FOURTH AMENDMENT TO
                       AGREEMENT OF LIMITED PARTNERSHIP OF
              LOUISIANA LITHOTRIPSY INVESTMENT LIMITED PARTNERSHIP


                  THIS AMENDMENT, effective as of the 1st day of April, 1999, is
entered into by and among Lithotripters,  Inc., a North Carolina corporation and
the General Partner of Louisiana Lithotripsy  Investment Limited Partnership,  a
North Carolina limited partnership (the "Partnership"), and the Limited Partners
of the Partnership.

                                R E C I T A L S:
                                 ---------------

                  1. The General Partner and the Limited  Partners,  hereinafter
collectively  referred to as the  "Partners",  entered into that certain Amended
and  Restated  Agreement  of  Limited   Partnership  of  Louisiana   Lithotripsy
Investment Limited Partnership, dated as of October 30, 1989, as amended by that
certain First Amendment to Agreement of Limited  Partnership of the Partnership,
effective as of January 1, 1990, and as amended by that certain Second Amendment
to Agreement of Limited Partnership of the Partnership,  effective as of January
1, 1997, and as amended by that certain Third  Amendment to Agreement of Limited
Partnership of the Partnership,  effective as of July 1, 1998 (the  "Partnership
Agreement").

                  2. The  Partners  desire  to  further  amend  the  Partnership
Agreement to reflect the Partners's adjusted Percentage Interests resulting from
the  Partnership's  Dilution  Offering,  and  the  subsequent  admission  of the
following new Limited Partners to the Partnership; Christopher P. Fontenot, M.D.
(1.000%),  Gordon Sean Healey  (0.500%),  Brad Johnson  (1.000%),  Chuen K. Kwok
(1.000%),  Steven A. Socher  (1.000%),  Lance Templeton  (1.000%) and Kenneth S.
Verheeck (1.000%).

                  NOW,  THEREFORE,  in  consideration  of the  mutual  promises,
covenants,  conditions and agreements herein contained, the parties hereto agree
as follows:

                           Schedule  A-2 is  deleted in its  entirety  and a new
                           Schedule A-3,  attached hereto, is substituted in its
                           place.

                  IN WITNESS WHEREOF, the Partners have hereunto set their hands
and seals effective as of the date first above written.

                                                     GENERAL PARTNER:

                                                     Lithotripters, Inc.


                                                     By:/s/ Joseph Jenkins, M.D.
                                                     ---------------------------
                                                            Joseph Jenkins, M.D.
                                                            President





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                                                     ALL THE LIMITED PARTNERS OF
                                                     THE PARTNERSHIP WHOSE NAMES
                                                     APPEARED ON SCHEDULE A-3

                                                     By:/s/ Joseph Jenkins, M.D.
                                                     ---------------------------
                                                            Joseph Jenkins, M.D.
                                                            Attorney-in-Fact1
--------
     1            Pursuant to a Power of Attorney given by the Limited Partners.



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                                                                    SCHEDULE A-3

                        Schedule of Partnership Interests

              LOUISIANA LITHOTRIPSY INVESTMENT LIMITED PARTNERSHIP

            CONTRIBUTIONS OF CAPITAL TO THE PARTNERSHIP AND INTERESTS

                                 Cash Contribution(1)     Percentage Interest(2)
                                  -----------------        -------------------
General Partner

Lithotripters, Inc.                  $1,000.00                   1.165%
2008 Litho Place, Suite 201
Fayetteville, NC  28304
Limited Partners

Thomas Alderson, M.D.                $2,000.00                   2.281%
234 S. Ryan
Lake Charles, LA  70601
David Autin, M.D.                    $2,500.00                   2.853%
4212 W. Congress
Lafayette, LA  70503
Bruce Bass, M.D.                     $1,000.00                   1.136%
234 S. Ryan
Lake Charles, LA  70601
Al Beachum, M.D.                     $3,500.00                   3.989%
913 S. College Road
Lafayette, LA  70503
Maged R. Botros, M.D.                $2,500.00                   2.853%
Mary Dickerson Hospital
Jasper, TX  75951
J. Bourdreau, M.D.                   $1,000.00                   1.136%
4212 W. Congress
Lafayette, LA  70503
Charles Bowie, M.D.                  $1,000.00                   0.757%
4400 Moosa Blvd.
Eunice, LA  70535
Edward Breaux, M.D.                  $2,000.00                   2.281%
118 Hospital Drive
Lafayette, LA  70503




