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                                                                 Exhibit 10.7

                                   CONFIDENTIAL TREATMENT HAS BEEN SOUGHT FOR
                              PORTIONS OF THIS EXHIBIT PURSUANT TO RULE 24B-2
                        UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                LICENSE AGREEMENT

         THIS AGREEMENT, effective as of September 30, 1999 ("EFFECTIVE
DATE") between THE GENERAL HOSPITAL CORPORATION, a not-for-profit corporation
doing business as Massachusetts General Hospital, having a place of business
at Fruit Street, Boston, Massachusetts 02114 ("GENERAL") and PHOTOGEN, Inc.,
a Tennessee corporation having offices at 7327 Oak Ridge Highway, Knoxville,
Tennessee 37931 ("COMPANY").

                                    RECITALS

         WHEREAS, under research programs funded by GENERAL and the U.S.
Government, GENERAL through research conducted by Gerald L. Wolf, Ph.D., M.D.
("Dr. Wolf") has developed an invention pertaining to Enhanced Radiation
Therapy;

         WHEREAS, GENERAL has prepared and filed a U.S. Patent Application
No. [****] covering said invention and all of Dr. Wolf's right, title and
interest in said application has been assigned to GENERAL;

         WHEREAS, Nycomed Imaging AS, a Norwegian corporation, having a place
of business at Nycoveien 2, Post Office Box 4220, Torshov N-0401, Oslo,
Norway ("NYCOMED") through research funded by NYCOMED and conducted at
General by Dr. Wolf and at NYCOMED by [****], [****] and [****] have
developed patentable information entitled [****].

         WHEREAS, NYCOMED has prepared and filed a US provisional patent
application entitled [****], and a provisional British patent application
entitled [****], covering said patentable information (copies of which are
attached as Exhibits A-1 and A-2 hereto) and all of Dr. Wolf's rights, title
and interest have been assigned to GENERAL, and [****], [****] and [****]
rights, title and interest therein have been assigned to NYCOMED (copies of
such assignment documents are attached as Exhibit B hereto). These patent
applications cover a compound closely related to [****] for both imaging and
therapy;

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         WHEREAS, GENERAL and NYCOMED have agreed, if feasible to unite the
above patent applications into a single PCT filing listing all the above
inventors;

         WHEREAS, GENERAL and NYCOMED have agreed, if feasible to unite the
above patent applications into a single PCT filing listing all the above
inventors;

         WHEREAS, NYCOMED has appointed GENERAL as its agent, to act on
NYCOMED'S behalf in licensing and sublicensing NYCOMED's intellectual
property rights described above in the fourth and fifth Recitals of the
Agreement to COMPANY, pursuant to the Invention and License Administration
Agreement attached as Exhibit C hereto;

         WHEREAS, NYCOMED has a worldwide, exclusive license, with
sublicensing rights, under the [****] Agreement, dated [****] between [****]
and Nycomed Imaging AS (hereinafter the [****] Agreement), solely to
manufacture, use, sell or otherwise dispose of human ethical pharmaceutical
products containing the diagnostic imaging compound [****] (now known as
[****]) under the [****]Intellectual Property (as defined in the [****]
Agreement which includes US Patent [****] issued [****] and other patent
rights as described in Schedule 2 of the [****] Agreement). The [****]
Agreement is set forth in Exhibit D hereto.

         WHEREAS, NYCOMED has developed know-how and improvements to the
rights licensed to Nycomed with respect to [****] under the [****] Agreement,
including Phase I and Phase II clinical trial data;

         WHEREAS, NYCOMED has appointed GENERAL as its agent pursuant to the
Invention and License Administration Agreement attached as Exhibit hereto to
sublicense all of its rights under the [****] Agreement with respect to [****]
(described in the seventh Recital to this Agreement to COMPANY) and to
sublicense all of Nycomed's know-how and improvements to said rights
(described in the eighth Recital to this Agreement) to Company;

         WHEREAS, GENERAL and NYCOMED each hereby represent to the COMPANY
that, to the best of their respective knowledge and belief, subject to the
rights of the U.S. Government, GENERAL and NYCOMED are the respective owners
of all right, title and interest in the patent application(s) (and the
inventions covered thereby) described in the second Recital in this Agreement
in the case of GENERAL and in the fourth Recital to this Agreement in the
case of NYCOMED, and each has the right, ability and authority to grant the
license hereinafter described;

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         WHEREAS, as a center for research and education, GENERAL is
interested in licensing PATENT RIGHTS and thus benefitting the public and
GENERAL by facilitating the dissemination of the results of its research in
the form of useful products, but is without capacity to commercially develop,
manufacture, and distribute any such product; and

         WHEREAS, COMPANY desires to commercially develop, manufacture, use
and distribute such products throughout the world;

         NOW THEREFORE, in consideration of the premises and of the faithful
performance of the covenants herein contained, the parties hereto agree as
follows:

                                 1. DEFINITIONS

1.1      The term "ACCOUNTING PERIOD" shall mean each six month period ending
         June 30 and December 31 of each year during the Term of this Agreement.

1.2      The term "AFFILIATE" shall mean any corporation or other legal entity
         controlling, controlled by or under common control with, COMPANY, in
         the case of a COMPANY AFFILIATE and with GENERAL, in the case of a
         GENERAL AFFILIATE. The term "control" means possession, direct or
         indirect, of the power to direct or cause the direction of the
         management and policies of an entity, whether through the ownership of
         voting securities, by contract or otherwise.

1.3      The term "FIRST COMMERCIAL SALE" shall mean in each country the first
         sale of a PRODUCT to a final customer who will be the end user of the
         PRODUCT.

1.4      The term "LICENSE FIELD" shall mean the research, development,
         manufacture and commercialization of diagnostic imaging agents for
         medical location, treatment and diagnosis of tumors and other diseased
         tissues or other material in human, animal or plant life. The term
         "[****] LICENSE FIELD" shall mean the research, development,
         manufacture and commercialization of human ethical pharmaceutical
         products containing the diagnostic imaging compound [****].

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

1.5      The term "NET SALES PRICE" shall mean the GROSS SALES PRICE as
         defined in (b) below actually received in cash by COMPANY or any of
         its AFFILIATES or the COMPANY's immediate SUBLICENSEE (collectively,
         sometimes hereafter "SELLERS" or individually, a "SELLER") for the
         sale or distribution of a PRODUCT by a SELLER, less (to the extent
         appropriately documented) the following amounts actually paid out by
         SELLER or credited against the amounts received by such SELLER from
         the sale or distribution of a PRODUCT:

         (a)  (i)      credits and allowances for price adjustment, rejection,
                       or return of PRODUCTS previously sold;

              (ii)     rebates, customary trade, quantity and cash discounts
                       and non-affiliated brokers' or agents' for
                       commissions allowed and taken; provided, however,
                       that such broker's or agent's commissions shall not
                       exceed [****]%; and further, provided, that the term
                       "non-affiliated brokers' or agents'" does not include
                       distributors;

              (iii)    amounts for transportation, insurance, handling or
                       shipping charges;

              (iv)     taxes, duties and other governmental charges levied
                       on or measured by the sale of PRODUCTS, whether
                       absorbed by a SELLER or paid by the purchaser so long
                       as a SELLER's price is reduced thereby, but not
                       franchise or income taxes of any kind whatsoever;

              (v)      for any sale in which the United States government on
                       the basis of its royalty-free license pursuant to 35
                       U.S.C. Section 202(c) to any PATENT RIGHTS requires
                       that the GROSS SALES PRICE of any PRODUCT subject to
                       such PATENT RIGHTS be reduced by the amount of such
                       royalty owed GENERAL pursuant to paragraph 3.1, the
                       amount of such royalty.

