corporation,  a Delaware corporation ("Thermo Electron")
and Trex Medical Corporation, a Delaware corporation (the "Subsidiary").

                                   WITNESSETH:

      WHEREAS,  Thermo  Electron  and  the  Subsidiary  are  party  to a  Master
Repurchase   Agreement,   which  contains  terms  governing  a  cash  management
arrangement  between  them  and  a  Master  Guarantee   Reimbursement  and  Loan
Agreement,   as  amended  and  restated,   which   contains  terms  relating  to
intercompany credit support and a short term borrowing facility;

      WHEREAS, Thermo Electron and the Subsidiary desire to establish a new cash
management arrangement and short term borrowing facility between them in lieu of
the  arrangements  set forth in the Master  Repurchase  Agreement and the Master
Guarantee  Reimbursement  and Loan Agreement and also to  consolidate  the terms
relating to intercompany credit support in one agreement;

      WHEREAS,  the Subsidiary and other majority owned  subsidiaries  of Thermo
Electron  that  join  in  this  Agreement  (collectively,   the  "Majority-Owned
Subsidiaries")  and their  wholly-owned  subsidiaries wish to enter into various
financial  transactions,  such as convertible  or  nonconvertible  debt,  loans,
equity  offerings,  and other  contractual  arrangements with third parties (the
"Underlying Obligations") and may provide credit support to, on behalf of or for
the  benefit  of,  other   subsidiaries  of  Thermo  Electron  ("Credit  Support
Obligations");

      WHEREAS,  the Majority Owned Subsidiaries and Thermo Electron  acknowledge
that the Majority Owned Subsidiaries and their wholly-owned  subsidiaries may be
unable to enter into many kinds of Underlying Obligations without a guarantee of
their  performance  thereunder  from Thermo  Electron (a "Parent  Guarantee") or
without   obtaining  Credit  Support   Obligations  from  other  Majority  Owned
Subsidiaries;

      WHEREAS,  certain Majority Owned Subsidiaries ("Second Tier Majority Owned
Subsidiaries")  may themselves be majority owned  subsidiaries of other Majority
Owned Subsidiaries ("First Tier Majority Owned Subsidiaries");

      WHEREAS, for various reasons,  Parent Guarantees of a Second Tier Majority
Owned Subsidiary's  Underlying Obligations may be demanded and given without the
respective First Tier Majority Owned Subsidiary also issuing a guarantee of such
Underlying Obligation;

      WHEREAS, Thermo Electron may itself make a loan or provide other credit to
a Second Tier Majority Owned Subsidiary or its wholly-owned  subsidiaries  under
circumstances where the applicable First Tier Majority Owned Subsidiary does not
provide such credit; and
<PAGE>

      WHEREAS, Thermo Electron is willing to consider continuing to issue Parent
Guarantees and providing credit, and the Majority Owned Subsidiaries are willing
to consider continuing to provide Credit Support  Obligations,  on the terms and
conditions set forth below;

      NOW,  THEREFORE,  in  consideration  of the  foregoing  and other good and
valuable  consideration,  the  receipt  and  sufficiency  of  which  are  hereby
acknowledged by each party hereto, the parties agree as follows:

