Exhibit
4.1


ALLIANCE
IMAGING, INC.


FIFTH
AMENDMENT


TO CREDIT AGREEMENT


This FIFTH AMENDMENT TO CREDIT AGREEMENT (this “Amendment”) is dated as of April      ,
2007 and entered into by and among Alliance Imaging, Inc., a Delaware
corporation (“Company”), the financial
institutions listed on the signature pages hereof (“Lenders”),
Deutsche Bank Trust Company Americas, as administrative agent for Lenders (“Administrative Agent”),
Citigroup North America, Inc. as Syndication Agent (“Syndication
Agent”), Lehman Commercial Paper Inc. and Merrill Lynch & Co.,
Merrill Lynch, Pierce, Fenner & Smith Incorporated as Co-Documentation
Agents (each, a “Co-Documentation Agent” and
collectively, “Documentation Agent”),  Deutsche Bank Trust Company Americas, as collateral agent (“Collateral Agent”)
and, for purposes of Section 4 hereof, the Credit Support Parties (as
defined in Section 4 hereof) listed on the signature pages hereof, and is
made with reference to that certain Credit Agreement, dated as of November 2,
1999, as amended by that certain First Amendment dated as of May 11, 2000,
that certain Second Amendment dated as of June 10, 2002, that certain Third
Amendment dated as of December 29, 2004 and that certain Fourth Amendment dated
as of December 19, 2005 (as so amended, the “Credit
Agreement”), by and among Company, Lenders, Administrative Agent,
Syndication Agent and Documentation Agent. 
Capitalized terms used herein without definition shall have the same
meanings herein as set forth in the Credit Agreement.


RECITALS


WHEREAS,
Company and Lenders desire to amend the Credit Agreement to permit a sale by
KKR and/or certain of its Affiliates of all or substantially all of their
shares of the Company (the “Sale”) to
Oaktree Capital Management LLC and MTS Health Investors LLC (the “New Investors”) and/or certain of their Affiliates.


Section 1.              AMENDMENTS
TO THE CREDIT AGREEMENT


1.1          Amendments
to Section 1:  Provisions Relating
to Defined Terms.


A.      Subsection 1.1
of the Credit Agreement is hereby amended by deleting the definition of “Change
of Control” in its entirety and by substituting therefor the following:


“Change of
Control” means, and shall be deemed to have occurred, if: (i)(a) the
New Investors, their Affiliates and the Management Investors shall at any time
not own, in the aggregate, directly or indirectly, beneficially and of record,
at least 35% of the outstanding Voting Stock of Company (other than as the
result of one or more widely distributed offerings of common stock of Company,
in each case whether by Company or by the New Investors, their Affiliates or
the Management Investors) and/or (b) any person, entity



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or “group” (within the
meaning of Section 13(d) or 14(d) of the Exchange Act) shall at any time have
acquired direct or indirect beneficial ownership of a percentage of the
outstanding Voting Stock of Company that exceeds the percentage of such Voting
Stock then beneficially owned, in the aggregate, by the New Investors, their
Affiliates and the Management Investors, unless, in the case of either
clause (a) or (b) above, the New Investors, their Affiliates and the Management
Investors shall, at the relevant time, have the collective right or ability,
either by contract or pursuant to a written proxy or other written evidence of
voting power, to elect or designate for election a majority of the Board of
Directors of Company; and/or (ii) at any time Continuing Directors shall not
constitute a majority of the Board of Directors of Company.  For purposes of this definition, “Continuing Director” means, as of any date of determination,
an individual (A) who is a member of the Board of Directors of Company on the
Closing Date, (B) who, as of such date of determination, has been a member of
such Board of Directors for at least the 12 preceding months (or, if such date
of determination occurs during the period comprising the first 12 months after
the Closing Date, since the Closing Date), or (C) who has been nominated to be
a member of such Board of Directors, directly or indirectly, by the New
Investors or their Affiliates or Persons nominated by the New Investors or
their Affiliates or who has been nominated to be a member of such Board of
Directors by a majority of the other Continuing Directors then in office.”


