<PAGE>
                                                                 Exhibit 10.24
                 IMRT OPENSUITE(TM) INTEROPERABILITY AGREEMENT

This IMRT OpenSuite(TM) Interoperability Agreement (Agreement) is entered into
between IMPAC Medical Systems, Inc., with its principal place of business at
100 West Evelyn Avenue, Mountain View, California 94041 (IMPAC), and NOMOS
Corporation, with its principal place of business at 2591 Wexford Bayne Road,
Sewickley, Pennsylvania, 15143 (NOMOS).

                                  BACKGROUND

NOMOS provides systems to radiation oncology centers used to plan radiation
therapy treatments. IMPAC provides information systems to oncology centers
(including radiation oncology centers) that are utilized for the
administrative and clinical information management of oncology patients
including, but not limited to, interfacing with radiation therapy treatment
planning systems and linear accelerators. NOMOS and IMPAC recognize that each
has a leading position in their respective market segments and that by
cooperating to support and enhance the interfaces between their respective
systems, they will enhance the prospects of their respective products. In
pursuit of this enhanced position, the parties agree as follows.

1. CONFORMANCE STATEMENTS
(a) Each of the parties hereto agrees to publish conformance statements for
both the DICOM-RT and RTPConnect interfaces as these interfaces relate to its
products. As soon as the conformance statements have been finalized, and
whenever the statements are revised, each party further agrees to use
commercially reasonable efforts to provide these conformance statements to the
other party no later than one month prior to releasing them to its customers.

(b) In an effort to afford customers the optimum solution, each of the parties
agree to work together to establish minimum conformance and performance level
standards for the interfaces as these interfaces relate to its products. The
minimum standards will be established in conjunction with the creation of the
conformance statements.

(c) The conformance statements and the minimum standards developed by each
party pursuant to subsections 1 (a) and (b), shall be owned by the developing
party.

2. VERIFICATION AND VALIDATION OF INTERFACES
The parties agree to use commercially reasonable efforts to conduct joint
testing of interface enhancements before they are released for commerce. Both
parties agree that this testing may not always be possible due to resource,
regulatory, safety, and other considerations.

3. INTERFACE VALIDATION PROCEDURE
In an effort to reduce the difficulty of deploying interfaces between the
respective parties and in establishing their proper interoperability, the
parties agree to jointly develop an Interface Validation Procedure (IVP) that
can be utilized by either party to "commission"




IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01
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                                                                 Exhibit 10.24


the interfaces between the respective systems. The master IVP document and
revision control shall be the responsibility of IMPAC. The IVP shall be
jointly owned by NOMOS and IMPAC with no duty to account.

4. INSTALLATIONS
(a) Each party agrees to provide notice to the other party when it becomes
aware of an impending installation of its product at a customer site that
utilizes the other party's system and for which an interface between the two
systems will be installed. This notification shall be made via e-mail as soon
as is practicable, but in no event later than five (5) business days after the
notifying party becomes aware of the installation.

(b) For the purposes of the installation notice requirement of this section 4,
each party shall designate a primary and secondary contact within fifteen (15)
business days of the signing of this Agreement.

5. COMBINED USER'S GUIDE
The parties agree to create a joint User's Guide for the use of the interface
between the systems. This guide shall be limited to the sequencing required to
operate the bi-directional transfer of data between the respective systems.
Each company shall have full rights to reproduce and use this document as it
sees fit, but in no way to the other party's detriment. The master document
and revision control shall be the responsibility of IMPAC. The joint User's
Guide shall be jointly owned by NOMOS and IMPAC with no duty to account.

6. CUSTOMER SUPPORT CALL TRIAGING
(a) The parties agree to establish a customer call triaging procedure to route
support calls to the appropriate organization. Furthermore, the parties agree
to expedite the availability of technical support whenever it is not readily
apparent which system is malfunctioning and system level trouble-shooting must
be initiated.

(b) The parties further agree to make support personnel available via
telephone to assist in the installation and commissioning of interfaces
between their respective systems whenever an installation of either or both
systems is occurring.

