<PAGE>
                                                                    EXHIBIT 10.5

                                PROMISSORY NOTE

                                 Sept. 24, 2003
                               ------------------
                                     (Date)


FOR VALUE RECEIVED, CHROMAVISION MEDICAL SYSTEMS, INC. a corporation located at
the address stated below ("MAKER") promises, jointly and severally if more than
one, to pay to the order of GENERAL ELECTRIC CAPITAL CORPORATION or any
subsequent holder hereof (each, a "PAYEE") at its office located at 401 MERRITT
7 SUITE 23, NORWALK, CT 06851-1177 or at such other place as Payee or the
holder hereof may designate, the principal sum of THREE MILLION--00/00 DOLLARS
($3,000,000.00), with interest on the unpaid principal balance, from the date
hereof through and including the dates of payment, at a fixed interest rate of
Eight and Sixteen Hundredths percent (8.16%) per annum, to be paid in lawful
money of the United States, in Thirty Three (33) consecutive monthly
installments of principal and interest as follows:

<Table>
<Caption>

      Periodic
     Installment             Amount
     -----------             ------
<S>                          <C>
     Thirty Two (32)         $101,797.70
</Table>


each ("Periodic Installment") and a final installment which shall be in the
amount of the total outstanding principal and interest. The first Periodic
Installment shall be due and payable on Nov. 1, 2003 and the following Periodic
Installments and the final installment shall be due and payable on the same day
of each succeeding month (each, a "Payment Date"). Such installments have been
calculated on the basis of a 360 day year of twelve 30-day months. Each payment
may, at the option of the Payee, be calculated and applied on an assumption that
such payment would be made on its due date.

The acceptance by Payee of any payment which is less than payment in full of
all amounts due and owing at such time shall not constitute a waiver of Payee's
right to receive payment in full at such time or at any prior or subsequent
time.

The Maker hereby expressly authorizes the Payee to insert the date value is
actually given in the blank space on the face hereof and on all related
documents pertaining hereto.

This Note may be secured by a security agreement, chattel mortgage, pledge
agreement or like instrument (each of which is hereinafter called a "SECURITY
AGREEMENT").

Time is the essence hereof. If any installment or any other sum due under this
Note or any Security Agreement is not received within ten (10) days after its
due date, the Maker agrees to pay, in addition to the amount of each such
installment or other sum, a late payment charge of five percent (5%) of the
amount of said installment or other sum, but not exceeding any lawful maximum.
If (i) Maker fails to make payment of any amount due hereunder within ten (10)
days after the same becomes due and payable; or (ii) Maker is in default under,
or fails to perform under any term or condition contained in any Security
Agreement, then the entire principal sum remaining unpaid, together with all
accrued interest thereon and any other sum payable under this Note or any
Security Agreement, at the election of Payee, shall immediately become due and
payable, with interest thereon at the lesser of eighteen percent (18%) per annum
or the highest rate not prohibited by applicable law from the date of such
accelerated maturity until paid (both before and after any judgment).

The Maker may prepay in full, but not in part, its entire indebtedness
hereunder upon payment of the entire indebtedness plus an additional sum as a
premium equal to the following percentages of the remaining principal balance
for the indicated period:
Prior to the first annual anniversary date of this Note: five percent (5%)
Thereafter and prior to the second annual anniversary date of this Note: three
percent (3%)
Thereafter and prior to the third annual anniversary date of this Note: One
percent (1%)
and zero percent (0%) thereafter, plus all other sums due hereunder or under
any Security Agreement.

