Document:

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                                                                 Exhibit 10.2(a)

                              SHAREHOLDER AGREEMENT

         This Agreement is made as of March 2, 2001, among NOMOS CORPORATION, a
Delaware corporation (the "COMPANY") and the persons listed on SCHEDULE A hereto
(each a "SHAREHOLDER", and, collectively, the "SHAREHOLDERS"). The Shareholders
include John A. Friede, founder, chairman and chief operating officer of the
Company (sometimes referred to herein as the "FOUNDER").

                                    PREAMBLE

         The Company presently has authorized capital stock consisting of 25
million shares of common stock, par value $.0001 per share ("COMMON"), 1 million
shares of Series A Preferred, par value $.0001 per share, 4 million shares of
Series B Preferred, par value $.0001 per share, and 3 million shares of Series C
Preferred, par value $.0001 per share ("PREFERRED"). Pursuant to a Subscription
Agreement of even date herewith, the Company has sold shares of its Series C
Preferred Stock to certain of the Shareholders. The Shareholders own or vote the
number of shares of the Common or Preferred shown on SCHEDULE A hereto. (The
Common and the Preferred are collectively referred to herein as the "SHARES".)

         The Company, the Founder and each of the Shareholders desire to enter
into this Agreement for the purposes, among others, of (a) assuring continuity
in the ownership and management of the Company and (b) limiting the manner and
terms by which the Company's capital stock may be transferred. Therefore, the
parties agree as follows with the intent to be legally bound.

                                    AGREEMENT

         1. CERTAIN DEFINITIONS. Capitalized terms used herein and not otherwise
defined shall have the following meanings:

         "AFFILIATE" means, with respect to any Shareholder, any Person who
directly or indirectly controls, is controlled by or is under common control
with such Shareholder, and the term "CONTROL" shall mean, with respect to any
Person, the possession, direct or indirect, of the power to direct or cause the
direction of the management and policies of such Person, whether through
ownership of voting securities, by contract or otherwise.

         "FAMILY GROUP" means, with respect to any individual Shareholder, (a)
the parents (whether natural or adoptive) and the descendants (whether natural
or adopted) of such Shareholder, (b) the siblings (whether natural or adopted)
and the descendants (whether natural or adopted) of the siblings of such
Shareholder, (c) the spouse of such Shareholder and the spouses of any of the
foregoing Persons and (d) any trust established solely for the benefit of any of
the foregoing Persons.

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         "INDEPENDENT THIRD PARTY" means any Person who, immediately prior to
the contemplated transaction, (a) is not an owner of 5% or more of the Company's
capital stock on a fully diluted basis, (b) is not an Affiliate of any such
owner or (c) is not a member of any such owner's Family Group.

         "PERSON" means any individual, partnership, corporation, trust, limited
liability company, joint venture, unincorporated organization or other entity.

         "PRO RATA SHARE" means, with respect to any Shareholder, an amount
equal to the percentage determined by dividing the number of Shares held by such
Shareholder on a fully diluted basis by the number of Shares held by all
Shareholders on a fully diluted basis.

         "PUBLIC SALE" means any sale of Shares to the public (a) pursuant to an
offering registered under the Securities Act or (b) through a broker, dealer or
market maker pursuant to the provisions of Rule 144 (other than Rule 144(k))
under the Securities Act.

         "QUALIFIED PUBLIC OFFERING" means any firm underwritten public offering
of the Company's common stock registered under the Securities Act, the proceeds
of which to the Company and/or the selling shareholders (if any), net of the
reasonable expenses of the Company incurred in effecting such public offering,
are at least $10,000,000.

         "SALE OF THE COMPANY" means (a) the sale of all or substantially all of
the Company's assets or (b) the consummation of any business combination,
approved by the holders of a requisite majority of the outstanding Shares, in
which the Company shall be the acquired corporation and the acquiring
corporation shall be an Independent Third Party.

         "SECURITIES ACT" means the Securities Act of 1933 and all rules,
regulations and orders issued thereunder, as any of the same may be amended.

         "TRANSFER" means, with respect to any Shares, any sale or other
transfer of such Restricted Security, whether voluntary, involuntary or by
operation of law.

         2. RESTRICTIONS ON TRANSFER.

            (a) TRANSFER RESTRICTED. Except for Transfers described in Section
2(e), no Shareholder shall Transfer any interest in any Shares unless and until
the requirements of Sections 2(b) and 2(c) shall be fulfilled. Any Transfer made
or purportedly made in violation of this restriction shall be null and void and
the Company shall not register or record such attempted Transfer in its books
and records.

