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                                      LEASE

1. PARTIES

Westborough Mill, LLC, with an address at 13 Water Street, Holliston, MA, 01746
("LESSOR"), which expression shall include heirs, successors, and assigns where
the context so admits, does hereby lease to:

                                 PHOTOGEN, INC.

with an address at 69 Milk Street, Suite 308, 310, Westborough, MA 10581
("LESSEE"), which expression shall include successors, executors,
administrators, and assigns where the context so admits, and the LESSEE hereby
leases the following described premises:

2. PREMISES

Those certain premises consisting of 3,127 rentable square feet of office space
located on the third floor, suite 308, 310, as shown on attached exhibit A
("Leased Premises") with the right to use in common, with others entitled
thereto, the hallways, stairways, necessary for access to said Leased Premises,
parking lot, bathrooms, dumpster, and loading docks.

3. TERM

The term of this Lease shall be for five (5) years commencing on November 1,
1999 and ending on October 31, 2004.

4. RENT

LESSEE shall pay to the LESSOR, rent at the rate of:

November 1-30, 1999 $3,056.62 per month for Suite 308
December 1-31, 1999 $3,056.62 per month for Suite 308

Commencing January 1, 2000 for Suites 308 and 310: Forty-Three Thousand Dollars
($43,000.00) for the ten month period ending October 31, 2000, payable in
advance in monthly installments of Four Thousand Three Hundred Dollars
($4,300.00).

Year Two: Fifty-One Thousand Five Hundred Ninety-Five and 50/100 Dollars
($51,595.50) per year, payable in advance in monthly installments of Four
Thousand Three Hundred Dollars ($4,300.00).


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Year Three: Fifty-Three Thousand One Hundred Fifty-Nine Dollars ($53,159.00) per
year, payable in advance in monthly installments of Four Thousand Four Hundred
Thirty Dollars ($4,430.00).

Years Four and Five: Fifty-Four Thousand Seven Hundred Twenty-Two Dollars
($54,722) per year, payable in advance in monthly installments of Four Thousand
Five Hundred Sixty Dollars ($4,560.00).

LESSEE shall incur a late payment penalty equal to 5% of the monthly installment
payment for payments not received by the 7th day of each month.

Upon execution of this lease, LESSEE shall deposit an amount equal to Seven
Thousand Six Hundred Sixteen Dollars and 62/100 ($7,616.62), which amount shall
be LESSEE's first and last month's lease payment.

5. SECURITY DEPOSIT

Upon execution of this lease, LESSEE shall pay a security deposit equal to Four
Thousand Five Hundred Sixty Dollars ($4,560.00), which amount shall be held as
security for the LESSEE's performance as herein provided and refunded to the
LESSEE at the end of the Lease, subject to the LESSEE's satisfactory compliance
with the conditions hereof. In no event shall the security deposit be considered
prepaid rent.

6.   RENT ADJUSTMENTS

     A. COMMON AREA CHARGES Intentionally omitted

     B. REAL ESTATE TAXES

        If in any tax year commencing with the fiscal year 2001, the real estate
        taxes paid on the land and buildings, of which the Leased Premises are a
        part, are in excess of the amount of the current real estate taxes
        thereon for the fiscal year 2000 (hereinafter called the "Base Year") as
        a sole result of a change in that tax rate, LESSEE will pay to LESSOR as
        additional rent hereunder, when and as designated by notice in writing
        by LESSOR, LESSEE's percentage share, 7.8 percent of such excess that
        may occur in each year of the term of this Lease or any extension or
        renewal thereof and proportionately for any part of a fiscal year.

7.  UTILITIES

Except to the extent that the same are furnished through separately metered
utilities, LESSOR agrees to provide all utility service in common areas and to
furnish reasonable hot and cold water and reasonable heat and air conditioning
such that the LESSEE is comfortable in the leased


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premises, the hallways, stairways and lavatories during normal business hours
(8am to 6pm) on regular business days of the heating and air conditioning
seasons of each year, and to light passageways and stairways during business
hours, all subject to interruption due to any accident, to the making of
repairs, alterations, or improvements, to labor difficulties, to trouble in
obtaining fuel, electricity, service or supplies from the sources from which
they are usually obtained for said building, or to any cause beyond LESSOR's
control. The LESSOR shall maintain heating and air conditioning equipment in
good operating order.

