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                                                                   Exhibit 10.11



                                NOMOS CORPORATION
                             2591 Wexford Bayne Road
                               Sewickley, PA 15143

                                February 11, 2002


John W. Manzetti
504 Appleridge Court
Gibsonia, PA  15044

Dear John:

         NOMOS Corporation (the "Company") considers it essential to the best
interests of its stockholders to foster the continuous employment of key
management personnel.

         In order to induce you to remain in the employ of the Company, the
Company agrees that you shall receive the severance benefits set forth in this
letter agreement (the "Agreement"). This benefit replaces and supersedes the
benefits set forth in those certain letter agreements dated April 16, 1999 and
June 30, 2000, both between you and the Company, which prior agreements are
deemed null and void.

         1. SEVERANCE. Subject to Section 3 of this letter, you will receive a
severance payment equal to twelve months of your base salary in the event your
employment with the Company is terminated at any time after this agreeement.

         2. PAYMENT TERMS. The severance payment contemplated by this Agreement
shall be payable in cash in a single lump sum within seven days after the
termination of your employment except as noted below.

         3. SEVERANCE TERMS. The severance shall be payable to you if your
employment with the Company is terminated, unless such termination is (a)
because of your death or Disability; (b) by the Company for Cause; or (c) by you
for other than Good Reason.

         4. DISABILITY. If, as a result of your incapacity due to physical or
mental illness, you shall have been absent from the full-time performance of
your duties with the Company for six (6) consecutive months, and within thirty
(30) days after written notice of termination is given you shall not have
returned to the full-time performance of your duties, your employment may be
terminated for "Disability."

         5. CAUSE. Termination by the Company of your employment for "Cause"
shall mean termination (a) upon the willful and continued failure by you to
substantially perform your duties with the Company (other than any such failure
resulting from your incapacity due to physical or mental illness), after a
written demand for substantial performance is delivered to you by the Board, or
(b) the willful engaging by you in conduct which is demonstrably and materially
injurious to the Company, monetarily or otherwise. For purposes of this Section,
no act, or failure to

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John W. Manzetti
February 13, 2002
Page 2



act, on your part shall be deemed "willful" unless done, or omitted to be done,
by you not in good faith and without reasonable belief that your action or
omission was in the best interest of the Company.

         6. GOOD REASON. You shall be entitled to terminate your employment for
Good Reason. For purposes of this Agreement, "Good Reason" shall mean the
occurrence of:

            (a) the assignment to you of any material duties inconsistent
     (unless in the nature of a promotion) with the position in the Company that
     you hold, or a significant adverse reduction or alteration in the nature or
     status of your position, duties, status or responsibilities or the
     conditions of your employment;

            (b) a reduction by the Company in your annual base salary as the
     same may be increased from time to time, except for across-the-board salary
     reductions similarly affecting all management personnel of the Company; and

            (c) the Company's requiring you to be based more than 50 miles from
     the location at which you were based, except for required travel on the
     Company's business to an extent substantially consistent with your present
     business travel obligations.

         7. SUCCESSORS; BINDING AGREEMENT. (i) The Company will require any
successor (whether direct or indirect, by purchase, merger, consolidation or
otherwise) to all or substantially all of the business and/or assets of the
Company to expressly assume and agree to perform this Agreement in the same
manner and to the same extent that the Company would be required to perform it
if no such succession had taken place.

         (ii) This Agreement shall inure to the benefit of and be enforceable by
you and your personal or legal representatives, executors, administrators,
successors, heirs, distributees, devisees and legatees.

         8. MISCELLANEOUS. No provision of this Agreement may be modified,
waived or discharged unless such waiver, modification or discharge is agreed to
in writing and signed by you and such officer as may be specifically designated
by the Board. No waiver by either party hereto at any time of any breach by the
other party hereto of, or compliance with, any condition or provision of this
Agreement to be performed by such other party shall be deemed a waiver of
similar or dissimilar provisions or conditions at the same or at any prior or
subsequent time. No agreements or representations, oral or otherwise, express or
implied, with respect to the subject matter hereof have been made by either
party which are not expressly set forth in this Agreement. The validity,
interpretation, construction and performance of this Agreement shall be governed
by

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John W. Manzetti
February 13, 2002
Page 3



the laws of the Commonwealth of Pennsylvania without regard to its conflicts of
law principles.

         9. VALIDITY. The invalidity or unenforceability of any provision of
this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement, which shall remain in full force and effect.

         10. COUNTERPARTS. This Agreement may be executed in several
counterparts, each of which shall be deemed to be an original but all of which
together will constitute one and the same instrument.

         11. ENTIRE AGREEMENT. This Agreement sets forth the entire agreement of
the parties hereto in respect of the subject matter contained herein and
supersedes all prior agreements, promises, covenants, arrangements,
communications, representations or warranties, whether oral or written, by any
officer, employee or representative of any party hereto; and any prior agreement
of the parties hereto in respect of the subject matter contained herein is
hereby terminated and cancelled.

         If this letter sets forth our agreement on the subject matter hereof,
kindly sign and return to the Company the enclosed copy of this letter, which
will then constitute our agreement on this subject.

                                   Sincerely,

                                   NOMOS CORPORATION



                                   By:    /s/ David J. Haffner
                                      --------------------------------
                                      Name: David J. Haffner
                                      Title: Vice President and
                                             Chief Financial Officer
                                             NOMOS Corporation


Agreed to this 28TH day of MARCH, 2002



     /s/ John W. Manzetti
------------------------------------
Name:  John W. Manzetti