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            (b) FIRST OFFER RIGHTS.

                (i) At least 30 days prior to making any Transfer of any Shares,
a transferring Shareholder (the "TRANSFERRING SHAREHOLDER") shall give written
notice (an "OFFER NOTICE") to the Company and each other Shareholder (each an
"OFFEREE SHAREHOLDER"), which Offer Notice shall disclose in reasonable detail
the proposed number of Shares to be transferred, the identity of the prospective
transferee(s) and the proposed terms and conditions of the Transfer (including
representations, warranties, covenants and indemnities); provided, that if the
consideration being offered to the Transferring Shareholder consists in whole or
in part of something other than U.S. dollars, then such notice shall also
contain a good faith estimate of the value of such consideration in U.S. dollars
and an explanation of the manner in which such estimate was made. The
Transferring Shareholder shall have the right to modify any Offer Notice to
reflect changed terms by giving notice to the Company and the Offeree
Shareholders to such effect until the earlier to occur of (A) the date when the
Company or any Offeree Shareholder elects to purchase any of such Shares, as
provided below, or (B) the date which is seven days prior to the end of such
30-day period.

                (ii) The Company shall have the first right to purchase all (but
not less than all) of the offered Shares, at the price and on the terms
specified in the Offer Notice, by giving written notice of such election to the
Transferring Shareholder and the Offeree Shareholders within 15 days after the
Offer Notice is given. Such notice may also specify a lesser number of the
offered Shares which the Company is willing to purchase pursuant to paragraph
(iv) below.

                (iii) If the Company does not so elect to purchase all of the
offered Shares, each Offeree Shareholder shall have the right to purchase all
(but not less than all) of its Pro Rata Share of the offered Shares as to which
the Company has not elected to purchase pursuant to paragraph (ii) above, at the
price and on the terms specified in the Offer Notice, by giving written notice
of such election to the Transferring Shareholder and the Company within 30 days
after the Offer Notice is given. Such notice may also specify a greater number
of the offered Shares which such Offeree Shareholder is willing to purchase
pursuant to paragraph (iv) below.

                (iv) Any of the offered Shares not elected to be purchased
pursuant to the first sentences of paragraphs (ii) and (iii) above shall be
divided among the Company and/or the Offeree Shareholders in accordance with the
second sentences of paragraphs (ii) and (iii) above, with the Company to have
the first right to purchase such remaining Shares. If two or more Offeree
Shareholders are willing to purchase more of such remaining Shares than are
available, then such remaining Shares shall be divided among such Offeree
Shareholders in the same proportion as the number of Shares then owned by each
such Offeree Shareholder on a fully diluted basis bears to the total number of
Shares owned by all such Offeree Shareholders on a fully diluted basis.

                                      -3-
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                (v) If the Company and/or the Offeree Shareholders elect to
purchase all of the offered Shares then, within 45 days after the Offer Notice
is given, the Transferring Shareholder shall give written notice to the Company
and the Offeree Shareholders to such effect, which notice shall also specify the
number of the offered Shares that each of them is entitled to purchase. The
closing of the sale of the offered Shares to the Company and/or the Offeree
Shareholders shall occur within 30 days after such notice is given, and the
consideration therefor shall be paid in (A) U.S. dollars (calculated using the
estimate set forth in the Offer Notice, if applicable) in immediately available
funds at such closing or (B) in accordance with the terms and conditions of
purchase set forth in the Offer Notice, if such terms and conditions provide for
a purchase other than for cash at closing.

                (vi) If the Company and/or the Offeree Shareholders do not elect
to purchase all of the offered Shares then, during the 90-day period commencing
30 days after the Offer Notice is given, the Transferring Shareholder shall have
the right to Transfer all (but not less than all) of the offered Shares to the
transferee(s), and on terms no more advantageous to such transferee(s) than
those, specified in the Offer Notice. If such offered Shares are not so
transferred within such time period, then any subsequent Transfer of such
securities shall be subject to all of the provisions of this Section 2(b).

            (c) PARTICIPATION RIGHTS.

