<PAGE>
                                                                    Exhibit 10.4


                            [NOMOS Corporation Logo]


                             1993 STOCK OPTION PLAN


1. Purpose.

The purpose of the 1993 Stock Option Plan (the "Plan") is to induce key
personnel, including employees, officers, directors and consultants of NOMOS
Corporation (the "Company") to remain in the employ or service of the Company,
to attract new key personnel, and to encourage such persons to secure or
increase on reasonable terms their stock ownership in the Company. The Board of
Directors of the Company (the "Board") believes that the granting of stock
options (the "Options") under the Plan will promote continuity of management and
increased incentive and personal interest in the welfare of the Company and aid
in securing its continued growth and financial success. Options granted
hereunder are intended to be either (a) "incentive stock options" (which term,
when used herein, shall have the meaning ascribed thereto by the provisions of
Section 422(b) of the Internal Revenue Code of 1986, as amended [the "Code"]) or
(b) options which are not incentive stock options ("non-incentive stock
options") as determined at the time of the grant thereof by the Board.

2. Effective Date of the Plan.

The Plan shall become effective on April 1, 1993, by resolution of the Board,
subject to ratification of the Plan by the vote of the holders of (i) a majority
of all of the outstanding shares of the Common Stock of the Company (the "Common
Stock") present in person or by proxy at the next meeting of the Shareholders of
the Company or (ii) by unanimous written consent of such shareholders.

3. Stock Subject to Plan.

One million, five hundred thousand (1,500,000) of the authorized but unissued
shares of the Common Stock are hereby reserved for issue upon the exercise of
Options which may be granted under the Plan; PROVIDED, HOWEVER, that the number
of shares so reserved may from time to time be reduced to the extent that a
corresponding number of issued and outstanding shares of the Common Stock are
purchased by the Company and set aside for issue upon the exercise of Options
which may be granted under the Plan. If any Option expires or terminates for any
reason without having been exercised in full, the unpurchased shares subject
thereto shall again be available for the purposes of the Plan.

4. Administration.

The Plan shall be administered by the Board. Subject to the express provisions
of the Plan, the Board shall have complete authority, in its discretion, to
interpret the Plan, to


<PAGE>


prescribe, amend and rescind rules and regulation relating to it, to determine
the terms and provisions of the respective option certificates (which need not
be identical) to determine the individuals (each a "participant") to whom and
the times and the prices at which Options shall be granted, the periods during
which each Option shall be exercisable, the number of shares of the Common Stock
to be subject to each Option and whether such Option shall be an incentive stock
option or a non-incentive stock option and to accelerate the vesting or extend
the period of time during which an Option shall be exercisable and make all
other determinations necessary or advisable for the administration of the Plan.
In making such determinations, the Board may take into account the nature of the
services rendered by their respective participants, their present and potential
contributions to the success of the Company and such other factors as the Board
in its discretion shall deem relevant. The Board's determination on the matters
referred to in this Section 4 shall be conclusive. Any dispute or disagreement
which may arise under or as a result of or with respect to any Option shall be
determined by the Board, in its sole discretion, and any interpretations by the
Board of the terms of the Plan or any Option shall be final, binding and
conclusive.

5. Eligibility.

An Option may be granted only to key employees of the Company (including
officers and/or directors), directors of the Company who are not employees and
independent contractors hired or retained by the Company to provide on a regular
basis, consulting services for the Company.

6. Option Prices.

A. The initial per share option price of any Option which is an incentive stock
option shall not be less than the fair market value of a share of the Common
Stock on the date of grant; PROVIDED, HOWEVER, that, in the case of a
Participant who owns more than 10% of the total combined voting power of the
Common Stock at the time an Option which is an incentive stock option is granted
to him, the initial per share option price shall not be less than 110% of the
fair market value of a share of the Common Stock on the date of grant.

B. The initial per share option price of any Option which is a non-incentive
stock option shall not be less than 50% of the fair market value of a share of
the Common Stock on the date of grant.

C. For all purposes of the Plan, the fair market value of a share of the Common
Stock on any date shall be equal to the value thereof as determined in good
faith by the Board in its sole discretion; PROVIDED, HOWEVER, that, at such time
as shares of the Common Stock are publicly traded, following a public offering
under the Securities Act of 1933 as amended or otherwise, the fair market value
of a share of Common Stock shall be determined by the Board with reference to
the appropriate market prices for such shares.

