SEC Info℠

Home

Search

My Interests

Help

Sign In

Please Sign In

North American Scientific Inc – ‘S-4/A’ on 3/12/04

On:  Friday, 3/12/04, at 6:11am ET   ·   Accession #:  1047469-4-7576   ·   File #:  333-110766

Previous ‘S-4’:  ‘S-4/A’ on 1/26/04   ·   Next & Latest:  ‘S-4/A’ on 3/23/04

in

this entire Filing. an “Entity” Search.

Show

Documents searched

and

each “hit”. the 1st “hit”.

↓↑Hints

 Text Wildcards:  ? (any letter/digit),  * (many).  Search Logic:  for Documents:  & (and),  | (or);  for Text:  | (anywhere),  "(&)" (near).  Details... 

  As Of                Filer                Filing    For·On·As Docs:Size              Issuer               Agent

 3/12/04  North American Scientific Inc     S-4/A                  8:2.2M                                   Merrill Corp/New/FA

Document/Exhibit                   Description                      Pages   Size 

 1: S-4/A       Pre-Effective Amendment to Registration of          HTML   2.13M 
                          Securities Issued in a                                 
                          Business-Combination Transaction                       
 2: EX-8.1      Opinion re: Tax Matters                             HTML     13K 
 3: EX-10.28    Material Contract                                   HTML     75K 
 4: EX-10.29    Material Contract                                   HTML     26K 
 5: EX-23.1     Consent of Experts or Counsel                       HTML      8K 
 6: EX-23.2     Consent of Experts or Counsel                       HTML      8K 
 7: EX-99.1     Miscellaneous Exhibit                               HTML     15K 
 8: EX-99.2     Miscellaneous Exhibit                               HTML     13K 

As filed with the Securities and Exchange Commission on March 12, 2004

Registration No. 333-110766

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

AMENDMENT
No. 2
to
FORM S-4
REGISTRATION STATEMENT
Under
THE SECURITIES ACT OF 1933

NORTH AMERICAN SCIENTIFIC, INC.
(Exact name of registrant as specified in its charter)

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effectiveness of this Registration Statement and the effective time of the merger of NOMOS Corporation with and into AM Capital I, Inc., a wholly owned subsidiary of the Registrant, as described in the Agreement and Plan of Merger, dated as of October 26, 2003, as amended, included as Annex A-1, Annex A-2 and Annex A-3 to the joint proxy statement/prospectus forming a part of this Registration Statement.

        If the securities being registered on this form are being offered in connection with the formation of a holding company and are in compliance with General Instruction G, check the following box.    o

        If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o                

        If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration for the same offering.    o                

        THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT SHALL BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF THE SECURITIES ACT OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON SUCH DATE AS THE SECURITIES AND EXCHANGE COMMISSION, ACTING PURSUANT TO SECTION 8(a), MAY DETERMINE.

The information in this joint proxy statement/prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission of which this joint proxy statement/prospectus is a part is effective. This joint proxy statement/prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. This joint proxy statement/prospectus does not constitute a solicitation of a proxy in any jurisdiction in which it is unlawful to make such proxy solicitation.

Subject to Completion, Dated March 12, 2004

MERGER PROPOSAL—YOUR VOTE IS IMPORTANT

        The boards of directors of North American Scientific, Inc. (NASI) and NOMOS Corporation (NOMOS) unanimously have approved a merger designed to continue NASI's and NOMOS' growth and leadership in the field of radiation therapy. We believe the combined company will be able to create more stockholder value than could be achieved by either company individually.

        If the merger is consummated, NOMOS stockholders will receive, subject to certain escrow arrangements for indemnification obligations, 0.891 shares of NASI common stock for each share of NOMOS common stock they hold, approximately 1.212 shares of NASI common stock for each share of NOMOS series A preferred stock they hold, 0.603 shares of NASI common stock and $2.15 per share in cash for each share of NOMOS series B preferred stock they hold, and 0.340 shares of NASI common stock and $5.99 per share in cash for each share of NOMOS series C preferred stock they hold, plus, in each case cash, in lieu of fractional shares. NASI stockholders will continue to own their existing NASI shares. Pursuant to the merger, NOMOS will merge with and into AM Capital I, Inc., a wholly owned subsidiary of NASI formed for the purpose of effecting the merger. AM Capital I, Inc. will be the surviving corporation in the merger and will change its name immediately following the merger to "NOMOS Corporation". The shares of the combined company will be traded on the Nasdaq National Market under the symbol "NASI".

        We are asking NASI stockholders to approve the merger agreement, the proposed merger and the issuance of the shares of NASI common stock in connection with the merger and two amendments to the Amended and Restated 1996 Stock Option Plan, one of which would to permit the issuance of replacement options in connection with a merger or consolidation and, and the other of which would to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares. NASI's special meeting will be held on:

Monday, May 3, 2004

10:00 a.m.

at the following location:

Warner Center Marriott Hotel
21850 Oxnard Street
Woodland Hills, California 91367

        The board of directors of NOMOS is asking NOMOS stockholders to approve the merger agreement and the proposed merger. NOMOS' special meeting will be held on:

Monday, May 3, 2004

10:00 a.m.

at the following location:

Cohen & Grigsby, P.C.
11 Stanwix Street, 15th Floor
Pittsburgh, Pennsylvania 15222

        We are enthusiastic about the merger and the strength and capabilities of the combined company. We join our respective boards of directors in recommending that you vote in favor of the proposals to be presented at our respective company's special meetings.

        We encourage you to read carefully this joint proxy statement/prospectus, including the section entitled "Risk Factors" beginning on page 21, before voting your shares.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the merger or the securities to be issued in the merger or determined if this joint proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

        This joint proxy statement/prospectus is dated March     , 2004 and is first being mailed to the stockholders of NASI and NOMOS on or about March     , 2004.

REFERENCES TO ADDITIONAL INFORMATION

        This joint proxy statement/prospectus incorporates important business and financial information about NASI from other documents that are not included in or delivered with this joint proxy statement/prospectus. This information is available to you without charge upon your request. You can obtain the documents incorporated by reference in this joint proxy statement/prospectus by requesting them in writing or by telephone from NASI at the following address and telephone number:

North American Scientific, Inc.
20200 Sunburst Street
Sunburst, California 91311
(818) 734-8600
Attention: Investor Relations

        If you would like to request documents, NASI must receive your request by April 23, 2004 (which is at least five business days before the date of the special meetings) in order for you to receive them before your special meeting.

        See "Where You Can Find More Information" beginning on page 178.

