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                                                                   EXHIBIT 10.73


                   [FORM OF IMAGING CENTER SECURITY AGREEMENT]

                               SECURITY AGREEMENT
                                  [CENTER NAME]


      This Security Agreement ("Security Agreement") is made as of the ____ day
of November, 2001 by and between [P.C. NAME] ("PC") and [RAYTEL ENTITY NAME]
("Manager"; and, together with PC, "Pledgors"), in favor of HEALTHCARE BUSINESS
CREDIT CORPORATION, a Delaware corporation with an address at 700 East Gate
Drive, Suite 100, Mount Laurel, New Jersey 08054 ("Secured Party").

                                   BACKGROUND

      A. Manager is operator of a diagnostic imaging center located at [LOCATION
ADDRESS] (the "Imaging Center").

      B. PC is a medical practice.

      C. PC and Manager are parties to a certain [TITLE OF AGREEMENT BETWEEN
P.C. AND MANAGER] dated [DATE OF AGREEMENT BETWEEN P.C. AND MANAGER] (as
amended, renewed or replaced from time to time, "Agreement"), a true and correct
copy of which is attached hereto as Exhibit "A," providing for the operation of
the Imaging Center.

      D. Pursuant to the terms of a Loan and Security Agreement dated as of the
date hereof (as may be amended, restated, supplemented or modified from time to
time, the "Loan Agreement"), Secured Party has extended to Manager, Raytel
Medical Corporation ("RMC") and certain of their affiliates (Manager, RMC and
such affiliates are hereinafter referred to as "Borrowers") a credit facility in
the original maximum principal amount of $15,000,000.00 (the "Loan").

      E. [INSERT APPLICABLE RELATIONSHIP, E.G., MANAGER IS A SUBSIDIARY OF RMC
AND IT] is contemplated that a portion of the proceeds of the Loan will be
indirectly available to finance the operations of the Imaging Center. Each
Pledgor acknowledges that it will be materially benefited as a result thereof.

      F. Secured Party desires to obtain, and each of the Pledgors desires to
grant to Secured Party, a first priority security interest in the Collateral (as
defined below) to secure all of the Obligations (as defined below) of the
Borrowers to Secured Party.

NOW, THEREFORE, with the foregoing Background incorporated by reference and made
part hereof, Pledgors and Secured Party, intending to be legally bound hereby,
promise and agree as follows:

      1. Each of the Pledgors hereby grants to Secured Party a continuing lien
on and security interest in the following property of such Pledgor and in the
following property which may be jointly owned by Pledgors, whether now or
hereafter owned and wherever located (collectively, the "Collateral"):


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            (i) all accounts (including without limitation, the Accounts)
whether now existing or hereafter arising or acquired, (ii) all contract rights,
instruments, chattel paper, documents, general intangibles, rights, remedies,
guarantees and collateral evidencing, securing or otherwise relating to such
accounts, including without limitation, all rights of enforcement and
collection, (iii) all lockboxes, all collection accounts and other accounts into
which any of the proceeds and/or payments on the accounts are deposited, all
funds received thereby or deposited therein, and any checks or instruments from
time to time representing or evidencing the same, (iv) all books and records of
Pledgors evidencing or relating to such accounts, (v) all information and data
compiled or derived by Pledgors with respect of such accounts (other than any
such information and data subject to legal restrictions of patient
confidentiality) and (vi) all collections, receipts and other proceeds (cash and
noncash) derived from any of the foregoing.

      For purposes hereof "Account" means (a) the third party reimbursable
portion of accounts receivable owing to the Pledgors arising out of the delivery
by the Pledgors of medical, surgical, diagnostic or other professional or
medical or dental services, including all rights to reimbursement under any
agreements with a third party obligor, (b) all other healthcare insurance
receivables and accounts as defined in the Uniform Commercial Code as in effect
in the State of New Jersey (the "UCC"), (c) all rights, remedies, guarantees,
and security interests in respect of the foregoing, all rights of enforcement
and collection, all books and records evidencing or related to the foregoing,
and all rights under this Security Agreement in respect of the foregoing, (d)
all information and data compiled or derived by the Pledgors in respect of such
accounts receivable (other than any such information and data subject to legal
restrictions of patient confidentiality), and (e) all proceeds of any of the
foregoing.