                (i) At least 15 days prior to making any Transfer of any Shares,
the Founder shall give written notice (a "SALE NOTICE") to the Company and each
other Shareholder (each a "PARTICIPATING SHAREHOLDER"), which Sale Notice shall
disclose in reasonable detail the proposed number of Shares to be transferred,
the identity of the prospective transferee(s) and the proposed terms and
conditions of the Transfer (including representations, warranties, covenants and
indemnities); provided, that if the consideration being offered to the Founder
consists in whole or in part of something other than U.S. dollars, then such
notice shall also contain a good faith estimate of the value of such
consideration in U.S. dollars and an explanation of the manner in which such
estimate was made. The Founder shall have the right to modify any Sale Notice to
reflect changed terms by giving notice to the Company and the Participating
Shareholders to such effect until the date which is seven days prior to the end
of such 15-day period; provided, that any Participating Shareholder who has
elected to participate prior to its receipt of such further notice may
thereafter revoke such election.

                (ii) Each Participating Shareholder shall have the right to
participate in the proposed Transfer by giving written notice of such election
to the Founder within 10 days after the Sale Notice is given.

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                (iii) If any Participating Shareholders have so elected to
participate in a proposed Transfer, each of the Founder and such Participating
Shareholders shall be entitled to sell in such Transfer, at the same price and
upon the same terms, a number of Shares equal to the product of (A) the quotient
determined by dividing the percentage of Shares owned by such Shareholder on a
fully diluted basis by the aggregate percentage of Shares owned by the Founder
and all such Participating Shareholders on a fully diluted basis, multiplied by
(B) the number of Shares to be sold in the contemplated Transfer on a fully
diluted basis.

          FOR EXAMPLE, if (A) the Sale Notice contemplates a sale of 100 shares
          of Shares, (B) the Founder owns 30% of all Shares on a fully diluted
          basis and (C) one Participating Shareholder elects to participate and
          owns 20% of all Shares on a fully diluted basis, the Founder would be
          entitled to sell 60 shares (30% / 50% x 100 shares) and the
          Participating Shareholder would be entitled to sell 40 shares (20% /
          50% x 100 shares).

                (iv) The Founder shall use its reasonable best efforts to obtain
the agreement of the prospective transferee(s) to the participation of the
Participating Shareholders, and to the inclusion of all types of Shares, in any
proposed Transfer, and the Founder shall not Transfer any Shares to the
prospective transferee(s) if (A) any Participating Shareholders elect to
participate in such Transfer and (B) the prospective transferee(s) refuses to
allow the participation of such Participating Shareholders or to purchase the
type of Shares owned by such Participating Shareholders.

                (v) After compliance with the foregoing provisions of this
Section 2(c), the Founder and the Participating Shareholders who have so elected
shall be permitted to Transfer the number of Shares specified in the Sale Notice
to the transferee(s) specified in such Sale Notice on terms no more advantageous
to such Shareholders than those specified in such Sale Notice. Unless all of the
Shareholders have elected to participate and are permitted to participate in the
proposed Transfer, the closing of such Transfer shall occur during the 90-day
period following the period which is 45 days after the Sale Notice is given to
the Company. If such Shares are not so transferred within such time period, then
any subsequent Transfer of such securities shall be subject to all of the
provisions of this Section 2(c).

            (d) INTERPLAY BETWEEN FIRST OFFER RIGHTS AND PARTICIPATION RIGHTS.
The following provisions shall govern the interplay between Sections 2(b) and
2(c):

                (i) If the Company and/or the Offeree Shareholders exercise
their rights to purchase all of the Shares being offered pursuant to Section
2(b), then Section 2(c) shall not apply to the proposed Transfer.

                                      -5-

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                (ii) A Transfer otherwise permitted by Section 2(b)(vi) will not
be permitted if such Transfer is prohibited by Section 2(c)(iv).

                (iii) The requirement in Section 2(b)(vi) that a Transferring
Shareholder Transfer all of the offered Shares shall be satisfied by the Founder
if the Founder and the Participating Shareholders Transfer such number of Shares
in accordance with Section 2(c)(v).

            (e) PERMITTED TRANSFERS. The following Transfers may be made free
from the restrictions set forth in Sections 2(b) and (except as otherwise
provided) 2(c):

                (i) in the case of a Shareholder who is an individual, Transfers
(A) to any trust maintained solely for the benefit of such Shareholder, (B) to
the legal guardian of such Shareholder, in the event of the mental incapacity of
such Shareholder, or (C) to such Shareholder's estate or Family Group, in the
event of the death of such Shareholder;

                (ii) in the case of a Shareholder who is not an individual,
Transfers to any Affiliate of such Shareholder;

                (iii) in the case of Corporate Opportunities Fund, L.P. and
Corporate Opportunities Fund (Institutional), L.P. (together, the "SANDERS
FUNDS"), transfers between the Sanders Funds and from the Sanders Funds to their
partners;

                (iv) Transfers to the Company by the holders of Series C
Preferred Stock pursuant to the redemption provisions of the Amended and
Restated Certificate of Incorporation of the Company; and

                (v) Transfers constituting a Sale of the Company.