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

        To All Stockholders of North American Scientific, Inc.:

        NOTICE IS HEREBY GIVEN that North American Scientific, Inc. (NASI) will hold a special meeting of its stockholders on Monday, May 3, 2004, 10:00 a.m., local time, at the Warner Center Marriott Hotel, 21850 Oxnard Street, Woodland Hills, California 91367 for the following purposes:

1.

to consider and vote on a proposal to approve the Agreement and Plan of Merger, dated as of October 26, 2003, by and among NASI, AM Capital I, Inc. and NOMOS Corporation (NOMOS), as amended by the First Amendment to Agreement and Plan of Merger, dated as of November 25, 2003 and by the Second Amendment to Agreement and Plan of Merger, dated as of March 2, 2004, the proposed merger, the issuance of the shares of NASI common stock in connection with the merger and the other transactions contemplated by the merger agreement. A copy of the merger agreement, as amended, is included as Annex A-1, Annex A-2 and Annex A-3 to the accompanying joint proxy statement/prospectus;



2.

to consider and vote on a proposal to approve an amendment to the Amended and Restated 1996 Stock Option Plan to permit the issuance of replacement options in connection with a merger or consolidation;



3.

to consider and vote on a proposal to approve an amendment to the Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares;



4.

to consider and vote on any proposal to adjourn the special meeting to a later date, if necessary, to solicit additional proxies if there are not sufficient votes in favor of the foregoing proposals; and



5.

to transact such other business as may properly come before the special meeting.

        Holders of record of NASI common stock at the close of business on March 10, 2004, the record date, are entitled to receive this notice and to vote their shares at the special meeting or any adjournment or postponement of that meeting. As of the record date, there were 10,353,807 shares of NASI common stock outstanding. Each share of NASI common stock is entitled to one vote on each matter properly brought before the special meeting.

        You should contact the Secretary of NASI at NASI's corporate offices located at 20200 Sunburst Street, Chatsworth, California 91311 if you wish to review the list of stockholders.

        After careful consideration, NASI's board of directors unanimously has determined that the merger is advisable, fair to and in the best interests of NASI and its stockholders and unanimously has approved each of the following:

•

the merger agreement, the proposed merger, the issuance of shares of NASI common stock in connection with the merger and the other transactions contemplated by the merger agreement;



•

the amendment to the Amended and Restated 1996 Stock Option Plan to permit the issuance of replacement options in connection with a merger or consolidation;



•

the amendment to the Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares; and



•

the adjournment of the special meeting, if necessary, to solicit additional votes relating to any of the foregoing.

        NASI's board of directors unanimously recommends that you vote to approve each of NASI's proposals listed above, all of which are described in detail in the accompanying joint proxy statement/prospectus.

		By Order of the Board of Directors,
		L. Michael Cutrer President and Chief Executive Officer
March     , 2004 Chatsworth, California

IMPORTANT

        Your vote is important. Even if you plan to attend the special meeting, please vote by completing and mailing the enclosed proxy card as promptly as possible in the enclosed postage-paid envelope.

        If your shares are held in the name of a bank, broker or other fiduciary, please follow the instructions on the voting instruction card furnished by the record holder. REMEMBER, YOUR VOTE IS IMPORTANT, SO PLEASE ACT TODAY.

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

        To All Stockholders of NOMOS Corporation:

        NOTICE IS HEREBY GIVEN that NOMOS Corporation (NOMOS) will hold a special meeting of its stockholders on Monday, May 3, 2004, 10:00 a.m., local time, at the offices of Cohen & Grigsby, P.C., 11 Stanwix Street, 15th Floor, Pittsburgh, Pennsylvania 15222 for the following purposes:

1.

to consider and vote on a proposal to approve the Agreement and Plan of Merger, dated as of October 26, 2003, by and among North American Scientific, Inc. (NASI), AM Capital I, Inc. and NOMOS, as amended by the First Amendment to Agreement and Plan of Merger, dated as of November 25, 2003 and by the Second Amendment to Agreement and Plan of Merger, dated March 2, 2004, the proposed merger and the other transactions contemplated by the merger agreement. A copy of the merger agreement, as amended, is included as Annex A-1, Annex A-2 and Annex A-3 to the accompanying joint proxy statement/prospectus;



2.

to consider and vote on any proposal to adjourn the special meeting to a later date, if necessary, to solicit additional proxies if there are insufficient votes in favor of the foregoing proposal; and



3.

to transact such other business as may properly come before the special meeting.

        Holders of record of NOMOS common stock and preferred stock at the close of business on March 10, 2004, the record date, are entitled to receive this notice and to vote their shares at the special meeting or any adjournment or postponement of that meeting. As of the record date, there were 3,632,777 shares of NOMOS common stock outstanding, 374,748 shares of series A preferred stock outstanding, 1,861,908 shares of series B preferred stock outstanding, and 1,336,152 shares of series C preferred stock outstanding. Each share of NOMOS' common stock, series B preferred stock and series C preferred stock is entitled to one vote at the special meeting. Each share of series A preferred stock is entitled to approximately 1.3605 votes at the special meeting. The chairman of the board of directors of NOMOS, John A. Friede, has agreed to vote certain shares beneficially owned by him, representing approximately 41% of the voting power of the NOMOS common stock and preferred stock voting together on an as-converted-to-common stock basis outstanding as of the record date, in favor of the proposal to approve the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement.

        If the merger is consummated, NOMOS stockholders will receive, subject to certain escrow arrangements for indemnification obligations, 0.891 shares of NASI common stock for each share of NOMOS common stock they hold, approximately 1.212 shares of NASI common stock for each share of NOMOS series A preferred stock they hold, 0.603 shares of NASI common stock and $2.15 per share in cash for each share of NOMOS series B preferred stock they hold, and 0.340 shares of NASI common stock and $5.99 per share in cash for each share of NOMOS series C preferred stock they hold, plus in each case cash in lieu of fractional shares.

        After careful consideration, NOMOS' board of directors unanimously has determined that the merger is advisable, fair to and in the best interests of NOMOS and its stockholders and unanimously has adopted and approved the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement. NOMOS' board of directors unanimously recommends that you vote to approve the merger agreement, the proposed merger and the other transactions

contemplated by the merger agreement and each of the other proposals listed above, all of which are described in detail in the accompanying joint proxy statement/prospectus.

		By Order of the Board of Directors,
		John W. Manzetti President and Chief Executive Officer
March     , 2004 Cranberry Township, Pennsylvania

IMPORTANT

        Your vote is important. Even if you plan to attend the special meeting, please complete and mail to NOMOS at the address provided the enclosed proxy card. If your shares are held in the name of a bank, broker or other fiduciary, please follow the instructions on the voting instruction card furnished by the record holder. REMEMBER, YOUR VOTE IS IMPORTANT, SO PLEASE ACT TODAY.

TABLE OF CONTENTS

i

ii

iii

ANNEXES

iv

QUESTIONS AND ANSWERS ABOUT THE MERGER

Q:

Why are the companies proposing the merger?

A:

We believe that a combination of NASI and NOMOS will capitalize on the complementary strengths of each company and produce greater stockholder value than would be expected absent the proposed merger.

Q:

What do I need to do now?