         (b)  For any bona fide sale by a SELLER, the GROSS SALES PRICE shall
              be the gross billing price of the PRODUCT. None of the PRODUCTS
              shall be sold for consideration other than cash or a receivable
              payable in cash.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

         (c)  If a SELLER sells any PRODUCT in a bona fide sale as a
              component of a combination of active functional elements, the
              GROSS SALES PRICE of the

<PAGE>

              PRODUCT shall be determined by multiplying the GROSS SALES
              PRICE of the combination by the fraction A over A + B, in which
              "A" is the GROSS SALES PRICE of the PRODUCT portion of the
              combination when sold separately during the ACCOUNTING PERIOD
              in the country in which the sale was made, and "B" is the GROSS
              SALES PRICE of the other active elements of the combination
              sold separately during said ACCOUNTING PERIOD in said country.
              In the event that no separate sale of either such PRODUCT or
              active elements of the combination is made during said
              ACCOUNTING PERIOD in said country, the GROSS SALES PRICE of the
              PRODUCT shall be determined by multiplying the GROSS SALES
              PRICE of such combination by the fraction C over C + D, in
              which "C" is the standard fully-absorbed cost of the PRODUCT
              portion of such combination, and "D" is the sum of the standard
              fully-absorbed costs of the other active elements component(s),
              such costs being arrived at using the standard accounting
              procedures of COMPANY which will be in accord with United
              States generally accepted accounting principles.

         (d)  If a SELLER commercially uses or disposes of any PRODUCT by
              itself (as opposed to a use or disposition of the PRODUCT as a
              component of a combination of active functional elements) other
              than in a bona fide sale, the GROSS SALES PRICE hereunder shall
              be the price which would be then payable in an arm's length
              transaction. If a SELLER commercially uses or disposes of any
              PRODUCT as a component of a combination of active functional
              elements other than in a bona fide sale, the GROSS SALES PRICE
              of the PRODUCT shall be determined in accordance with paragraph
              (c) above, using as the GROSS SALES PRICE of the combination
              that price which would be then payable in an arm's length
              transaction. A "commercial use or disposition" of a PRODUCT
              does not include (i) the use of a PRODUCT for research,
              clinical testing or educational purposes for which no payment
              is made to or received by the Company or (ii) a disposition of
              a PRODUCT which, in the opinion of the COMPANY, is damaged,
              obsolete or not usable for the purposes intended and for which
              no payment is made to or received by the COMPANY.

         (e)  Transfer of a PRODUCT within COMPANY or between COMPANY and an
              AFFILIATE or the COMPANY's immediate SUBLICENSEE for sale by
              the transferee shall not be considered a sale, commercial use
              or disposition for the purpose of the foregoing paragraphs; in
              the case of such transfer the GROSS SALES PRICE shall be based
              on sale of the PRODUCT by the transferee.

1.6      (a)  The term "GENERAL PATENT RIGHTS" shall mean the [****],
              and the equivalent of such application filed in any foreign
              jurisdictions, together with the inventions described and
              claimed therein. The term "GENERAL PATENT

<PAGE>

              RIGHTS" shall also include any division, continuation or
              Letters Patent or the equivalent thereof issuing thereon or
              reissue, reexamination or extension thereof of any of the above
              patent applications or patents as well as any claims in any
              continuation-in-part of the aforementioned patent applications
              which claim an invention described or claimed in said patent
              applications or patents.

         (b)  The term "JOINT PATENT RIGHTS" shall mean [****] and the
              equivalent of such applications filed in any foreign
              jurisdictions, together with the inventions described and
              claimed therein. The term "JOINT PATENT RIGHTS"shall also
              include any division, continuation or Letters Patent or the
              equivalent thereof issuing thereon or reissue, reexamination
              or extension thereof of any of the above patent applications
              or patents as well as any claims in any continuation-in-part
              of the aforementioned patent applications which claim an
              invention described or claimed in said patent applications or
              patents.

         (c)  The term "[****] PATENT RIGHTS"  shall mean [****]

         (d)  The term "PATENT RIGHTS" shall mean any GENERAL PATENT RIGHTS,
              JOINT PATENT RIGHTS or [****] PATENT RIGHTS.

1.7      The term "PRODUCT" shall mean any article, device, composition,
         method or service, the manufacture, use, or sale of which, absent
         the licenses granted herein, would infringe a VALID CLAIM of any
         PATENT RIGHT.

1.8      The term "SUBLICENSEE" shall mean any third party licensed by
         COMPANY to make, have made, use, market, distribute, lease, import,
         offer to sell and sell any PRODUCT.

1.9      The term "VALID CLAIM" shall mean any claim of any PATENT RIGHT (i)
         that has not been finally rejected, (ii) that has not been declared
         invalid by a patent office or court of competent jurisdiction in any
         unappealed and unappealable decision or (iii) as to which patent
         protection has not expired.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

                                   2. LICENSE

2.1      In connection with the license granted in Section 2.2, GENERAL
         and NYCOMED, each represents and warrants to COMPANY that, to the
         best of their respective knowledge, based on a review of their
         respective files and documents as of the EFFECTIVE DATE

<PAGE>

         hereof, it (I.E., GENERAL and NYCOMED, each with respect to
         themselves only) is not prohibited or prevented from granting the
         following license to COMPANY.

2.2      GENERAL hereby grants to COMPANY to the extent not prohibited by
         contractual obligations to any other sponsor of research at GENERAL
         and pursuant to the Invention and License Administration Agreement
         (and said grant is joined into by NYCOMED to the extent necessary)
         and COMPANY accepts, subject only to the terms of this Agreement and
         the rights reserved in Section 2.3. below.

         (a)  (i)      on behalf of GENERAL and NYCOMED, an [****]
                       royalty-bearing license in the LICENSE FIELD under
                       GENERAL PATENT RIGHTS and JOINT PATENT RIGHTS to
                       make, have made, use, market, distribute, lease,
                       import, offer to sell, and sell PRODUCTS; and

              (ii)     on behalf of NYCOMED, an exclusive, worldwide,
                       royalty-bearing sublicense in the [****] LICENSE
                       FIELD under [****] PATENT RIGHTS to make, have made,
                       use, market, distribute, lease, import, offer to
                       sell, and sell PRODUCTS.

         (b)  to the extent an exclusive license is not available to COMPANY in
              a country (other than the United States) which prohibits the
              granting of an exclusive license as a matter of law,

              (i)      on behalf of GENERAL and NYCOMED, a non-exclusive,
                       royalty-bearing license in the LICENSE FIELD under
                       GENERAL PATENT RIGHTS and JOINT PATENT RIGHTS; and

              (ii)     on behalf of NYCOMED, a [****], royalty-bearing
                       sublicense in the [****] LICENSE FIELD under [****]
                       PATENT RIGHTS,

                       in either case, to make, have made, use, market,
                       distribute, lease, import, offer to sell and sell
                       PRODUCTS;

         (c)  the right to sublicense PATENT RIGHTS exclusively licensed or
              sublicensed to COMPANY including the right to grant
              SUBLICENSEES the right to further sublicense.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.