            (f) TERMINATION OF RESTRICTIONS. The restrictions on Transfer set
forth in Sections 2(b) and 2(c) shall automatically terminate and be of no
further force and effect upon the occurrence of (i) a Qualified Public Offering
or (ii) a Sale of the Company.

         3. RESTRICTIONS ON ENCUMBRANCES. No Shareholder shall assign, pledge,
grant a security interest in or otherwise permit any lien or encumbrance to
attach to any interest in any Shares, unless (a) the Company is the beneficiary
of the same or (b) the beneficiary of the same agrees that (i) it will not
Transfer or cause the Transfer of such Shares until Section 2 has been complied
with and (ii) it will cause the transferee(s) of such Shares to execute and
deliver to the Company a copy of this Agreement. Any action taken in violation
of this restriction shall be null and void. The foregoing restriction shall not
apply to Shares which have been transferred pursuant to a Public

                                      -6-
<PAGE>

Sale, and shall automatically terminate and be of no further force and effect
upon the occurrence of (i) a Qualified Public Offering or (ii) a Sale of the
Company.

         4. TRANSFEREES BOUND. As a condition precedent to any Transfer of any
Shares by any Shareholder, the Transferring Shareholder shall cause the
transferee(s) to execute and deliver to the Company a copy of this Agreement,
whereupon such transferee(s) shall be included in the definition of
"Shareholders" hereunder.

         5. PREEMPTIVE RIGHTS.

            (a) The Company hereby grants to each Shareholder the right
("PREEMPTIVE RIGHTS"), for so long as he or it shall own any Shares, to purchase
his or its pro rata share (determined by dividing (A) the total number of shares
of Common issuable upon conversion of the Series C Preferred Stock held of
record by such holder by (B) the total maximum number of shares of Common
issuable on a fully diluted basis) of any equity securities of the Company
issued or sold by the Company from time to time (collectively, "NEW
SECURITIES").

            (b) If the Company proposes to issue or sell any New Securities, it
shall give each Shareholder fifteen (15) days written notice (a "PREEMPTIVE
NOTICE") of its intention, which notice shall describe in reasonable detail the
type of New Securities to be issued or sold, the identity of the prospective
transferee(s) and the consideration and the terms upon which the Company
proposes to issue the same; provided, that if the proposed consideration for
such New Securities consists in whole or in part of something other than U.S.
dollars, then such notice shall also contain a good faith estimate of the value
of such consideration in U.S. dollars and an explanation of the manner in which
such estimate was made. Each Shareholder shall have 10 days from the date such
notice is given to elect to purchase all, but not less than all, of its pro rata
share of such New Securities by giving written notice to such effect to the
Company.

            (c) Following the expiration of such 10-day period, the Company
shall sell to the Shareholders the New Securities, if any, which they have
elected to purchase, and may sell to the transferee(s) identified in the
Preemptive Notice any New Securities which such Persons have not elected to
purchase for the consideration and upon the other terms specified in the
Preemptive Notice; provided, that each purchaser hereunder shall pay for the New
Securities purchased by it in U.S. dollars (calculated using the estimate set
forth in the Preemptive Notice, if applicable) in immediately available funds at
such closing. Any issuance or sale of New Securities made other than in
accordance with the foregoing sentence shall be subject to all of the provisions
of this Section.

            (d) The rights created by this Section 5 shall not apply (i) to any
offering or sale of securities by the Company in connection with a Qualified
Public Offering, (ii) to the exercise of any options to purchase, or other
security convertible

                                      -7-
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into, shares of Common granted to employees, officers or directors of the
Company pursuant to stock option agreements, stock option plans or management
incentive plans adopted by the Board of Directors of the Company, (iii) to
shares issued pursuant to the exercise of currently outstanding options or
warrants, or the conversion of any currently outstanding convertible securities,
(iv) to shares issued as paid-in-kind dividends or pursuant to anti-dilution
rights granted to any holder of the Company's securities, (v) to shares issued
in the acquisition of another company or (vi) to the issue or exercise of any
warrants or any "equity kicker" to any bank, finance company, leasing company,
insurance company or institutional lender in connection with the procurement of
debt or lease financing accommodations for the Company or any subsidiaries.

            (e) The Preemptive Rights granted under this Section shall terminate
upon the completion by the Company of an initial public offering.