B.      Subsection
1.1 of the Credit Agreement is hereby amended by adding the following
definition in appropriate alphabetical order:


“New Investors” means Oaktree Capital Management LLC and MTS
Health Investors LLC.


1.2          Amendments
to Section 6:  Affirmative Covenants.


A.      Subsection 6.8
of the Credit Agreement is hereby amended by deleting it in its entirety and by
substituting therefor the following:


“6.8.  Transactions with
Affiliates


Company shall, and
shall cause each of its Subsidiaries to, conduct all transactions with any of
its Affiliates (other than Company or any of its Subsidiaries) upon terms that
are substantially as favorable to Company or such Subsidiary as it would obtain
in a comparable arm’s-length transaction with a Person not an Affiliate of
Company or such Subsidiary; provided that the foregoing restrictions
shall not apply to (a) reasonable and customary fees paid to members of the
Board of Directors of Company and its Subsidiaries, and (b) transactions
otherwise expressly permitted hereunder between Company or any of its
Subsidiaries and any such Affiliate.”



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Section 2.              CONDITIONS
TO EFFECTIVENESS


This Amendment
shall become effective only upon the satisfaction of all of the following
conditions precedent (the date of satisfaction of such conditions being
referred to herein as the “Fifth Amendment Effective
Date”) set forth in this Section 2:


A.      Loan Documents. 
On or before the Fifth Amendment Effective Date, Company shall, and
shall cause each other Credit Support Party to, deliver to Lenders (or to
Administrative Agent for Lenders with sufficient originally executed copies,
where appropriate, for each Lender and its counsel), with respect to Company or
such other Credit Support Party, as the case may be, the following:


1.             The
signature and incumbency certificate of Company and each other Credit Support
Party;


2.             Copies
of this Amendment executed by Company and such Credit Support Parties; and


3.             An
Officer’s Certificate certifying that the Sale shall have been consummated.


B.      Lender
Documents.  Administrative Agent
shall have received from the Requisite Lenders, Administrative Agent and
Issuing Lender a counterpart of this Amendment signed on behalf of such party.


C.      Completion of Proceedings. 
On or before the Fifth Amendment Effective Date, all corporate and other
proceedings taken or to be taken in connection with the transactions
contemplated hereby and all documents incidental thereto not previously found
acceptable by Administrative Agent, acting on behalf of Lenders, and its
counsel shall be satisfactory in form and substance to Administrative Agent and
such counsel, and Administrative Agent and such counsel shall have received all
such counterpart originals or certified copies of such documents as
Administrative Agent may reasonably request.


Section 3.              COMPANY’S
REPRESENTATIONS AND WARRANTIES


In order to induce
Lenders and Administrative Agent to enter into this Amendment and to amend the
Credit Agreement in the manner provided herein, Company represents and warrants
to Administrative Agent and each Lender that the following statements are true,
correct and complete:


A.      Corporate
Power and Authority.  Each Loan Party
has all requisite corporate, limited partnership or limited liability company
power and authority to enter into this Amendment and to carry out the
transactions contemplated by, and perform its obligations under, the Credit
Agreement as amended by this Amendment (the “Amended
Agreement”).


B.      Authorization
of Agreements.  The execution and
delivery of this Amendment and the performance of the Amended Agreement have
been duly authorized by all necessary corporate, limited partnership or limited
liability company action on the part of each Loan Party, as the case may be.



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C.      No
Conflict.  The execution and delivery
by each Loan Party of this Amendment do not and will not (i) violate any
provision of any law or any governmental rule or regulation applicable to such
Loan Party, the Certificate or Articles of Incorporation or other
organizational documents or Bylaws of such Loan Party or any order, judgment or
decree of any court or other agency of government binding on such Loan Party,
(ii) conflict with, result in a breach of or constitute (with due notice or
lapse of time or both) a default under any Contractual Obligation of such Loan
Party, (iii) result in or require the creation or imposition of any Lien
upon any of the properties or assets of such Loan Party (other than Liens
created under any of the Loan Documents in favor of Collateral Agent on behalf
of Lenders), or (iv) require any approval of stockholders or any approval
or consent of any Person under any Contractual Obligation of such Loan Party,
except for such approvals or consents which have been obtained on or before the
Fifth Amendment Effective Date and disclosed in writing to Lenders.


