FOURTH AMENDMENT TO
                       AGREEMENT OF LIMITED PARTNERSHIP OF
                   INDIANA LITHOTRIPTERS LIMITED PARTNERSHIP I

                  THIS  AMENDMENT,  effective  as of the 30th day of  September,
1999,  is  entered  into by and  among  Lithotripters,  Inc.,  a North  Carolina
corporation and the General Partner of Indiana Lithotripters Limited Partnership
I, an Indiana 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,"  are  parties  to  that  certain
Agreement of Limited Partnership of Indiana Lithotripters Limited Partnership I,
as amended (the "Agreement").

                  2. Effective as of September 30, 1999, the General Partner and
the  requisite  percentage of the Limited  Partners  consented in writing to the
following  amendments to the Agreement,  such amendments  intended to: (i) allow
the General  Partner the  authority to  periodically  offer and sell  additional
limited  partner  interests  (a  "Dilution  Offering")  to local  investors;(ii)
clarify and strengthen the  noncompetition  provisions of Articles 15.3 and 18.3
of the  Agreement;  (iii) add a new  provision  to the  Agreement to prevent the
disclosure  of  Confidential   Partnership   Information  that  might  harm  the
Partnership and its Partners;  and (iv) allow the General  Partner,  in its sole
discretion, to elect to assign to the Partnership its rights under Article 18 of
the Agreement to purchase the Partnership Interest of any deceased, insolvent or
competing Limited Partner:

                  NOW,  THEREFORE,  in accordance with Articles 28 and 29 of the
Partnership Agreement and pursuant to the written consent of the General Partner
and the requisite  percentage of the Limited Partners,  the parties hereto agree
as follows:

                           The  Agreement  is  hereby  amended  as set  forth in
                           Exhibits A, B and C attached hereto.

                            [Signature Page Follows]



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

                           GENERAL PARTNER:

                           LITHOTRIPTERS, INC., a North Carolina corporation and
                              sole general partner of the Partnership

                               By:_________________________________________
                               Title:________________________________________



                                                 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-Fact*
--------
     *Pursuant  to a Power of  Attorney  given by the  Limited  Partners  in the
Agreement.



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                                    EXHIBIT A

                           DILUTION OFFERING AMENDMENT

1.       Capitalized  terms used in this Exhibit and not otherwise defined shall
         have  the  same  meaning  as  provided  in  the  Agreement  of  Limited
         Partnership  (the  "Partnership  Agreement")  of Indiana  Lithotripters
         Limited Partnership I (the "Partnership").

2.       The purpose of this Exhibit is to set forth a proposed amendment to the
         Partnership Agreement that would give the General Partner the authority
         periodically  to offer and sell additional  limited  partner  interests
         ("Dilution  Offerings") to local investors who are not Limited Partners
         in the Partnership ("Qualified  Investors").  As required by Article 29
         of the  Partnership  Agreement,  to be effective this amendment must be
         approved  by the  Partners  representing  two-thirds  of the  aggregate
         interests in the Partnership.

3.   The purposes of a Dilution Offering are (i) to raise additional capital for
     any valid Partnership  purposes,  and (ii) to assure the highest quality of
     patient care by admitting  Qualified  Investors to the Partnership who will
     be dedicated and motivated as owners to follow the Partnership's  treatment
     protocol,  and comply  with its  quality  assurance  and  outcome  analysis
     programs.  Any additional  capital raised by the  Partnership in a Dilution
     Offering  can be used for any  legitimate  Partnership  purpose,  including
     upgrading   the   imaging   components   of   the   Partnership's   Siemens
     Lithostar(TM)extracorporeal  shockwave lithotripter and funding Partnership
     expenses as the General Partner deems appropriate.

4.       In the event the Dilution  Offering  Amendment  receives the  requisite
         approval  of the  Limited  Partners,  the  General  Partner  intends to
         conduct a Dilution  Offering  for the  purposes  of raising  additional
         capital  to  upgrade  the  imaging   components  of  the  Partnership's
         Lithostar(TM) and to fund other Partnership expenses deemed appropriate
         by the General Partner.

5.       Any sale of limited  partner  interests  to  Qualified  Investors  will
         result in the  proportionate  dilution  of the  Partnership  Percentage
         Interests of the existing Partners;  i.e., the interests of the General
         Partner  and the  Limited  Partners in  Partnership  allocations,  cash
         distributions  and voting rights will be  proportionately  reduced by a
         successful Dilution Offering.

6.       The  General  Partner has  determined  that the  purchase  price per 1%
         Partnership  Interest offered in the initial planned Dilution  Offering
         will be at its fair market value as determined by an independent  third
         party appraiser.  The price for Units sold in future Dilution Offerings
         also must be at a price no less than fair market value as determined by
         the General Partner.

