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                                                                   EXHIBIT 10.52
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                                PROMISSORY NOTE

$1,400,000.00                                                  November 14, 1996

     1.   FOR VALUE RECEIVED, on or before June 30, 1997 (the "Maturity Date"), 
POSITRON CORPORATION, a Texas corporation ("Maker"), promises to pay to the 
order of PROFUTURES BRIDGE CAPITAL FUND, L.P., a Delaware limited partnership 
("Payee"), at its offices at 1720 South Bellaire Street, Suite 500, Denver, 
Colorado 80222, the principal amount of $1,400,000.00 (the "Total Principal 
Amount"), or such amount less than the Total Principal Amount which has been 
advanced to Maker pursuant to the terms of the Loan and Security Agreement 
dated this date between Maker and Payee (the "Loan Agreement") if the total 
amount advanced under this Promissory Note (this "Note") is less than the Total 
Principal Amount, together with interest on such portion of the Total Principal 
Amount which has been advanced to Maker from the date advanced until paid. 
Capitalized terms used herein, but not defined, shall have the same meanings 
assigned to them in the Loan Agreement.

     2.   (a)  Prior to the Maturity Date, interest shall accrue on the 
outstanding principal balance at the following rates of interest:

               (i)  From the date of this Note to April 1, 1997: 12% per annum

               (ii) From April 1, 1997 to June 30, 1997: 15% per annum

          (b)  From and after the Maturity Date, interest shall accrue on 
matured unpaid amounts at the following rates of interest:

               (i)  From the Maturity Date to December 1, 1997: 15% per annum

               (ii) After November 30, 1997: 18% per annum

     3.   Maker shall have the right to prepay this Note in whole or in part at
any time without penalty or premium.

     4.   Principal and interest are payable in monthly installments until the
Maturity Date, at that time the entire amount of principal and interest
remaining unpaid will be payable. The monthly installment due is the greater
of: (a) $50,000.00, or (b) the aggregate amount received by Payee from BCPA
under the BCPA Contract during the calendar month in which the monthly
installment is due. Maker shall pay to Payee an amount equal to the payment
received by Maker from BCPA under the BCPA Contract each month prior to the
Maturity Date; such payment by Maker shall be due not later than one day after
Maker receives the BCPA payment. If the amount paid by Maker to payee pursuant
to the immediately preceding sentence prior to the 25th day of each month is
less than $50,000.00, Maker shall pay not later than the 25th day of the month
the difference between $50,000.00 and the amount previously paid by Maker during
such month. All amounts due hereunder shall be paid to Payee at its address in
the State of Colorado specified in Section 1.

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     5.   All amounts paid hereunder shall be applied first to all interest then
accrued and unpaid hereunder, and the balance, if any, to principal. All sums 
called for, payable or to be paid hereunder shall be paid in lawful money of the
United States of America which at the time of payment is legal tender for the 
payment of public and private debts therein. All amounts paid hereunder will be 
credited to the payment due effective as of the date Payee actually receives 
such payment at its address specified herein.

     6.   If default is made in the payment of this Note at maturity 
(regardless of how its maturity may be brought about) or the same is placed in 
the hands of an attorney for collection, or if suit is filed hereon, or 
proceedings are had in bankruptcy, probate, receivership, reorganization, or 
other judicial proceedings for the establishment or collection of any amount 
called for hereunder, or any amount payable or to be payable hereunder is 
collected through any such proceedings, Maker agrees to pay the holder of this 
Note a reasonable amount as attorney's or collection fees.

     7.   Maker hereby waives presentment and demand for payment, notice of 
intent to accelerate maturity, notice of acceleration of maturity, protest or 
notice of protest and nonpayment, bringing of suit and diligence in taking any 
action to collect any sums owing hereunder and in proceeding against any of the 
rights and properties securing payment hereof, and agrees that its liability on 
this Note shall not be affected by any release of or change in any security for 
the payment of this Note.

     8.   This Note evidences obligations and indebtedness from time to time 
owing by Maker to Payee pursuant to and secured by, among other things, the Loan
Agreement. The holder of this Note is entitled to the benefits and security
provided in the Loan Documents. Under the Loan Agreement, Borrower may request 
two advances of $700,000.00 each. The unpaid balance of this Note shall increase
with each such advance and shall decrease with each payment made hereunder;
provided, however, that this Note is not a revolving line of credit note and
principal amounts repaid hereunder may not be reborrowed.