7. "IMRT OPENSUITE(TM)  COMPLIANT" BRANDING
(a) GRANT OF LICENSE
Upon the successful completion of the duties and obligations set out in
sections 1 through 6 above, and in IMPAC's sole discretion, IMPAC may grant
NOMOS a worldwide, non-exclusive, non-transferable, revocable right to use and
display IMPAC's trademarked phrase "IMRT OpenSuite(TM)" for the express sole
purpose of public notification of the conformance of the RTP System and its
internal process to the requirements set out in this Agreement. Any such use
shall be consistent with the IMPAC guidelines on use of the IMRT OpenSuite(TM)
mark.







IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01                              2
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                                                                 Exhibit 10.24


(b) RESTRICTIONS
Except as otherwise expressly provided herein, NOMOS is granted no other
right, title, or license to the OpenSuite(TM) logo or any other IMPAC
trademark, and is specifically granted no right or license to sublicense the
OpenSuite(TM) Logo or any other IMPAC trademarks; provided, that a License
shall be provided by IMPAC to NOMOS' distributors who distribute NOMOS'
products as transferred by NOMOS (i.e., without any modifications to the
product, product packaging, documentation or other materials). NOMOS shall
enforce the terms of any such sublicense with its distributors. IMPAC shall be
entitled to enforce the terms of this license directly against any NOMOS
distributor in the event NOMOS fails to do so.

(c) CERTIFICATION
The license rights granted under subsection 7 (a) apply only in connection
with versions of products that have successfully complied with the
requirements of this Agreement.

8. CROSS-SALE OF INTERFACES
(a) In order to simplify the sales process with the end-user by allowing
either party to fulfill the end-user's needs when selling into the other
party's installed base, the parties agree to negotiate in good faith to
establish a sales agreement and transfer pricing for their respective RTP
interface products. Any such cross-sale arrangement shall be governed by a
separate signed written agreement between the parties.

(b) In an effort to facilitate cross-sale of interfaces, the parties will work
together to create a products requirement matrix that will list those products
necessary for the provision of a complete Intensity Modulated Radiation
Therapy (IMRT) solution for the customer. The matrix will be distributed to
each party's sales force. The matrix and matrix revision control shall be the
responsibility of IMPAC. The product requirements matrix shall be jointly
owned by NOMOS and IMPAC with no duty to account.

9. MUTUAL REFERRAL LIST
The parties agree to create and maintain a joint customer reference list of
those customers utilizing IMRT OpenSuite(TM) solutions. Each party may utilize
this list for sales and marketing activities as it sees fit. The master list
and revision control shall be the responsibility of IMPAC. The joint customer
reference list shall be jointly owned by NOMOS and IMPAC with no duty to
account.

10. DEVELOPMENT COLLABORATION
(a) Within three (3) months of signing this Agreement, the parties agree to
conduct a functional evaluation of the combined systems (RTP and IS) to
determine if there are opportunities for enhancing the interfaces or workflow
of the combined systems.

(b) Each of the parties agrees to use its commercially reasonable efforts to
develop a system specification for those enhancements and to implement those
enhancements in their respective systems based on their own internal
development priorities and timeframes.



IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01                              3
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                                                                 Exhibit 10.24


11. QUALITY SYSTEM REGULATIONS
Nothing in this Agreement shall be construed to hinder either party hereto
from abiding by the Quality System Regulations of the U.S. Food and Drug
Administration or the equivalent medical device regulations promulgated by
foreign governments in non-US markets.

12. TERM AND TERMINATION
(a) TERM
The initial term of this Agreement shall be two years from the date upon which
the last party to sign this agreement does so (Effective Date). Thereafter,
this Agreement shall automatically renew for successive one-year terms unless
either party provides the other party notice of its intent not to renew within
thirty (30) days of the end of the then current term.

(b) TERMINATION
Notwithstanding any provision in this Agreement to the contrary, either party
may terminate this Agreement upon thirty- (30) days notice by providing
written notification of termination via registered mail to the other party.

(c) EFFECT OF TERMINATION
         (i) Immediately upon termination of this Agreement, the Interface
         Validation Procedure identified in Section 3 shall cease to be
         utilized for any new system revision not specifically enumerated in
         the document (i.e., it can be used post termination but only for
         system revisions for which it was expressly written).

         (ii) Immediately upon termination of this Agreement, the User's Guide
         identified in Section 5.6 shall cease to be utilized for any new
         system revision not specifically enumerated in the document (i.e., it
         can be used post termination but only for system revisions for which
         it was expressly written).