<PAGE>

         The above licenses and sublicenses to make, have made, use, market,
         distribute, lease, import, offer to sell and sell PRODUCTS includes the
         right to grant to the CUSTOMER the right to use a purchased PRODUCT in
         a method coming within the scope of PATENT RIGHTS.

2.3      It is understood that the granting of any license hereunder
         is subject to GENERAL's and GENERAL's AFFILIATES' right to make and
         to use the subject matter described and claimed in GENERAL PATENT
         RIGHTS OR JOINT PATENT RIGHTS for all uses other than Commercial
         Purposes, and that if federal funding supported the GENERAL PATENT
         RIGHTS OR JOINT PATENT RIGHTS, COMPANY's license will be subject to
         the rights, conditions and limitations imposed by U.S. law including
         without limitation the royalty-free non-exclusive license granted to
         the U.S. Government (see 35 U.S.C. Section 202 ET SEQ. and
         regulations pertaining thereto). For the purposes of this Section,
         "Commercial Purposes" shall mean use of the subject matter described
         and claimed in PATENT RIGHTS in any product, or for the purpose of
         producing a product, which is made, sold, leased or otherwise
         commercially distributed.

2.4      Subject to confidential treatment under Section 10, within three (3)
         months of EFFECTIVE DATE, GENERAL, Dr. Wolf and NYCOMED shall
         disclose all know-how relating to [****], including [****] data,
         pre-clinical safety toxicity information, results of human clinical
         trials and IND information regarding [****] to COMPANY and provide
         all technological information with respect to prosecution of patent
         applications included in PATENT RIGHTS which GENERAL and/or NYCOMED
         are not prohibited from disclosing to COMPANY.

2.5      GENERAL shall have the right to license any GENERAL PATENT RIGHTS OR
         JOINT PATENT RIGHTS to any other party for the purpose of
         manufacturing, using or selling any PRODUCT outside of the LICENSE
         FIELD.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

2.6      It is understood that nothing herein shall be construed to grant
         COMPANY a license express or implied under any patent owned solely
         or jointly by GENERAL or NYCOMED other than the PATENT RIGHTS
         expressly licensed hereunder.

                             3. COMPANY OBLIGATIONS

3.1      COMPANY shall itself, or through its AFFILIATES or SUBLICENSEES, use
         reasonable efforts to develop and make commercially available a
         PRODUCT for commercial sale and distribution throughout the world in
         the LICENSE FIELD and the

<PAGE>

         [****] LICENSE FIELD; provided, however, that the final decision as
         to where the PRODUCT will be distributed shall vest in the COMPANY.
         Such efforts shall consist of achieving the following objectives
         within the time period designated below:

         (a)  within [****] months after the EFFECTIVE DATE, complete all
              animal toxicity tests required in connection with seeking to
              obtain U.S. Food and Drug Administration approval of clinical
              evaluations of a PRODUCT.

         (b)  within [****] months after obtaining FDA approval in (a) above,
              initiate and thereafter diligently pursue clinical evaluations
              of a PRODUCT and in connection therewith take all actions
              necessary under the Food, Drug and Cosmetic Act (21 USC
              301-391);

         (c)  within [****] months after obtaining FDA approval in (b)
              above, file documents with the FDA to obtain approval to
              manufacture such a PRODUCT for commercial sale and to inform
              GENERAL of such determination;

         (d)  within [****] months after the EFFECTIVE DATE initiate and
              thereafter diligently pursue clinical evaluations of a PRODUCT
              in either the European Community or Japan;

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         GENERAL shall not unreasonably withhold its consent to any revision
         in such time periods whenever requested in writing by COMPANY and
         supported by reasonable evidence of technical difficulties or delays
         in animal or clinical studies, regulatory processes or other events
         that the parties could not have reasonably avoided or anticipated.
         Failure to achieve one or more of the above objectives within the
         above stated time periods or within any extension granted by GENERAL
         shall result in GENERAL having the right to cancel upon sixty (60)
         days prior written notice any [****] license granted hereunder, or
         to convert any [****]license to a [****] license; provided that
         COMPANY does not demonstrate to GENERAL's satisfaction, which shall
         not be unreasonably withheld, during said sixty (60) day period, its
         ability to cure such failure(s) within a reasonable time period
         thereafter and that such objectives are in fact materially achieved
         in such time period; further, provided, that COMPANY makes no
         representation or warranty that it can achieve success in the
         development or marketing of any PRODUCTS, the profitability of
         PRODUCTS or the amount of royalties payable to GENERAL hereunder.

3.2      At intervals no longer than every six (6) months, COMPANY shall
         report in writing to GENERAL on progress made toward the foregoing
         objectives.

3.3      This Agreement shall not be deemed to prohibit COMPANY from
         developing, making, using, marketing or otherwise distributing or
         promoting products competitive (as hereafter defined) with the
         PRODUCTS, provided that COMPANY shall not disparage any of the
         PRODUCTS or the PATENT RIGHTS and that COMPANY remains in compliance
         with the milestones of Article 3.1. When COMPANY does so develop,
         make, use, market or otherwise distribute or promote products
         competitive with the PRODUCTS, any licenses granted hereunder shall
         become non-exclusive. For purposes of this Section, the term
         "competitive" is limited to a product, method or service that is in
         direct competition with a PRODUCT and not a product, method or
         service that is an alternative to a PRODUCT.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.


<PAGE>

3.4      The COMPANY shall mark all PRODUCTS with the appropriate patent
         words and numbers as contemplated by Section 287(a) of the U.S.
         Patent Code. GENERAL and NYCOMED each agree to require all of their
         respective licensees in all fields under all patents relating to
         this Agreement to similarly mark all of their PRODUCTS under such
         patents as contemplated under said Section 287(a) and in compliance
         with applicable laws.

             4. FILING, PROSECUTION AND MAINTENANCE OF PATENT RIGHTS

4.1      Notwithstanding anything to the contrary in this Agreement, [****]
         or [****] successor in interest to the [****] Agreement, has the
         sole and exclusive right to take any action that it considers
         appropriate in connection with the prosecution and maintenance of
         the `Nano Patents' (as that term is defined in the [****] Agreement)
         as provided in Section 4.5 of the [****] Agreement. It is understood
         that [****] can take actions that NYCOMED cannot control including
         abandonment of patents without the requirement to notify NYCOMED or
         GENERAL.

4.2      In accordance with the Invention and License Administration
         Agreement (Exhibit C), GENERAL shall be responsible for the
         preparation, filing, prosecution and maintenance of all patent
         applications and patents included in GENERAL PATENT RIGHTS and JOINT
         PATENT RIGHTS and shall, after the EFFECTIVE DATE promptly and
         diligently pursue such activities in the United States and foreign
         jurisdictions mutually agreeable to the parties (such agreement not
         to be unreasonably withheld) ("Patent Activities"). GENERAL may
         select patent counsel and other advisors to assist in such Patent
         Activities, subject to COMPANY approving same (which approval shall
         not be unreasonably withheld). So long as COMPANY holds an exclusive
         license hereunder to the GENERAL PATENT RIGHTS and the JOINT PATENT
         RIGHTS, such patent counsel and advisors shall be advised by
         GENERAL, to the extent consistent with their obligations to GENERAL,
         to be promptly available to COMPANY and/or its counsel for
         information and advice regarding such Patent Activities. COMPANY
         shall reimburse GENERAL for all reasonable costs ("Costs") incurred
         by GENERAL for the preparation, filing, prosecution and maintenance
         of all PATENT RIGHTS as follows:

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (a)  Subject to paragraph 4.3, for all Costs incurred by GENERAL
              from and after the EFFECTIVE DATE, COMPANY shall reimburse
              GENERAL within thirty (30) days of receipt of invoices from
              GENERAL;

         (b)  For all Costs incurred by GENERAL prior to the EFFECTIVE
              DATE, not to exceed [****], COMPANY shall reimburse GENERAL
              upon execution of this Agreement.