LESSOR shall have no obligation to provide utilities or equipment other than the
utilities and equipment within the premises as of the commencement of this
lease. In the event LESSEE requires additional utilities or equipment, as
confirmed by LESSEE, the installation and maintenance thereof shall be the
LESSEE's sole obligation, provided that such installation shall be subject to
the written consent of the LESSOR.

8. USE OF LEASED PREMISES

The LESSEE shall use the premises only for the purpose of:

                         GENERAL OFFICE AND RELATED USES

9. COMPLIANCE WITH LAWS

LESSEE acknowledges that no trade or occupation shall be conducted in the Leased
Premises or use made thereof which will be unlawful, improper, noisy or
offensive, or contrary to any law or municipal by-law or ordinance in force in
the town in which the premises are situated.

LESSOR acknowledges that it shall not rent or lease any portion of the building
for any use, which will be unlawful, improper, noisy or offensive, or contrary
to any law or municipal by-law or ordinance in force in the town in which the
premises are situated.

10. FIRE

LESSEE shall not permit any use of the Leased Premises which will make voidable
any insurance on the property of which the Leased Premises are a part, or on the
contents of said property or which shall be contrary to any law or regulation
from time to time established by the New England Fire Insurance Rating
Association, or any similar body succeeding to its powers.

11. MAINTENANCE

    A.  LESSEE agrees to maintain the Leased Premises in substantially the same
        condition as it is on the commencement of the term of this Lease,
        ordinary wear and tear, damage by fire and other casualty only excepted
        subject to buildout. The LESSEE shall not permit the Leased Premises to
        be overloaded, damaged,


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        stripped, or defaced, nor suffer any waste. The LESSEE shall obtain the
        written consent of the LESSOR before erecting any sign in or on the
        premises. LESSOR shall place signs naming the LESSEE on the building
        directory and on the LESSEE's door.

    B.  LESSOR agrees to maintain the structure and heating, cooling systems of
        the building of which the Leased Premises are a part in the same
        condition as it is on the commencement of the term of this lease,
        reasonable wear and tear, damage by fire and other casualty only
        excepted. The LESSOR warrants that the structure and the mechanical
        systems of the building of which the Leased Premises are a part are in
        good operating order and/or condition at the time of the commencement of
        the Lease.

12. ALTERATIONS/ADDITIONS

In the event that LESSEE performs any work on the premises, LESSEE shall not
permit any mechanic's liens, or similar liens, to remain upon the Leased
Premises for labor and materials furnished to LESSEE or claim to have been
furnished to LESSEE in connection with work of any character performed or
claimed to have been performed at the direction of LESSEE and shall cause any
lien to be released of record forthwith without cost to LESSOR. Any alterations
or improvements made by the LESSEE shall become the property of the LESSOR at
the termination of occupancy as provided herein.

13. ASSIGNMENT/SUBLEASING

LESSEE shall not assign or sublet the whole or any part of the Leased Premises
without LESSOR's prior written consent, which shall not be unreasonably withheld
or delayed. In the event of an attempted assignment without Lessor's prior
written consent, LESSOR reserves the right to release LESSEE from obligations
under this Lease. LESSEE shall engage the brokerage services of the real estate
broker currently representing the building in the event LESSEE seeks to sublet
the premises.

14. SUBORDINATION/NON-RECORDING/NON-DISTURBANCE AGREEMENT

This lease shall be subject and subordinate to any and all mortgages, deeds of
trust and other instruments in the nature of a mortgage, now or at any time
hereafter placed upon the property of which the Leased Premises are a part and
the LESSEE shall, when requested, promptly execute and deliver such written
instruments as shall be necessary to show the subordination of this Lease and to
said mortgages, deeds of trust or other such instruments in the nature of a
mortgage. LESSEE shall not record this lease. Any attempted recording shall be
considered a default under this lease. LESSOR agrees to make reasonable efforts
to obtain a Non-Disturbance Agreement from any future Mortgagee on behalf of the
LESSEE in the event that LESSOR is unable to


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provide said Non-Disturbance Agreement then Lessee may contact Mortgagee
directly to seek same.