      1. Cash Management  Arrangement.  The Subsidiary directly,  or through its
wholly-owned U.S. subsidiaries,  may, from time to time, lend its excess cash to
Thermo Electron (a "Transaction"),  on an unsecured basis, bearing interest at a
rate equal to the 30-day  Dealer  Commercial  Paper Rate as reported in the Wall
Street  Journal  (the "DCP  Rate")  plus 50 basis  points,  which  rate shall be
adjusted on the second  business day of each fiscal month of the  Subsidiary and
shall be in effect for the entirety of such fiscal month.  The Subsidiary  shall
institute  a  Transaction  by  depositing  its excess  cash in the  Subsidiary's
concentration  account at BankBoston  Corporation  ("BankBoston")  or other bank
designated by Thermo Electron. At the end of each business day, the cash balance
deposited in the  Subsidiary's  concentration  account shall be  transferred  to
Thermo Electron's intercompany account at BankBoston or other bank designated by
Thermo Electron.  Thermo Electron shall indicate on its books the balance of the
Subsidiary's  cash held by Thermo  Electron under this  arrangement.  After each
fiscal  month  end,  Thermo  Electron  shall  provide  the  Subsidiary  a report
indicating  the  Subsidiary's  aggregate  cash balance  ("Excess  Cash") held by
Thermo Electron  hereunder.  The Subsidiary shall have the right to withdraw all
or part of its Excess Cash upon 30 days' prior notice to Thermo Electron. Within
30 days of receipt of such withdrawal notice, Thermo Electron shall transfer the
portion of the Excess Cash requested for withdrawal to an account  designated by
the  Subsidiary.  Thermo  Electron  shall  maintain,  at all times,  cash,  cash
equivalents and/or immediately  available bank lines of credit equal to at least
50% of the  cash  balances  of the  Subsidiary  and of all  other  participating
subsidiaries of Thermo Electron, other than wholly-owned  subsidiaries of Thermo
Electron,  held by Thermo  Electron  under this  arrangement.  Interest shall be
payable on the Excess  Cash by Thermo  Electron  to the  Subsidiary  each fiscal
month in arrears. In addition, the Subsidiary's non-U.S.  subsidiaries may, from
time to time,  lend or  advance  their  excess  cash to Thermo  Electron,  on an
unsecured  basis,  bearing  interest  at rates  set by  Thermo  Electron  at the
beginning of each month, based to the extent practicable on comparable  interest
rates  generally  available  in the  local  jurisdiction  of such  participating
non-U.S.  subsidiary.  Further,  Thermo Electron and such non-U.S.  subsidiaries
participating  in the cash  management  arrangement  with Thermo  Electron shall
establish   mutually  agreeable   procedures   governing  such  cash  management
arrangement.

      2. Loans and Advances.  Upon request from the Subsidiary,  Thermo Electron
may make loans and advances to the Subsidiary on a short-term,  revolving credit
basis,  from time to time,  in such  amounts as  mutually  determined  by Thermo
Electron and the Subsidiary.  The aggregate  principal  amount of such loans and
advances  shall be  reflected  on the books and  records of the  Subsidiary  and
Thermo  Electron.  All such loans and advances  shall be on an  unsecured  basis
unless  specifically  provided  otherwise in separate loan documents executed at
that time. The Subsidiary  shall pay interest on the aggregate  unpaid principal
amount of such  loans from time to time  outstanding  at a rate equal to the DCP