A:

After you carefully read this document, including the annexes, please vote your shares as soon as possible so that your shares will be represented at your company's special meeting. Please follow the instructions set forth on the proxy card or on the instruction card provided by the record holder if your shares are held in the name of your broker, a bank or other nominee.

Q:

Why is my vote important?

A:

If you are a NASI stockholder and you do not submit a proxy or vote in person at your special meeting, it will not have any effect on the proposals to be presented at the special meeting, assuming a quorum is otherwise present at the special meeting. If you submit a proxy and affirmatively elect to abstain from voting, your proxy will be counted as present for purposes of determining the presence of a quorum and will have the same effect as a vote against each of the proposals to be voted on at the special meeting. NASI stockholder approval of each of the merger agreement, the proposed merger, the issuance of shares in connection with the merger and the other transactions contemplated by the merger agreement and the amendment to NASI's Amended and Restated 1996 Stock Option Plan to permit the issuance of replacement options in connection with a merger or consolidation is a condition to the consummation of the merger under the merger agreement. NASI stockholder approval of the amendment to NASI's Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan is not a condition to the consummation of the merger. See "Information About the Meetings and Voting—The NASI Special Meeting" on page 152.

If you are a NOMOS stockholder and you do not submit a proxy or vote in person at your special meeting, it will have the same effect as a vote against approval of the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement but will not have any effect on the other proposals. If you submit a proxy and affirmatively elect to abstain from voting, your proxy will be counted as present for purposes of determining the presence of a quorum and will have the same effect as a vote against the approval of the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement and as a vote against each of the other proposals. NOMOS stockholder approval of the merger agreement is a condition to the consummation of the merger under the merger agreement. See "Information About the Meetings and Voting—The NOMOS Special Meeting" on page 156.

Q:

If my shares are held in street name by my broker, will my broker vote my shares for me?

A:

If you hold your shares in a stock brokerage account or if your shares are held by a bank or nominee (that is, in street name), you must provide the record holder of your shares with instructions on how to vote your shares. Please refer to the voting instruction card used by your broker nominee to see if you may submit voting instructions by Internet or telephone. You cannot vote shares held in street name by returning a proxy card directly to NASI or to NOMOS or by voting in person at your stockholders' meeting.

1

Q:

Can I change my vote after I have mailed my proxy card?

A:

Yes. Stockholders who hold shares in their own name can change their vote at any time before their proxy is voted at their company's special meeting. You can do this by using any of the following methods:

NASI Stockholders:

•

timely delivery by mail, telephone or the Internet of a valid, subsequently dated proxy;



•

delivery to NASI's secretary before or at the special meeting of written notice revoking your proxy or of your intention to vote by ballot at the special meeting; or



•

submitting a vote by ballot at the special meeting.

NOMOS Stockholders:

•

timely delivery by mail of a valid, subsequently dated proxy;



•

delivery to NOMOS' secretary before or at the special meeting of written notice revoking your proxy or of your intention to vote by ballot at the special meeting; or



•

submitting a vote by ballot at the special meeting.

If you have instructed a broker to vote your shares, you must follow your broker's directions in order to change those instructions.

Q:

When and where are the special meetings?

A:

NASI's special meeting will take place on Monday, May 3, 2004, at the Warner Center Marriott Hotel, 21850 Oxnard Street, Woodland Hills, California 91367, at 10:00 a.m., local time.

NOMOS' special meeting will take place on Monday, May 3, 2004, at the offices of Cohen & Grigsby, P.C., 11 Stanwix Street, 15th Floor, Pittsburgh, Pennsylvania 15222 at 10:00 a.m., local time.

Q:

Should NOMOS stockholders send in their stock certificates now?

A:

No. After the merger is consummated, NASI will send NOMOS stockholders written instructions for exchanging their stock certificates. NASI stockholders may keep their existing stock certificates.

Q:

When do you expect the merger to be completed?

A:

We hope to complete the merger as soon as possible after the special meetings occur and all closing conditions under the merger agreement are satisfied, which we currently anticipate to occur on or about May 4, 2004.

Q:

Who do I call if I have questions about the special meetings or the merger?

A:

If you have any questions about the merger, or if you need additional copies of this joint proxy statement/prospectus or the enclosed proxy, you should contact:

You may also obtain additional information about NASI from documents filed with the Securities and Exchange Commission by following the instructions in the section entitled "Where You Can Find More Information" on page 178.

2

SUMMARY

        This summary highlights information from this joint proxy statement/prospectus that we believe is important information to be considered by stockholders in determining how to vote on the proposals described in this joint proxy statement/prospectus. This summary may not contain all of the information that is important to you, and we encourage you to read this joint proxy statement/prospectus in its entirety. The information contained in this summary is qualified in its entirety by, and should be read in conjunction with, the detailed information and financial statements, including the notes thereto, appearing elsewhere in this joint proxy statement/prospectus and the documents incorporated into this joint proxy statement/prospectus by reference. In the event there is any material change in this joint proxy statement/prospectus, we will resolicit stockholder votes. See "Where You Can Find More Information" on page 178. We have included references to other portions of this joint proxy statement/prospectus to direct you to a more complete description of the topics presented in this summary.

The Companies

North American Scientific, Inc. (see page 66)
AM Capital I, Inc. (see page 68)
20200 Sunburst Street
Chatsworth, California 91311
(818) 734-8600
Internet Address: www.NASI.net (Information set forth in NASI's website is not incorporated herein by reference.)

        North American Scientific, Inc. is engaged in the design, development and production of innovative radioactive products, including sealed radioactive sources about the size of a grain of rice, that are implanted into the prostate gland, delivering a prescribed, therapeutic dose of radiation to treat prostate cancer, which we refer to as brachytherapy seeds. Brachytherapy is minimally invasive means to treat prostate cancer with reduced side effects. We also are developing a radioactive imaging agent which is intended to be used primarily to determine the efficacy of chemotherapy which we refer to as a radiopharmaceutical. NASI's brachytherapy seeds are marketed under the trade name Prospera®. NASI's lead radiopharmaceutical product candidate is Hynic-Annexin V. It is administered intravenously and is intended for the in vivo imaging of apoptosis and necrosis, two common forms of cell death.

        AM Capital I, Inc. is a Delaware corporation and a wholly owned subsidiary of NASI. AM Capital I, Inc. was organized for the purpose of entering into the merger agreement with NOMOS, completing the merger and being the surviving corporation in the merger. It has not conducted any business operations. If the merger is consummated, NOMOS will cease to exist following the merger of it with and into AM Capital I, Inc. and AM Capital I, Inc. will change its name immediately following the merger to NOMOS Corporation.

NOMOS Corporation (see page 69)
200 West Kensinger Drive, Suite 100
Cranberry Township, PA 16066
(724) 741-8200
Internet Address: www.NOMOS.com (Information set forth in NOMOS' website is not incorporated herein by reference.)