It is the intention of the parties hereto to comply with the applicable usury
laws; accordingly, it is agreed that, notwithstanding any provision to the
contrary in this Note or any Security Agreement, in no event shall this Note
or any Security Agreement require the payment or permit the collection of
interest in excess of the maximum amount permitted by applicable law. If any
such excess interest is contracted for, charged or received under this Note or
any Security Agreement, or if all of the principal balance shall be prepaid, so
that under any of such circumstances the amount of interest contracted for,
charged or received under this Note or any Security Agreement on the principal
balance shall exceed the maximum amount of interest permitted by applicable
law, then in such event (a) the provisions of this paragraph shall govern and
control, (b) neither Maker nor any other person or entity now or hereafter
liable for the payment hereof shall be obligated to pay the amount of such
interest to the extent that it is in excess of the maximum amount of interest
permitted by applicable law, (c) any such excess which may have been collected
shall be either applied as a credit against the then unpaid principal balance
or refunded to Maker, at the option of the Payee, and (d) the effective rate of
interest shall be automatically reduced to the maximum lawful contract rate
allowed under applicable law as now or hereafter construed by the courts having
jurisdiction thereof. It is further agreed that without limitation of the
foregoing, all calculations of the rate of interest contracted for, charged or
received under this Note or any Security Agreement which are made for the
purpose of determining whether such rate exceeds the maximum lawful contract
rate, shall be made, to the extent permitted by applicable law, by amortizing,
prorating, allocating and spreading in equal parts during the period of the
full stated term of the indebtedness evidenced hereby, all interest at any
time contracted for, charged or received from Maker or otherwise by Payee in
connection with such indebtedness; provided, however, that if any applicable
state law is amended or the law of the United States of America preempts any
applicable state law, so that it becomes lawful for the Payee to receive a
greater interest per annum rate than is presently allowed, the Maker agrees
that, on the effective date of such amendment or preemption, as the case may
be, the lawful maximum hereunder shall be increased to the maximum interest per
annum rate allowed by the amended state law or the law of the United States of
America.

The Maker and all sureties, endorsers, guarantors or any others (each such
person, other than the Maker, an "OBLIGOR") who may at any time become liable
for the payment hereof jointly and severally consent hereby to any and all
extensions of time, renewals, waivers or modifications of, and all
substitutions or releases of, security or of any party primarily or secondarily
liable on this Note or any Security Agreement or any term and provision of
either, which may be made, granted or consented to by Payee, and agree that
suit may be brought and maintained against any one or more of them, at the
election of Payee without joinder of any other as a party thereto, and that
Payee shall not be required first to foreclose, proceed against, or exhaust any
security hereof in order to enforce payment of this Note. The Maker and each
Obligor hereby waives presentment, demand for payment, notice of nonpayment,
protest, notice of protest, notice of dishonor, and all other notices in
connection herewith, as well as filing of suit (if permitted by law) and
diligence in collecting this Note or enforcing any of the security hereof, and
agrees to pay (if permitted by law) all expenses incurred in collection,
including Payee's actual attorneys' fees. Maker and each Obligor agrees that
fees not in excess of twenty percent (20%) of the amount then due shall be
deemed reasonable.

THE MAKER HEREBY UNCONDITIONALLY WAIVES ITS RIGHT TO A JURY TRIAL OF ANY CLAIM
OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF, DIRECTLY OR INDIRECTLY, THIS
NOTE, ANY OF THE RELATED DOCUMENTS, ANY DEALINGS BETWEEN MAKER AND PAYEE
RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS,
AND/OR THE RELATIONSHIP THAT IS BEING ESTABLISHED BETWEEN MAKER AND PAYEE. THE
SCOPE OF THIS WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES
THAT MAY BE FILED IN ANY COURT (INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS,
TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY
CLAIMS.) THIS WAIVER IS IRREVOCABLE MEANING THAT IT MAY NOT BE MODIFIED EITHER
ORALLY OR IN WRITING, AND THE WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS,
RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THE NOTE, ANY RELATED DOCUMENTS, OR
TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR ANY
RELATED TRANSACTION. IN THE EVENT OF LITIGATION, THIS NOTE MAY BE FILED AS A
WRITTEN CONSENT TO A TRIAL BY THE COURT.

This Note and any Security Agreement constitute the entire agreement of the
Maker and Payee with respect to the subject matter hereof and supercedes all
prior understandings, agreements and representations, express or implied.

No variation or modification of this Note, or any waiver of any of its
provisions or conditions, shall be valid unless in writing and signed by an
authorized representative of Maker and Payee. Any such waiver, consent,
modification or change shall be effective only in the specific instance and for
the specific purpose given.

Any provision in this Note or any Security Agreement which is in conflict with
any statute, law or applicable rule shall be deemed omitted, modified or
altered to conform thereto.

                                            CHROMAVISION MEDICAL SYSTEMS, INC.


                                            By:     /s/ Stephen Dixon
------------------------------------           ---------------------------------
(Witness)

                                            Name:   Stephen Dixon
------------------------------------             -------------------------------
(Print name)

                                            Title:        EUP-CFO
------------------------------------              ------------------------------
(Address)

                                            Federal Tax ID #:  752649072
                                                             -------------------

                                            Address: 33171 Paseo Cerveza,
                                                     San Juan Capistrano,
                                                     Orange County, CA 92675