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<PAGE>

Rate plus one hundred fifty (150) basis points,  which rate shall be adjusted on
the second  business day of each fiscal month of the  Subsidiary and shall be in
effect for the entirety of such fiscal month.  If,  however,  one or more of the
Subsidiary's  majority-owned U.S.  subsidiaries (i.e., not wholly-owned) is also
participating in the cash management arrangement with Thermo Electron,  then the
rate  payable  on  the  Subsidiary's  outstanding  principal  balance  shall  be
calculated   as  follows:   If  the   aggregate   amount  of  the   Subsidiary's
majority-owned  U.S.  subsidiaries'  cash  balances  under  the cash  management
arrangement  ("Majority-Owned  Excess Cash") equals or exceeds the  Subsidiary's
outstanding  principal  balance,  then the Subsidiary  shall pay interest on the
aggregate unpaid principal amount of such loans at a rate per annum equal to the
DCP  Rate  plus  fifty  (50)  basis  points.  If  the  aggregate  amount  of the
Majority-Owned  Excess Cash is less than the Subsidiary's  outstanding principal
balance, then (A) the Subsidiary shall pay interest at a rate per annum equal to
the DCP Rate  plus  fifty  (50)  basis  points  on that  portion  of the  unpaid
principal amount equal to the Majority-Owned Excess Cash, and (B) the Subsidiary
shall pay  interest  at a rate per annum  equal to the DCP Rate plus one hundred
fifty (150) basis points on that portion of the unpaid principal amount equal to
(i)  the   Subsidiary's   outstanding   principal   balance,   minus   (ii)  the
Majority-Owned  Excess  Cash.  The  interest  rates  set  forth in the prior two
sentences  shall be adjusted on the second  business day of each fiscal month of
the  Subsidiary  and shall be in effect for the  entirety of such fiscal  month.
Interest shall be computed on a 360-day  basis.  Interest is payable each fiscal
month in arrears.  The aggregate  principal amount  outstanding shall be payable
within 30 days of demand by Thermo  Electron.  Overdue  principal  and  interest
shall bear interest at a rate per annum equal to the rate of interest  published
from  time to time in the Wall  Street  Journal  as the  "prime  rate"  plus one
percent (1%).  The principal and accrued  interest may be paid by the Subsidiary
at any time or from  time to time,  in whole  or in  part,  without  premium  or
penalty.  All payments  shall be applied  first to accrued  interest and then to
principal.  At the end of each business  day,  Thermo  Electron  shall apply the
balance of the  Subsidiary's  Excess Cash held by Thermo Electron under the cash
management  arrangement  toward  the  payment  of any loans or  advances  to the
Subsidiary.  Principal  and  interest  shall be payable  in lawful  money of the
United  States of America,  in  immediately  available  funds,  at the principal
office  of  Thermo  Electron  or at such  other  place as  Thermo  Electron  may
designate from time to time in writing to the Subsidiary.  The unpaid  principal
amount of any such  borrowings,  and  accrued  interest  thereon,  shall  become
immediately  due and payable,  without  demand,  upon  occurrence  of any of the
following events:

      (a) the failure of the  Subsidiary to pay any amount due hereunder  within
      fifteen (15) days of the date when due;

      (b) the failure of the Subsidiary to pay its debts as they become due, the
      filing  by or  against  the  Subsidiary  of any  petition  under  the U.S.
      Bankruptcy  Code  (or  the  filing  of  any  similar  petition  under  the
      insolvency law of any jurisdiction), or the making by the Subsidiary of an
      assignment  or  trust  mortgage  for  the  benefit  of  creditors  or  the
      appointment of a receiver,  custodian or similar agent with respect to, or
      the taking by any such person of possession  of, any material  property of
      the Subsidiary;

      (c) the sale by the Subsidiary of all or substantially all of its assets;


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<PAGE>



      (d) the merger or  consolidation  of the Subsidiary with or into any other
      corporation  in a transaction in which the Subsidiary is not the surviving
      entity;

      (e) the  issuance  of any  writ  of  attachment,  by  trustee  process  or
      otherwise, or any restraining order or injunction against or affecting the
      person or  property of the  Subsidiary  that is not  removed,  repealed or
      dismissed  within  thirty  (30)  days of  issuance  and as a result  has a
      material adverse effect on the business,  operations, assets or condition,
      financial or otherwise,  of the Subsidiary or its ability to discharge any
      of its liabilities or obligations to Thermo Electron; and

      (f)   the  suspension  of the  transaction  of the usual  business  of the
      Subsidiary.

