Exhibit 10.56

SECOND AMENDMENT TO
FIRST AMENDED AND RESTATED CREDIT AGREEMENT

                THIS SECOND AMENDMENT TO FIRST AMENDED AND RESTATED CREDIT
AGREEMENT (this “Amendment”) is made and dated as of the 21st day of December,
2001 by and among the Lenders currently party to the Credit Agreement referred
to below, BANK ONE, NA, as administrative agent for the Lenders (in such
capacity, the “Administrative Agent”), THE BANK OF NOVA SCOTIA, as documentation
agent (in such capacity, the “Documentation Agent”), SYNCOR INTERNATIONAL
CORPORATION, a Delaware corporation (the “Parent”), and SYNCOR MANAGEMENT
CORPORATION, a Delaware corporation (the “Borrower”). 

RECITALS

                A.            Pursuant to that certain First Amended and
Restated Credit Agreement dated as of May 10, 2001, by and among the
Administrative Agent, the Documentation Agent, the Lenders, the Parent and the
Borrower (as amended, extended and replaced from time to time, the “Credit
Agreement”), the Lenders agreed to extend credit to the Borrower on the terms
and subject to the conditions set forth therein.  All capitalized terms not
otherwise defined herein are used with the meanings given such terms in the
Credit Agreement.

                B.            The parties to the Credit Agreement have agreed to
amend the same in certain respects and desire to set forth the terms and
conditions of such amendment pursuant hereto.

                NOW, THEREFORE, in consideration of the foregoing Recitals and
for other valuable consideration, the receipt and adequacy of which are hereby
acknowledged, the parties hereto hereby agree as follows:

AGREEMENT

                1.             Limited Recourse Sales of Assets.  To reflect
certain agreements of the parties hereto with respect to securitization
transactions which may be entered into from time to time by the Parent and the
Borrower, effective as of the Second Amendment Effective Date (as defined in
Paragraph 4 below):

                                (a)           Subsection (iii) of Section 6.13
of the Credit Agreement is hereby amended to read in its entirety as follows:

          

                           “(iii)  Any transfer of an interest in accounts or
notes receivable on a limited recourse basis, provided that such transfer
qualifies as a sale under Agreement Accounting Principles and, notwithstanding
that such transaction may not qualify as such a sale, the Initial Permitted
Accounts Receivable Financing Facility; provided, however, that the aggregate
dollar amount owing by the obligors under the assets which are the subject of
such sales or secure the Initial Permitted Accounts Receivable Financing
Facility does not exceed at any time $100,000,000.”

                                (b)           A new subsection (viii) is hereby
added in correct numerical order to Section 6.15 of the Credit Agreement to read
in its entirety as follows:

         

                          “(viii)  Liens granted in connection with transfers of
interests in accounts or notes receivable permitted pursuant to Section
6.13(iii) of this Agreement, including, without limitation, pursuant to the
Initial Permitted Accounts Receivable Financing Facility; provided, however,
that:  (1) such Liens secure only the obligations of the Parent and its
Subsidiaries, as applicable, arising under such transactions, (2) such
obligations remain non-recourse to the Parent and its Subsidiaries, as
applicable, except to the extent of such Person’s interest in the assets
transferred, the proceeds thereof and rights associated therewith arising in
connection with such transactions (the “Securitization Assets”) and with respect
to customary indemnification provisions provided in connection with such
transactions, and (3) such Liens attach only to the Securitization Assets.”

                                (c)           The definition of “Indebtedness”
set forth in Article I of the Credit Agreement is hereby amended to read in its
entirety as follows:

            

                         “’Indebtedness’ of a Person means, without duplication,
such Person's (i) obligations for borrowed money, (ii) obligations representing
the deferred purchase price of Property or services (other than accounts payable
arising in the ordinary course of such Person's business payable on terms
customary in the trade), (iii) obligations, whether or not assumed, secured by
Liens or payable out of the proceeds or production from Property now or
hereafter owned or acquired by such Person, (iv) obligations which are evidenced
by notes, acceptances, or other instruments, (v) Capitalized Lease Obligations,
(vi) Contingent Obligations, and (vii) to the extent not otherwise included in
subsections (i) through (vi) hereof, obligations arising under transactions
permitted pursuant to Section 6.13(iii).

                                (d)           A new definition of “Initial
Permitted Accounts Receivable Financing Facility” is hereby added to Article I
of the Credit Agreement in correct alphabetical order to read in its entirety as
follows:

           

                       "’Initial Permitted Accounts Receivable Financing
Facility’ means that certain accounts receivable financing facility which will
be consummated in or around January 2002 evidenced by:  (i) that certain
Receivables Financing Agreement among Syncor Financing Corporation, as seller,
the Borrower, as servicer, Jupiter Securitization Corporation and the other
financial institutions party thereto, as purchasers, and Bank One, as agent,
(ii) that certain Receivables Sale Agreement between the Borrower, as selling
subsidiary, and Syncor Financing Corporation, as buyer, and (c) that certain
Receivables Sale Agreement between the Parent, as originator, and the Borrower,
as buyer, as each such agreement may be amended, restated, supplemented or
otherwise modified from time to time.”