4.3      NYCOMED shall provide to GENERAL and COMPANY all documentation
         pertaining to the filing and prosecution of JOINT PATENT RIGHTS
         within 30 days of the signing of this Agreement.

4.4      With respect to any GENERAL or JOINT PATENT RIGHT, each document or
         a draft thereof, including all related correspondence and memoranda
         pertaining to the filing, prosecution, or maintenance of such
         GENERAL or JOINT PATENT RIGHT, including but not limited to each
         patent application, office action, response to office action,
         request for terminal disclaimer, and request for reissue or
         reexamination of any patent issuing from such application shall be
         provided to COMPANY as follows: Documents received from or delivered
         to any patent office and counsel's analysis thereof, if any, shall
         be provided promptly to the COMPANY upon receipt or preparation by
         counsel. For a document to be filed in any patent office, a draft of
         such document shall be provided sufficiently prior to its filing, to
         the parties hereto to allow for review and comment by the other
         party. The parties hereto shall maintain all such documents in
         accordance with Article 10 hereof, and each party hereto shall take
         whatever other steps are necessary to preserve the attorney-client
         privilege of any such document, including limiting photocopies and
         internal disclosure. If as a result of the review of any such
         document, COMPANY shall elect not to pay or continue to pay the
         Costs for such GENERAL or JOINT PATENT RIGHT, COMPANY shall so
         notify GENERAL within thirty (30) days of COMPANY's receipt of such
         document and COMPANY shall thereafter be relieved of the obligation
         to pay any additional Costs regarding such GENERAL or JOINT PATENT
         RIGHT incurred after the receipt of such notice by GENERAL. Such
         U.S. or foreign patent application or patent shall thereupon cease
         to be a GENERAL or JOINT PATENT RIGHT hereunder and GENERAL shall be
         free without further obligations to COMPANY to license the rights to
         that particular U.S. patent application or patent to any

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         other party on any terms; provided, however, that the foregoing
         shall not apply if COMPANY indicates that its election not to pay or
         continue to pay such Costs is based upon a good faith objection to
         the reasonableness of such Costs or the quality of services being
         performed, in which event the dispute shall be resolved as provided
         in paragraph 12.9 hereafter if such dispute cannot first be resolved
         in discussions with GENERAL's patent counsel.

4.5      COMPANY acknowledges that patent counsel selected by GENERAL as
         provided hereinabove shall have a fiduciary duty to GENERAL;
         however, so long as COMPANY is an exclusive licensee hereunder of
         the GENERAL and JOINT PATENT RIGHTS and so long as COMPANY is
         obligated to pay the costs and fees of such counsel, such counsel
         shall to the extent consistent with his obligations to GENERAL, be
         available to discuss patent matters with the COMPANY's counsel.

4.6      In the event that GENERAL shall fail or refuse to diligently pursue
         its responsibilities in GENERAL's name described in paragraph 4.2,
         then COMPANY shall, upon 60 days notice with a right to cure by
         GENERAL during said notice period, have the right at its expense but
         in GENERAL's and NYCOMED's name to take over such responsibilities
         and to select patent counsel and advisors to assist it in such
         matters. In such event, COMPANY shall be bound by the other
         provisions of this Article 4.

                                  5. ROYALTIES

5.1      Beginning with the FIRST COMMERCIAL SALE in any country, on all
         sales of PRODUCTS anywhere in the world by COMPANY, its AFFILIATES
         or SUBLICENSEES, COMPANY shall pay GENERAL royalties in accordance
         with the following schedule, such undertaking and schedule having
         been agreed to for the purpose of reflecting and advancing the
         mutual convenience of the parties. For each PRODUCT sold by COMPANY
         or its AFFILIATES and SUBLICENSEES;

         (a)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having both a diagnostic and therapeutic
              application so long as such PRODUCT, its manufacture, use
              or sale is covered by a VALID CLAIM of any PATENT RIGHT
              licensed exclusively to COMPANY;

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (b)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having both a diagnostic and therapeutic
              application so long as such PRODUCT, its manufacture, use
              or sale is covered by a VALID CLAIM of any PATENT RIGHT
              licensed non-exclusively to COMPANY in the country in
              question;

         (c)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having only a diagnostic application so
              long as such PRODUCT, its manufacturer, use or sale is
              covered by a VALID CLAIM of any PATENT RIGHT licensed
              exclusively to COMPANY;

         (d)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having only a diagnostic application so
              long as such PRODUCT, its manufacturer, use or sale is
              covered by a VALID CLAIM of any PATENT RIGHT licensed
              non-exclusively to COMPANY in the country in question;

         (e)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having only a therapeutic application so
              long as such PRODUCT, its manufacturer, use or sale is
              covered by a VALID CLAIM of any PATENT RIGHT licensed
              exclusively to COMPANY;

         (f)  Subject to subparagraph 5.1(i) below, [****] of the NET SALES
              PRICE of a PRODUCT having only a therapeutic application so
              long as such PRODUCT, its manufacturer, use or sale is
              covered by a VALID CLAIM of any PATENT RIGHT licensed
              non-exclusively to COMPANY in the country in question;

         (g)  In the event that more than one royalty rate under
              paragraph 5.1 is applicable to a PRODUCT, the highest of
              the applicable royalties shall apply;

         (h)  Only one royalty under paragraph 5.1 shall be due and
              payable to GENERAL by COMPANY for any PRODUCT regardless of
              the number of PATENT RIGHTS covering such PRODUCT; and

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (i)  Royalties payable hereunder shall be offset by all filing,
              prosecution and maintain costs and attorney's fees paid by
              the COMPANY with respect to PATENT RIGHTS pursuant to
              Article 4 of this Agreement ("Costs"), through the end of
              the COMPANY's immediately preceding fiscal year end on the
              following basis: GENERAL and NYCOMED will share [****] of
              such Costs; COMPANY will share the [****] of such
              Costs; provided, however, that the aggregate offset against
              royalties payable hereunder when combined with the
              deductions against royalty payments under Section 7.4,
              shall not exceed in any one calendar year, [****] of
              royalties payable under this Agreement. Such Costs that are
              not used to offset royalties hereunder because of
              insufficient NET SALES shall be carried forward to future
              years for offset, limited as provided in the previous
              sentence, against royalties otherwise due in such future
              years.

5.2      If any license or sublicense granted pursuant to Article 2 shall be
         or become non-exclusive and GENERAL shall license or sublicense on
         behalf of NYCOMED any PATENT RIGHT to another licensee or
         sublicensee for the purpose of making, using or selling PRODUCTS in
         the LICENSE FIELD or the [****] LICENSE FIELD and accept a royalty
         or royalties more favorable to such licensee or sublicensee than
         herein provided for COMPANY, GENERAL shall give written notice
         thereof to COMPANY and as of the EFFECTIVE DATE of such more
         favorable royalty or royalties, COMPANY's obligation hereunder to
         pay royalty or royalties to GENERAL shall be revised to the more
         favorable rate.