      3.     Guarantee Arrangements.

      (a) If  Thermo  Electron  provides  a Parent  Guarantee  of an  Underlying
      Obligation,  and the  beneficiary(ies) of the Parent Guarantee enforce the
      Parent  Guarantee,  or Thermo Electron performs under the Parent Guarantee
      for  any  other  reason,  then  the  Majority  Owned  Subsidiary  that  is
      obligated,   either   directly  or  indirectly   through  a   wholly-owned
      subsidiary,  under such  Underlying  Obligation  shall  indemnify and save
      harmless  Thermo  Electron  from any  liability,  cost,  expense or damage
      (including  reasonable  attorneys'  fees) suffered by Thermo Electron as a
      result of the Parent Guarantee.  If the Underlying Obligation is issued by
      a Second Tier  Majority  Owned  Subsidiary  or a  wholly-owned  subsidiary
      thereof, and such Second Tier Majority Owned Subsidiary is unable to fully
      indemnify Thermo Electron (because of the poor financial condition of such
      Second Tier Majority Owned Subsidiary,  or for any other reason), then the
      First Tier Majority Owned  Subsidiary  that owns the majority of the stock
      of such Second Tier Majority  Owned  Subsidiary  shall  indemnify and save
      harmless Thermo Electron from any remaining  liability,  cost,  expense or
      damage (including  reasonable attorneys' fees) suffered by Thermo Electron
      as a result of the Parent  Guarantee.  If a Majority Owned Subsidiary or a
      wholly-owned  subsidiary  thereof provides a Credit Support Obligation for
      any  subsidiary  of  Thermo  Electron,  other  than a  subsidiary  of such
      Majority Owned Subsidiary,  and the beneficiary(ies) of the Credit Support
      Obligation  enforce the Credit Support  Obligation,  or the Majority Owned
      Subsidiary  or its  wholly-owned  subsidiary  performs  under  the  Credit
      Support  Obligation  for any other  reason,  then  Thermo  Electron  shall
      indemnify  and  save  harmless  the  Majority  Owned   Subsidiary  or  its
      wholly-owned subsidiary, as applicable,  from any liability, cost, expense
      or damage (including  reasonable attorneys' fees) suffered by the Majority
      Owned  Subsidiary or its  wholly-owned  subsidiary,  as  applicable,  as a
      result of the Credit Support  Obligation.  Without limiting the foregoing,
      Credit  Support  Obligations  include  the  deposit of funds by a Majority
      Owned  Subsidiary  or  a  wholly-owned  subsidiary  thereof  in  a  credit
      arrangement  with a banking  facility  whereby such funds are available to
      the banking  facility as  collateral  for overdraft  obligations  of other
      Majority Owned  Subsidiaries or their  subsidiaries also  participating in
      the credit  arrangement with such banking facility.  Nothwithstanding  the
      foregoing,  in  order  to  obtain  the  benefits  of  the  indemnification
      obligations of the First Tier Majority Owned Subsidiary set forth above in


                                       4
<PAGE>

      this  Section  3(a),  Thermo  Electron  must have  notified the First Tier
      Majority Owned  Subsidiary  prior to  guaranteeing  the obligations of the
      Second Tier Majority  Owned  Subsidiary.  If after five (5) business days,
      Thermo  Electron  has not  received  from the First  Tier  Majority  Owned
      Subsidiary  a notice of  objection  stating  that the First Tier  Majority
      Owned Subsidiary  objects to Thermo Electron  guaranteeing the obligations
      of the Second Tier Majority  Owned  Subsidiary,  then Thermo  Electron may
      proceed  to issue its  guarantee  of the  Underlying  Obligation  and such
      guarantee  shall  be  subject  to  the  benefits  of  the  indemnification
      obligations of the First Tier Majority Owned Subsidiary set forth above in
      this  Section  3(a).  If  Thermo  Electron  does  receive  such  notice of
      objection,  then Thermo  Electron's  guarantee shall not be subject to the
      indemnification  obligations of the First Tier Majority  Owned  Subsidiary
      set forth above in this Section 3(a).

      (b) For purposes of this Agreement, the term "guarantee" shall include not
      only a formal guarantee of an obligation,  but also any other  arrangement
      where Thermo  Electron is liable for the  obligations  of a Majority Owned
      Subsidiary  or its  wholly-owned  subsidiaries.  Such  other  arrangements
      include  (a)   representations,   warranties  and/or  covenants  or  other
      obligations joined in by Thermo Electron,  whether on a joint or joint and
      several  basis,  for the benefit of the Majority  Owned  Subsidiary or its
      wholly-owned  subsidiaries  and (b)  responsibility  of Thermo Electron by
      operation  of law  for  the  acts  and  omissions  of the  Majority  Owned
      Subsidiary or its wholly-owned subsidiaries,  including controlling person
      liability under securities and other laws.