        NOMOS Corporation is a leading supplier of planning and delivery technology for Intensity Modulated Radiation Therapy, or IMRT. IMRT allows an escalated radiation dose to be delivered to a tumor while limiting exposure and damage to nearby healthy tissue. In addition, NOMOS offers both BAT®, an ultrasound-based targeting and organ locator system used primarily in prostate cancer treatments, and PEREGRINE™, the first commercially available photon-based dose calculation system

3

to incorporate state-of-the-art Monte Carlo radiation transport techniques to more accurately predict the radiation dose delivered to tumors and other structures within a patient's body "before" radiation treatment is delivered. NOMOS recently introduced NOMOS Rx^SM, a remote treatment planning service that makes IMRT feasible for many facilities that, due to staffing or financial constraints, might otherwise not be able to take advantage of the potential benefits of IMRT. NOMOS' products are used at over 400 institutions, including some of the world's preeminent cancer institutions. These products are currently used predominantly in the treatment of tumors of the prostate, head, neck and spinal cord.

        NOMOS®, PEACOCK®, MIMiC®, CORVUS®, BAT®, BEAK®, TALON® and CRANE® are registered trademarks of NOMOS Corporation. PEREGRINE™ is a trademark of The Regents of the University of California. All other service marks, trademarks and trade names referred to in this joint proxy statement/prospectus are the property of their respective owners.

The Proposed Merger (see page 42)

        Under the terms of the proposed merger, NOMOS will merge with and into AM Capital I, Inc., a wholly owned subsidiary of NASI formed for the purpose of the merger. AM Capital I, Inc. will survive the merger as a wholly owned subsidiary of NASI and will change its name immediately following the merger to "NOMOS Corporation".

        The merger agreement, as amended, is included as Annex A-1, Annex A-2 and Annex A-3 to this joint proxy statement/prospectus. We encourage you to read carefully the merger agreement in its entirety, as it is the principal legal document that sets forth the terms of and governs the merger. References throughout this joint proxy statement/prospectus to the merger agreement shall mean the merger agreement as amended by the first amendment and the second amendment as discussed below in the section entitled "The Merger Agreement—Amendments, Extensions and Waivers".

What NOMOS Stockholders Will Receive in the Merger (see "The Merger Agreement—Consideration to be Received in the Merger; Treatment of Stock Options" on page 126)

        If the merger is consummated, NOMOS stockholders will receive:

•

0.891 shares of NASI common stock for each share of NOMOS common stock they hold;



•

approximately 1.212 shares of NASI common stock for each share of NOMOS series A preferred stock they hold;



•

0.603 shares of NASI common stock and $2.15 per share in cash for each share of NOMOS series B preferred stock they hold; and



•

0.340 shares of NASI common stock and $5.99 per share in cash for each share of NOMOS series C preferred stock they hold.

        The exchange ratio is fixed and will not be adjusted for changes in the market value of the common stock of NASI. NASI will not issue fractional shares in the merger. Therefore, the total number of shares of NASI common stock that each NOMOS stockholder will receive in the merger will be rounded down to the nearest whole number, and each NOMOS stockholder will receive a cash payment for the remaining fraction of a share of NASI common stock that he or she would otherwise receive, if any, based on the average closing price of NASI common stock for the 10 consecutive trading days ending on and including the last trading date prior to the date of the consummation of the merger.

        Pursuant to the merger agreement, approximately 15.8% of the shares of NASI common stock and cash otherwise payable to NOMOS stockholders in the merger will automatically be deposited in two separate escrow funds upon consummation of the merger. With respect to the first escrow fund, up to

4

approximately 526,810 shares of NASI common stock and approximately $1.2 million of cash will be held for a period of two years following the effective time of the merger to serve as a source of reimbursement to NASI and certain related parties for losses arising from any breach by NOMOS of its representations or obligations under the merger agreement. With the respect to the second escrow fund, 307,617 shares of NASI common stock and $700,800 of cash will be held to serve solely as a source of reimbursement to NASI and certain related parties for any losses incurred by NASI or NOMOS in connection with the demand made against NOMOS by Parker/Hunter incorporated as discussed in "Information Regarding NOMOS—Legal Proceedings" of this joint proxy statement/prospectus.

        In addition, certain non-corporate holders of NOMOS stock may be subject to backup withholding, at applicable federal rates, on amounts received pursuant to the merger. See "The Proposed Merger—Backup Withholding" on page 61.

Amendment of NOMOS Certificate of Incorporation (see "The Merger Agreement—Amendment of NOMOS Certificate of Incorporation" on page 127)

        On November 25, 2003, NOMOS' board of directors, by unanimous written consent, adopted an amended and restated certificate of incorporation, to become effective immediately prior to the consummation of the merger, which amended certificate would confirm that, upon the consummation of the merger, the holders of NOMOS' common stock and each of NOMOS' series of preferred stock would be entitled to receive, and would only be entitled to receive, the merger consideration and other treatment provided for in the merger agreement. Under NOMOS' existing certificate of incorporation, an amendment to outstanding series B preferred stock and (iv) at least 75% of the outstanding series C preferred stock, voting both together as one class, on an as-converted-to-common stock basis, and as separate classes. Pursuant to a written consent dated January 6, 2004, NOMOS stockholders having sufficient votes to do so, approved and adopted the amended and restated certificate of incorporation. The amended and restated certificate of incorporation will be filed and will take effect immediately prior to the consummation of the merger. If the merger is not consummated, the amended and restated certificate of incorporation will not become effective.

Recommendations to Stockholders

To NASI Stockholders (see "The Proposed Merger—Reasons of NASI's Board of Directors for the Merger" on page 52):

        NASI's board of directors believes that the merger is advisable, fair to and in the best interests of NASI stockholders and unanimously recommends that NASI stockholders vote FOR the proposals to:

•

approve the merger agreement, the proposed merger and the issuance of shares of NASI common stock in connection with the merger;



•

approve the amendment to the Amended and Restated 1996 Stock Option Plan to permit the issuance of replacement options in connection with a merger or consolidation;



•

approve the amendment to the Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares; and



•

adjourn the special meeting, if necessary, to solicit additional votes relating to the merger agreement.

5

To NOMOS Stockholders (see "The Proposed Merger—Reasons of NOMOS' Board of Directors for the Merger" on page 55):

        NOMOS' board of directors believes that the merger is advisable, fair to and in the best interests of NOMOS stockholders and recommends that NOMOS stockholders vote FOR the proposals to:

•

approve the merger agreement and the proposed merger; and



•

adjourn the special meeting, if necessary, to solicit additional votes relating to the foregoing proposal.

