THE  SECURITIES  REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
     SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND MAY NOT
     BE  SOLD,  TRANSFERRED,  ASSIGNED,  PLEDGED  OR HYPOTHECATED EXCEPT IN
     ACCORDANCE  WITH  THE PROVISIONS OF REGULATION S PROMULGATED UNDER THE
     SECURITIES  ACT,  PURSUANT TO REGISTRATION UNDER THE SECURITIES ACT OR
     PURSUANT  TO  AN  AVAILABLE  EXEMPTION  FROM  REGISTRATION.

     THIS  NOTE  IS  RESTRICTED  BY  THE  TERMS  OF,  AND  IS  SUBJECT  TO
     RESTRICTIONS  ON  TRANSFER  AND  RIGHTS  OF SALE AS PROVIDED IN A LOAN
     AGREEMENT BETWEEN THE COMPANY AND THE HOLDER HEREOF, OR ITS SUCCESSOR,
     A  COPY  OF  WHICH  IS  AVAILABLE  FROM  THE  COMPANY


                              POSITRON CORPORATION


                       SECURED CONVERTIBLE PROMISSORY NOTE


$__________                                                       Houston, Texas
                                                                  ________, 2004


     POSITRON  CORPORATION,  a  Texas corporation (the "Company"), the principal
                                                        -------
office  of  which  is  located at 1304 Langham Creek Drive, #300, Houston, Texas
77084,  for  value received hereby promises to pay to IMAGIN Diagnostic Centres,
Inc., located at 1835 Yonge St., Suite 500, Toronto, Ontario, Canada M4S 1XB, or
its  registered  assigns  ("IMAGIN"  or  the  "Holder"),  the  sum  of
                                               ------
____________________________  ($_________),  or such lesser amount as shall then
equal  the  outstanding  principal amount hereof on the terms and conditions set
forth hereinafter.  The principal hereof and any unpaid accrued interest hereon,
as  set  forth  below,  shall  be due and payable on the earlier to occur of (i)
______, 2006 (two years from the date of this Note, the "Maturity Date") or (ii)
                                                         -------------
when  declared  due and payable by the Holder upon the occurrence of an Event of
Default  (as defined below).  Commencing on the Maturity Date, all principal and
accrued  interest  hereunder  shall  be  payable  upon  demand.  Payment for all
amounts  due  hereunder  shall  be made by mail to the registered address of the
Holder.  All  numbers  expressed herein as "$" or "dollars" are in United States
dollars.

     The  following  is a statement of the rights of the Holder of this Note and
the conditions to which this Note is subject, and to which the Holder hereof, by
the  acceptance  of  this  Note,  agrees:

          1.   Definitions.  As  used  in this Note, the following terms, unless
               -----------
the  context  otherwise  requires,  have  the  following  meanings:

                    (a)  "Business  Day"  shall  mean a day other than Saturday,
                          -------------
Sunday  or  a  public  holiday  under  the  laws  of  the  State  of  Texas.


                                      -1-
<PAGE>
                    (b)  "Company"  includes  any corporation that shall succeed
                          -------
to  or  assume  the  obligations  of  the  Company  under  this  Note.

                    (c)  "Holder,"  when  the context refers to a holder of this
                          ------
Note,  shall  mean  any person who shall at the time be the registered holder of
this  Note.

                    (d)  "Loan  Agreement" shall mean the Loan Agreement between
                          ---------------
the  Company  and  IMAGIN,  dated  as  of  May  21,  2004.

                    (e)  "Operating Cash Flow" shall mean the sum of net income,
                          -------------------
depreciation, change in accruals and change in accounts payable, minus change in
accounts receivable, minus change in inventories.

                    (f)  "Purchase Agreement" shall mean the Note Purchase
                          ------------------
Agreement between the Company and IMAGIN, dated as of May 21, 2004.

                    (g)  "Securities Act" shall mean the Securities Act of 1933,
                          --------------
as  amended,  including  the  rules promulgated thereunder by the Securities and
Exchange  Commission.