      (c) Promptly after Thermo Electron receives notice that a beneficiary of a
      Parent  Guarantee  is seeking to enforce  such  Parent  Guarantee,  Thermo
      Electron shall notify the Majority Owned Subsidiary(s)  obligated,  either
      directly  or  indirectly  through  a  wholly-owned  subsidiary,  under the
      relevant  Underlying  Obligation.  Such Majority  Owned  Subsidiary(s)  or
      wholly-owned  subsidiary thereof, as applicable,  shall have the right, at
      its own expense,  to contest the claim of such beneficiary.  If a Majority
      Owned Subsidiary or wholly-owned  subsidiary  thereof,  as applicable,  is
      contesting the claim of such beneficiary, Thermo Electron will not perform
      under the relevant Parent Guarantee unless and until, in Thermo Electron's
      reasonable judgment,  Thermo Electron is obligated under the terms of such
      Parent Guarantee to perform. Subject to the foregoing, any dispute between
      a  Majority  Owned  Subsidiary  or  wholly-owned  subsidiary  thereof,  as
      applicable,  and a beneficiary of a Parent Guarantee shall not affect such
      Majority  Owned  Subsidiary's  obligation  to  promptly  indemnify  Thermo
      Electron  hereunder.   Promptly  after  a  Majority  Owned  Subsidiary  or
      wholly-owned  subsidiary  thereof,  as applicable,  receives notice that a
      beneficiary  of a Credit  Support  Obligation  is seeking to enforce  such
      Credit  Support  Obligation,  the Majority Owned  Subsidiary  shall notify
      Thermo Electron. Thermo Electron shall have the right, at its own expense,
      to  contest  the  claim of such  beneficiary.  If Thermo  Electron  or the
      subsidiary  of  Thermo   Electron  on  whose  behalf  the  Credit  Support
      Obligation  is given is  contesting  the  claim of such  beneficiary,  the
      Majority  Owned  Subsidiary  or  wholly-owned   subsidiary   thereof,   as
      applicable,  will not perform under the relevant Credit Support Obligation
      unless and until, in the Majority Owned Subsidiary's  reasonable judgment,
      the Majority  Owned  Subsidiary or  wholly-owned  subsidiary  thereof,  as
      applicable, is obligated under the terms of such Credit Support Obligation
      to perform.  Subject to the foregoing, any dispute between Thermo Electron
      or the  subsidiary of Thermo  Electron on whose behalf the Credit  Support
      Obligation  was  given,  on the one hand,  and a  beneficiary  of a Credit
      Support  Obligation,  on the  other,  shall not affect  Thermo  Electron's
      obligation  to promptly  indemnify  the Majority  Owned  Subsidiary or its
      wholly-owned subsidiary, as applicable, hereunder.

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<PAGE>

      (d) If Thermo  Electron  makes a loan or provides  other  credit  ("Credit
      Extension")  to a Second Tier Majority  Owned  Subsidiary,  the First Tier
      Majority  Owned  Subsidiary  that owns the  majority  of the stock of such
      Second Tier Majority Owned  Subsidiary  hereby  guarantees the Second Tier
      Majority Owned  Subsidiary's  obligations to Thermo  Electron  thereunder.
      Such  guaranty  shall be  enforced  only  after  Thermo  Electron,  in its
      reasonable  judgment,  determines  that the  Second  Tier  Majority  Owned
      Subsidiary  is unable to fully  perform its  obligations  under the Credit
      Extension.  If Thermo Electron provides Credit Extension to a wholly-owned
      subsidiary of a Second Tier  Majority  Owned  Subsidiary,  the Second Tier
      Majority Owned Subsidiary hereby  guarantees it wholly-owned  subsidiary's
      obligations  to Thermo  Electron  thereunder  and the First Tier  Majority
      Owned  Subsidiary  that owns the majority of the stock of such Second Tier
      Majority Owned Subsidiary hereby guarantees the Second Tier Majority Owned
      Subsidiary's  obligations to Thermo Electron  hereunder.  Such guaranty by
      the First Tier  Majority  Owned  Subsidiary  shall be enforced  only after
      Thermo Electron,  in its reasonable  judgment,  determines that the Second
      Tier  Majority  Owned  Subsidiary  is unable to fully perform its guaranty
      obligation hereunder. Notwithstanding the foregoing, in order for a Credit
      Extension  to be  deemed  guaranteed  by the  First  Tier  Majority  Owned
      Subsidiary as set forth above in this Section 3(d),  Thermo  Electron must
      have notified the First Tier Majority Owned  Subsidiary prior to providing
      the Credit  Extension to the Second Tier  Majority  Owned  Subsidiary.  If
      after five (5) business  days,  Thermo  Electron has not received from the
      First Tier Majority  Owned  Subsidiary a notice of objection  stating that
      the First  Tier  Majority  Owned  Subsidiary  objects  to Thermo  Electron
      providing a Credit Extension to the Second Tier Majority Owned Subsidiary,
      then  Thermo  Electron  may proceed to issue the Credit  Extension  to the
      Second Tier Majority  Owned  Subsidiary  and the First Tier Majority Owned
      Subsidiary shall be deemed to have guaranteed such Credit Extension as set
      forth above in this Section  3(d).  If Thermo  Electron  does receive such
      notice of objection,  then Thermo Electron's Credit Extension shall not be
      deemed guaranteed by the First Tier Majority Owned Subsidiary as set forth
      in this Section 3(d).

