EXHIBIT 3.21

                                                         
                           ARTICLES OF INCORPORATION
                                      OF
                    MAXUM HEALTH SERVICES OF DALLAS, INC.
                                                                Corporations Section



         I, the undersigned, a natural person of the age of eighteen years or
more acting as the Incorporator under the Texas Business Corporation Act, do
hereby adopt the following Article of Incorporation for the Corporation:

                                  ARTICLE I

         The name of the Corporation is MAXUM HEALTH SERVICES OF DALLAS, INC.

                                  ARTICLE II

         The period of duration of the Corporation is perpetual.

                                 ARTICLE III

         The Corporation is organized for the purpose of transacting any and
all lawful business for which corporations may be organized under the Texas
Business Corporation Act.

                                  ARTICLE IV

         The aggregate number of shares which the Corporation shall have
authority to issue is 1,000 shares of Common Stock of the par value of $.01
each.

                                  ARTICLE V

         No shareholder of the Corporation shall have the right of cumulative
voting at any election of directors or upon any other matter.

                                  ARTICLE VI

         Shareholders of the Corporation shall have no preemptive right to
acquire additional unissued, or treasury shares of the Corporation.

                                 ARTICLE VII

         The following provisions are inserted herein for the purpose of
defining, limiting, and regulating the powers of the Corporation and of the
directors and of the shareholders, provided, however, that said provisions
shall not be deemed exclusive of any rights or liabilities otherwise granted
or imposed by the laws of the State of Texas:


                                   Page - 1



         1.       The liability of the directors of the Corporation is
eliminated to the fullest extent permitted by the provisions of the Texas
Business Corporation Act and by the provisions of the Texas Miscellaneous
Corporation Laws Act, as the same may be amended and supplemented.

         2.       The Corporation shall, to the fullest extent permitted by the
provisions of the Texas Business Corporation Act, as the same may be amended
and supplemented, indemnify any and all persons whom it shall have power to
indemnify under said Article from and against any and all of the expenses,
liabilities, or other matters referred to or covered by said Article.

         3.       With respect to any matter for which the affirmative vote of
the holders of at least a two-thirds portion of the shares entitled to vote is
otherwise required by the Texas Business Corporation Act, the act of the
shareholders on that matter shall be the affirmative vote of the holders of at
least a majority of the shares entitled to vote on the matter, rather than the
affirmative vote otherwise required by the Texas Business Corporation Act.
With respect to any matter for which the affirmative vote of the holders of at
least two-thirds portion of the shares of any class is otherwise required by the
Texas Business Corporation Act, the act of the holders of shares of that class
on that matter shall be the affirmative vote of the holders of at least a
majority of the shares of that class, rather than the affirmative vote of the
holders of shares of that class otherwise required by the Texas Business
Corporation Act.

         4.       Any action required by the Texas Business Corporation Act to
be taken at an annual or special meeting of shareholders, or any action which
may be taken at an annual or special meeting of shareholders, may be taken
without a meeting, without prior notice, and without a vote, if a consent or
consents in writing, setting forth the action so taken, shall be signed by the
holder or holders of shares having not less than the minimum number of votes
that would be necessary to take such action at a meeting at which the holders
of all shares entitled to vote on the action were present and voted.

                                 ARTICLE VIII

         The Corporation will not commence business until it has received from
the issuance of its shares consideration of the value of One Thousand Dollars
($1,000), consisting of money, labor done, or property actually received.

                                  ARTICLE IX

         The address of the registered office of the Corporation is 400 N. St.
Paul, Suite 1025, Dallas, Texas 75201, end the name of its initial registered
agent at such address is The Prentice-Hall Corporation System, Inc.



                                   Page - 2




                                  ARTICLE X


         The business and affairs of the Corporation shall be managed by a
board of directors (the "board of directors") composed of such number
of persons as may be filed by the bylaws of the Corporation. Until changed by
the bylaws, the number of directors constituting the board of directors shall
be three (3). The name and address of each person who shall serve as initial
directors of the Corporation are as follows:



            NAME                                             ADDRESS
            ----                                             -------
                                            
         Glenn P. Cato                          14850 Quorum Drive, Suite 400
                                                Dallas, Texas 75240

         Don O. Hicks                           14850 Quorum Drive, Suite 400
                                                Dallas, Texas 75240

         Joseph F. Denninger                    14850 Quorum Drive, Suite 400
                                                Dallas, Texas 75240



                                  ARTICLE XI

         The initial bylaws of the Corporation shall be adopted by the board
of directors and the power to alter, amend or repeal the bylaws or adopt new
bylaws subject to repeal or change by action of the shareholders, shall be
vested in the board of directors.