      2. The security interest hereby granted by Pledgors secures (collectively,
the "Obligations") all now existing or hereafter arising debts, obligations,
covenants, and duties of payment or performance of every kind, matured or
unmatured, direct or contingent, owing, arising, due or payable to Secured Party
by or from any Borrower arising out of the Loan Agreement or any other document
executed and delivered in connection therewith (collectively, such documents and
the Loan Agreement are referred to herein as the "Loan Documents").

      3. The Pledgors hereby agree that if the location of the Collateral
changes from the location identified in Background paragraph A hereof, the
Pledgors will immediately notify the Secured Party in writing of the additions
or changes to the locations of the Collateral.

      4. Each of the Pledgors covenants that it shall do, obtain, make, execute
and deliver all such additional and further acts, things, deeds, assurances and
instruments as Secured Party may require to vest in and assure to Secured Party
its rights hereunder and in or to the Collateral, and the proceeds thereof.

      5. Each Pledgor represents, warrants and covenants that it has not granted
or suffered or will grant or suffer the imposition of a lien or security
interest upon the Collateral, other than the lien granted herein in favor of
Secured Party, and that it has not and will not use any portion thereof in any
manner inconsistent with this Security Agreement.

      6. At the request of the Secured Party, the Pledgors will join with the
Secured Party in executing one or more financing, continuation or amendment
statements pursuant to the UCC


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in form satisfactory to the Secured Party. A carbon, photographic or other copy
of this Security Agreement or of a UCC-1 financing statement may be filed as and
in lieu or a UCC-1 financing statement.

      7. The happening of any of the following events or conditions shall
constitute an "Event of Default" hereunder:

            (a) Dissolution, termination of existence, insolvency, business
suspension or failure, appointment of a receiver of any part of the property of
a Pledgor, assignment for the benefit of creditors by a Pledgor, or the
commencement of any proceedings under any federal bankruptcy or state insolvency
laws (now or hereafter enacted for the relief of Pledgors) by or against a
Pledgor, or

            (b) The failure of either Pledgor to comply with the terms of this
Agreement; or

            (c) The occurrence of an Event of Default under the Loan Agreement.

      Upon the occurrence and during the continuance of an Event of Default, the
Secured Party may declare all Obligations secured hereby immediately due and
payable and shall have, in addition to any remedies provided herein, in any
other Loan Document or by any applicable law, all the remedies of a secured
party under the UCC, as permitted therein, and the Secured Party may (i) dispose
of the Collateral on the Pledgors' premises, (ii) require the Pledgors to
assemble the Collateral and make it available to the Secured Party at a place
reasonably designated by the Secured Party and/or (iii) subject to applicable
laws and regulations governing payment of Medicare/Medicaid receivables, take
possession of the Collateral and notify all account debtors of Secured Party's
security interest in the Collateral and require payment under the Collateral to
be made directly to Secured Party and exercise all rights of a secured party
with respect to the Collateral and collect, sue for and receive payment on all
accounts, and settle, compromise and adjust the same on any term as may be
satisfactory to Secured Party, in its respective sole and absolute discretion
and such party may do all of the foregoing with or without judicial process
(including, without limitation, notifying the United States Postal Authorities
to redirect mail addressed to Pledgors to an address designated by Secured
Party). Unless the Collateral is of a type customarily sold on a recognized
market, the Secured Party will give the Pledgors reasonable notice of the time
and place of any public sale thereof or of the time after which any private sale
or any other intended disposition thereof is to be made. The requirements of
reasonable notice shall be met if such notice is mailed, postage prepaid, to the
business address of the Pledgors shown in this Security Agreement at least
fifteen (15) days before the time of the intended sale or disposition. Expenses
of retaking, holding, preparing for sale, selling or the like shall include the
Secured Party's reasonable attorneys' fees and legal expenses, incurred or
expended by the Secured Party to enforce any payment due it under this Security
Agreement either as against the Pledgors or in the prosecution or defense of any
action, or concerning any matter growing out of or connection with the subject
matter of this Security Agreement and the Collateral pledged hereunder.