                    (h)  "Security  Agreement" shall mean the Security Agreement
                          -------------------
between  the  Company  and  IMAGIN,  dated  as  of  May  21,  2004.

          2.   Interest.  Simple  interest  shall  accrue  at  the  rate  of ten
               --------
percent  (10%)  per  annum  on the principal of this Note outstanding during the
period beginning the date of this Note and ending on the date that the principal
amount  of  this Note is repaid.  Interest shall be calculated on the basis of a
365-day  year  for the actual number of days elapsed.  Accrued interest shall be
payable in cash annually on the anniversary date of this note; provided however,
that  in the event the accrued interest on this Note together with the aggregate
accrued  interest  on  all  outstanding  notes  issued  pursuant to the Purchase
Agreement  and  pursuant  to  the  Loan Agreement (such notes collectively being
hereinafter  referred  to  as  the  "Imagin Notes") exceeds 50% of the Company's
                                     ------------
Operating  Cash Flow during the twelve month period ending on the last completed
calendar  quarter  which  preceded the interest payment date by at least 60 days
("50%  of  cash  flow"),  at the Company's option, the accrued interest shall be
  -------------------
payable  (i)  in  cash pro-rata among the Imagin Notes up to an aggregate amount
equal  to  50%  of  cash  flow,  and  (ii)  by  issuance to Holder of a new note
identical  in  form  to this Note and in an amount equal to the accrued interest
not  otherwise  paid  in  cash.  In  the  event  that  a payment date falls on a
non-Business  Day,  payment shall be made on the next Business Day, while taking
into  account such extra days in calculating the accrued interest.  In the event
of an earlier conversion, acceleration or payment of the Note, interest shall be
payable  in  cash  on  such  date.

          3.   Events  of  Default.  If  any  of  the  events  specified in this
               -------------------
Section  3  shall  occur  (herein  individually  referred  to  as  an  "Event of
                                                                        --------
Default"), the Holder of the Note may, so long as such condition exists, declare
-------
the  entire  principal  and  unpaid  accrued interest hereon immediately due and
payable,  by  notice  in  writing  to  the  Company:


                                      -2-
<PAGE>
                    (a)  The Company shall default in the payment of any part of
the  principal or accrued and unpaid interest on this Note after it shall become
due  and  payable,  whether  at maturity or at a date fixed for prepayment or by
acceleration  or  otherwise;  or

                    (b)  The  institution  by  the  Company of proceedings to be
adjudicated  as  bankrupt  or  insolvent, or the consent by it to institution of
bankruptcy  or  insolvency  proceedings  against  it  or  the  filing by it of a
petition  or  answer  or  consent  seeking  reorganization  or release under the
federal  Bankruptcy  Act,  or  any other applicable federal or state law, or the
consent  by  it  to  the  filing  of  any  such petition or the appointment of a
receiver,  liquidator,  assignee,  trustee  or  other  similar  official  of the
Company,  or  of any substantial part of its property, or the making by it of an
assignment  for  the  benefit of creditors, or the taking of corporate action by
the  Company  in  furtherance  of  any  such  action;  or

                    (c)  If, within sixty (60) days after the commencement of an
action  against  the Company, without the consent or acquiescence of the Company
(and  service  of  process  in  connection therewith on the Company) seeking any
bankruptcy,  insolvency,  reorganization,  liquidation,  dissolution  or similar
relief under any present or future statute, law or regulation, such action shall
not  have  been  resolved  in  favor of the Company or all orders or proceedings
thereunder affecting the operations or the business of the Company stayed, or if
the  stay  of any such order or proceeding shall thereafter be set aside, or if,
within sixty (60) days after the appointment without the consent or acquiescence
of  the  Company of any trustee, receiver or liquidator of the Company or of all
or any substantial part of the properties of the Company, such appointment shall
not  have  been  vacated;  or

                    (d)  Any  material  breach  by  the  Company  of  any
representation,  warranty  or  covenant  contained in the Loan Agreement or this
Note.

                    (e)  As  of  January  1,  2005,  the  Company shall not have
obtained stockholder approval to amend its Articles of Incorporation to increase
the  number  of  shares  of  its  authorized  Common  Stock  to  account for the
conversion  of  Series  D Preferred Stock issuable upon conversion of this Note.