Reasons for the Merger (see pages 52 and 55)

        The boards of directors of both companies believe that the combined company will benefit from:

•

the strategic nature of the business combination, the complementary nature of the companies' products, coordination of research and development expertise and the belief that combining the two companies likely will create a stronger company with an expanded product line, the ability to be a major force in the cancer treatment industry and the ability to deliver enhanced stockholder value;



•

becoming a larger organization with over 200 combined employees, which could provide access to greater financial, development, distribution channels and other resources;



•

the belief that the combined company will result in a stronger company, better able to improve its existing products and develop new products;



•

the ability to leverage both companies' sales forces in order to broaden the customer base and expand offerings for national accounts; and



•

the synergies and cost savings that could be achieved as a result of the merger, particularly by leveraging certain sales and marketing expenses and administrative expenses.

        The boards of directors of both companies also recognize that there are risks associated with the merger, including:

•

the challenges of integrating the businesses of the combined company and management;



•

the limitations imposed by the merger agreement on the parties' conduct of business prior to the completion of the merger;



•

the uncertainty created by the fixed exchange ratio as to the value of NASI common stock that NOMOS stockholders will receive in the merger; and



•

the risks set forth in the "Risk Factors" section of this joint proxy statement/prospectus.

Opinion of NASI's Financial Advisor (see page 105)

        On October 25, 2003, Bear, Stearns & Co. Inc., or Bear Stearns, financial advisor to NASI, rendered to NASI's board of directors its oral opinion, subsequently confirmed by delivery of a written opinion dated October 25, 2003, that, as of that date, and based upon and subject to the facts, assumptions and limitations set forth in the opinion, the aggregate amount of shares to be issued and cash to be paid to holders of capital stock of NOMOS (the "Merger Consideration") in connection with the merger was fair from a financial point of view to NASI. The opinion of Bear Stearns did not address the fairness of the Merger Consideration to NASI stockholders. The full text of Bear Stearns' written opinion is included as Annex H to this joint proxy statement/prospectus. We encourage you to read carefully Bear Stearns' opinion in its entirety and the description on page 105 of this joint proxy statement/prospectus for a discussion of the procedures followed, assumptions made, matters

6

considered and limitations on the review undertaken. Bear Stearns provided its opinion for the use and benefit of NASI's board of directors in its consideration of the merger and Bear Stearns' opinion did not constitute a recommendation to the board of directors to approve the merger and does not constitute a recommendation as to how any stockholder should vote on the merger or any matter related thereto.

Opinion of NOMOS' Financial Advisor (see page 115)

        In connection with the merger, the NOMOS board of directors received a written opinion of NOMOS' financial advisor, CIBC World Markets Corp., referred to as CIBC World Markets, as to the fairness, from a financial point of view, to the holders of NOMOS common stock of the 0.891 common stock exchange ratio provided for in the merger. The full text of CIBC World Markets' written opinion, dated October 24, 2003, is attached to this joint proxy statement/prospectus as Annex I. We encourage you to read this opinion carefully in its entirety for a description of the assumptions made, procedures followed, matters considered and limitations on the review undertaken. CIBC World Markets' opinion was provided to the NOMOS board of directors in connection with its evaluation of the common stock exchange ratio and relates only to the fairness, from a financial point of view, of the common stock exchange ratio to the holders of NOMOS common stock. The opinion does not address any other aspect of the merger and does not constitute a recommendation as to how any stockholder should vote or act with respect to any matters relating to the merger.

Consequences of Merger Not Being Approved

        If the stockholders of either company fail to approve the proposals required to effect the merger at their respective meetings, or if the merger is not otherwise completed, the ongoing businesses of each of NASI and NOMOS may suffer. Under specified circumstances, either NASI or NOMOS may be required to pay a termination fee to the other party. Additionally, both parties will have incurred costs associated with the merger without realizing the benefits of having the merger completed. In the event the merger is not approved, each of NASI and NOMOS will continue to operate their respective existing businesses and may evaluate opportunities to merge with or acquire companies with complementary businesses. See the section entitled "Risk Factors" beginning on page 21.

Risks Associated with the Merger

        While the merger is pending and if the merger is completed, stockholders of NASI and NOMOS will be subject to a number of risks to which they are not currently subject. These risks include, among others, the following:

•

the fixed exchange ratio for the merger which will not be adjusted in the event of any change in NASI's stock price;



•

the potential inability of the combined company to integrate successfully NASI's and NOMOS' businesses;



•

legislative and governmental regulation of the combined company, including obtaining regulatory approvals for the merger; and



•

legal proceedings affecting each of NASI and NOMOS.

        For a complete discussion of these and other risks relating to the merger, see the section entitled "Risk Factors" beginning on page 21.

7

Board of Directors and Management Following the Merger (see "Interests of Certain Persons in the Merger" on page 123 and "The Merger Agreement—Other Covenants and Agreements" on page 131)

        Upon completion of the merger, L. Michael Cutrer, president and chief executive officer of NASI, will remain as president and chief executive officer of NASI and John W. Manzetti, president and chief executive officer of NOMOS, will serve as president of the surviving corporation of the merger, which will be a wholly owned subsidiary of NASI and will change its name immediately following the merger to "NOMOS Corporation".

        NASI and NOMOS have agreed that, immediately after the consummation of the merger, NASI will take all actions necessary to expand its board of directors to consist of nine members. Seven of the nine members will be persons who served on NASI's board of directors immediately prior to the consummation of the merger. The two additional members will be John W. Manzetti and John A. Friede, chairman of the board of directors of NOMOS.

Stockholder Votes Required

For NASI Stockholders (see page 152):

        Approval of each of:

•

the merger agreement, the proposed merger and the issuance of shares of NASI common stock in the merger; and



•

the amendment to the Amended and Restated 1996 Stock Option Plan to permit the issuance of replacement options in connection with a merger or consolidation

requires the affirmative vote of at least a majority of the voting power present at the special meeting, as long as a quorum, which is a majority of the shares entitled to vote, is present in person or by proxy at the special meeting. Stockholder approval of each of the foregoing proposals is a condition to the consummation of the proposed merger, which cannot be waived by the parties.

        Approval of the amendment to the Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares requires the affirmative vote of at least a majority of the voting power present at the special meeting, as long as a quorum, which is a majority of the shares entitled to vote, is present in person or by proxy at the special meeting. Stockholder approval of the amendment to the Amended and Restated 1996 Stock Option Plan to increase the maximum number of shares available for issuance under the plan from 4,000,000 to 4,600,000 shares is not a condition to the consummation of the merger. If this proposal is not approved, the proposed merger can still be consummated. If approved, this proposal will still be effective even if the merger is not consummated.

        Approval of any proposal to adjourn the special meeting, if necessary, to solicit additional votes in favor of the foregoing proposals requires the affirmative vote of at least a majority of the voting power present at the special meeting, as long as a quorum is present in person or by proxy at the special meeting.

        On the record date, directors and executive officers of NASI and their affiliates beneficially owned or had the right to vote 1,858,472 shares of NASI common stock, representing approximately 11.2% of the shares of NASI common stock outstanding on the record date. To NASI's knowledge, the directors and executive officers of NASI and their affiliates intend to vote their common stock in favor of the proposals described in the preceding paragraph.