D.      Governmental
Consents.  The execution and delivery
by each Loan Party of this Amendment, the performance by such Loan Party of the
Amended Agreement by the Company do not and will not require any registration
with, consent or approval of, or notice to, or other action to, with or by, any
federal, state or other governmental authority or regulatory body.


E.       Binding
Obligation.  This Amendment and the
Amended Agreement have been duly executed and delivered by each Loan Party
party thereto and are the legally valid and binding obligations of such Loan
Party, enforceable against such Loan Party in accordance with their respective
terms, except as may be limited by bankruptcy, insolvency, reorganization,
moratorium or similar laws relating to or limiting creditors’ rights generally
or by equitable principles relating to enforceability.


F.       Incorporation
of Representations and Warranties From Credit Agreement.  The representations and warranties contained
in Section 5 of the Amended Agreement are and will be true, correct and
complete in all material respects on and as of the Fifth Amendment Effective
Date to the same extent as though made on and as of that date, except to the
extent such representations and warranties specifically relate to an earlier
date, in which case they were true, correct and complete in all material
respects on and as of such earlier date.


G.      Absence
of Default.  No event has occurred
and is continuing or will result from the consummation of the transactions
contemplated by this Amendment that constitutes or would constitute an Event of
Default or a Potential Event of Default after giving effect to this Amendment.


Section 4.              ACKNOWLEDGEMENT
AND CONSENT


Company is a party
to the Collateral Account Agreement, pursuant to which Company has created
Liens in favor of Administrative Agent on a certain deposit account of Company
upon the occurrence of an event stated therein; the Amended and Restated Pledge
Agreement, pursuant to which Company has affirmed, among other things, the
pledge to Collateral Agent for the benefit of Secured Parties of certain
capital stock and intercompany indebtedness owned by it to secure the Secured
Obligations; and the Security Agreement, pursuant to which Company has granted
Liens in favor of Collateral Agent on certain



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Collateral to secure the
Secured Obligations, in each case as amended through the Fifth Amendment
Effective Date.


Each Subsidiary Guarantor
is a party to the Subsidiary Guaranty pursuant to which such Subsidiary
Guarantor has guarantied the Obligations; the Amended and Restated Pledge
Agreement pursuant to which such Subsidiary Guarantor has affirmed, among other
things, the pledge to Collateral Agent for the benefit of Secured Parties of
certain capital stock and intercompany indebtedness owned by it to secure the
obligations of such Subsidiary Guarantor under the Subsidiary Guaranty and
Additional Debt (as defined in the Security Agreement); and the Security
Agreement pursuant to which such Subsidiary Guarantor will grant Liens in favor
of Collateral Agent on certain Collateral to secure the obligations of such
Subsidiary Guarantor under the Subsidiary Guaranty and Additional Debt (as
defined in the Security Agreement), in each case as amended through the Fifth
Amendment Effective Date.  Company and
the Subsidiary Guarantors are collectively referred to herein as the “Credit Support Parties”, and the Collateral Account
Agreement, the Amended and Restated Pledge Agreement and the Security Agreement
are collectively referred to herein as the “Credit
Support Documents.”


Each Credit Support Party
hereby acknowledges that it has reviewed the terms and provisions of the Credit
Agreement and this Amendment and consents to the amendment of the Credit
Agreement effected pursuant to this Amendment. 
Each Credit Support Party hereby confirms that each Credit Support
Document to which it is a party or otherwise bound and all Collateral
encumbered thereby will continue to guaranty or secure, as the case may be, to
the fullest extent possible the payment and performance of all Secured
Obligations, as the case may be (in each case as such terms are defined in the
applicable Credit Support Document), including without limitation the payment
and performance of all such Secured Obligations, as the case may be, in respect
of the Obligations of Company now or hereafter existing under or in respect of
the Amended Agreement and the Notes defined therein.  Each Credit Support Party acknowledges and
agrees that any of the Credit Support Documents to which it is a party or otherwise
bound shall continue in full force and effect and that all of its obligations
thereunder shall be valid and enforceable and shall not be impaired or limited
by the execution or effectiveness of this Amendment.  Each Credit Support Party represents and
warrants that all representations and warranties contained in the Amended
Agreement and the Credit Support Documents to which it is a party or otherwise
bound are true, correct and complete in all material respects on and as of the
date hereof to the same extent as though made on and as of that date, except to
the extent such representations and warranties specifically relate to an
earlier date, in which case they were true, correct and complete in all
material respects on and as of such earlier date.