7.       Upon  the  successful  sale  of  Partnership  Interests  in a  Dilution
         Offering,  the General Partner will prepare and attach a new Schedule A
         to the  Partnership  Agreement  to reflect (i) the  Partners'  adjusted
         Percentage Interests in the Partnership,  and (ii) the admission of the
         new Limited Partners to the Partnership.



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                                    EXHIBIT B

                          NONCOMPETITION PROVISION AND
                      CONFIDENTIALITY PROVISION AMENDMENTS

                  Capitalized  terms  used in  this  Exhibit  and not  otherwise
defined  shall have the same  meaning as  provided in the  Agreement  of Limited
Partnership  (the  "Partnership  Agreement")  of Indiana  Lithotripters  Limited
Partnership I (the "Partnership").

                       Noncompetition Provision Amendment

                  Article 15.3 of the Partnership Agreement is hereby amended by
deleting the current  provision in its entirety and by substituting the language
set forth below:

                           15.3 Outside  Activities.  The Limited Partners agree
         that  they  owe  fiduciary   duties  to  the  Partnership   and,  as  a
         consequence,  each Limited  Partner (that is not the General Partner or
         an  Affiliate of the General  Partner)  agrees that he or she shall not
         engage in "Outside  Activities" (as defined below) in the "Market Area"
         (as  defined  below)  while  he or  she  is a  Limited  Partner  in the
         Partnership.   The  phrase  "Outside   Activities"  means  directly  or
         indirectly owning, leasing or subleasing a lithotripter (or any similar
         equipment or competing devices used for treating renal or biliary stone
         disease) or any other therapeutic equipment acquired by the Partnership
         as permitted by Article 4. Prohibited  indirect ownership shall include
         the direct or indirect  ownership of any interest in a business venture
         (through stock ownership,  partnership interest ownership, ownership by
         or through a close family  member,  or as otherwise  determined in good
         faith by the General Partner) involving the ownership, purchase, lease,
         sublease,  promotion,  management  or operation of a  lithotripter  (or
         similar  equipment  or competing  devices  used for  treating  renal or
         biliary stone disease) or other competing  device or equipment,  unless
         the  General  Partner  determines  that such  activity  by the  Limited
         Partners is not detrimental to the best interests of the Partnership.

                           Upon  the   termination  or  transfer  of  a  Limited
         Partner's  interest  in the  Partnership  for any  reason,  including a
         transfer  pursuant to Article  18.3  hereof,  the  withdrawing  Limited
         Partner shall not, for a period of two (2) years  following the date of
         his or her withdrawal,  engage in any Outside Activities in any "Market
         Area" in which the  Partnership is  transacting  business or within the
         prior  twelve  months  has   transacted   business   (the   "Restricted
         Facilities").  For the purposes of this Article 15.3,  the term "Market
         Area"  shall  mean  (i)  the  area  within  a ten  mile  radius  of any
         Restricted  Facility,  but if such  area is  determined  by a court  of
         competent  jurisdiction  to be too  broad,  then it shall mean (ii) the
         area within a five mile radius of any Restricted Facility,  but if such
         area is determined by a court of competent jurisdiction



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         to be too broad  then it shall  mean  (iii) the area  within a two mile
         radius of any Restricted Facility.

                           In the event a Limited  Partner wishes and intends to
         engage in an Outside  Activity in a Market Area, he or she must provide
         written notice of such intent to the General  Partner prior to engaging
         in the Outside Activity. The written notice shall be deemed an election
         by the Limited Partner to withdraw from the Partnership (the "Notice of
         Withdrawal"), and shall give the General Partner the purchase rights as
         provided in Article 18.3 hereof.  After the Notice of  Withdrawal,  the
         former Limited Partner may engage in an Outside  Activity in the Market
         Area only  after  waiting  the  period of two years  specified  in this
         Article  15.3.  In the  event of  breach  of the  waiting  period,  the
         Partnership  shall be  entitled  to any  remedy at law or  equity  with
         respect to such breach,  including without  limitation an injunction or
         suit for damages.

                           If a Limited Partner during his or her  participation
         in the  Partnership  engages in an Outside  Activity  in a Market  Area
         without  first  notifying  the  General  Partner in  violation  of this
         Article  15.3,  the  Limited  Partner  shall be deemed to have  given a
         Notice of  Withdrawal  on the date the General  Partner  first  becomes
         aware of the Limited  Partner's  Outside  Activity in the Market  Area.
         Upon receiving a Limited  Partner's  Notice of Withdrawal or equivalent
         thereof, the General Partner may invoke the purchase rights provided in
         Article 18.3 and shall be entitled to any other remedy at law or equity
         including without limitation an injunction or suit for damages.

                  Article 18.3 of the Partnership Agreement is hereby amended by
deleting the current  provision in its entirety and by substituting the language
set forth below.