For NOMOS Stockholders (see page 156):

        Approval of the merger agreement and the proposed merger requires the affirmative vote of at least a majority of the outstanding shares of NOMOS common stock and preferred stock, voting

8

together as a group, on an as-converted-to-common stock basis. Approval of any proposal to adjourn the special meeting, if necessary, to solicit additional votes in favor of the merger requires the affirmative vote of at least a majority of the votes of NOMOS common stock and preferred stock present at the special meeting, voting together as a group, on an as-converted-to-common stock basis.

        On the record date, directors and executive officers of NOMOS and their affiliates had the right to vote 4,191,769 shares of NOMOS common stock and preferred stock on an as-converted-to-common stock basis, representing approximately 57% of the outstanding shares of NOMOS stock on an as-converted-to-common stock basis as of the record date. John A. Friede, chairman of the board of NOMOS, has entered into a voting agreement with NASI whereby he has agreed to vote certain shares beneficially owned by him, representing approximately 41% of the outstanding voting shares of NOMOS stock on an as-converted-to-common stock basis outstanding on the record date, in favor of the merger agreement and the proposed merger. This voting agreement is attached to this joint proxy statement/prospectus as Annex B. In addition, to NOMOS' knowledge, the other directors and executive officers of NOMOS and their affiliates intend to vote their common stock and preferred stock in favor of the merger agreement and the proposed merger and, if necessary, the proposal to adjourn the special meeting to solicit additional votes.

Ownership of Common Stock of NASI After the Merger

        Upon consummation of the merger, NASI stockholders will own approximately 63% of the outstanding common stock of NASI and NOMOS stockholders will own approximately 37% of the outstanding common stock of NASI, measured on a fully diluted basis. For purposes of the preceding sentence, fully diluted means that the number of shares of common stock issuable upon conversion or exercise, as applicable, of outstanding convertible securities (including, without limitation, warrants to purchase stock) and stock options with conversion prices or exercise prices, as applicable, that are less than the market price of the applicable company's common stock minus the number of shares of stock that could be purchased with the proceeds that would be received by the companies from the conversion or exercise of such securities or options (assuming such securities or options were actually converted or exercised), are deemed to be outstanding. The ownership percentages are based on the number of shares of NASI and NOMOS common stock, convertible preferred stock, warrants and stock options outstanding on October 24, 2003.

Treatment of NOMOS Stock Options and Warrants (see "The Merger Agreement—Consideration to be Received in the Merger; Treatment of Stock Options and Warrants" on page 126)

        In the merger, each outstanding stock option exercisable for NOMOS common stock will be converted into an option to purchase a number of shares common stock of NASI equal to the number (rounding down any fractional shares) of shares of NOMOS common stock acquirable upon the exercise of the option multiplied by 0.891. The per share exercise price of each new NASI option will be equal to the per share exercise price of the corresponding NOMOS stock option divided by 0.891. In addition, effective upon the consummation of the merger, all outstanding unvested NOMOS stock options held by current NOMOS directors and employees will immediately vest. Each outstanding warrant to purchase shares of NOMOS common stock shall by virtue of the merger be assumed by NASI. Each warrant assumed by NASI under the merger agreement will continue to have, and be subject to, the same terms and conditions of the original warrant, except that: (1) each assumed warrant will be exercisable for an applicable number of shares of NASI common stock equal to the number (rounding down any fractional shares) of shares of NOMOS common stock previously acquirable upon the exercise of the warrant multiplied by 0.891 and (2) the per share exercise price of each assumed warrant will be equal to the previous per share exercise price divided by 0.891

9

Conditions to Completion of the Merger (see page 133)

        The obligations of NOMOS and NASI to effect the merger are subject to the satisfaction of the following conditions:

•

the approval of the proposed merger, merger agreement and the other transactions contemplated by the merger agreement by NOMOS stockholders and NASI stockholders;



•

the approval by NASI stockholders of the issuance of shares of NASI common stock in connection with the merger;



•

the approval by NASI stockholders of any amendments to NASI's stock option plans necessary or advisable in connection with the transactions contemplated by the merger agreement;



•

the absence of any law, order or injunction prohibiting completion of the merger;



•

the receipt of all other governmental and regulatory consents, approvals and authorizations necessary for the merger;



•

the Securities and Exchange Commission having declared effective the NASI registration statement, of which this joint proxy statement/prospectus forms a part with respect to shares of NASI common stock to be issued to NOMOS stockholders in the merger; and



•

the approval of the Nasdaq National Market to list the additional shares of NASI common stock to be issued pursuant to the transactions contemplated by the merger agreement.

        Neither NASI nor NOMOS currently intends to waive any of the foregoing conditions to the extent such waiver would otherwise be permissible.

        The obligations of NOMOS to effect the merger are subject to the satisfaction or waiver of the following additional conditions:

•

the receipt of an opinion by NOMOS' company counsel (or NASI's company counsel if such opinion is not provided by NOMOS' company counsel) to the effect that the merger will qualify as a "reorganization" under the Internal Revenue Code;



•

the receipt of an opinion of NASI's company counsel; and



•

NASI shall have executed a registration rights agreement with John A. Friede and other signatories thereto.

        The obligations of NASI to effect the merger are subject to the satisfaction or waiver of the following additional conditions:

•

the receipt of an opinion by NASI's company counsel (or NOMOS' company counsel if such opinion is not provided by NASI's company counsel) to the effect that the merger will qualify as a "reorganization" under the Internal Revenue Code;



•

the receipt of an opinion of NOMOS' company counsel;



•

the receipt of all consents, waivers and assignments regarding the merger as set forth in an exhibit to the merger agreement;



•

the receipt of affiliate letters executed by all persons required under the merger agreement to execute an affiliate letter;



•

the receipt of lock-up agreements executed by all persons required under the merger agreement to execute a lock-up agreement;



•

dissenters' rights shall not have been exercised by more than 5% of the outstanding shares of NOMOS common stock;

10

•

the receipt of an indemnification escrow agreement executed by NOMOS, on behalf of its stockholders, and the escrow agent;



•

the receipt of a voting agreement and voting trust agreement executed by John A. Friede; and



•

the receipt of a stockholders' voting agreement executed by all applicable NOMOS stockholders.

        Where the law permits, a party to the merger agreement could elect to waive a condition to its obligation to complete the merger although that condition has not been satisfied. NASI has received an executed copy of the stockholders' voting agreement referenced in the final bullet point above. In addition, the parties do not believe that a filing or waiting period under the Hart-Scott Rodino Antitrust Improvements Act of 1976, as amended, is required in connection with the proposed merger, nor are the parties aware of any other filings or waiting periods that would apply to the proposed merger under applicable anti-trust laws. We cannot be certain when (or if) the other conditions to the merger will be satisfied or waived or that the merger will be completed. We do not intend to consummate the merger if the shares of NASI common stock to be issued in the merger are not approved for quotation on the NASDAQ National Market System. In the event that either party waives any of the other conditions to the merger, we do not intend to amend this joint proxy statement/prospectus or resolicit proxies to vote in favor of the merger prior to the special meeting except for a waiver of the condition by either party that it receive an opinion of legal counsel stating that the merger will qualify as a reorganization under the Internal Revenue Code or, in the case of the waiver of any other conditions, unless we deem such condition to be material.

