Exhibit 3.231

Delaware	PAGE 1
The First State

     I, JEFFREY W. BULLOCK, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY CERTIFY THE ATTACHED ARE TRUE AND CORRECT COPIES OF ALL DOCUMENTS ON FILE OF “OPELOUSAS IMAGING CENTER PARTNER, LLC” AS RECEIVED AND FILED IN THIS OFFICE.

     THE FOLLOWING DOCUMENTS HAVE BEEN CERTIFIED:

     CERTIFICATE OF FORMATION, FILED THE TWENTY-THIRD DAY OF MAY, A.D. 2005, AT 12:23 O’CLOCK P.M.

     AND I DO HEREBY FURTHER CERTIFY THAT THE AFORESAID CERTIFICATES ARE THE ONLY CERTIFICATES ON RECORD OF THE AFORESAID LIMITED LIABILITY COMPANY, “OPELOUSAS IMAGING CENTER PARTNER, LLC”.

3974175   8100H
110293691

You may verify this certificate online
at corp. Delaware. gov/authver.shtml /s/ Jeffrey W. Bullock   Jeffrey W. Bullock, Secretary of State

AUTHENTICATION: 8620751

DATE: 03-14-11

Certificate of Formation
Of
Opelousas Imaging Center Partner, LLC

     The undersigned, an authorized natural person, for the purpose of forming a limited liability company, under the provisions and subject to the requirements of the State of Delaware, particularly Chapter 18, Title 6 of the Delaware Code and the acts amendatory thereof and supplemental thereto, and known, identified, and referred to as the Delaware Limited Liability Company Act (the “Act”), hereby certifies that:

     FIRST: The name of the limited liability company is Opelousas Imaging Center Partner, LLC (the “Company”).

     SECOND: The address of the registered office and the name and address of the registered agent of the Company required to be maintained by Section 18-104 of the Act is The Corporation Trust Company, Corporation Trust Center, 1209 Orange Street, Washington, Delaware 19801.

     IN WITNESS WHEREOF, the undersigned has executed this Certificate of Formation as of May 20, 2005.

By:	/s/ Mary Kim E. Shipp
	Mary Kim E. Shipp
	Authorized Person

State of Delaware

Secretary of State

Division of Corporations

Delivered 12:59 PM 05/23/2005

FILED 12:23 PM 05/23/2005

SRV 050422664 — 3974175 FILE