<PAGE>
                                                                  Exhibit 10.18


                        IMAGING BIOPHARMACEUTICALS, INC.

                             1997 STOCK OPTION PLAN

      1. PURPOSE OF PLAN

            The purpose of this plan (the "Plan") is to encourage key employees
(including officers and directors who are employees), and officers, directors
and consultants who are not employees, of Imaging Biophmaecuticals, Inc., a
Massachusetts corporation, and any present or future subsidiary and parent of
Imaging Biopharmaecuticals, Inc. (hereinafter collectively referred to as the
"Company") to acquire shares of common stock of Imaging Biopharmaecuticals,
Inc., $.01 par value, (the "Common Stock") and thereby increase their
proprietary interest in the Company's success and provide an added incentive to
remain in the employ of, or continue to render services to, the Company. The
words "parent" and "subsidiary" shall be interpreted in accordance with Section
422 and Section 424 of the Internal Revenue Code of 1986, as amended from time
to time (the "Code"). It is intended that options granted under the Plan shall
constitute either "incentive stock options" within the meaning of-Section 422 of
the Code or "non-qualified options" as determined by the Board of Directors of
Imaging Biophmaecuticals, Inc. in its sole discretion and indicated on each form
of option grant (the "Option Grant"). The terms of the Plan and Option Grants
shall be construed accordingly. Only employees of the Company shall be eligible
to receive incentive stock options.

      2. SHARES RESERVED UNDER THE PLAN

            Subject to the adjustment provided in Section 9, the aggregate
number of shares of Common Stock of Imaging Biophannaecuticals, Inc. which may
be issued and sold pursuant to options granted under the Plan shall not exceed
178,200 shares of Common Stock, which may be either authorized and unissued
shares or treasury shares. If any options granted under the Plan shall terminate
or expire without being fully exercised, the shares that have not been purchased
will again become available for purposes of the Plan.

      3. ADMINISTRATION

            The Plan shall be administered solely by the Board of Directors. A
majority of the members present at any meeting at which a quorum is present, and
any acts approved in writing by all of the members of the Board of Directors
without a meeting, shall constitute the acts of the Board of Directors. The
Board of Directors shall have the powers granted to it throughout this Plan. The
Board of Directors is authorized to interpret the Plan and, subject to the
provisions of the Plan, to prescribe, amend, and rescind rules and regulations
relating thereto. The Board of Directors is further authorized, subject to the
express provisions of the Plan, to alter or amend the form of Option Grant
attached hereto and to make all other determinations necessary or advisable in
the administration of the Plan. The interpretation and administration by the
Board of Directors of any provisions of the Plan and the Option Grant shall be
find and conclusive on all


<PAGE>

persons having any interest therein

            No member of the Board of Directors shall be held liable for any
action or determination made in good faith with respect to the Plan or any
option granted thereunder.

      4. OPTION GRANTS

            Options to purchase shares of Common Stock under the Plan may be
granted to key employees (including officers and directors who are employees)
and officers, directors and consultants of the Company who are not employees of
the Company. In selecting the individuals to whom options will be granted and in
deciding how many shares of Common Stock will be subject to each option, the
Board of Directors shall give consideration to the importance of an individual's
duties, experience with the Company, future value to the Company, present and
potential contribution to the success of the Company, and to such other factors
as the Board of Directors may deem relevant. Subject to the express provisions
of the Plan and the forms of Option Grant incorporated herein by reference as
from time to time altered or amended, the Board of Directors shall have
authority to determine with respect to each option Grant the number of
installments, the number of shares of Common Stock in each installment and the
exercise dates, and, to the extent not inconsistent with the applicable
provisions of the Code, if any, the Board of Directors may specify additional
restrictions and conditions. Each incentive stock option shall expire not later
than ten years from the date of the grant of such option.

            Except as provided in Section 7 below, no incentive stock option may
be granted to any employee who, at the time such option is granted, owns stock
possessing more than 10 percent of the total combined voting power of all
classes of stock of the Company within the meaning of Section 422 of the Code.

            The date of grant of an option to an individual under the Plan
shall be the date the Board of Directors votes to grant the option, but no
optionee shall have the right to exercise his option until the Company has
executed and delivered the Option Grant to such optionee. Each option granted
under the Plan shall be evidenced by and subject to the terms and conditions of
the Option Grant which is incorporated into the Plan by reference as from time
to time altered or amended.

            No stock option may be transferred by the optionee other than by
will or the laws of descent and distribution, and, solely in the case of
non-qualified options, by a distribution pursuant to a qualified domestic
relations order as defined by the Code or Title I of the Employee Retirement
Income Security Act or the rules thereunder, and can be exercised during the
optionees life only by him.