5.3      In addition to the payments provided for in paragraph 5.1, COMPANY
         shall pay GENERAL the following amounts upon the occurrence of the
         following events:

         (a)  [****] upon the issuance by the United States Patent and
              Trademark Office of a notice of allowance covering a
              material portion of the claims in GENERAL or JOINT PATENT
              RIGHTS;

         (b)  [****] upon filing with the FDA of the first NDA, 510(k),
              PMA or PMA Supplement, or comparable application with
              respect to a PRODUCT; and

         (c)  [****] upon approval by the FDA of the first NDA, 510(k),
              PMA or PMA Supplement, or comparable application with
              respect to a PRODUCT.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

5.4      In the event that the royalty paid to GENERAL is a significant
         factor in the return

<PAGE>

         realized by COMPANY so as to diminish COMPANY's capability to
         respond to competitive pressures in the market, GENERAL agrees to
         consider a reasonable reduction in the royalty paid to GENERAL as to
         each such PRODUCT for the period during which such market condition
         exists. Factors determining the size of the reduction will include
         profit margin on PRODUCT and on analogous or competitive products,
         prices of competitive products, total prior sales by COMPANY, and
         COMPANY's expenditures in PRODUCT development.

5.5      In addition to the royalties provided for above, COMPANY shall pay
         GENERAL [****] of any and all non-royalty income (as defined in
         accordance with United States generally accepted accounting
         principles), including without limitation license and sublicense
         fees and milestone payments, received from COMPANY AFFILIATES and
         SUBLICENSEES in consideration for the sublicensing by COMPANY of any
         right, license or sublicense granted to it hereunder.

5.6      The payments due under this Agreement shall, if overdue, bear
         interest until payment at a per annum rate equal to one percent (1%)
         above the prime rate in effect at the Bank of Boston on the due
         date, not to exceed the maximum permitted by law. The payment of
         such interest shall not preclude GENERAL from exercising any other
         rights it may have as a consequence of the lateness of any payment.

                            6. REPORTS AND PAYMENTS

6.1      COMPANY shall keep, and shall cause each of its AFFILIATES and
         SUBLICENSEES, if any, to keep full and accurate books of accounts on
         both the cash and accrual basis, containing all particulars that may
         be necessary for the purpose of calculating all royalties payable to
         GENERAL. Such books of account shall be kept at their principal
         place of business and, with all necessary supporting data shall,
         during all reasonable times for the three (3) years next following
         the end of the calendar year to which each shall pertain be open for
         inspection at reasonable times upon reasonable prior notice by
         GENERAL or its designee at GENERAL's expense for the purpose of
         verifying royalty statements or compliance with this Agreement.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

6.2      In each year the amount of royalty due shall be calculated
         semiannually as of the end of each ACCOUNTING PERIOD and shall be
         paid semiannually within the sixty (60) days next following such
         date, every such payment to be supported by the accounting
         prescribed in paragraph 6.3 and to be made in United States
         currency. Whenever conversion from any foreign currency shall be
         required, such conversion shall be at the rate of exchange
         thereafter published in the Wall Street Journal for the business day
         closest to the end of the applicable ACCOUNTING PERIOD.

6.3      With each semiannual payment, COMPANY shall deliver to GENERAL a
         full and accurate accounting to include the following information
         and such other reasonable additional information relevant to the
         calculation of royalty payments as may be requested by GENERAL from
         time to time:

         (a)  Quantity of each PRODUCT sold or leased (by country) by COMPANY,
              and its AFFILIATES or SUBLICENSEES;

         (b)  Total billings for each PRODUCT (by country);

         (c)  Names and addresses of all SUBLICENSEES of COMPANY; and

         (d)  Total royalties payable to GENERAL.

                                7. INFRINGEMENT

7.1      Notwithstanding anything to the contrary in this Agreement, [****]
         or [****] successor in interest to the [****] Agreement, has the
         sole and exclusive right to take, at its sole discretion and at its
         own expense, any action that it considers appropriate in connection
         with any actual or threatened infringement of the [****] PATENT
         RIGHTS to defend the validity and enforceability of such property in
         any litigation as provided in Section 5.1 of the [****] Agreement.

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

7.2      COMPANY, to the extent it has an exclusive license regarding PATENT
         RIGHTS, shall have first obligation to protect the GENERAL PATENT
         RIGHTS and JOINT PATENT RIGHTS from infringement and prosecute
         infringers in the LICENSE FIELD when, in its judgement, such action
         may be reasonably necessary, proper and justified. GENERAL and
         NYCOMED may join COMPANY in such action or if COMPANY fails to take
         such action, GENERAL may separately initiate such action, at its
         discretion and at its own expense.

7.3      If GENERAL shall have supplied COMPANY with written evidence
         demonstrating prima facie infringement of a claim of a GENERAL
         PATENT RIGHT or JOINT PATENT RIGHT by a third party in the LICENSE
         FIELD, GENERAL may by notice request COMPANY to take steps to
         protect the GENERAL PATENT RIGHT or JOINT PATENT RIGHT. COMPANY
         shall notify GENERAL within three (3) months of the receipt of such
         notice whether COMPANY intends to prosecute the alleged
         infringement. If COMPANY notifies GENERAL that it intends to so
         prosecute, COMPANY shall, within three (3) months of its notice to
         GENERAL either (i) cause infringement to terminate or (ii) initiate
         legal proceedings against the infringer. No settlement, consent
         judgment or other voluntary final disposition of any suit by either
         COMPANY or GENERAL shall be entered into without the mutual consent
         of COMPANY and GENERAL, which consent shall not be unreasonably
         withheld.

7.4      If COMPANY elects to commence an action as described above, COMPANY
         may deduct from its royalty payments to GENERAL with respect to the
         GENERAL PATENT RIGHTS or JOINT PATENT RIGHTS subject to suit an
         amount not exceeding [****]percent [****] of COMPANY's expenses and
         costs of such action, including reasonable attorneys' fees;
         provided, however, that such reduction together with the offset
         against royalty payable under Section 5.1(i) shall not exceed [****]
         percent [****] of the total royalty due to GENERAL with respect to
         the NET SALES of PRODUCTS utilizing the GENERAL PATENT RIGHTS or
         JOINT PATENT RIGHTS subject to suit for each calendar year. If such
         [****] percent [****] of COMPANY's expenses and costs and offset
         under Section 5.1(i) exceeds the amount of royalties deducted by
         COMPANY for

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         any calendar year, COMPANY may to that extent reduce the royalties
         due to GENERAL from COMPANY in succeeding calendar years, but never
         by more than [****] percent [****] of the total royalty due GENERAL
         in any one year with respect to the GENERAL PATENT RIGHTS or JOINT
         PATENT RIGHTS subject to suit. In the event that COMPANY shall
         recover its expenses and costs, by settlement or judgment of such
         action, the same will be shared equally by the COMPANY and GENERAL,
         to the extent necessary for GENERAL to recoup the royalty payments
         which GENERAL contributed to the cost of such action pursuant to
         this Section.

