ELEVENTH AMENDMENT TO LOAN AND SECURITY AGREEMENT

THIS ELEVENTH AMENDMENT to Loan and Security Agreement (this   “Amendment”) is entered into on October 10, 2008, by and between

NORTH AMERICAN SCIENTIFIC, INC., a Delaware corporation (“NASI”); and

NORTH AMERICAN SCIENTIFIC, INC., a California corporation (“NASI-CA”).

A.   Bank and Borrower have entered into that certain Loan and Security Agreement, with an Effective Date of October 5, 2005 (as the same has been, and may hereafter from time to time be amended, modified, supplemented or restated, the “Loan Agreement”).

B.   Bank has extended credit to Borrower for the purposes permitted in the Loan Agreement.

C.   Borrower has requested that Bank amend the Loan Agreement, as herein set forth, and Bank has agreed to the same, but only to the extent, in accordance with the terms, subject to the conditions and in reliance upon the representations and warranties set forth herein.

Now, Therefore, in consideration of the foregoing recitals and other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, and intending to be legally bound, the parties hereto agree as follows:

1.   Definitions. Capitalized terms used but not defined in this Amendment shall have the meanings given to them in the Loan Agreement.

2.   Amendments to Loan Agreement. The Loan Agreement is hereby amended as follows, effective as of the date hereof:

2.1   Modified Definition of Eligible Accounts . Subclause (a) of the definition of Eligible Accounts, which describes certain Accounts that are not included in the definition of Eligible Accounts, as set forth in Section 13.1 of the Loan Agreement is hereby amended to read as follows:

(a)   Accounts that the account debtor has not paid within 90 days of invoice date; provided , however , that with respect to the following account debtors, Accounts that the account debtor has not paid within 150 days of invoice date (the “Extended Terms Accounts”): (i) Premier Brachytherapy, (ii) Richmond University, (iii) MPM Medical Products, (iv) Bahman Daneshfar MD, (v) Piedmont Prostate Center, (vi) California Pacific Medical Center, (vii) Rochester General Hospital, (viii) Bellevue Urology Associates, (ix) Prologics and (x) Servicios De Radioterapia Oncologica, provided that the aggregate amount of such Extended Term Accounts shall not exceed $300,000 at any one time outstanding for all such account debtors combined and provided , further , that Borrower shall deliver to Bank as soon as available, but no later than 30 days after the end of each month, a report showing the Extended Term Accounts, by account debtor, the amounts outstanding with respect thereto, the days outstanding of such Extended Term Accounts and such other information as Bank may require.

2.2   Modified Disbursement of Growth Capital Loan. Paragraph 2 of Section 1 of the Amended and Restated Schedule 2 to Loan and Security Agreement that currently reads as follows:

2.   Growth Capital Loan . An amount equal to the unpaid principal balance from time to time outstanding of the Loan (the “ Growth Capital Loan ”) in the original principal amount of up to $3,000,000 to be disbursed as follows: (i) $1,500,000 disbursed concurrently herewith and (ii) up to $1,500,000 to be disbursed prior to September 30, 2008. The Growth Capital Loan may be used for working capital purposes of Borrower. Once any portion of the Growth Capital Loan is repaid, it cannot be reborrowed.

is hereby amended to read as follows:

2.   Growth Capital Loan . An amount equal to the unpaid principal balance from time to time outstanding of the Loan (the “ Growth Capital Loan ”) in the original principal amount of up to $3,000,000 to be disbursed as follows: (i) $1,500,000 disbursed on May 28, 2008 and (ii) up to $1,500,000 to be disbursed prior to March 31, 2009; provided that any disbursement made pursuant to subclause (ii) above shall only be made after Borrower provides Bank evidence, satisfactory to Bank in its good faith business judgment, that Borrower has completed nine (9) additional in-patient trials with respect to Borrower’s ClearPath product which trials must be completed on or after October 8, 2008. The Growth Capital Loan may be used for working capital purposes of Borrower. Once any portion of the Growth Capital Loan is repaid,