          (iii) All jointly owned assets shall be provided to each of the
         parties hereto and each of the parties hereto may use such jointly
         owned assets subject to the restrictions set out in this Agreement.

13. CONFIDENTIALITY
This Agreement shall be governed by that Mutual Nondisclosure Agreement (NDA)
entered into by the parties on June 1, 2001. The parties hereby agree to
extend the three-year term of the NDA to run concurrent with the term of this
Agreement.

14. GOVERNING LAW, JURISDICTION AND VENUE
This Agreement shall be governed by and construed under applicable U.S.
federal law and the laws of the State of California, without regard to
conflicts of laws principles and without regard to the United Nations
Convention on Contracts for the International Sale of Goods.





IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01                              4
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                                                                 Exhibit 10.24

15. GENERAL PROVISIONS
(a) ASSIGNMENT
Neither party may assign or subcontract its rights or obligations under this
agreement, either in whole or in part, without the prior written consent of
the other party, which consent shall be in the sole discretion of the other
party. Any attempt to do so shall be void and of no effect. However, either
party may assign without prior written consent its rights and obligations
under this agreement to a successor in interest due to that party's
acquisition, merger, or reorganization.

(b) ENTIRE AGREEMENT
This Agreement together with all exhibits, appendices or other attachments,
which are incorporated herein by reference, is the sole and entire agreement
between the parties relating to the subject matter hereof. This Agreement
supersedes all prior understandings, agreements and documentation relating to
such subject matter.

(c) MODIFICATIONS TO AGREEMENT
Modifications and amendments to this Agreement, including any exhibit or
appendix hereto, shall be enforceable only if they are in writing and are
signed by authorized representatives of both parties.

(d) WAIVER
No term or provision of this Agreement shall be deemed waived and no breach
excused unless the waiver or consent is in writing and signed by the party
claimed to have waived or consented.

(e) NOTICES
All notices and other communications required or permitted under this
Agreement shall be in writing and shall be deemed given when delivered
personally, or by facsimile, or overnight mail, or confirmed email, or five
days after being deposited in the United States mail, postage prepaid and
addressed as each party may designate in writing:

(f) FEES AND EXPENSES
Each party shall be responsible for the payment of its own costs and expenses,
including attorneys' fees and expenses, in connection with the negotiation and
execution of this Agreement and the consummation of the transactions
contemplated pursuant to this Agreement.

(g) COUNTERPARTS
This Agreement may be executed in counterparts, each of which shall be deemed
an original, and all of which together shall constitute one in the same
instrument. The execution of this Agreement may be evidenced by facsimile
transmission of signatures, in which case the parties agree to exchange
originally executed versions of this Agreement promptly thereafter.





IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01                              5
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(h) INDEPENDENT CONTRACTORS
The parties acknowledge and agree that they are dealing with each other
hereunder as independent contractors. Nothing contained in this Agreement
shall be interpreted as constituting either party the joint venturer, employee
or partner of the other party or as conferring upon either party the power of
authority to bind the other party in any transaction with third parties.

(i) SEVERABILITY
If any provision of this Agreement is held invalid, void or unenforceable
under any applicable statute or rule of law, it shall to that extent be deemed
omitted, and the balance of this Agreement shall be enforceable in accordance
with its terms.

(j) SURVIVAL
The following provisions shall survive the expiration or termination of this
Agreement for any reason: Section 7. In addition, provisions of this Agreement
that, by their nature, are intended to remain in effect beyond the termination
or expiration of this Agreement, shall survive the termination or expiration
of this Agreement.

(k) HEADINGS NOT CONTROLLING
The headings in this Agreement are for reference purposes only and shall not
be construed as a part of this Agreement.

16. SIGNATURES
Each party represents and warrants that on this date they are duly authorized
to bind their respective principals by their signatures below.


------------------------------------- ---------------------------------------
IMPAC MEDICAL SYSTEMS, INC.            NOMOS CORPORATION


By:   /s/ Joseph K. Jachinowski        By:   /s/ John W. Manzetti
   ---------------------------------      -----------------------------------

Title:   CEO                           Title:  President & CEO
      ------------------------------         --------------------------------

Date:   9/23/01                        Date:   Sept. 11, 2001
     -------------------------------        ---------------------------------

------------------------------------- ---------------------------------------




IMPAC--NOMOS IMRT OpenSuite Agreement 9-10-01                              6