         6. SALE OF THE COMPANY. If the Shareholders entitled to cast at least
51% of the votes which all Shareholders are entitled to cast approve a Sale of
the Company on an arms-length basis to an Independent Third Party or an
Affiliated group of Independent Third Parties, then the remaining Shareholders
will consent to and raise no objections against such sale and, if such sale is
structured as a sale of stock, the remaining Shareholders will agree to sell
their Shares on the terms and conditions approved by the Board and Shareholders
entitled to cast at least 51% of the votes which all Shareholders are entitled
to cast; provided, that the foregoing obligations of the Shareholders are
subject to the satisfaction of the following conditions:

            (a) upon the consummation of such sale, all of the holders of a
particular type or class of Shares will receive the same form and amount of
consideration per Share or, if an option is given as to the form or amount of
consideration, each such holder will be given the same option; and

            (b) all holders of then currently exercisable rights to acquire
shares of the Company's capital stock will be given an opportunity to either (i)
exercise such rights prior to the consummation of such sale and participate in
such sale as holders of capital stock or (ii) receive upon the consummation of
such sale the same amount of consideration received by holders of such capital
stock in connection with such sale less the exercise price of such rights.

         7. BOARD OF DIRECTORS. Except as otherwise set forth in this Section 7,
the members of the Company's Board of Directors shall be elected in accordance
with the provisions of the Company's Amended and Restated Certificate of
Incorporation, as amended from time to time. Notwithstanding the foregoing, at
all times during which Cross-Atlantic Partners, Cross-Atlantic Partners II and
Cross-Atlantic Partners III (collectively "CROSS-ATLANTIC") hold at least
100,000 shares of Preferred Stock, each Shareholder shall vote the Shares owned
by such Shareholder or over which it has

                                      -8-
<PAGE>

voting control for the Cross-Atlantic Director nominated by Cross-Atlantic
pursuant to that certain Letter Agreement dated September 28, 1999 among
Cross-Atlantic, the Company and the Founder. In addition, each Shareholder shall
vote the Shares owned by such Shareholder or over which it has voting control so
that each institutional investor that is a holder of Series C Preferred Stock
and that does not have Board representation shall have the right to appoint one
observer to the Board of Directors, and the Company shall reimburse the
reasonable expenses of such observer in attending meetings of the Board.

         8. FINANCIAL STATEMENTS. So long as 10% or more of the Series C
Preferred Stock remains outstanding, the Company agrees to provide to the
Shareholders quarterly unaudited financial statements and annual audited
financial statements of the Company, in the case of the quarterly unaudited
financial statements within 30 days of the end of the period, and in the case of
the audited annual financial statements within 90 days of the end of the fiscal
year.

         9. MISCELLANEOUS.

            (a) ACTION BY SHAREHOLDERS. Whenever any consent, waiver, agreement
or other action of the Shareholders as a group is required or permitted
hereunder, such action shall be effective if it is taken by Shareholders who own
or vote at least 50% of the Common and Shareholders who own or vote at least 50%
of the Preferred.

            (b) AMENDMENTS. This Agreement may be amended or terminated only by
a writing signed by the Company and the requisite number of Shareholders as set
forth in Section 9(a), and any such amendment or termination shall be effective
only to the extent specifically set forth in such writing.

            (c) COUNTERPARTS; TELEFACSIMILE EXECUTION. This Agreement may be
executed in any number of counterparts, and by each of the parties on separate
counterparts, each of which, when so executed, shall be deemed an original, but
all of which shall constitute but one and the same instrument. Delivery of an
executed counterpart of this Agreement by telefacsimile shall be equally as
effective as delivery of a manually executed counterpart of this Agreement. Any
party delivering an executed counterpart of this Agreement by telefacsimile also
shall deliver a manually executed counterpart of this Agreement, but the failure
to deliver a manually executed counterpart shall not affect the validity,
enforceability or binding effect of this Agreement.

            (d) ENTIRE AGREEMENT. This Agreement contains the entire agreement
of the parties with respect to the subject matter hereof and supersedes all
prior written and oral agreements, and all contemporaneous oral agreements,
relating to such matters.

                                      -9-
<PAGE>

            (e) EQUITABLE RELIEF. The parties acknowledge and agree that each
would be irreparably damaged in the event that any of the provisions of this
Agreement are not performed by the others in accordance with their specific
terms or are otherwise breached. Accordingly, it is agreed that the parties
shall be entitled to an injunction or injunctions to prevent breaches of this
Agreement, and shall have the right to specifically enforce this Agreement and
the terms and provisions hereof, in addition to any other remedies available at
law or in equity.