7.5      For the purpose of the proceedings referred to in this Article 7,
         GENERAL, NYCOMED and COMPANY shall permit the use of their names and
         shall execute such documents and carry out such other acts as may be
         necessary to prosecute or defend any such proceeding, including
         joining into such proceeding. The party initiating or carrying on
         such legal proceedings shall keep the other party informed of the
         progress of such proceedings and said other party shall be entitled
         to counsel in such proceedings but at its own expense, said expenses
         to be off-set against any damages received by the party bringing
         suit in accordance with the foregoing paragraph 7.3.

7.6      In the event a party hereto shall initiate or carry on legal
         proceedings to enforce any GENERAL PATENT RIGHT or JOINT PATENT
         RIGHT against any alleged infringer, the other party (including
         NYCOMED) shall fully cooperate with and supply all assistance
         reasonably requested by the party initiating or carrying on such
         proceedings.  The party which institutes any suit to protect or
         enforce a GENERAL PATENT RIGHT or JOINT PATENT RIGHT shall have sole
         control of that suit and subject to paragraph 7.3 shall bear the
         reasonable expenses (excluding legal fees) incurred by said other
         party in providing such assistance and cooperation as is requested
         pursuant to this paragraph.  The party initiating or carrying on
         such legal proceedings shall keep the other party informed of the
         progress of such proceedings and said other party shall be entitled
         to counsel in such proceedings but at its own expense. Any award
         paid by third parties as the result of such proceedings (whether by
         way of settlement or otherwise) shall first be applied as provided
         in Section 7.3, if applicable, to reimbursement of the unreimbursed
         legal fees and expenses incurred by either party and then the
         remainder shall be divided between the parties as follows:

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (a)  (i)      If the amount is based on lost profits, COMPANY
                       shall receive an amount equal to the damages the
                       court determines COMPANY has suffered as a result
                       of the infringement less the amount of any royalties
                       that would have been due GENERAL on sales of PRODUCT
                       lost by COMPANY as a result of the infringement had
                       COMPANY made such sales; and

              (ii)     GENERAL shall receive an amount equal to the royalties
                       it would have received if such sales had been made by
                       COMPANY; and

         (b)  As to awards other than those based on lost profits,
              [****]percent to the party initiating such proceedings and
              [****]percent to the other party.

                               8. INDEMNIFICATION

8.1      (a)  COMPANY shall indemnify, defend and hold harmless GENERAL,
              NYCOMED and their trustees, officers, medical and professional
              staff, employees, and agents and their respective successors,
              heirs and assigns including claims by NYCOMED against GENERAL
              and claims by GENERAL against NYCOMED (the "Indemnitees"),
              against any liability, damage, loss or expense (including
              reasonable attorney's fees and expenses of litigation) incurred
              by or imposed upon the Indemnitees or any one of them in
              connection with any claims, suits, actions, demands or
              judgments (i) arising out of any theory of product liability
              (including, but not limited to, actions in the form of tort,
              warranty, or strict liability) concerning any PRODUCT, process
              or service made, used or sold by the COMPANY, its AFFILIATE, or
              a SUBLICENSEE or agent of the COMPANY pursuant to a license or
              sublicense granted under this Agreement, (ii) arising out of
              the maintenance or enforcement of [****] PATENT RIGHTS and
              including its related US Patent [****], (iii) the maintenance
              and enforcement of the [****] Agreement, or (iv) the
              infringement of the [****] PATENT RIGHTS upon the rights of
              third parties.

         (b)  COMPANY's indemnification under (a) above shall not apply to
              any liability, damage, loss or expense to the extent that it is
              directly attributable to the negligent activities or omissions,
              reckless misconduct or intentional misconduct of any of the
              Indemnitees.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (c)  COMPANY agrees, at its own expense to provide attorneys
              reasonably acceptable to GENERAL to defend against any actions
              brought or filed against any party indemnified hereunder with
              respect to the subject of indemnity contained herein, whether
              or not such actions are rightfully brought.

         (d)  This paragraph 8.1 shall survive expiration or termination of
              this Agreement.

8.2      (a)  Beginning at such time as any such PRODUCT, process or service
              is being commercially distributed or sold (other than for the
              purpose of obtaining regulatory approvals) by COMPANY or by an
              agent, SUBLICENSEE or AFFILIATE of COMPANY, COMPANY shall, at
              its sole cost and expense, procure and maintain commercial
              general liability insurance in amounts not less than $2,000,000
              per incident and $2,000,000 annual aggregate and naming the
              Indemnitees as additional insureds. Such commercial general
              liability insurance shall provide (i) product liability
              coverage and (ii) broad form contractual liability coverage for
              COMPANY's indemnification under paragraph 8.1 of this
              Agreement. If COMPANY elects to self-insure all or part of the
              limits described above (including deductibles or retentions
              which are in excess of $250,000 annual aggregate) such
              self-insurance program must be acceptable to GENERAL and the
              Risk Management Foundation. The minimum amounts of insurance
              coverage required under this paragraph 8.2 shall not be
              construed to create a limit of COMPANY's liability with respect
              to its indemnification under paragraph 8.1 of this Agreement.

         (b)  COMPANY shall provide GENERAL with written evidence of such
              insurance upon request of GENERAL. COMPANY shall provide
              GENERAL with written notice at least fifteen (15) days prior to
              the cancellation, non-renewal or material change in such
              insurance; if COMPANY does not obtain replacement insurance
              providing comparable coverage prior to the expiration of such
              fifteen (15) day period, GENERAL shall have the right to
              terminate this Agreement effective at the end of such fifteen
              (15) day period without notice or any additional waiting
              periods.

         (c)  COMPANY shall maintain such commercial general liability
              insurance beyond the expiration or termination of this
              Agreement during (i) the period that any such PRODUCT, process,
              or service is being commercially distributed or sold (other
              than for the purpose of obtaining regulatory approvals) by
              COMPANY or by an agent, SUBLICENSEE or AFFILIATE of COMPANY and
              (ii) a reasonable period after the period referred to in (c)
              (i) above which in no event shall be less than six (6) years.

<PAGE>

         (d)  This paragraph 8.2 shall survive expiration or termination of
              this Agreement.

                                 9. TERMINATION

9.1      Unless otherwise terminated as provided for in this Agreement, a
         license or sublicense to PATENT RIGHTS granted hereunder will
         continue on a country by country basis:

         (a)  for [****] after the date COMPANY, its agents, AFFILIATES, or
              SUBLICENSEES shall last sell any PRODUCT in such country, it
              being understood that GENERAL shall have the right to terminate
              such license or sublicense upon written notice in any country
              in the event that after the FIRST COMMERCIAL SALE of a PRODUCT
              in such country there is a continuous [****] period in which no
              PRODUCT is sold in such country, provided such sale is not
              prevented by force majeure, government regulation or
              intervention, or institution of a law suit by any third party,
              or that COMPANY can show to the reasonable satisfaction of
              GENERAL that it is using substantial economic and other assets
              and efforts to effect sales in such country, or

         (b)  until the last to expire of all PATENT RIGHTS, the claims of
              which but for this Agreement would be infringed by the
              manufacture, use or sale of any PRODUCT in the applicable
              country, whichever shall first occur.