      8. The Secured Party shall not be deemed to have waived any of the Secured
Party's rights hereunder or under any other agreement, instrument or paper
signed by the Pledgors unless


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such waiver is in writing and signed by the Secured Party. No delay or omission
on the part of the Secured Party in exercising any right shall operate as a
waiver of such right or any other right. A waiver on any one occasion shall not
be construed as a bar to or waiver of any right or remedy on any other occasion.

      9. Each of the Pledgors does hereby make, constitute and appoint any
officer or agent of the Secured Party as such Pledgor's true and lawful
attorney-in-fact, with power to sign and file on such Pledgor's behalf any and
all UCC financing statements, and, after an Event of Default, to endorse the
name of such Pledgor or any of such Pledgor's officers or agents upon any notes,
checks, drafts, money orders, or other instruments of payment or Collateral that
may come into the possession of the Secured Party in full or part payment of any
amounts owing to the Secured Party; granting to such Pledgor's said attorney
full power to do any and all things necessary to be done in and about the
premises as fully and effectually as such Pledgor might or could do, including
the right to compromise, settle and release all claims and disputes with respect
to the Collateral, and such Pledgor hereby ratifies all that said attorney shall
lawfully do or cause to be done by virtue hereof. This power of attorney shall
be irrevocable for the life of this Security Agreement and all transactions
hereunder.

      10. All provisions herein shall inure to, and become binding upon, the
successors, representatives, receivers, trustees and assigns of the parties;
provided, however, that neither Pledgor will delegate its duty of performance
hereunder without the Secured Party's prior written consent. The term "Security
Agreement", as used in this instrument, shall mean and include this Security
Agreement, all amendments and supplements to any of the foregoing, and all
assignments, instruments and documents submitted to the Secured Party in
connection with any transaction between the Pledgors and the Secured Party. Each
of the Pledgors hereby waives notice of default, and presentment, demand,
protest, and notice of dishonor as to any instrument. Each of the Pledgors
hereby releases Secured Party from all claims for loss or damage caused by any
act or omission on the part of Secured Party, its officers, agents, and
employees, except for willful misconduct.

      11. This Security Agreement and all acts, transactions, agreements,
certificates, assignments and transfers thereunder, and all rights of the
parties hereto, shall be governed as to their validity, enforcement,
construction and effect, and in all other respects, by New Jersey law. The
provisions hereof are severable, and the invalidity or unenforceability of any
provision shall not affect or impair the remaining provisions which shall
continue in full force and effect. No modification hereof shall be binding or
enforceable unless in writing and signed on behalf of the party against whom
enforcement is sought.

      12. Each of the Pledgors irrevocably consents to the exclusive
jurisdiction of any state or Federal court located in the State of New Jersey in
any and all actions and proceedings whether arising hereunder or under any other
agreement or undertaking and irrevocably agrees to service of process by
certified mail, return receipt requested to the address of Pledgors set forth
herein. PLEDGORS AND SECURED PARTY AS AN INDEPENDENT COVENANT IRREVOCABLY WAIVE
JURY TRIAL AND THE RIGHT THERETO IN ANY AND ALL DISPUTES BETWEEN PLEDGORS AND
SECURED PARTY WHETHER HEREUNDER OR UNDER ANY OTHER AGREEMENTS, NOTES, PAPERS,
INSTRUMENTS OR DOCUMENTS, WHETHER SIMILAR OR DISSIMILAR.


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      13. This Security Agreement may be executed in one or more counterparts
which, when taken together, will constitute one and the same document.

      IN WITNESS WHEREOF, the parties hereto, intending to be legally bound
hereby, have set their hands and seals on the day and year first above written.


                                         PLEDGORS:

[P.C. NAME] P.C.                         [RAYTEL ENTITY NAME]


By:                                      By:
    -------------------------------          -----------------------------------
    Name:                                    Name:
    Title:                                   Title:



                                         SECURED PARTY:

                                         HEALTHCARE BUSINESS CREDIT
                                         CORPORATION


                                         By:
                                             -----------------------------------
                                             Name:
                                             Title:


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