Material U.S. Federal Income Tax Consequences of the Merger (see page 58)

        Assuming the merger qualifies as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, or the Code, for U.S. federal income tax purposes, which NASI and NOMOS anticipate, holders of NOMOS capital stock whose shares of NOMOS common stock and preferred stock are exchanged in the merger for shares of common stock of NASI will not recognize gain or loss, except to the extent of the cash received by certain preferred stockholders and the cash, if any, received in lieu of a fractional share of common stock of the combined company.

        The discussion of material U.S. federal income tax consequences of the merger contained in this joint proxy statement/prospectus is intended to provide only a general summary and is not a complete analysis or description of all potential U.S. federal income tax consequences of the merger. The discussion does not address tax consequences that may vary with, or are contingent on, individual circumstances. In addition, it does not address any foreign, state or local taxes. NASI and NOMOS strongly urge each holder of NOMOS common stock and preferred stock to consult his or her tax advisor to determine the particular U.S. federal, state, or local or foreign income or other tax consequences of the merger to that stockholder.

        It is a condition to the completion of the merger that NASI receive a written opinion from McDermott, Will & Emery and that NOMOS receive a written opinion from Cohen & Grigsby, P.C., in each case dated as of the effective date of the merger, to the effect that the merger will qualify as a reorganization within the meaning of Section 368(a) of the Code. Neither NASI nor NOMOS currently intends to waive this closing condition. However, in the event that either NASI or NOMOS waives receipt of such written opinion from its counsel, NASI and NOMOS will file a new joint proxy statement/prospectus and resolicit the approval of each of our stockholders which includes disclosure that does not characterize the merger as a reorganization within the meaning of Section 368(a) of the Code.

11

Listing of Common Stock of NASI (see page 65)

        It is expected that the shares of common stock of NASI to be issued in the merger will be listed for trading on the Nasdaq National Market under the ticker symbol "NASI".

Dissenters' Appraisal Rights (see page 62)

        Each of NASI and NOMOS is incorporated under the laws of the State of Delaware. Under Delaware law, NASI stockholders will not have dissenters' rights of appraisal in connection with the issuance of shares of NASI's common stock in the merger.

        Under Delaware law, NOMOS stockholders are entitled to appraisal rights in connection with the proposed merger, which rights are subject to certain conditions discussed more fully elsewhere in this joint proxy statement/prospectus. Appraisal rights entitle NOMOS stockholders who:

•

submit a proper written demand for appraisal to NOMOS prior to the special meeting;



•

do not otherwise vote in favor of the merger; and



•

meet certain other conditions

to receive a valuation of their shares and a payment of that value in cash in lieu of the consideration called for by the merger agreement.

        Failure by a dissenting stockholder to follow the steps required by law for perfecting appraisal rights may lead to the loss of those rights, in which case such dissenting stockholder will be treated in the same manner as a non-dissenting stockholder.

        See Annex J for a reproduction of Section 262 of the Delaware General Corporation Law, which relates to the appraisal rights of dissenting stockholders. In view of the complexity of law relating to appraisal rights, NOMOS stockholders who are considering objecting to the merger and seeking such appraisal rights are encouraged to consult their own legal advisors.

        Pursuant to the terms of the merger agreement, NASI will be released from its obligation to consummate the merger if the shares of NOMOS common stock held by stockholders who have exercised appraisal rights exceed 5% of the outstanding shares of NOMOS common stock.

 Interests of Certain Persons in the Merger (see page 123)

        When stockholders of NASI and NOMOS consider the respective recommendations of the board of directors thereof that such stockholders vote in favor of the proposals relating to the merger, they should be aware that certain directors and executive officers of NASI and NOMOS have interests in the merger that may be different from, or in addition to, the interests of stockholders generally. These interested individuals, including Messrs. Manzetti, Friede and Cassis, participated in the deliberation of NOMOS board of directors regarding the merger; however, the interests of such individuals were (to the extent they then existed) fully disclosed to the disinterested directors at the time of such deliberations.

        All NOMOS executive officers, including Mr. Manzetti, William W. Wells (NOMOS' executive vice president of sales), David J. Haffner (NOMOS' chief financial officer), Fred L. Marroni (NOMOS' vice president of engineering), Joseph M. Argyros (NOMOS' vice presient of operations) and Francis X. Dobscha (NOMOS' vice president of quality and regulatory affairs) have interests in the combined company as employees in terms of job responsibilities, working environment and compensation which are in addition to and different from their interests as stockholders and/or the rights to receive payment under existing severance agreements with NOMOS in the event they are not retained as employees. All continuing directors, including Messrs. Manzetti and Friede, will have the responsibility for being directors of a larger company after the merger.

12

        Immediately after the consummation of the merger, NASI will take all actions necessary to expand its board of directors to consist of nine members. Seven of the nine members will be persons who served on NASI's board of directors immediately prior to the completion of the merger. The two additional members will be John W. Manzetti, NOMOS' president and a director, and John A. Friede, NOMOS' largest stockholder and chairman of NOMOS' board of directors.

        Mr. Manzetti, the president and chief executive officer of NOMOS, will have an employment agreement pursuant to which he will continue to be employed by the combined company after the consummation of the merger. If the merger is consummated, Mr. Manzetti will be employed as the president of the surviving corporation of the merger, which will be a wholly owned subsidiary of NASI and change its name immediately following the merger to "NOMOS Corporation". The employment agreement includes rights to receive options in NASI and right to severance payments upon the occurrence of certain events such as a change of control of the company.

        The merger agreement provides for a combination of cash and NASI common stock to be paid to the NOMOS stockholders. All of the cash consideration in the merger, other than with respect to fractional shares, will be paid to the holders of NOMOS series B preferred stock and series C preferred stock. Mr. Friede, chairman of the board of directors of NOMOS, beneficially owns approximately 80% of the outstanding NOMOS series B preferred stock and John L. Cassis, a member of the NOMOS board of directors, beneficially owns approximately 32% of the outstanding NOMOS series C preferred stock. For more information regarding the cash component of the merger consideration, see "The Merger Agreement" beginning on page 126 and "Beneficial Ownership of Capital Stock of NOMOS" beginning on page 98.

        Mr. Friede currently owes NOMOS $287,160, plus interest, which principal amount was loaned to Mr. Friede on May 22, 2003. In partial consideration for the time, efforts and resources that Mr. Friede has provided NOMOS in the past, NOMOS has agreed, subject to the consummation of the merger, to cancel this indebtedness which cancellation will be effective prior to the consummation of the merger. See "Information Regarding NOMOS—Certain Relationships and Related Transactions of NOMOS" beginning on page 104.