     9.   Maker agrees that upon the occurrence of an Event of Default, the
holder of this Note may, at its option, without further notice or demand, (a)
declare the outstanding principal balance of and accrued but unpaid interest on
this Note at once due and payable, (b) refuse to advance any additional amounts
under this Note, (c) foreclose all liens securing payment hereof, (d) pursue any
and all other rights, remedies and recourses available to the holder hereof,
including but not limited to any such rights, remedies or recourses under the
Loan Documents, at law or in equity, or (e) pursue any combination of the
foregoing.

     10.  The failure to exercise the option to accelerate the maturity of this 
Note or any other right, remedy or recourse available to the holder hereof upon 
the occurrence of an Event of Default hereunder shall not constitute a waiver of
the right of the holder of this Note to exercise the same at that time or at any
subsequent time with respect to such Event of Default or any other Event of 
Default. The rights, remedies and recourses of the holder hereof, as provided in
this Note and in any of the other Loan Documents, shall be cumulative and 
concurrent and may be pursued separately, successively or together as often as 
occasion therefore shall arise, at the sole discretion of the holder hereof. The
acceptance by the holder

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hereof of any payment under this Note which is less than the payment in full of 
all amounts due and payable at the time of such payment shall not (a) constitute
a waiver of or impair, reduce, release or extinguish any right, remedy or 
recourse of the holder hereof, or nullify any prior exercise of any such right, 
remedy or recourse, or (b) impair, reduce, release or extinguish the obligations
of any party liable under any of the Loan Documents as originally provided 
herein or therein.

     11.  All notices permitted hereunder shall be given to the addressee at the
following address: if to Payee, at the address specified in Section 1, or at 
such other address as Payee may provide by notice to Maker; if to Maker, 16350
Park Ten Place, Houston, Texas 77084, Attention: CFO. All notices given
hereunder shall be in writing and shall be considered properly given if mailed
by first-class United States mail, postage prepaid, registered or certified with
return receipt requested, or by delivering same in person to the addressee, or
by prepaid telegram. Any notice given in accordance herewith shall be effective
as provided in the Loan Agreement.

     12.  WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW, THIS NOTE SHALL BE 
CONSTRUED AND ENFORCED IN ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE 
OF COLORADO AND THE LAWS OF THE UNITED STATES OF AMERICA, EXCEPT THAT TO THE 
EXTENT THAT THE LAW OF THE STATE IN WHICH A PORTION OF THE COLLATERAL IS LOCATED
(OR WHICH IS OTHERWISE APPLICABLE TO A PORTION OF THE COLLATERAL) NECESSARILY 
OR, IN THE SOLE DISCRETION OF PAYEE, APPROPRIATELY GOVERNS WITH RESPECT TO 
PROCEDURAL AND SUBSTANTIVE MATTERS RELATING TO THE CREATION, PERFECTION AND 
ENFORCEMENT OF THE LIENS, SECURITY INTERESTS AND OTHER RIGHTS AND REMEDIES OF 
PAYEE GRANTED HEREIN, THE LAWS OF SUCH STATE SHALL APPLY AS TO THAT PORTION OF 
THE COLLATERAL LOCATED IN (OR OTHERWISE SUBJECT TO THE LAWS OF) SUCH STATE.

     13.  Maker and Payee intend to conform strictly to applicable usury laws.
All agreements between Maker and Payee whether now existing or hereafter arising
and whether written or oral, are expressly limited so that in no event
whatsoever, whether by reason of acceleration of the maturity of the
indebtedness evidenced hereby or otherwise, shall the interest contracted for,
charged or received by Payee or otherwise exceed the maximum amount permissible
under Applicable Law. If from any circumstances whatsoever interest would
otherwise be payable to Payee in excess of the maximum lawful amount, the
interest payable to Payee shall be reduced automatically to the maximum amount
permitted under Applicable Law. If Payee shall ever receive anything of value
deemed to be interest under Applicable Law which would apart from this provision
be in excess of the maximum lawful amount, the amount which would have been
excessive interest shall be applied to the reduction of the principal amount
owing on the principal amount owed hereunder in inverse order of maturity and
not to the payment of interest, or if such amount which would have been
excessive interest exceeds the unpaid principal balance of this Note, such
excess shall be refunded Maker. All interest paid or agreed to be paid to Payee
shall, to the extent permitted by Applicable Law, be amortized, prorated,
allocated and spread throughout the full stated term, including any renewal of
extension, of such indebtedness so that the amount of interest on account of
such indebtedness does not exceed the maximum permitted by Applicable Law. The
terms and
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provisions of this Section shall control and supersede every other provision of 
all existing and future agreements between Maker and Payee.

     EXECUTED as of the date first written above.

                                      POSITRON CORPORATION

                                      By: /s/ David O. Rodrigue  
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                                          David O. Rodrigue, Vice President

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