14A. ESTOPPEL CERTIFICATES

Each party agrees, at any time, and from time to time, upon not less than
fifteen (15) days prior notice by the other party, to execute, acknowledge, and
deliver to the other party, a statement in writing addressed to the other party,
certifying that this Lease is unmodified and in full force and effect (or, if
there have been modifications, that the same is in full force and effect as
modified and stating the modifications), stating the date to which the fixed
minimum rent, additional rent and other charges have been paid, and stating
whether or not to the best knowledge of the signer of such certificate, there
exists any default in the performance of any covenant, agreement, term,
provision, or condition contained in this lease, and if so, specifying each such
default of which the signer may have knowledge, it being intended that any such
statement delivered pursuant hereto may be relied upon by the other party and by
any Mortgagee or prospective Mortgagee or any mortgage affecting this lease and
by any LESSOR or LESSEE interest in this lease.

15. LESSOR'S ACCESS

The LESSOR or agents of the LESSOR may, at reasonable times and with reasonable
notice given to LESSEE (except in the case of emergencies), enter to view the
Leased Premises and make repairs as LESSOR shall elect to do and may show the
Leased Premises to others, and at any time within three (3) months before the
expiration of the term, may affix to any suitable part of the building of which
the Leased Premises are a part (but not the suite entrance of the LESSEE's
premises) a sign or notice for letting or selling the Leased Premises or
property of which the Leased Premises are a part and keep the same so affixed
without hindrance or molestation. LESSOR's entry of the Leased Premises shall
not interrupt the normal operation of the LESSEE's business or interfere with
the quiet enjoyment of the premises (except in the case of emergencies).

16. INDEMNIFICATION AND LIABILITY

LESSEE shall save the LESSOR harmless from all loss and damage to LESSEE's
property occasioned by the use or escape of water or by the bursting of pipes or
by any nuisance made or suffered on the Leased Premises, unless such loss is
caused by the neglect of the LESSOR.

17. FIRE, CASUALTY, EMINENT DOMAIN

Should a substantial portion of the Leased Premises, or of the property of which
they are a part, be substantially damaged by fire or other casualty, or be taken
by eminent domain, LESSOR may elect to terminate this Lease. When such fire,
casualty, or taking renders the Leased Premises substantially unsuitable for
their intended use, a just and proportionate abatement of rent shall be made,
and LESSEE may elect to terminate this lease if:


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    A.  LESSOR fails to give written notice within thirty (30) days of intention
        to restore Lease Premises, or

    B.  LESSOR fails to restore the Leased Premises to a condition substantially
        suitable for their intended use within ninety (90) days of said fire,
        casualty or taking.

LESSOR reserves, and LESSEE grants to LESSOR, all rights which LESSEE may have
for damages or injury to the Leased Premises for any taking by eminent domain,
except for damages to the LESSEE's fixtures, property or equipment or relocation
expenses of LESSEE.

18. DEFAULT AND BANKRUPTCY

In the event that:

    A.  LESSEE shall default in the payment of any installment of rent or other
        sum herein specified and such default shall continue for ten (10) days
        after written notice thereof; or

    B.  LESSEE shall default in the observance or performance of any of the
        LESSEE's covenants, agreement, or obligations hereunder and such default
        shall not be corrected within thirty (30) days after written notice
        thereof; or

    C.  LESSEE shall be declared bankrupt or insolvent according to law, or, if
        any assignment shall be made of LESSEE's property for the benefit of
        creditors;

        then the LESSOR shall have the right thereafter, while such default
        continues, to re-enter and take complete possession of the Leased
        Premises, to declare the term of this lease ended, and remove LESSEE's
        effects, without prejudice to any remedies which might be otherwise
        available to LESSOR. LESSEE shall indemnity LESSOR against all loss of
        rent and other payments, which LESSOR may incur by reason of such
        termination during the residue of the term. If LESSEE shall default,
        after reasonable notice thereof, in the observance or performance of any
        conditions or covenants on LESSEE's part to be performed or observed
        under or by virtue of any of the provisions in any article of this
        lease, LESSOR, without being under any obligation to do so and without
        thereby waiving such default, may remedy such default for the account
        and at the expense of LESSEE. If LESSOR makes any expenditures or incurs
        any obligations for the payment of money in connection therewith, such
        sums paid or obligations insured, with the interest at the rate of
        twelve percent (12%) per annum and costs shall be paid to the LESSOR by
        the LESSEE as additional rent.