            (f) GOVERNING LAW. This Agreement shall be a contract under the laws
of the State of Delaware and for all purposes shall be governed by and construed
and enforced in accordance with the laws of said State.

            (g) NOTICES. All notices, consents, requests, demands and other
communications required or permitted hereunder:

                (i) shall be in writing;

                (ii) shall be sent by messenger, certified or registered U.S.
mail, a reliable express delivery service or telecopier (with a copy sent by one
of the foregoing means), charges prepaid as applicable, to the appropriate
address(es) or number(s) set forth below; and

                (iii) shall be deemed to have been given on the date of receipt
by the addressee (or, if the date of receipt is not a business day, on the first
business day after the date of receipt), as evidenced by (A) a receipt executed
by the addressee (or a responsible person in his or her office) or a notice to
the effect that such addressee refused to accept such communication, if sent by
messenger, U.S. mail or express delivery service, or (B) a receipt generated by
the sender's telecopier showing that such communication was sent to the
appropriate number on a specified date, if sent by telecopier.

All such communications shall be sent to the following addresses or numbers:

                         If to the Company:

                         NOMOS Corporation
                         2591 Wexford Bayne Road, Suite 400
                         Sewickley, PA  15143
                         Attn:  John Manzetti
                         Telecopier No.:  (724) 934-5488

If to any Shareholder, to the address or number set forth in the records of the
Company for the purpose of giving notice to such Shareholder.

                                      -10-
<PAGE>

            (h) SEVERABILITY. Any provision of this Agreement which is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining portions hereof or affecting the validity or
enforceability of such provision in any other jurisdiction.

            (i) SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and
shall inure to the benefit of each of the parties and their respective heirs,
successors and permitted assigns.

            (j) WAIVERS. The due performance or observance by the parties of
their respective obligations hereunder shall not be waived, and the rights and
remedies of the parties hereunder shall not be affected, by any course of
dealing or performance or by any delay or failure of any party in exercising any
such right or remedy. The due performance or observance by a party of any of its
obligations hereunder may be waived only by a writing signed by the party or
parties against whom enforcement of such waiver is sought, and any such waiver
shall be effective only to the extent specifically set forth in such writing.

                                      -11-
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the date first above written.

                                  COMPANY

                                  NOMOS CORPORATION

                                  By:     /s/ John W. Manzetti
                                     ------------------------------------------
                                  Title:    President & COO
                                        ---------------------------------------

                                  FOUNDER

                                        /s/ John A. Friede
                                  ---------------------------------------------
                                      John A Friede

                                  SHAREHOLDERS

                                  CORPORATE OPPORTUNITIES FUND, L.P.
                                  By:  SMM Corporate Management, LLC,
                                  General Partner

                                  By:     /s/ Robert Weinstein
                                     ------------------------------------------
                                              Robert Weinstein, Manager

                                  CORPORATE OPPORTUNITIES FUND
                                  (INSTITUTIONAL), L.P.
                                  By:  SMM Corporate Management, LLC,
                                  General Partner

                                  By:      /s/ Robert Weinstein
                                     ------------------------------------------
                                               Robert Weinstein, Manager

                                  CROSS ATLANTIC PARTNERS
                                  CROSS ATLANTIC PARTNERS II
                                  CROSS ATLANTIC PARTNERS III

                                  By:    /s/ John Cassis
                                     ------------------------------------------
                                  Title:    Partner

                                      -12-

<PAGE>

                                                                 Exhibit 10.2(a)

                                   SCHEDULE A

                                  SHAREHOLDERS
                                  ------------

Corporate Opportunities Fund, L.P.:     131,500 Series C Preferred

Corporate Opportunities Fund (Institutional), L.P.:  708,500 Series C Preferred

Cross Atlantic Partners:            184,500 Common
                                    143,500 Series A Preferred
                                    344,400 Series C Preferred

Cross Atlantic Partners II:          90,000 Common
                                     70,000 Series A Preferred
                                    168,000 Series C Preferred

Cross Atlantic Partners III:        175,500 Common
                                    136,500 Series A Preferred
                                    327,600 Series C Preferred

John A. Friede:   2,337,932 Common
                  3,689,140 Series B Preferred<PAGE>
                                                                 Exhibit 10.2(b)

                    FIRST AMENDMENT TO SHAREHOLDER AGREEMENT
                    ----------------------------------------

         This Agreement is made as of March 26, 2001 (the "AMENDMENT") among
NOMOS CORPORATION, a Delaware corporation (the "COMPANY"), and the persons
listed on the signature pages hereto (each a "SHAREHOLDER", and collectively,
the "SHAREHOLDERS").