                                 ARTICLE XII


         The name and address of the incorporator is Glenn P. Cato, 14850
Quorum Drive, Suite 400, Dallas, Texas 75240.

                                 ARTICLE XIII

         From time to time any of the provisions of these Articles of
Incorporation may be amended, altered, or repealed, and other provisions
authorized by the laws of the State of Texas at the time in force may be added
or applied in the matter and at the time prescribed by said laws and all
contracts and rights at any time conferred upon the shareholders of the
Corporation by these Articles of Incorporation are granted subject to the
provision of this Article.

                                   Page - 3



         IN WITNESS WHEREOF, I have hereunto set my hand this 28th day of
September, 1993.

                                             /s/ GLENN P. CATO
                                             -----------------------------
                                             Glenn P. Cato, Incorporator

                                   Page - 4


                                                               FILED
                                                        In the Office of the
                                                    Secretary of State of Texas

                            ASSUMED NAME CERTIFICATE        OCT 09 1995

                                                       Corporations Section

     1.  The name of the corporation as stated in its articles of
         incorporation is Maxum Health Services of Dallas, Inc.


     2.  The assumed name under which the business or professional service is
         or is to be conducted or rendered is Maxum Diagnostic Center -
         Preston Road.


     3.  The state under the laws of which it was incorporated, organized or
         associated is Texas, and the address of its registered or similar
         office in that jurisdiction is 400 North St. Paul, Suite 1025,
         Dallas, Texas 75201.

     4.  The period, not to exceed 10 years, during which the assumed name
         will be used is October 1, 1995 until September 30, 2004.

     5.  The entity is a business corporation.

     6.  The entity's registered office in Texas, is 400 North St. Paul, Suite
         1025, Dallas, Texas 75201 and the name of its registered agent at
         such address is CSC/Prentice Hall Corporation System. The address of
         the principal office is 14850 Quorum Drive, Suite 400, Dallas, Texas
         75240.

     7.  The county where business or professional services are being or are
         to be conducted or rendered under such assumed name is Dallas County.


                                     /s/ DON G. HICKS
                                     ------------------------------------------
                                     Don G. Hicks, Chief Accounting Officer


         Before me on this 5th day of October, 1995, personally appeared Don
G. Hicks, an Officer of Maxum Health Services of Dallas, Inc. and acknowledged
to me that he he executed the foregoing certificate for the purposes therein
expressed.

==============================
         KIMBERLY BERTRAND
[SEAL] MY COMMISSION EXPIRES
          December 1, 1997
==============================
(Notary Seal)


                                                /s/ KIMBERLY BERTRAND
                                                -------------------------------
                                                Notary Public, State of Texas

                                      1


                                                               FILED
                                                        In the Office of the
                                                    Secretary of State of Texas

                            ASSUMED NAME CERTIFICATE      OCTOBER 09 1995

                                                        Corporations Section

     1.  The name of the corporation as stated in its articles of
         incorporation is Maxum Health Services of Dallas, Inc.


     2.  The assumed name under which the business or professional service is
         or is to be conducted or rendered is Maxum Diagnostic Center -
         Hillcrest.


     3.  The state under the laws of which it was incorporated, organized or
         associated is Texas, and the address of its registered or similar
         office in that jurisdiction is 400 North St. Paul, Suite 1025,
         Dallas, Texas 75201.

     4.  The period, not to exceed 10 years, during which the assumed name
         will be used is October 1, 1995 until September 30, 2004.

     5.  The entity is a business corporation.

     6.  The entity's registered office in Texas, is 400 North St. Paul, Suite
         1025, Dallas, Texas 75201 and the name of its registered agent at
         such address is CSC/Prentice Hall Corporation System. The address of
         the principal office is 14850 Quorum Drive, Suite 400, Dallas, Texas
         75240.

     7.  The county where business or professional services are being or are
         to be conducted or rendered under such assumed name is Dallas County.


                                     /s/ DON G. HICKS
                                     ------------------------------------------
                                     Don G. Hicks, Chief Accounting Officer


         Before me on this 5th day of October, 1995, personally appeared Don
G. Hicks, an Officer of Maxum Health Services of Dallas, Inc. and acknowledged
to me that he he executed the foregoing certificate for the purposes therein
expressed.

=============================
         KIMBERLY BERTRAND
[SEAL] MY COMMISSION EXPIRES
          December 1, 1997
=============================
(Notary Seal)


                                                /s/ KIMBERLY BERTRAND
                                                -------------------------------
                                                Notary Public, State of Texas

                                      1