    D.  If LESSOR breaches or defaults on its obligations under sections 7 and
        23D of this lease, which breach or default continues for thirty days
        after written notice of


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        said breach to LESSOR by LESSEE, then in that event, LESSEE may cure the
        breach or default on LESSOR's behalf and make the appropriate deduction
        from LESSEE's rent.

19. NOTICE

Any notice from the LESSOR to the LESSEE relating to the Leased Premises or to
the occupancy thereof, shall be deemed duly served, if mailed to LESSEE at 69
Milk Street, Westborough, MA, with a copy to Photogen Technologies, Inc., 7327
Oakridge Highway, Knoxville, TN 37831, Attention: President, registered mail,
return receipt requested, postage prepaid or at such address as the LESSEE may
from time to time advise in writing. All rent and notices shall be paid and sent
to LESSOR's address written above.

20. SURRENDER

LESSEE shall at the expiration date or other termination of this lease remove
all LESSEE's goods and effects from the Lease Premises (including, without
hereby limiting the generality of the foregoing, all signs and lettering affixed
or painted by the LESSEE, either inside or outside the Leased Premises). LESSEE
shall deliver to the LESSOR the Leased Premises and all keys, locks thereto, and
other fixtures connected therewith and all alterations and additions made to or
upon the Leased Premises, in substantially the same condition as it is on the
commencement of the term of this lease, ordinary wear and tear, damage by fire
or other casualty only excepted, subject to buildout. In the event of the
LESSEE's failure to remove any of LESSEE's property from the premises, LESSOR is
hereby authorized, without liability to LESSEE for loss and damage thereof, and
at the sole risk of LESSEE to remove, store or dispose of any of the property at
LESSEE's expense, or to retain same under LESSOR's control or to sell at public
or private sale as the case may be, without notice and to apply the net proceeds
of such sale to the payment of any sum due hereunder. In the event that LESSEE
has not vacated the Leased Premises upon the expiration of the lease term, then
in that event the per diem rent for the demised premises shall be one and
one-half (1-1/2) times the most recent per diem amount.

21. BROKERAGE

The parties acknowledge that there is a broker's commission due to Investment
Property Specialists, Inc., payable by the LESSOR as a result of this lease.

22. INSURANCE

    A.  LESSEE INSURANCE

        LESSEE shall maintain insurance coverage for worker compensation,
        general liability, and hazards covering LESSEE's employees, visitors,
        and LESSEE's premises and contents. Coverage shall be no less than
        $2,000,000 general liability


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        and $2,000,000 property naming LESSOR as additional insured. Each policy
        of insurance shall contain a provision requiring no less than ten (10)
        days notice to LESSOR prior to cancellation of the policy.

    B.  LESSOR INSURANCE

        LESSOR shall maintain general liability coverage for the property
        covering the common areas. Coverage shall be no less than $2,000,000.

23. OTHER PROVISIONS

    A.  GENERAL BUILDOUT

        LESSOR will build out Suites 308 and 310 to a similar level of finish
        and with the same color schemes as exist in the finished areas of the
        third floor for a turnkey delivery to LESSEE. LESSOR shall complete all
        items described on Exhibit B that is attached hereto and made a part
        here (LESSOR's Work) at its sole cost and expense, in a good and
        workmanlike manner.

    B.  PHONE DATA/CABLING

        LESSEE shall be solely responsible for contracting with and paying for a
        phone/data cabling company to install phone/data wiring and outlets in
        Suites 308 and 310. LESSEE may commence installation of phone/data
        wiring in the Leased Premises upon execution of this lease and receipt
        by LESSOR of payment of the first month's rent, last month's rent and
        security deposit. Such wiring and outlets shall become the property of
        the LESSOR at the termination of this lease.