                                    PREAMBLE

         The Shareholders and the Company desire to amend the Shareholder
Agreement dated March 2, 2001 (the "SHAREHOLDER AGREEMENT") in order to provide
that Article Fourth, Section E.2(b) of the Company's Amended and Restated
Certificate of Incorporation (the "RESTATED CERTIFICATE") be amended to reflect
that the approval of the holders of at least 75% of the outstanding shares of
the Series C Preferred Stock of the Company be required for the taking of
certain actions described therein.

         NOW, THEREFORE, in consideration of the foregoing and the mutual
agreements hereinafter set forth, the parties hereto, intending to be legally
bound hereby, agree as follows:

                                    AGREEMENT

         1. DEFINED TERMS. Capitalized terms used herein and not otherwise
defined shall have the meanings assigned to such terms in the Shareholder
Agreement.

         2. AMENDMENT TO RESTATED CERTIFICATE. Notwithstanding the provisions of
Article Fourth, Section E.2(b) of the Restated Certificate, the Company and the
Shareholders agree that so long as at least 300,000 shares of the Series C
Preferred Stock remain outstanding, then, unless the consent or approval of a
`greater number of shares shall then be required by law, without first obtaining
the approval of the holders of at least 75% of the number of shares of the
Series C Preferred Stock at the time outstanding, given either by vote or
written consent, voting or consenting as a distinct and separate class, the
Company shall not take any of the actions described in Article Fourth, Sections
E.2(b)(i) - (v). Each Shareholder shall vote the Shares owned by such
Shareholder or over which it has voting control in a manner which will carry out
the intent of the foregoing.

         3. REVISED SCHEDULE A. The Parties hereto acknowledge and agree that
the revised SCHEDULE A attached hereto represents the current shareholdings of
each Shareholder as of the date hereof.

         4. EFFECT ON OTHER PROVISIONS. All other provisions of the Shareholder
Agreement shall remain in full force and effect.

<PAGE>

         5. MISCELLANEOUS. This Amendment shall be binding upon and shall inure
to the benefit of the parties hereto, and their respective successors and
assigns. This Amendment shall not be waived, changed or discharged, except by
written agreement as provided in Section 9(b) of the Shareholder Agreement. This
Amendment is executed in and shall be construed and enforced in accordance with
the laws of the Commonwealth of Pennsylvania. This Amendment may be executed in
any number of counterparts all of which shall be considered one and the same
Amendment.

                                      -2-

<PAGE>

                                                                 Exhibit 10.2(b)

         IN WITNESS WHEREOF, this Amendment to Shareholder Agreement has been
executed as of the date first above written.

                                  COMPANY

                                  NOMOS CORPORATION

                                  By:   /s/  John W. Manzetti
                                     ------------------------------------------
                                  Title:   President & COO
                                        ---------------------------------------

                                  FOUNDER

                                       /s/ John A. Friede
                                  ---------------------------------------------
                                    John A Friede

                                  SHAREHOLDERS

                                  CORPORATE OPPORTUNITIES FUND, L.P.
                                  CORPORATE OPPORTUNITIES FUND
                                  (INSTITUTIONAL), L.P.

                                  By:  SMM Corporate Management, LLC,
                                  General Partner

                                 By:     /s/ Robert Weinstein
                                    -------------------------------------------
                                             Robert Weinstein, Manager

                                  CROSS ATLANTIC PARTNERS
                                  CROSS ATLANTIC PARTNERS II
                                  CROSS ATLANTIC PARTNERS III

                                  By:   /s/  JOHN L. CASSIS
                                     ------------------------------------------
                                  Title:   Partner

                                        /s/ Howard Silverman
                                  ---------------------------------------------
                                       Howard Silverman

                                        /s/ Phyllis Silverman
                                  ---------------------------------------------
                                        Phyllis Silverman

                                      -3-

<PAGE>

                                   SCHEDULE A

                                  SHAREHOLDERS
                                  ------------

Corporate Opportunities Fund, L.P.:     219,500 Series C Preferred

Corporate Opportunities Fund (Institutional), L.P.:  1,180,500 Series C
                                                     Preferred

Cross Atlantic Partners:        184,500 Common
                                143,500 Series A Preferred
                                344,400 Series C Preferred