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                          Cash Contribution(1)            Percentage Interest(2)
Joseph Busby, M.D.              $2,500.00                        2.853%
2104-G Loop Road
Winnsboro, LA  71295
J. Michael Cage, M.D.           $2,500.00                        1.902%
711 St. John Street
Monroe, LA  71201
Gerardo Chica, M.D.             $2,000.00                        2.281%
1323 S. 27th, Suite 300
Nederland, TX  77627
Martin Ducote, M.D.             $3,500.00                        3.989%
604 St. Landry Street
Lafayette, LA  70506
Edwin Edgerton, M.D.            $1,000.00                        0.757%
2417 N. 7th Street
West Monroe, LA  71291
John Enright, M.D.              $2,000.00                        2.281%
234 S. Ryan
Lake Charles, LA  70601
Christopher P. Fontenot(3)     $32,028.00                        1.180%
Carroll Guinn, M.D.             $1,000.00                        1.136%
602 N. Lewis
New Iberia, LA  70560
James M. Harris, M.D.           $2,000.00                        2.281%
810 Hospital Drive
Beaumont, TX  77701
John Denton Harris, M.D.        $3,500.00                        3.989%
810 Hospital Drive
Beaumont, TX  77701
G. Bruce Healey, M.D.           $2,000.00                        2.281%
3020 Allison
Groves, TX  77619
Gordon Sean Healey(3)          $16,014.00                        0.590%
John Henderson, M.D.            $2,500.00                        2.853%
810 Hospital Drive
Beaumont, TX  77701




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                                  Cash Contribution(1)    Percentage Interest(2)
George Hoffman, M.D.                 $2,500.00                   2.853%
3212 Concord Dr., Suite F
Orange, TX  77630
Brad Johnson(3)                     $32,028.00                   1.180%
Thomas Jordan                          $281.25                   0.425%
233 W. Broadway, Suite 501
Louisville, KY  40202
Chuen K. Kwok(3)                    $32,028.00                   1.180%
Edmond Lamperez, M.D.                $1,000.00                   0.757%
602 N. Lewis
New Iberia, LA  70560
Arthur Liles, M.D.                   $2,500.00                   2.853%
711 St. John Street
Monroe, LA  71201
Lithotripters, Inc.(4)               $2,000.00                   8.467%
2008 Litho Place
Fayetteville, NC  28304
Leo Lowentritt, M.D.                 $2,500.00                   2.853%
3311 Prescott Road
Alexandria, LA  71301
Don F. Marx, M.D.                    $2,500.00                   2.853%
North Monroe Medical Plaza
Suite I
Monroe, LA  71203

Robert Marx, M.D.                    $2,000.00                   2.281%
417 Wood Street
Monroe, LA  71201
James Meek, M.D.                     $2,000.00                   1.523%
301 4th Street
Alexandria, LA  71301
Charles E. Moss, M.D.                $2,000.00                   2.281%
118 Hospital Drive
Lafayette, LA  70503
Seth Novoselsky, M.D.                $1,000.00                   1.136%
3311 Prescott Road
Suite 103
Alexandria, LA  71301




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                            Cash Contribution(1)          Percentage Interest(2)
Tika Ranjitkar, M.D.            $2,000.00                             2.281%
1200 S. Farmerville
Ruston, LA  71270
James Rounder, M.D.             $1,000.00                             1.136%
3311 Prescott Road
Suite 103
Alexandria, LA  71301
Manuel Soasai, M.D.             $2,500.00                             2.853%
710 S. 8th Street
Beaumont, TX  77701
Steven A. Socher(3)             $32,028.00                            1.180%
Benjamin Stage, M.D.             $2,500.00                            2.853%
612 S. Washington
Bastrop, PA  71220
Charles Tanner, M.D.             $1,000.00                            0.757%
1200 S. Farmerville
Ruston, LA  71270
Lane Templeton(3)               $32,028.00                            1.180%
Paul Tennis, M.D.                $2,500.00                            2.853%
711 St. John Street
Monroe, LA  71201
Richard Texada, M.D.             $1,000.00                            1.136%
3311 Prescott Road
Alexandria, LA  71301
Jack Thielen, M.D.               $1,000.00                            1.136%
234 S. Ryan
Lake Charles, LA  70601
Kenneth S. Verheeck(3)          $32,028.00                            1.180%
J.W. Vildibill, M.D.             $3,500.00                            3.989%
604 St. Landry Street
Lafayette, LA  70506
         TOTAL                  286,463.25                           100.00%

(1)      The cash contributions  reflect the initial cash contributions of those
         Partners who currently hold an interest in the Partnership.

(2)      Percentage figures are approximated.



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(3)      Limited partnership interest was acquired pursuant to the Partnership's
         dilution offering which closed March 31, 1999.

(4) Lithotripters,  Inc. acquired a portion of its percentage interests pursuant
to various assignments from limited partners of the Partnership  effective as of
January 1,  1997,  and made no cash  contributions  to the  Partnership  for the
limited partner interests received as a result of such assignments.



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