EXHIBIT 10.3 AMENDMENT NO. 4 TO NOTE PURCHASE AGREEMENT

<PAGE>

                                                                    EXHIBIT 10.3

                   AMENDMENT NO. 4 TO NOTE PURCHASE AGREEMENT

      This Amendment No. 4 to Note Purchase Agreement (this "Amendment"), dated

as of May 12, 2004, amends that certain Note Purchase Agreement, dated as of

March 1, 2002, by and among Horizon Medical Products, Inc., a Georgia

corporation (the "Company"); ComVest Venture Partners, L.P., a Delaware limited

partnership ("ComVest," and together with its successors and assigns, the

"Purchaser"), and the Additional Note Purchasers (as defined therein), as

amended by Amendment No. 1 to Note Purchase Agreement, dated as of June 10,

2002, Amendment No. 2 to Note Purchase Agreement, dated as of July 29, 2002, and

Amendment No. 1 to Note Purchase Agreement dated as of October 21, 2003 (as

amended, the "Note Purchase Agreement"). Capitalized terms used in this

Amendment but not defined herein have the meanings given to such terms in the

Note Purchase Agreement.

      WHEREAS, the Company has requested an extension of the time to repay the

indebtedness and certain other modifications to the Note Purchase Agreement; and

      WHEREAS, the Purchaser and Medtronic, Inc. ("Medtronic") have agreed to

such modification subject to the terms and conditions set forth herein; and

      WHEREAS, the other Additional Note Purchasers have the right, but not the

obligation, to become parties to this Amendment.

      NOW, THEREFORE, in consideration of the premises and mutual covenants of

the parties hereunder, the Company, the Purchaser and the Electing Noteholders

(as defined below) agree as follows:

      Section 1. Amendments. The Note Purchase Agreement and, to the extent

applicable, the Notes are hereby modified as follows:

             (a) The definition of "Maturity Date" is hereby deleted in its

      entirety and replaced with the following:

                  ""Maturity Date" means (i) with respect to the Electing Notes,

            July 16, 2008 and (ii) with respect to the Non-Electing Notes, July

            16, 2005."

            (b) The following definitions are hereby added to Section 1 of the

      Note Purchase Agreement:

                  ""Electing Noteholders" means the Purchaser, Medtronic, and

            each Additional Note Purchaser who is a party to this Amendment."

                  ""Electing Notes" means the Purchaser Senior Subordinated

            Convertible Note, the Medtronic Additional Note, and the Additional

            Notes held by the Electing Noteholders."

<PAGE>

                  ""Medtronic Co-Marketing Agreement"" means that certain

            Co-Promotion Agreement dated as of March 15, 2002, between Medtronic

            and the Company, and as amended by that amendment thereto dated as

            of April 15, 2003.

                  ""Merger" means the Merger (as defined in the Merger

            Agreement) and the other transactions contemplated by the Merger

            Agreement."

                  ""Merger Agreement" means the Agreement and Plan of Merger,

            dated May 12, 2004, by and among RITA MEDICAL SYSTEMS, INC., a

            Delaware corporation ("Parent"), HORNET ACQUISITION CORP., a

            Delaware corporation and a wholly-owned subsidiary of Parent, and

            the Company."

                  ""Merger Closing Date" means the Closing Date as defined in

            the Merger Agreement."

                  ""Non-Electing Notes" means the Additional Notes held by the

            Additional Note Purchasers who do not execute this Amendment as

            Electing Noteholders."

            (c) Section 2.1(a) is hereby deleted in its entirety and replaced

      with the following:

            "(a)(i) The Company has duly authorized the issue, sale and delivery

            of (A) its Purchaser Senior Subordinated Convertible Note, in the

            aggregate principal amount of $4,400,000, to be dated the date of

            issue thereof, (B) its Medtronic Additional Note, in the aggregate

            principal amount of $4,000,000, to be dated the date of issue

            thereof and (C) its Additional Notes, in the aggregate principal

            amount of up to $6,600,000, to be dated the date of issue thereof.

            (ii) Each of the Electing Notes shall bear interest from such date

            on the unpaid principal amount thereof (calculated on the basis of a

            360-day year and actual days elapsed) at a rate per annum equal to

            (A) 6% per annum from the date thereof to and including the date

            that is the six month anniversary of the Closing Date, (B) 8% per

            annum from the date that is the six month anniversary of the Closing

            Date until the first anniversary of the Merger Closing Date, and (C)

            14% from the first anniversary of the Merger Closing Date until such

            time as the Electing Notes shall have been paid in full, such

            interest to be payable quarterly in arrears on the fifth day of each

            month (commencing on the date that is the three month anniversary of

            the Closing Date), and at maturity, to bear interest, payable on

            demand, on any overdue principal and, to the extent permitted by

            applicable law, on any overdue inter