      5. OPTION PRICE

            The price per share at which each option granted under the Plan may
be exercised shall be determined by the Board of Directors subject to the
provisions of this Section 5. In the case of an incentive stock option, the
exercise price shall not be less than the fair market value

                                                                               2

<PAGE>

per share on the date of grant, as determined by the Board of Directors in good
faith, in accordance with applicable provisions of the Code then in effect with
respect to incentive stock options.

      6. LIMITATION ON AMOUNT

            The aggregate fair market value (determined at the time the option
is granted) of the stock with respect to which incentive stock options are
exercisable for the first time by an individual during any calendar year under
all plans of the Company shall not exceed $100,000.

      7. SPECIAL RULE FOR 10 PERCENT SHAREHOLDERS

            The Board of Directors may grant incentive stock options under this
Plan to persons who own more than 10 percent of the combined voting stock of the
Company if (i) at the time of the Option Grant the price per share at which the
option may be exercised is at least 110 percent of the fair market value of the
stock subject to the option and (ii) such option is not exercisable after the
expiration of five years from the date such option is granted.

      8. NON-OUALIFIED OPTIONS

            Notwithstanding the provisions of Sections 4, 5,6 and 7 of this
Plan, the Board of Directors may grant options which in one or more respects do
not meet the requirements for incentive stock options established by Section 422
of the Code. The Board of Directors shall indicate on each Option Grant whether
an incentive stock option within the meaning of Section 422 of the Code or a
non-qualified option is thereby granted.

            Except as otherwise provided in this Plan, the Board of Directors,
in its sole discretion, shall establish the terms and conditions for each
non-qualified option which it grants. Such terms and conditions may, but need
not, include some or all of the provisions of Section 4, 5,6 and 7 of this Plan
with respect to incentive stock options. If the Board of Directors grants an
option which in all respects meets the requirements for incentive stock options
it may nonetheless designate such option a non-qualified option on the Option
Grant, in which case it shall be deemed not to be an incentive stock option.

      9. ADJUSTMENT OF SHARES RESERVED UNDER THE PLAN

            The aggregate number and kind of shares reserved under the Plan, the
maximum number of shares as to which options may be granted to any individual
and the option price per share shall be appropriately adjusted by the Board of
Directors in the event of any recapitalization of the Company.

      10. DISSOLUTION OR REORGANIZATION

            Prior to a dissolution, liquidation, merger, consolidation, or
reorganization of the Company (the "Event"), the Board of Directors may decide
to terminate each outstanding option. If the Board of Directors so decides, such
option shall terminate as of the effective date of the

                                                                               3


<PAGE>

Event, but the Board of Directors shall suspend the exercise of all outstanding
options a reasonable time prior to the Event, giving each optionee not less than
fourteen days' written notice of the date of suspension, prior to which an
optionee may purchase in whole or in part the shares available to him as of the
date of receipt of the notice. If the Event is not consummated, the suspension
shall be removed and all options shall continue in full force and effect.

      11. AMENDMENT AND TERMINATION OF PLAN

            The Board of Directors may amend, suspend, or terminate the Plan,
including the form of Option Grant incorporated herein by reference. No such
action, however, may, without approval or ratification by the shareholders, make
any change which, pursuant to the Code or regulations thereunder, requires
action by the shareholders. No such action may, without the consent of the
holder of the option, alter or impair any option previously granted.

            In any event, the Plan shall terminate 10 years from the date of
adoption by the Board of Directors. Any shares remaining under the Plan at the
time of termination which are not subject to outstanding options and any shares
which thereafter become available because of the expiration or termination of an
option shall cease to be reserved for purposes of the Plan.

      12. RIGHT TO TERMINATE EMPLOYMENT

            Nothing contained herein or in any Option Grant executed pursuant
hereto shall restrict the right of the Company to terminate the employment of
any optionee at any time.

      13. DATE OF ADOPTION AND APPROVAL

            The date of adoption of this Plan by the Board of Directors and the
Plan's effective date is January 9, 1997. The date of approval of this Plan by
the Shareholders of Imaging Biopharmaceuticals, Inc. is January 9, 1997.

                                                                               4

<PAGE>

                      Amendments to 1997 Stock Option Plan

      1. On March 5, 1998, Imaging Biopharmaceuticals, Inc. changed its name to
Biostream, Inc.

      2. On February 29,2000 the 1997 Stock Option Plan was amended by the
company's stockholders to increase the number of authorized shares of common
stock available for issuance thereunder from 178,200 shares to 678,200 shares of
Common Stock.

      3. On April 12,2000 the Board of Directors of Biostream, Inc. declared a
2-for-1 common stock split, which split was approved by the stockholders on
April 13,2000.

      4. On January 23,2003 the 1997 Stock Option Plan was amended by the
company's stockholders to increase the number of authorized shares of common
stock available for issuance thereunder to an aggregate total of 13,000,000
shares of Common Stock.

      5. On April 25,2003 Biostream, Inc. changed its name to Molecular Insight
Pharmaceuticals, Inc.

                                                                               5