Each Credit Support Party
(other than Company) acknowledges and agrees that (i) notwithstanding the
conditions to effectiveness set forth in this Amendment, such Credit Support
Party is not required by the terms of the Credit Agreement or any other Loan
Document to consent to the amendments to the Credit Agreement effected pursuant
to this Amendment and (ii) nothing in the Credit Agreement, this Amendment
or any other Loan Document shall be deemed to require the consent of such
Credit Support Party to any future amendments to the Credit Agreement.



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Section 5.              MISCELLANEOUS


A.      Reference
to and Effect on the Credit Agreement and the Other Loan Documents.


(i)            On
and after the Fifth Amendment Effective Date, each reference in the Credit
Agreement to “this Agreement”, “hereunder”, “hereof”, “herein” or words of like
import referring to the Credit Agreement, and each reference in the other Loan
Documents to the “Credit Agreement”, “thereunder”, “thereof” or words of like
import referring to the Credit Agreement shall mean and be a reference to the
Amended Agreement.


(ii)           Except
as specifically amended by this Amendment, the Credit Agreement and the other
Loan Documents shall remain in full force and effect and are hereby ratified
and confirmed.


(iii)          The execution, delivery and performance of
this Amendment shall not, except as expressly provided herein, constitute a
waiver of any provision of, or operate as a waiver of any right, power or
remedy of Administrative Agent or any Lender under, the Credit Agreement or any
of the other Loan Documents.


B.      Fees
and Expenses.  Payment of all costs,
fees and expenses as described in subsection 10.2 of the Credit Agreement
incurred by Administrative Agent or its counsel with respect to this Amendment
and the documents and transactions contemplated hereby shall be paid by Company
as agreed upon between Company and Agents.


C.      Headings.  Section and subsection headings in
this Amendment are included herein for convenience of reference only and shall
not constitute a part of this Amendment for any other purpose or be given any
substantive effect.


D.      Applicable
Law.  THIS AMENDMENT AND THE RIGHTS AND
OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE GOVERNED BY, AND SHALL BE
CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF
NEW YORK (INCLUDING WITHOUT LIMITATION SECTION 5-1401 OF THE GENERAL
OBLIGATIONS LAW OF THE STATE OF NEW YORK), WITHOUT REGARD TO CONFLICTS OF LAWS
PRINCIPLES.


E.       Counterparts.  This Amendment may be executed in any number
of counterparts and by different parties hereto in separate counterparts, each
of which when so executed and delivered shall be deemed an original, but all
such counterparts together shall constitute but one and the same instrument;
signature pages may be detached from multiple separate counterparts and
attached to a single counterpart so that all signature pages are physically
attached to the same document.



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IN WITNESS WHEREOF,
the parties hereto have caused this Amendment to be duly executed and delivered
by their respective officers thereunto duly authorized as of the date first
written above.


	
  

  	
  ALLIANCE IMAGING, INC.

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Howard K. Aihara

  	
   

  
	
   

  	
  Name:

  	
  Howard K. Aihara

  	
   

  
	
   

  	
  Title:

  	
  Executive Vice President and

  Chief Financial Officer

  	
   

  




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  ALLIANCE IMAGING CENTERS, INC.

  
	
   

  	
  ALLIANCE IMAGING MANAGEMENT, INC.

  
	
   

  	
  ROYAL MEDICAL HEALTH SERVICES, INC.

  
	
   

  	
  ALLIANCE IMAGING OF OHIO, INC.

  
	
   

  	
  ALLIANCE IMAGING OF MICHIGAN, INC.

  
	
   

  	
  MEDICAL CONSULTANTS IMAGING CO.