9.2      If either party shall fail to materially perform any of its
         obligations under this Agreement (except the COMPANY obligations
         specified in Article 3 herein, which are to be governed as to
         termination and cancellation of any license or sublicense by the
         provisions of Article 3), the nondefaulting party may give written
         notice of the default to the defaulting party. Unless such default
         is corrected within thirty (30) days after such notice, the
         notifying party may terminate this Agreement and the license or
         sublicense hereunder upon an additional thirty (30) days prior
         written notice, provided that only one such an additional thirty
         (30) day grace period shall be available in any twelve (12) month
         period with respect to a default of any applicable provision
         hereunder. Thereafter notice of default of said provision shall
         constitute termination.

9.3      In the event that any license or sublicense granted to COMPANY under
         this Agreement is terminated, all sublicenses under such license or
         sublicense shall at the option of GENERAL terminate at the time of
         termination of the COMPANY's license or sublicense; provided,
         however, that GENERAL and such SUBLICENSEES shall be free to
         negotiate a new license or sublicense relationship between them. All
         SUBLICENSE Agreements between COMPANY and a SUBLICENSEE shall
         provide the foregoing provisions. In the event that COMPANY, due to
         the provisions of this Section finds difficulty in establishing
         sublicenses after demonstrated good faith efforts to do so,

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT, AS AMENDED

<PAGE>

         GENERAL agrees to establish reasonable objective standards for the
         continuity of sublicenses in the event of the termination of a
         license or sublicense granted to COMPANY.

9.4      Upon termination of any license or sublicense granted hereunder
         COMPANY shall pay GENERAL all royalties due or accrued on (i) the
         sale of PRODUCT up to and including the date of termination and (ii)
         for twelve (12) months following the date of termination for the
         sale of PRODUCT manufactured prior to the termination date.

                              10. CONFIDENTIALITY

10.1     GENERAL and COMPANY recognize that performance under this Agreement
         may involve the exchange and/or development or discovery of
         proprietary information, confidential business, technical and
         scientific information or trade secrets (collectively, "proprietary
         information"). Accordingly, each party agrees to use reasonable
         efforts, no less than those used for its own information of similar
         nature, to retain in confidence all proprietary information of the
         other party identified as confidential at the time of disclosure and
         not to disclose such information to any other person or entity, nor
         use such information without written permission of the party owning
         such information, except in accordance with the terms of this
         Agreement. The obligations of this paragraph shall be binding upon
         the parties for a period of 5 years from the date of each disclosure

10.2     The term "proprietary information" as used herein shall not include
         any information which the recipient clearly shows by appropriate
         documentation:

         (a)  Was at the time of receipt both lawfully and independently
              known to the receiving party, its agents, or employees;

         (b)  Without breach of this Agreement by the receiving party has
              been published or is otherwise within the public knowledge or
              is generally known to the public at the time of disclosure;

         (c)  Becomes known or available to the receiving party without
              restriction from a source other than the disclosing party,
              provided that such source has an unqualified right to disclose
              such information without restriction;

         (d)  Becomes a part of the public domain after disclosure without
              breach of this Agreement by the receiving party; or

         (e)  Is required by law to be disclosed, in which case the receiving
              party will give the disclosing party prompt written notice of
              the required disclosure. The disclosing

<PAGE>

              party may, in good faith and at its own expense, contest
              disclosure or seek confidential treatment and the receiving
              party shall cooperate with the disclosing party in all
              reasonable respects.

                    11. GENERAL'S REPRESENTATIONS AND WARRANTIES

         GENERAL represents and warrants to COMPANY as follows:

11.1     GENERAL is the owner by assignment from Dr. Wolf of his entire
         right, title and interest in the GENERAL PATENT RIGHTS and the JOINT
         PATENT RIGHTS.

11.2     Pursuant to Exhibit C, GENERAL has been approved by NYCOMED to
         license or sublicense NYCOMED's rights in PATENT RIGHTS which are
         described in paragraph 1.6.

11.3     To the best of GENERAL's knowledge, no person or entity, other than
         GENERAL, the U.S. Government pursuant to 35 U.S.C. Section 202(c),
         NYCOMED and [****] or [****] successor in interest in the [****]
         Agreement, has any right, title or interest in the PATENT RIGHTS.

11.4     GENERAL has full right, power and authority to grant the license
         under the PATENT RIGHTS granted to COMPANY under Section 2.2 of this
         Agreement and to otherwise enter into this Agreement.

11.5     This Agreement is legally binding on GENERAL and does not conflict
         with or breach any other Agreement to which GENERAL is a party.

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

11.6     As of the EFFECTIVE DATE, GENERAL has no notice or actual knowledge
         (without having conducted any due diligence) that the GENERAL PATENT
         RIGHTS or JOINT PATENT RIGHTS conflict with or infringe the rights
         of any other person or entity (other than NYCOMED, [****] or its
         successor in interest) or that the rights of any other person or
         entity conflict with or infringe the GENERAL PATENT RIGHTS or JOINT
         PATENT RIGHTS.

                               12. MISCELLANEOUS

12.1     This Agreement constitutes the entire agreement between the parties
         with respect to the subject matter hereof and, supersedes all prior
         agreements, representations and negotiations concerning such subject
         matter (none of which prior matters shall be binding on the
         parties). OTHER THAN WARRANTIES EXPRESSLY SET FORTH IN THIS
         AGREEMENT, NEITHER GENERAL NOR COMPANY MAKES ANY REPRESENTATION OR
         WARRANTY, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY
         IMPLIED WARRANTY OF MERCHANTABILITY OR ANY IMPLIED WARRANTY OF
         FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT WITH RESPECT TO
         ANY PRODUCT, PATENT, TRADEMARK, SOFTWARE, TRADE SECRET, TANGIBLE
         RESEARCH PROPERTY, INFORMATION OR DATA AND EACH PARTY HEREBY
         DISCLAIMS THE SAME.

12.2     In order to facilitate implementation of this Agreement, GENERAL and
         COMPANY are designating the following individuals to act on their
         behalf with respect to this Agreement for the matter indicated below:

         (a)  with respect to all royalty payments, any correspondence
              pertaining to any PATENT RIGHT, or any notice of the use of
              GENERAL's name, for GENERAL, the Director, Office of Corporate
              Sponsored Research and Licensing, and for COMPANY, John T.
              Smolik; provided that correspondence relating to the billing of
              patent costs shall be copied to, for GENERAL, the Business
              Manager, Office of Technology Affairs; and for COMPANY, John T.
              Smolik.

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[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         (b)  any amendment of or waiver under this Agreement, any written
              notice including progress reports or other communication
              pertaining to the Agreement:  for GENERAL, the Director, Office
              Corporate Sponsored Research and Licensing; and for COMPANY,
              John T. Smolik.

         (c)  the above designations may be superseded from time to time by
              alternative designations made by: for GENERAL, the President or
              the Senior Vice President, Office of Corporate Sponsored
              Research and Licensing; and for COMPANY, Eric A. Wachter.

12.3     This Agreement may be amended and any of its terms or conditions may
         be waived only by a written instrument executed by the parties or,
         in the case of a waiver, by the party waiving compliance. The
         failure of either party at any time or times to require performance
         of any provision hereof shall in no manner affect its rights at a
         later time to enforce the same. No waiver by either party of any
         condition shall be deemed as a further or continuing waiver of such
         condition or term or of any other condition or term.

12.4     This Agreement shall be binding upon and inure to the benefit of and
         be enforceable by the parties hereto and their respective successors
         and permitted assigns.