      (e) All  payments  required to be made under this  Section 3 by a Majority
      Owned Subsidiary or its wholly-owned subsidiaries, as applicable, shall be
      made within two days after  receipt of notice from  Thermo  Electron.  All
      payments required to be made under this Section 3 by Thermo Electron shall
      be made within two days after  receipt of notice from the  Majority  Owned
      Subsidiary.

      4. Waivers. No delay or omission on the part of either party in exercising
any right  hereunder  shall  operate  as a waiver of such  right or of any other
right of the party, nor shall any delay,  omission or waiver on any one occasion
be  deemed a bar to or  waiver  of the  same or any  other  right on any  future
occasion. The Subsidiary hereby waives demand, notice of prepayment, protest and
all other  demands  and notices in  connection  with the  delivery,  acceptance,
performance,  default or enforcement of the Subsidiary's  obligations hereunder.
The  Subsidiary  hereby  assents to any indulgence and any extension of time for
payment of any indebtedness hereunder granted or permitted by the party.

                                       6
<PAGE>

      5.  Governing  Law. This  Agreement  shall be governed by and construed in
accordance  with the laws of the  Commonwealth  of  Massachusetts  applicable to
contracts made and performed  therein without giving effect to any choice of law
provision or rule that would cause the  application of laws of any  jurisdiction
other than the Commonwealth of Massachusetts.

      6.  Severability.  Each provision and agreement herein shall be treated as
separate and independent  from any other provision or agreement herein and shall
be enforceable  notwithstanding the unenforceability of any such other provision
or agreement.

      7. Non-assignability. The rights and obligations of the parties under this
Agreement  shall not be  assigned  by either  party  without  the prior  written
consent of the other party.  Subject to the foregoing,  this Agreement  shall be
binding upon and shall inure to the benefit of the parties and their  respective
successors and assigns.

      8. Other  Agreements.  The parties  agree that,  effective  as of the date
hereof,  each of the  Master  Repurchase  Agreement,  as amended  and  restated,
between  the   Subsidiary   and  Thermo   Electron  and  the  Master   Guarantee
Reimbursement  and  Loan  Agreement,  as  amended  and  restated,   between  the
Subsidiary and Thermo Electron,  is hereby terminated and is of no further force
and effect.


                                       7
<PAGE>





      IN WITNESS WHEREOF,  the parties have caused this Agreement to be executed
by their duly authorized officers as of the date first above written.


                                   THERMO ELECTRON CORPORATION


                                   By:    /s/ Theo Melas-Kyriazi
                                        ----------------------------------
                                          Theo Melas-Kyriazi

                                   Title: Vice President & Chief Financial
                                          Officer


                                   TREX MEDICAL CORPORATION


                                   By:    /s/ William Webb
                                        ----------------------------------
                                          William Webb
                                   Title: President and Chief Executive
                                          Officer








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