  
	
   

  	
  ALLIANCE IMAGING NC, INC. (f/k/a MOBILE TECHNOLOGY
  INC.)

  
	
   

  	
  MEDICAL DIAGNOSTICS, INC.

  
	
   

  	
  WESTERN MASSACHUSETTS MAGNETIC RESONANCE SERVICES,
  INC.

  
	
   

  	
  GREATER BOSTON MRI L.P.

  
	
   

  	
  GREATER SPRINGFIELD MRI L.P.

  
	
   

  	
  CURACARE, INC.

  
	
   

  	
  AMERICAN SHARED-CURACARE

  
	
   

  	
  SMT HEALTH SERVICES INC.

  
	
   

  	
  MID-AMERICAN IMAGING, INC.

  
	
   

  	
  RIA MANAGEMENT SERVICES, INC.

  
	
   

  	
  GREATER BOSTON MRI SERVICES, INC.

  
	
   

  	
  CENTRAL MASSACHUSETTS MRI SERVICES, INC.

  
	
   

  	
  DIMENSIONS MEDICAL GROUP, INC.

  
	
   

  	
  MERITUS PLS, INC.

  
	
   

  	
  QUINCY MRI, L.P.

  
	
   

  	
  THREE RIVERS HOLDING CORP.

  
	
   

  	
  SOUTHEAST ARIZONA, INC.

  
	
   

  	
  ALLIANCE IMAGING FINANCIAL SERVICES, INC.

  
	
   

  	
  ALLIANCE MEDICAL IMAGING SOLUTIONS, LLC

  
	
   

  	
  PET SCANS OF AMERICA CORP.

  
	
   

  	
  NEW ENGLAND MOLECULAR IMAGING, LLC

  
	
   

  	
   

  
	
   

  	
  (for purposes of Section 4 only) as a Credit
  Support Party

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Howard K. Aihara

  	
   

  
	
   

  	
  Name:

  	
  Howard K. Aihara

  	
   

  
	
   

  	
  Title:

  	
  Executive Vice President and

  Chief Financial Officer

  	
   

  
					



 


 



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  DEUTSCHE BANK TRUST COMPANY

  AMERICAS, individually and as Administrative

  Agent, Issuing Lender and Collateral Agent

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Carin Keegan

  	
   

  
	
   

  	
  Name:

  	
  Carin Keegan

  
	
   

  	
  Title:

  	
  Vice President

  



 


 


	
  

  	
  By:

  	
  /s/ Scottye Lindsey

  	
   

  
	
   

  	
  Name:

  	
  Scottye Lindsey

  
	
   

  	
  Title:

  	
  Director

  



 



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  CITIGROUP NORTH AMERICA, INC.,

  individually and as Syndication Agent and

  Lender

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Ryan Davis

  	
   

  
	
   

  	
  Name:

  	
   Ryan Davis

  
	
   

  	
  Title:

  




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  LEHMAN COMMERCIAL PAPER INC.,

  individually and as Co-Documentation Agent

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Craig Malloy

  	
   

  
	
   

  	
  Name:

  	
  Craig Malloy

  	
   

  
	
   

  	
  Title:

  	
  Authorized Signatory

  	
   

  



 


 


	
  

  	
  LEHMAN BROTHERS INC., individually and

  as Lender

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
  /s/ Craig Malloy

  	
   

  
	
   

  	
  Name:

  	
  Craig Malloy

  	
   

  
	
   

  	
  Title:

  	
  Vice President

  	
   

  



 



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  MERRILL LYNCH & CO.,

  
	
   

  	
   

  
	
   

  	
  MERRILL LYNCH, PIERCE, FENNER &

  SMITH INCORPORATED, as Co-

  Documentation Agent

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
   

  	
   

  
	
   

  	
  Name:

  
	
   

  	
  Title:

  



 


 


	
  

  	
  MERRILL LYNCH CAPITAL

  CORPORATION, as Lender

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
  By:

  	
   

  	
   

  
	
   

  	
  Name:

  
	
   

  	
  Title:

  



 



 S-6
 









 


	
  

  	
  By:

  	
   

  	
   

  
	
   

  	
  Name:

  
	
   

  	
  Title:

  



 



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