12.5     Any delays in or failures of performance by either party under this
         Agreement shall not be considered a breach of this Agreement if and
         to the extent caused by occurrences beyond the reasonable control of
         the party affected, including but not limited to: Acts of God; acts,
         regulations or laws of any government; strikes or their concerted
         acts of worker; fires; floods; explosions; riots; wars; rebellion;
         and sabotage. Any time for performance hereunder shall be extended
         by the actual time of delay caused by such occurrence.

12.6     Neither party shall use the name of the other party or of any staff
         member, officer, employee or student of the other party or any
         adaptation thereof in any advertising, promotional or sales
         literature, publicity or in any document employed to obtain funds or
         financing without the prior written approval of the party or
         individual whose name is to be used. For GENERAL, such approval
         shall be obtained from the Director of Public Affairs and for
         COMPANY from John T. Smolik. The foregoing, however, shall not
         restrict the COMPANY's obligation to make all disclosures and
         filings required by the Securities and Exchange Commission or any
         stock exchange on which the COMPANY's stock is listed.

12.7     This Agreement shall be governed by and construed and interpreted in
         accordance with the laws of the Commonwealth of Massachusetts.

<PAGE>

12.8     This Agreement shall not be assignable by GENERAL without COMPANY's
         prior written consent except for the right to receive royalties or
         other payments payable herein. COMPANY may at its own discretion and
         without approval by GENERAL transfer its interest or any part
         thereof under this Agreement to a wholly-owned subsidiary or any
         assignee or purchaser of the portion of its business associated with
         the manufacture and sale of PRODUCT. In the event of any such
         transfer, the transferee shall assume and be bound by the provisions
         of this Agreement. Otherwise this Agreement shall be assignable by
         COMPANY only with the consent in writing of GENERAL.

12.9     For any and all claims, disputes, or controversies arising under,
         out of, or in connection with this Agreement, except issues relating
         to the validity, construction or effect of any PATENT RIGHT, which
         the parties shall be unable to resolve within sixty (60) days, the
         party raising such dispute shall promptly advise the other party of
         such claim, dispute, or controversy in a writing which describes in
         reasonable detail the nature of such dispute. By not later than five
         (5) business days after the recipient has received such notice of
         dispute, each party shall have selected for itself a representative
         who shall have the authority to bind such party and shall
         additionally have advised the other party in writing of the name and
         title of such representative. By not later than ten (10) business
         days after the date of such notice of dispute, such representatives
         shall agree upon a third party which is in the business of providing
         Alternative Dispute Resolution (ADR) services (hereinafter, "ADR
         Provider") and shall schedule a date with such ADR Provider to
         engage in mediation as an ADR. All parties to this Agreement shall
         be equally responsible for all costs and fees of the ADR.
         Thereafter, the representatives of the parties shall engage in good
         faith in an mediation/ADR process under the auspices of the selected
         ADR Provider. If within the aforesaid thirty (30) business days
         after the date of the notice of dispute the representatives of the
         parties have not been able to agree upon an ADR Provider and
         schedule a date to engage in ADR, or if they have not been able to
         resolve the dispute within thirty (30) business days after the
         termination of ADR, the parties shall have the right to pursue any
         other remedies legally available to resolve such dispute in either
         the Courts of the State of Illinois or in the United States District
         Court for the Northern District of Illinois, in either case sitting
         in Chicago, to whose jurisdiction for such purposes GENERAL and
         COMPANY hereby irrevocably consents and submits. Notwithstanding the
         foregoing, nothing in this Paragraph shall be construed to waive any
         rights or timely performance of any obligations existing under this
         Agreement.

<PAGE>

12.10     The parties acknowledge and incorporate the Recitals into the body
         of this Agreement and GENERAL and NYCOMED each acknowledge and agree
         that all statements of fact in said Recitals attributable or
         relating to them constitute representations of fact which COMPANY
         may rely upon as an inducement to entering into this Agreement.

12.11    If any provision(s) of this Agreement are or become invalid, are
         ruled illegal by any court of competent jurisdiction or are deemed
         unenforceable under then current applicable law from time to time in
         effect during the term hereof, it is the intention of the parties
         that the remainder of this agreement shall not be effected thereby.
         It is further the intention of the parties that in lieu of each such
         provision which is invalid, illegal or unenforceable, there be
         substituted or added as part of this Agreement a provision which
         shall be as similar as possible in economic and business objectives
         as intended by the parties to such invalid, illegal or enforceable
         provision, but shall be valid, legal and enforceable.

12.12    All notices and other communications between the parties in
         connection with this Agreement shall be in writing and such notices,
         communications and all payments hereunder shall be deemed
         sufficiently given when delivered by messenger or overnight courier
         providing for receipted delivery, transmitted by fax with
         confirmation of transmission or sent by prepaid United States mail
         or other recognized carrier, addressed as follows:

         If to COMPANY:

              John T. Smolik
              President, CEO
              Photogen, Inc.
              7327 Oak Ridge Highway
              Knoxville, TN 37931
              Fax number:  (423) 769-4013

         If to GENERAL:

              Director, Office of Corporate Sponsored Research and Licensing
              Massachusetts General Hospital
              13th Street, Building 149
              Suite 1101
              Charleston, MA  02129
              Fax number:  (617) 726-1668

Either party may change its address by written notice given to the other party.

12.13    The COMPANY hereby waives its right to bring any claim, suit or
         action against GENERAL or any of its affiliates for any liability
         arising out of NYCOMED's

<PAGE>

         maintenance or enforcement of the [****] Agreement or the [****]
         PATENT RIGHTS, or NYCOMED's failure to meet any of its obligations
         under this Agreement.

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.

<PAGE>

         THE PARTIES have duly executed this Agreement as of the date first
shown above written.

PHOTOGEN, INC.                         THE GENERAL HOSPITAL CORPORATION


BY:      /s/ John Smolik               BY:     /s/
      -----------------------------          ----------------------------

TITLE:   President                     TITLE:  Associate Director, CSRL
      -----------------------------          ----------------------------


DATE:    10/20/99                      DATE:   10/21/99
      -----------------------------          ----------------------------

         The undersigned, Gerald L. Wolf, Ph.D., M.D., has reviewed the
foregoing Agreement, hereby acknowledges the terms and conditions of the
foregoing Agreement, insofar as such terms and conditions have any
application to him and consents to the same.

DATE:    10/20/99                              /s/ Gerald L. Wolf
      -----------------------------          ----------------------------
                                             Gerald L. Wolf, Ph.D., M.D.

<PAGE>

     The undersigned, ___________________, PRESIDENT of NYCOMED and the duly
authorized representative of NYCOMED, confirms, represents and agrees that
NYCOMED has appointed GENERAL its agent pursuant to Exhibit C for purposes of
licensing and sublicensing all of NYCOMED's right, title, and interest in the
JOINT PATENT RIGHTS and in the [****] PATENT RIGHTS as described in this
Agreement. NYCOMED agrees to comply with Sections 2.4, 4.3, 7.5, 7.6 of this
Agreement and NYCOMED acknowledges and agrees with Section 12.10 of this
Agreement.

Date:      10/20/99
      ---------------------------

  /s/
-----------------------------------

----------------

[****]   REPRESENTS MATERIAL WHICH HAS BEEN REDACTED PURSUANT TO A REQUEST
         FOR CONFIDENTIAL TREATMENT PURSUANT TO RULE 24B-2 UNDER THE
         SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.