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                                                                Exhibit 10.6 (b)


                        REVOLVING CREDIT PROMISSORY NOTE

                                  (FACILITY A)

$1,000,000                                                      Phoenix, Arizona
                                                                  April 24, 2000

        FOR VALUE RECEIVED, ALLIANCE MEDICAL CORPORATION, a Delaware corporation
("BORROWER") promises to pay to the order of IMPERIAL BANK, a California banking
corporation ("LENDER", with Lender and each subsequent transferee and/or owner
of this Note, whether taking by endorsement or otherwise, being herein
successively called "HOLDER"), at Imperial Bank, One Arizona Center, 400 East
Van Buren, Phoenix, Arizona 85004, or at such other place as Holder may from
time-to-time designate in writing, the principal sum of ONE MILLION AND NO/100
DOLLARS ($1,000,000), or so much thereof as may be from time-to-time
outstanding, together with interest thereon, to be computed on each Advance
thereof from the date of its disbursement, at the interest rates stated in the
Credit and Reimbursement Agreement of even date herewith executed by Borrower,
as borrower, and Lender, as lender (the "CREDIT AGREEMENT").

        This Note is issued pursuant to the Credit Agreement and is secured by
the Loan Documents and the Related Documents. Capitalized terms used and not
otherwise defined herein shall have the meanings assigned to such terms in the
Credit Agreement. In the event of any conflict between the provisions of this
Note and the provisions of the Credit Agreement, the provisions of the Credit
Agreement shall govern. All notices required or permitted in connection with
this Note shall be given in the manner provided in the Credit Agreement for the
giving of notices.

        All amounts advanced by Lender under this Note shall be Advances under
Facility A as defined in the Credit Agreement. Advances hereunder shall be made
in accordance with the provisions of the Credit Agreement pertaining to Advances
under Facility A, and the principal of the indebtedness evidenced hereby, and
interest thereon, shall be payable in the manner and on the dates stated in the
Credit Agreement. All principal, interest and other charges and amounts to be
paid hereunder shall be due and payable, in full, on the date that is one
Business Day before the first anniversary of the date of this Note. Payments
under this Note shall be applied in the manner provided in the Credit Agreement.

        If Borrower fails to make any payment of the Indebtedness evidenced by
this Note within ten (10) days after the date on which such payment becomes due
and payable under the Credit Agreement, Borrower shall pay to Holder, in
addition to all other charges and amounts then due and payable, a late charge
equal to five percent (5.0%) of the amount of the overdue payment.

        Borrower may prepay the indebtedness evidenced by this Note in
accordance with the provisions of the Credit Agreement, and, if at any time the
aggregate principal amount outstanding hereunder exceeds the then applicable
Facility A Borrowing Base (computed as provided in the Credit Agreement),
Borrower shall prepay the amount by which such aggregate outstanding amount
exceeds such borrowing base, together with interest accrued on the amount of the
prepayment.
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        This Note evidences a revolving credit, all or any part of which may be
advanced to Borrower, repaid by Borrower, and re-advanced to Borrower from
time-to-time, subject to the other provisions hereof and the provision of the
Credit Agreement; provided that the principal balance outstanding hereunder at
any one time shall not exceed the lesser of (i) the face amount hereof, or (ii)
the applicable Facility A Borrowing Base.

        Time is of the essence of this Note.

        Borrower shall pay all costs and expenses, including reasonable
attorneys' fees and court costs, incurred in the collection or enforcement of
all or any part of this Note. All such costs and expenses shall be secured by
the Loan Documents and the Related Documents.

        Failure or delay of Holder to exercise any right or remedy hereunder or
under the Credit Agreement with respect to any Default, Event of Default or
other circumstance shall not constitute a waiver of the right to exercise the
same with respect to any subsequent Default, Event of Default or other
circumstance or in the event of continuance of any existing Default or Event of
Default after demand for performance hereof

        Borrower and all sureties, guarantors and/or endorsers hereof, or of any
obligation hereunder, and all accommodation parties hereon (severally each
hereinafter called a "SURETY") each: (a) agree that the liability under this
Note of all parties hereto is joint and several; (b) to the maximum extent
allowed by law, severally waive any and all formalities in connection with this
Note, including (but not limited to) demand, diligence, presentment for payment,
protest and demand, and notice of extension, dishonor, protest, demand,
maturity, nonperformance and nonpayment; (c) agree that Holder may extend the
time of payment or otherwise modify the terms of payment of any part of the
whole or the indebtedness evidenced by this Note, at the request of any person
liable hereon, and that any such extension or modification shall not alter or
diminish the liability of any person hereon; (d) severally waive any homestead
or other exemption rights; and (e) severally waive any recourse to guaranty or
suretyship requirements or defenses.

        This Note shall be binding upon Borrower and its successors and assigns,
and shall inure to the benefit of Holder and any subsequent holders of this Note
and their respective successors and assigns.

        This Note shall be governed by and construed and enforced in accordance
with the substantive laws (other than conflict laws) of the State of Arizona,
except to the extent Holder has greater rights or remedies under Federal law, in
which case such choice of Arizona law shall not be deemed to deprive Holder of
any such rights and remedies as may be available under Federal law. Borrower
consents to the personal jurisdiction and venue of the state courts located in
Maricopa County, Arizona in connection with any controversy related to this
Note, waives any argument that venue in any such forum is not convenient and
agrees that, at the option of Holder, any litigation initiated by any of them in
connection with this Note may be venued in the Superior Court of Maricopa
County, Arizona.


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        EACH PARTY HERETO HEREBY KNOWINGLY, VOLUNTARILY, AND INTENTIONALLY
WAIVES ANY RIGHTS IT MAY HAVE TO REQUIRE A TRIAL BY JURY IN ANY COURT ACTION
PERTAINING TO THE OBLIGATIONS OR THE LOAN DOCUMENTS, AND AGREES THAT ANY SUCH
ACTION OR PROCEEDING SHALL BE TRIED BEFORE A COURT AND NOT BEFORE A JURY.

        IN WITNESS WHEREOF, these presents are executed as of the date first
written above.

                                            ALLIANCE MEDICAL CORPORATION,
                                            a Delaware corporation



                                            By:
                                               _________________________________
                                            Name:   Tim Einwechter
                                            Its:    Chief Financial Officer
ATTEST:

____________________________________
Name:
     _______________________________
Title:
      ______________________________


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