                           18.3 Breach of Article 15.3. In the event the General
         Partner  either  receives a Notice of Withdrawal as provided in Article
         15.3 or  receives  notice  of a breach  of  Article  15.3 by a  Limited
         Partner (the  "Defaulting  Limited  Partner"),  the General Partner may
         elect, in its sole  discretion,  to treat such event as a default under
         this  Agreement and enforce the provisions of this Article 18.3. If the
         General  Partner elects to enforce the provisions of this Article 18.3,
         the General  Partner  shall give written  notice of such  election (the
         "Notice of Default") to the Defaulting  Limited Partner within 180 days
         of the date the General Partner first received notice of the defaulting
         event.  Upon giving the Notice of Default,  the General  Partner  shall
         have the option to  purchase  at the  Closing  (as  defined  below) the
         Partnership   Interest  of  the  Defaulting   Limited   Partner  (which
         Defaulting  Limited  Partner  shall then become  obligated to sell such
         Partnership Interest) at the price determined in the manner provided in
         Article 18.5 of this Agreement and on the terms and conditions provided
         in Article 18.6 of this  Agreement.  The General  Partner  shall have a
         period of thirty (30) days  following the date of the Notice of Default
         (the "Option Period") within



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         which to notify in writing the Defaulting Limited Partner,  whether the
         General  Partner wishes to purchase all or a portion of the Partnership
         Interest of the Defaulting Limited Partner. If the General Partner does
         not elect to purchase the entire Partnership Interest of the Defaulting
         Limited  Partner  before the expiration of the Option Period and in the
         manner provided  herein,  the portion of the  Partnership  Interest not
         purchased shall be held by the Defaulting  Limited Partner  pursuant to
         the terms of this Agreement.

                       Confidentiality Provision Amendment

                  Article 15 of the  Partnership  Agreement is hereby amended by
adding a new Article 15.4 as set forth below:

                           15.4  Disclosure of  Confidential  Information.  Each
         Limited Partner  acknowledges and agrees that his or her  participation
         in the Partnership under this Agreement necessarily involves his or her
         understanding  of  and  access  to  certain  trade  secrets  and  other
         confidential information pertaining to the business of the Partnership.
         Accordingly,  each Limited  Partner (other than the General Partner and
         its Affiliates  that may also hold Limited  Partner  interests)  agrees
         that at all times during his or her participation in the Partnership as
         a Limited  Partner  and  thereafter,  he or she will not,  directly  or
         indirectly,  without the express written  authority of the Partnership,
         unless  required  by law or directed by a  applicable  legal  authority
         having  jurisdiction over the Limited Partner,  disclose or use for the
         benefit of any  person,  corporation  or other  entity  (other than the
         Partnership),   or  himself  or  herself,  (i)  any  trade,  technical,
         operational, management or other secrets, any patient or customer lists
         or  other  confidential  or  secret  data,  or any  other  proprietary,
         confidential  or  secret  information  of the  Partnership  or (ii) any
         confidential  information concerning any of the financial arrangements,
         financial positions, hospital or physician contracts, third party payor
         arrangements,   quality   assurance  and  outcome  analysis   programs,
         competitive   status,   customer   or   supplier   matters,    internal
         organizational matters,  technical abilities, or other business affairs
         of or relating to the Partnership. The Limited Partners (other than the
         General  Partner and its Affiliates  that may also hold Limited Partner
         interests)   acknowledge   that  all  of  the   foregoing   constitutes
         proprietary  information,  which  is  the  exclusive  property  of  the
         Partnership.  In the event of breach of this Article 15.4 as determined
         by the General Partner, the Partnership shall be entitled to any remedy
         at law or  equity  with  respect  to  such  breach,  including  without
         limitation, an injunction or suit for damages.



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                                    EXHIBIT C

                      PURCHASE OPTION ASSIGNMENT AMENDMENT
                       -----------------------------------


                  Capitalized  terms  used in  this  Exhibit  and not  otherwise
defined  shall have the same  meaning as  provided in the  Agreement  of Limited
Partnership  (the  "Partnership  Agreement")  of Indiana  Lithotripters  Limited
Partnership I (the "Partnership").

                      Purchase Option Assignment Amendment

                  Articles  18.1,  18.2 and 18.3 are hereby amended to allow the
General  Partner to either exercise its purchase option rights during the Option
Period,  as provided in such Articles,  or to assign such purchase option rights
in whole or in part to the Partnership. If the General Partner's purchase option
rights are assigned to the Partnership as provided herein, the Partnership shall
have the right to use  Partnership  revenues  or  borrowings  to  exercise  such
rights.  Further,  Articles 18.5 and 18.6 are also amended by  substituting  the
Partnership as a purchaser to the extent the General Partner elects to assign to
the  Partnership  its purchase option rights under Articles 18.1, 18.2 and 18.3.
If the Partnership acquires a Partnership Interest pursuant to the terms of this
Amendment, then the General Partner shall have the authority to amend Schedule A
to the  Partnership  Agreement to reflect the deletion of the interests  held by
the selling Limited Partners (or their  successors in interest),  and to reflect
the increased  Percentage Interests of the remaining Partners resulting from the
redemption.



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