                2.             Reaffirmation of Loan Documents.  The Parent and
Borrower hereby affirm and agree that except to the extent expressly provided
herein, the Credit Agreement, the Notes and the other Loan Documents remain in
full force and effect.

                3.             Reaffirmation of Guaranties.  By acknowledging
and agreeing to this Amendment as provided below, each of the Guarantors affirms
and agrees that:  (a) the execution and delivery by the Borrower and the Parent
and the performance of their obligations under this Amendment shall not in any
manner or to any extent affect any of the obligations of the Guarantors or the
rights of the Lenders and the Administrative Agent under the Guaranties or any
other document, instrument or agreement made or given by the Guarantors in
connection therewith, (b) the term “Obligations” as used in the Guaranties
includes, without limitation, the Obligations under the Credit Agreement as
amended hereby, and (c) the Guaranties remain in full force and effect.

                4.             Second Amendment Effective Date.  This Amendment
shall be effective as of the date (the “Second Amendment Effective Date”) the
Administrative Agent shall have received each of the following:

                                (a)           A copy of this Amendment duly
executed by the Borrower, the Parent and Lenders constituting not less than the
Required Lenders under the Credit Agreement; and

                                (b)           Such other documents, instruments,
agreements, corporate authorizations and opinions of legal counsel as the
Administrative Agent or the Lenders may reasonably request.

                5.             Representations and Warranties.  The Borrower and
the Parent hereby represent and warrant to the Administrative Agent and the
Lenders that as of the date hereof and at and as of the Second Amendment
Effective Date and both before and after giving effect hereto:

                                (a)           Each of the Borrower and the
Parent has the corporate power and authority and the legal right to execute,
deliver and perform the Amendment and has taken all necessary corporate action
to authorize such execution, delivery and performance.

                                (b)           The Amendment has been duly
executed and delivered on behalf of such Person and constitutes the legal, valid
and binding obligation of such Person, enforceable against such Person in
accordance with its terms, subject to the effect of applicable bankruptcy,
insolvency, reorganization, moratorium and other similar laws affecting the
rights of creditors generally and the effect of equitable principles whether
applied in an action at law or a suit in equity.

                                (c)           The representations and warranties
of the Borrower and the Parent contained in the Credit Agreement as amended
hereby are accurate and complete in all material respects.

                                (d)           There has not occurred a Default
or Unmatured Default. 

                6.             No Other Amendment.  Except as expressly amended
hereby, the Loan Documents shall remain in full force and effect as written and
amended to date.

                7.             Counterparts.  This Amendment may be executed in
any number of counterparts, each of which when so executed shall be deemed to be
an original and all of which when taken together shall constitute one and the
same agreement.

[Signature pages following]

                IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed as of the day and year first above written. 

                                                                SYNCOR
MANAGEMENT CORPORATION, as the Borrower

                                                                By: /s/William
P. Forster        
                                                                Name: William P.
Forster
                                                                Title: Vice
President

                                                                SYNCOR
INTERNATIONAL CORPORATION, as the Parent

                                                                By: /s/William
P. Forster         
                                                                Name: William P.
Forster
                                                                Title: Chief
Financial Officer

                                                                BANK ONE, NA, as
Administrative Agent and as a Lender

                                                                By: /s/Joseph R.
Perdenza        
                                                                Name: Joseph R.
Perdenza
                                                                Title: Associate
Director

                                                                THE BANK OF NOVA
SCOTIA, as Documentation Agent and as a Lender

                                                                By:/s/R.P.
Reynolds                 
                                                                Name: R.P.
Reynolds
                                                                Title: Director

                                                                FLEET NATIONAL
BANK, as a Lender

                                                                By:
                                             
                                                                Name:
                                        
                                                                Title:
                                          

                                                                MELLON BANK,
N.A., as a Lender

                                                                By:
                                             
                                                                Name:
                                        
                                                                Title:
                                          

                                                                THE NORTHERN
TRUST COMPANY, as a Lender

                                                                By: /s/Steven W.
Ryan               
                                                                Name: Steven W.
Ryan
                                                                Title: Vice
President

                                                                UNITED
CALIFORNIA BANK (formerly Sanwa Bank California), as a Lender

                                                                By:
                                               
                                                                Name:
                                          
                                                                Title:
                                            

                                                                UNION BANK OF
CALIFORNIA, N.A., as a Lender

                                                                By: /s/P M
Roesner                       
                                                                Name: Philip M.
Roesner
                                                                Title: Vice
President

                                                                KEY CORPORATE
CAPITAL INC., as a Lender

                                                                By:
                                                  
                                                                Name:
                                             
                                                                Title:
                                               

Acknowledged and agreed to
as of the __ day of December, 2001:

COMPREHENSIVE MEDICAL IMAGING, INC.,
as a Guarantor

By: /s/David Ward                       
Name: David Ward
Title: President

SYNCOR OVERSEAS LTD.,
as a Guarantor

By: /s/William P. Forster          
Name: William P. Forster
Title: Chief Financial Officer

SYNCOR INTERNATIONAL CORPORATION,
as a Guarantor

By: /s/William P. Forster          
Name: William P. Forster
Title: Chief Financial Officer