    C.  OCCUPANCY

    i.  LESSOR shall notify LESSEE in writing when the Leased Premises are ready
        for LESSEE's occupancy.

    ii. LESSOR will deliver Suite 308 on November 1, 1999. LESSEE acknowledges
        that some buildout of the two offices contained in that suite will occur
        after LESSEE's occupancy and some disruption of LESSEE's business may
        occur. Suite 310 shall be delivered to LESSEE in turnkey condition no
        later than January 1, 2000.


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    D.  QUIET ENJOYMENT

        Without limiting any rights LESSEE may have by statute or common law,
        LESSOR covenants and agrees that, so long as this lease is in full force
        and effect, LESSEE shall lawfully and quietly hold, occupy and enjoy the
        Lease Premises during the term of this lease without disturbance by
        LESSOR or by any person having title paramount to LESSOR's title or by
        any person claiming through or under the LESSOR.

    E.  LESSEE'S USE OF ANY HAZARDOUS SUBSTANCE

        The only Hazardous Substance LESSEE may use in its operations are
        cleaning solvents. LESSEE will manage such use in accordance with the
        environmental laws. Other than using the foregoing cleaning solvents,
        LESSEE does not have direct or indirect responsibility for or authority
        to manage or control use, transportation, generation or disposal of any
        hazardous substance on the premises, the building or the property.

    F.  MISCELLANEOUS

        i.   Window Blinds. LESSEE shall be solely responsible for purchase and
             installation of any window blinds LESSEE deems necessary in
             Suites 308 and 310. If purchased by LESSEE, such blinds shall be
             horizontal and match the dark green color of other blinds seen
             around the building, except as necessary for blocking light for
             LESSEE's special purposes.

        ii.  Cleaning. LESSEE shall be solely responsible for all cleaning
             within Suites 308 and 310, and for removal of any trash generated
             by LESSEE to the common dumpster at the first floor level.

        iii. Hours of Operation. Building hours of operation are normal
             business hours (8am to 6pm). Notwithstanding the normal building
             hours of operation, LESSEE shall have unrestricted twenty-four
             hour access to LESSEE's suites.

    G.  PARKING

        LESSEE will have the daily use of nine (9) parking spaces, non-assigned,
        in the parking lot in addition to reasonable visitor parking.

IN WITNESS WHEREOF, the said parties hereunto set their hands and seals this
26th day of October, 1999.


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Photogen, Inc.                            Westborough Mill, LLC

By:       /s/ John Smolik
   -------------------------------        By:      /s/ James E. Levin
                                             ----------------------------------
Its:       President                         James E. Levin
    ------------------------------           President

Photogen Technologies, Inc.
Guarantees LESSEE's compliance with the
terms and conditions of this lease

By:       /s/ John Smolik
   -------------------------------

Its:       President
    ------------------------------


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                                    EXHIBIT A

                          [Diagram of Leased Premises]



<PAGE>

                                    EXHIBIT B

As part of the buildout, LESSOR will provide:

-   In suite 308...

    a.  Construction of two (2) additional offices finished, insulated walls
        eight (8) feet in height with wood trim painted and finished to match
        existing offices.

    b.  Removal of interior windows and wall at hallway with an archway
        constructed that is the width and height of the windows removed and
        finished to match existing wall and trim.

-   Removal of the carpet in the hallway and carpeted to match existing.
-   Construction of a wall to close off the hallway immediately after the
    entrance to suite 308.


-   In suite 310...
    a.  Construction of a storage room with a wall eight (8) feet in height with
        wood trim painted and finished to match existing offices.
    b.  Sheetrock blocked window openings, paint and trim off windows to match.
    c.  carpeted to match existing.
    d.  electric writing, lighting and plugs throughout in accordance with code.
    e.  close up opening in floor in accordance with code.


Special Conditions:


    a.  All construction to be completed either prior to occupancy or with a
        minimum of disruption to LESSEE which shall be construed to mean after
        business hours (5pm) or on weekends for work in suite 308 and hallway
        (except for carpeting) or with large steel fire door closed for noisy
        work in suite 310.
    b.  LESSEE shall be responsible for all telephone and data cabling for
        suites 308 and 310 to be completed during construction with reasonable
        notice by LESSOR.