SUPPLEMENTAL
INDENTURE

     

    Supplemental
Indenture (this “Supplemental Indenture”),
dated as of January 10, 2011 among eRad, Inc. a Pennsylvania corporation (the
“Guaranteeing
Subsidiary”), a subsidiary of RadNet, Inc. (or its permitted successor),
a Delaware corporation (“Parent”), Radnet Management,
Inc., a California corporation (the “Issuer), the other Guarantors
(as defined in the Indenture referred to herein) and U.S. Bank National
Association, as trustee under the Indenture referred to below (the “Trustee”).

     

    WITNESSETH

     

    WHEREAS,
the Issuer has heretofore executed and delivered to the Trustee an indenture
(the “Indenture”),
dated as of April 6, 2010, providing for the issuance of 103⁄8% Senior Notes due
2018 (the “Notes”);

     

    WHEREAS,
the Indenture provides that under certain circumstances the Guaranteeing
Subsidiary shall execute and deliver to the Trustee a supplemental indenture
pursuant to which the Guaranteeing Subsidiary shall unconditionally guarantee
all of the Issuer’s Obligations under the Notes and the Indenture on the terms
and conditions set forth herein (the “Note Guarantee”);
and

     

    WHEREAS,
pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute
and deliver this Supplemental Indenture.

     

    NOW,
THEREFORE, in consideration of the foregoing and for other good and valuable
consideration, the receipt of which is hereby acknowledged, the Guaranteeing
Subsidiary and the Trustee mutually covenant and agree for the equal and ratable
benefit of the Holders of the Notes as follows:

     

    1.           Capitalized
Terms.  Capitalized terms used herein without definition shall
have the meanings assigned to them in the Indenture.

     

    2.           Agreement
to Guarantee.  The Guaranteeing Subsidiary hereby agrees to
provide an unconditional Guarantee on the terms and subject to the conditions
set forth in the Note Guarantee and in the Indenture including but not limited
to Article 10 thereof.

     

    4.           No
Recourse Against Others.  No director, officer, employee,
stockholder, general or limited partner or incorporator of the Issuers or any
Guarantor, as such, shall have any liability for any obligations of the Issuers
or the Guarantors under the Notes, this Indenture, the Note Guarantees or the
note documents or for any claim based on, in respect of, or by reason of, such
obligations or their creation. Each Holder of Notes by accepting a Note waives
and releases all such liability. The waiver and release are part of the
consideration for issuance of the Notes. The waiver may not be effective to
waive liabilities under the federal securities laws.

     

    5.           NEW
YORK LAW TO GOVERN.  THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL
GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE WITHOUT GIVING EFFECT
TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION
OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

     

    6.           Counterparts.  The
parties may sign any number of copies of this Supplemental
Indenture.  Each signed copy shall be an original, but all of them
together represent the same agreement.

     

    7.           Effect
of Headings.  The Section headings herein are for convenience
only and shall not affect the construction hereof.

    


    8.           The
Trustee.  The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guaranteeing Subsidiary and the
Issuer.


    
      
         


      

      
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    IN
WITNESS WHEREOF, the undersigned have executed this Supplemental Indenture as of
the date first set forth above.

    


    
      
        	
                ERAD,
      INC.

              
	 
      	 
      
	
                By:

              	
                  /S/ HOWARD G. BERGER,
      M.D.

              
	
                 Name:

              	
                  Howard
      G. Berger, M.D.

              
	
                 Title:

              	
                  President
      and Chief Financial Officer

              


      

    

    


    
      
        	
                PARENT,
      ISSUER AND OTHER GUARANTORS

              
	 
      	 
      
	
                By:

              	
                  /S/ HOWARD G. BERGER,
      M.D.

              
	
                 Name:

              	
                  Howard
      G. Berger, M.D.

              
	
                 Title:

              	
                  Authorized
      Officer of Parent, Issuer and the

                  other
      Guarantors

              


      

    

    


    [Signature
Page to Supplemental Indenture – eRad, Inc.]

    
      
         


      

      
         


        
          

        

      

      
         


      

    

    


    
      
        	
                U.S.
      BANK NATIONAL ASSOCIATION,

                as
      Trustee

              
	 
      	 
      
	
                By:

              	
                  /S/ GEORGINA
  THOMAS

              
	
                 Name:

              	
                  Georgina
      Thomas

              
	
                 Title:

              	
                  Trust
      Officer

              


      

    

    


    [Signature
Page to Supplemental Indenture – eRad, Inc.]