<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