        NOMOS is party to a letter agreement dated February 11, 2002 with Mr. Friede, which provides that if Mr. Friede's employment is terminated without cause, he will receive continued payment of his base salary, which is currently $180,000 per year, and health benefits for twelve months after the termination date. Mr. Friede will be terminated as an employee without cause following the consummation of the merger. Therefore, the surviving corporation to the merger will be obligated to pay this severance to Mr. Friede.

        In addition, pursuant to the terms of a voting agreement Mr. Friede has agreed to vote certain shares beneficially owned by him, representing approximately 41% of the voting shares of NOMOS common stock on an as-converted-to-common stock basis, outstanding on the record date in favor of the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement.

        Effective on the completion of the merger, all outstanding unvested NOMOS stock options held by current NOMOS directors and employees, including those held by NOMOS' executive officers, will immediately vest.

        Pursuant to the terms of a standstill agreement between NOMOS and certain of its holders of series C preferred stock, NOMOS has agreed to pay to each holder of its series C preferred stock, concurrently with the closing of the merger, an amount equal to $0.15 per share of series C preferred stock held by them, for an aggregate payment of $200,422.77. John L. Cassis, a member of the NOMOS board of directors, beneficially owns approximately 32% of the outstanding NOMOS series C preferred stock and, accordingly, he (or entities with which he is affiliated) would receive a significant

13

portion of such consideration if paid. See "Interest of Certain Persons in the Merger—Series C Standstill Agreement" beginning on page 123.

 Restrictions on Alternative Transactions (see "The Merger Agreement—Covenants—No Solicitation" on page 129)

        The merger agreement contains restrictions on the ability of each of NOMOS and NASI to solicit or engage in discussions or negotiations with a third party with respect to a proposal to acquire a significant interest in the respective companies. Notwithstanding these restrictions, the merger agreement provides that under specified circumstances, if either party receives an acquisition proposal from a third party that is a superior proposal, as defined in the merger agreement, such party may engage in negotiations regarding the superior proposal with that third party.

        If terminated, the merger agreement will become void and, except in circumstances where a termination fee is payable, neither party will have any liability to the other party under the merger agreement. Upon a termination, a party may become obligated to pay to the other party a termination fee, NOMOS will be obligated to pay a termination fee to NASI equal to $3,000,000 if certain circumstances are met. NASI will be obligated to pay a termination fee to NOMOS equal to $1,500,000 if certain circumstances are met. See "The Merger Agreement—Termination Fee" on page 137.

 Accounting Treatment of the Merger (see page 58)

        NASI will account for the merger under the purchase method of accounting for business combinations under accounting principles generally accepted in the United States, which means that the assets and liabilities of NOMOS will be recorded, as of the completion of the merger, at their fair values and added to those of NASI.

Summary Selected Historical Financial Information

        NASI and NOMOS are providing the following financial information to aid you in your analysis of the financial aspects of the merger. NASI derived the summary selected historical consolidated balance sheets data and consolidated statements of operations data as of and for the years ended October 31, 1999 through October 31, 2003 from the audited consolidated financial statements of NASI for those respective periods and derived statements of operations data for the three months ended January 31, 2003 and 2004 and the balance sheet data as of January 31, 2004 from the unaudited consolidated financial statements of NASI for those periods. NOMOS derived the summary selected historical consolidated balance sheets data and consolidated statements of operations data as of and for the years ended December 31, 1999 through December 31, 2003 from the audited consolidated financial statements of NOMOS for those respective periods.

        In the opinion of NASI's management, the unaudited consolidated financial statements for NASI have been prepared on a basis consistent with its audited consolidated financial statements and include all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation of the financial position and results of operations for the applicable periods. The operating results for the three months ended January 31, 2004 for NASI are not necessarily indicative of the results that may be expected for the entire fiscal year of NASI or the combined company after the merger.

        The tables below represent summary selected historical consolidated statements of operations and consolidated balance sheets data of NASI and NOMOS and you should read it together with the historical financial statements and related notes contained in the annual reports and other information that NASI has filed with the Securities and Exchange Commission and incorporated by reference into this joint proxy statement/prospectus, and read in conjunction with NOMOS' financial statements, the related notes and "Management's Discussion and Analysis of Financial Condition and Results of Operations" included elsewhere in this joint proxy statement/prospectus. See "Where You Can Find More Information" on page 178 for more information.

14

North American Scientific, Inc.
(in thousands, except per share data)

(1)

Represents the write-off of costs incurred related to two linear particle accelerators of $3,743,000 in 2001; write-off of abandoned licenses and related equipment costs of $2,714,000 related to certain technology licensed from third parties in 2002.

(2)

Represents cumulative effect for the change in recognizing future decommissioning costs of leased manufacturing and research and development facilities.

15

NOMOS Corporation
(in thousands, except per share data)

(1)

Amounts exclude stock-based compensation. See NOMOS Consolidated Statements of Operations on page F-4.

(2)

Loss on APMG disposition

(3)

Other income (expense) includes expense of $3.0 million in 2000 related to the Med-Tec write-off and income in the year ended December 31, 2003 represents Med-Tec and other litigation settlements

(4)

Represents the operating losses, asset write-offs and additional costs associated with the disposition of ROCS

(5)

Includes accrued but undeclared dividends

(6)

All share and per share information presented reflects a 1 for 1.97 reverse stock split that was effected June 19, 2002

(7)

Amounts in 2002 represent Offering and Relocation costs and amounts in 2003 represent professional fees associated with the planned merger

16

Summary Pro Forma Unaudited Financial Information

        The table below presents selected financial data from the NASI and NOMOS unaudited pro forma condensed consolidated financial statements for the combined company. The unaudited pro forma condensed combined consolidated balance sheet as of January 31, 2004 combines the historical consolidated balance sheets of NASI as of January 31, 2004 and NOMOS as of December 31, 2003, giving effect to the merger as if it occurred on January 31, 2004. The unaudited pro forma condensed combined consolidated statement of operations for the year ended October 31, 2003 and for the three months ended January 31, 2004 combines the historical consolidated statements of operations of NASI and NOMOS for the year ended October 31, 2003 and twelve months ended September 30, 2003, respectively, and the three months ended January 31, 2004 and the three months ended December 31, 2003, respectively, giving effect to the merger as if it occurred on November 1, 2002, reflecting only pro forma adjustments expected to have a continuing impact on the combined results. The unaudited pro forma condensed combined consolidated financial data is not necessarily indicative of the financial position or operating results that would have been achieved had the merger been consummated as of the dates indicated, nor is it necessarily indicative of future financial position or operating results. This information should be read in conjunction with the unaudited pro forma condensed combined consolidated financial statements and related notes and the historical financial statements and related notes of NASI and NOMOS included in, or incorporated by reference into, this joint proxy statement/prospectus.