Cross Atlantic Partners II:      90,000 Common
                                 70,000 Series A Preferred
                                168,000 Series C Preferred

Cross Atlantic Partners III:    175,500 Common
                                136,500 Series A Preferred
                                327,600 Series C Preferred

John A. Friede:   2,337,932 Common
                  3,689,140 Series B Preferred

Howard Silverman:   111,982 Series C Preferred

                                      -4-
<PAGE>
                                                                 Exhibit 10.2(b)

                                   JOINDER TO
                              SHAREHOLDER AGREEMENT

     In connection with the issuance to the undersigned by NOMOS CORPORATION, a
Delaware corporation (the "Company") of 111,982 shares of Class C Convertible
Preferred Stock, par value $.0001 per share, of the Company (the "Shares"), the
undersigned hereby agrees as follows:

            1. The Shares issued to the undersigned are deemed to be "Shares"
under and as defined in that certain Shareholder Agreement dated as of March 2,
2001 among the Company and the shareholder signatories thereto, a copy of which
is attached hereto as EXHIBIT A (the "Shareholder Agreement").

            2. By signing this Agreement the undersigned confirms that he is a
"Shareholder" under and as defined in the Shareholder Agreement and agrees to be
bound by all terms of the Shareholder Agreement. The undersigned shall have all
of the rights and obligations of a Shareholder thereunder.

            3. The undersigned confirms that he is not an "institutional
investor" for purposes of Section 7 of the Shareholder Agreement.

     WITNESS the due execution hereof as of March 26, 2001 with the intent to be
legally bound.

                                          /s/ Howard Silverman
                                       -----------------------------------------
                                       Howard Silverman

                                          /s/ Phyllis Silverman
                                       -----------------------------------------
                                       Phyllis Silverman

<PAGE>
                                                                 Exhibit 10.2(b)

                                   JOINDER TO
                              SHAREHOLDER AGREEMENT

     In connection with the issuance to the undersigned by NOMOS CORPORATION, a
Delaware corporation (the "Company") of 280,000 shares of Series C Convertible
Preferred Stock, par value $.0001 per share, of the Company (the "Series C
Shares"), the undersigned hereby agrees as follows:

            1. The Series C Shares issued to the undersigned and such other
shares of capital stock of the Company owned by the undersigned are deemed to be
"Shares" under and as defined in that certain Shareholder Agreement dated as of
March 2, 2001, as amended, among the Company and the shareholder signatories
thereto, a copy of which is attached hereto as EXHIBIT A (the "Shareholder
Agreement").

            2. By signing this Agreement the undersigned confirms that he is a
"Shareholder" under and as defined in the Shareholder Agreement and agrees to be
bound by all terms of the Shareholder Agreement. The undersigned shall have all
of the rights and obligations of a Shareholder thereunder.

            3. The undersigned confirms that he is not an "institutional
investor" for purposes of Section 7 of the Shareholder Agreement.

     WITNESS the due execution hereof as of March 30 , 2001 with the intent to
be legally bound.

                                        SMH NOMOS, L.L.C.

                                        By:    /s/ Bruce R. McMaken
                                           -------------------------------------
                                        Title:   President
                                              ----------------------------------

<PAGE>

                                                                 Exhibit 10.2(b)

                                   JOINDER TO
                              SHAREHOLDER AGREEMENT

     In connection with the issuance to the undersigned by NOMOS CORPORATION, a
Delaware corporation (the "Company") of 237 shares of Series C Convertible
Preferred Stock, par value $.0001 per share, of the Company (the "Series C
Shares"), the undersigned hereby agrees as follows:

            1. The Series C Shares issued to the undersigned and such other
shares of capital stock of the Company owned by the undersigned are deemed to be
"Shares" under and as defined in that certain Shareholder Agreement dated as of
March 2, 2001, as amended, among the Company and the shareholder signatories
thereto, a copy of which is attached hereto as EXHIBIT A (the "Shareholder
Agreement").

            2. By signing this Agreement the undersigned confirms that he is a
"Shareholder" under and as defined in the Shareholder Agreement and agrees to be
bound by all terms of the Shareholder Agreement. The undersigned shall have all
of the rights and obligations of a Shareholder thereunder.

            3. The undersigned confirms that he is not an "institutional
investor" for purposes of Section 7 of the Shareholder Agreement.

     WITNESS the due execution hereof as of March 29 , 2001 with the intent to
be legally bound.

                                          /s/ Andrew D. Zacks
                                        ----------------------------------------
                                        Andrew D. Zacks

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