7. Option Term.


                                                                          Page 2
<PAGE>


Options shall be granted for such term as the Board shall determine at the time
of the granting thereof, not in excess of ten (10) years from the date of the
granting thereof; PROVIDED, HOWEVER, that, in the case of a Participant who owns
more than 10% of the total combined voting power of the Common Stock at the time
an Option which is an incentive stock option is granted to him, the term with
respect to such Option shall not be in excess of five (5) years from the date of
the granting thereof.

8. Limitation on Amount of Incentive Stock Options Granted.

The aggregate fair market value of the shares of the Common Stock for which any
Participant may be granted Options which are incentive stock options which are
exercisable for the first time in any calendar year (whether under the terms of
the Plan or any other stock option plan of the Company) shall not exceed
$100,000.

9. Exercise of Options.

A. Except as otherwise determined by the Board at the time of the grant thereof,
a Participant may not exercise an Option during the period commencing on the
date of the granting of such Option to him and ending on the day preceding the
first anniversary of such date. Except as otherwise so provided, a Participant
may (i) during the period commencing on the first anniversary of the date of the
granting of an Option to him and ending on the day preceding the second
anniversary of such date, exercise such Option with respect to one-fifth of the
shares granted thereby, (ii) during the period commencing on such second
anniversary and ending on the day preceding the third anniversary of such date,
exercise such Option with respect to two-fifths of the shares granted thereby,
(iii) during the period commencing on such third anniversary and ending on the
day preceding the fourth anniversary of such date, exercise such Option with
respect to three-fifths of the shares granted thereby, (iv) during the period
commencing on such fourth anniversary and ending on the day preceding the fifth
anniversary of such date, exercise such Option with respect to four-fifths of
the shares granted thereby and (v) during the period commencing on such fifth
anniversary, exercise such Option with respect to all of the shares granted
thereby. Notwithstanding the foregoing, unless otherwise expressly provided by
the Board at the time of the granting of an Option, each Option shall
immediately become exercisable in full upon the death or permanent disability of
Participant.

B. To the extent then exercisable, an Option may be exercised either in whole at
any time or in part from time to time.

C. An Option may be exercised only by a written notice of intent to exercise
such Option with respect to a specific number of shares of the Common Stock and
payment to the Company of the amount of the Option price for the number of
shares of the Common Stock so specified.

D. The Board may, in its discretion, permit any Option to be exercised, in whole
or in part, prior to the time when it would otherwise be exercisable.

10. Transferability.


                                                                          Page 3
<PAGE>


Options granted under this Plan shall be exercisable by the Employee receiving
such Option or such Employee's guardian or legally appointed personal
representative. In no event shall the Option be transferable except, in the case
of death, by will or the laws of descent and distribution. No Option granted
under this Plan shall be subject to attachment, execution or other similar
process. In the event of an attempt to alienate, assign, pledge, hypothecate or
other dispose of the Option, except as otherwise provided in this Plan, or if a
levy of any attachment, execution or similar process upon the rights or interest
conferred under this Plan is attempted, the Corporation may terminate the Option
by notifying the Employee, and the Option shall thereupon become null and void.
No Option shall be assignable or transferable except by will and/or by the laws
of descent and distribution and, during the life of any Participant, each Option
granted to him may be exercised only by him.

11. Termination of Employment or Service.

Unless otherwise provided by the Board, either at the time of grant or at the
time of termination, in the event a participant leaves the employ or service of
the Company, whether voluntarily or otherwise, each Option therefore granted to
him shall, to the extent not theretofore exercised, terminate on the 30th day
after the date the Participant's employment or services terminate. In the event
an Employee exercises an Option intended to be an incentive stock option after
the aforementioned 30 day period, such exercise shall terminate the incentive
stock option and be deemed to be an exercise of a non-qualified stock option. If
an Employee's employment terminates because of death, such Employee's estate
shall have one year from the date of death to exercise any Option granted under
the Plan. In the event an Employee becomes permanently disabled, the Employee or
the Employee's legally appointed personal representative (if such an appointment
is necessary), shall have one year from the date such Employee becomes
permanently disabled to exercise the Option granted hereby; provided, however,
that the Board may, in its sole discretion, extend the exercise period for
longer than one year in the event of an Employee's death, but in no event shall
the Board extend such exercise period beyond the original option term.

12. Adjustment of Number of Shares.

In the event that a dividend shall be declared upon the Common Stock payable in
shares of the Common Stock, the number of shares of the Common Stock then
subject to any Option and the number of shares of the Common Stock reserved for
issuance in accordance with the provisions of the Plan but not yet covered by an
Option shall be adjusted by adding to each share the number of shares which
would be distributable thereon if such shares had been outstanding on the date
fixed for determining the shareholders entitled to receive such stock dividend.
In the event that the outstanding shares of the Common Stock shall be changed
into or exchanged for a different number or kind of shares of stock or other
securities of the Company or of another corporation, whether through
reorganization, recapitalization, stock split-up, combination of shares, sale of
assets, merger or consolidation in which the company is the surviving
corporation, then, there shall be substituted for each share of the Common Stock
then subject to any Option and for each share of the Common Stock reserved for
issuance in


                                                                          Page 4
<PAGE>


accordance with the provisions of the Plan but not yet covered by an Option, the
number and kind of shares of stock or other securities into which each
outstanding share of the Common Stock shall be so changed or for which each such
share shall be exchanged. In the case of any substitution or adjustment in
accordance with the provisions of this Section 12, the option price in each
stock option certificate for each share covered thereby prior to such
substitution or adjustment shall be the option price for all shares of stock or
other securities which shall have been substituted for such share or to which
such share shall have been adjusted in accordance with the provisions of this
Section 12. No adjustment or substitution provided for in this Section 12 shall
require the Company to sell a fractional share under any stock certificate. In
the event of the dissolution or liquidation of the Company, or a merger,
reorganization or consolidation in which the Company is not the surviving
corporation, then, except as otherwise provided in the second sentence of this
Section 12, each Option, to the extent not theretofore exercised, shall
terminate on fifteen (15) days' notice from the Company.

13. Conditions of Exercise.

A. Unless the shares to be issued upon the exercise of an Option by a
Participant shall be registered prior to the issuance thereof under the
Securities Act of 1933, as amended, such Participant will, as a condition of the
Company's obligation to issue such shares, be required to give a representation
in writing that he is acquiring such shares for his own account as an investment
and not with a view to, or for sale in connection with, the distribution of any
thereof.

B. In the case of each non-incentive stock option, a condition of exericising
the same shall be the entry by the Participant exercising the same into such
arrangements with the Company with respect to income tax withholding as the
Board may determine.

C. Unless expressly waived by the Board, it shall be a condition of any
Participant exercising any Option that such Participant agree, in an instrument
prescribed by the Board, to be bound by the restrictions on the sale or transfer
of shares of Common Stock in accordance with the restrictions set forth in the
Company's stock subscription agreement, a copy of which is annexed hereto.

14. No Shareholder Status.

Neither any Participant nor his legal representatives, legatees or distributees
shall be or be deemed to be the holder of any share of the Common Stock covered
by an Option unless and until a certificate for such share has been issued. Upon
payment of the purchase price thereof, a share issued upon exercise of an Option
shall be fully paid and non-assessable.

15. No Restrictions on Corporate Acts.

Neither the existence of the Plan or any Option shall in any way affect the
right or power of the Company or its shareholders to make or authorize any or
all adjustments, recapitalizations, reorganizations or other changes in the
Company's capital structure or its business, or any merger or consolidation of
the Company, or any issue of bonds,


                                                                          Page 5
<PAGE>


debentures, preferred or prior preference stock ahead of or affecting the Common
Stock or the rights thereof, or dissolution or liquidation of the Company, or
any sale or transfer of all or any part of its assets or business, or any other
corporate act or proceeding whether of a similar character or otherwise.

16. No Employment or Service Right.

Neither the existence of the Plan nor the grant of any Option shall require the
Company to continue any Participant in the employ or other service of the
Company.

17. Termination and Amendment of the Plan.

The Board may, at any time, terminate the Plan or make such modifications of the
Plan as it shall deem advisable; PROVIDED, HOWEVER, that the Board may not,
without further approval of the holders of a majority of the shares of the
Common Stock, present in person or by proxy at any special or annual meeting of
the shareholders, increase the number of shares as to which Options may be
granted under the Plan (as adjusted in accordance with the provisions of Section
12 hereof) or extend the period during which an Option may be granted or
exercised. Except as otherwise provided in Section 12 hereof, no termination or
amendment of the Plan may, without the consent of the Participant to whom any
Option shall theretofore have been granted, adversely affect the rights of such
Participant under such Option.

18. Expiration and Termination of the Plan.

The Plan shall terminate on March 31, 2003, or at such earlier time as the Board
may determine. Options may be granted under the Plan at any time and from time
to time prior to its termination. Any Option outstanding under the Plan at the
time of the termination of the Plan shall remain in effect until such Option
shall have been exercised or shall have expired in accordance with its terms.



                                                                          Page 6