In  the  case  of  an Event of Default pursuant to (b) or (c) above, all amounts
shall  automatically,  without  notice,  become  immediately due and payable and
collectible  by  Holder  pursuant  to  applicable  law.

          4.   Conversion.
               ----------

     4.1  Conversion.  The principal amount of this Note, or any portion thereof
          ----------
may  be converted by the Holder at any time prior to Maturity into the number of
fully  paid shares of the Company's Series D Preferred Stock as is determined by
dividing  the  unpaid  principal  under  the  Note  by  the Conversion Price (as
hereinafter  defined)  in  effect at the time of conversion.  Accrued but unpaid
interest  shall  be  payable  in  cash  at  the  time  of  conversion.


                                      -3-
<PAGE>
     4.2  Conversion  Price.  The  Conversion  Price  (the  "Conversion  Price")
          -----------------
applicable  per  share  of  Series D Preferred Stock shall initially be equal to
$1.00,  subject  to  adjustment from time to time in accordance with Section 4.3
below.

     4.3  Adjustments  to  the  Conversion  Price. The Conversion Price shall be
          ---------------------------------------
subject  to  adjustment  from  time  to  time  as  follows:

          4.3.1     Adjustment  Upon  Stock  Dividends,  Subdivisions or Splits.
                    -----------------------------------------------------------
If, at any time, the number of shares of Series D Preferred Stock outstanding is
increased  by  a stock dividend payable in shares of Series D Preferred Stock or
by  a  subdivision  or  split-up  of  shares  of Series D Preferred Stock, then,
following the record date for the determination of holders of Series D Preferred
Stock  entitled  to  receive  such  stock  dividend,  or  to be affected by such
subdivision  or  split-up, the Conversion Price shall be appropriately decreased
so  that the number of shares of Series D Preferred Stock issuable on conversion
of Note shall be increased in proportion to such increase in outstanding shares.

          4.3.2     Adjustment  Upon  Combinations.  If, at any time, the number
                    ------------------------------
of  shares of Series D Preferred Stock outstanding is decreased by a combination
of  the  outstanding shares of Series D Preferred Stock into a smaller number of
shares of Series D Preferred Stock, then, following the record date to determine
shares affected by such combination, the Conversion Price shall be appropriately
increased  so  that the number of shares of Series D Preferred Stock issuable on
conversion  of  the  Note  shall  be decreased in proportion to such decrease in
outstanding  shares.

          4.3.3     Adjustment  Upon  Reclassifications,  Reorganizations,
                    ------------------------------------------------------
Consolidations  or  Mergers.  If,  at  any  time  when  the  Note  is issued and
---------------------------
outstanding,  there  shall  be  any  merger,  consolidation,  share  exchange,
recapitalization,  reorganization, business combination, or other similar event,
as  a  result  of which shares of Series D Preferred Stock shall be changed into
the same or a different number of shares of another class or classes of stock or
securities  of  the  Company  or  another  entity,  or  in  case  of any sale or
conveyance  of  all  or  substantially all of the assets of the Company then the
Holder  shall  thereafter have the right to receive upon conversion of the Note,
upon the basis and upon the terms and conditions specified herein and in lieu of
the  shares  of  Series  D Preferred Stock immediately theretofore issuable upon
conversion,  such  stock,  securities,  cash or other assets which the Holder of
would  have  been  entitled  to  receive  in  such transaction had the Note been
converted  in  full immediately prior to such transaction (without regard to any
limitations  on  conversion  contained herein), and in any such case appropriate
provisions  shall be made with respect to the rights and interests of the Holder
to the end that the provisions hereof (including, without limitation, provisions
for adjustment of the applicable Conversion Price and of the number of shares of
Series  D Preferred Stock issuable upon conversion of the Note) shall thereafter
be  applicable, as nearly as may be practicable in relation to any securities or
assets  thereafter  deliverable  upon  the  conversion  of  the Note.  The above
provisions  shall  similarly  apply to successive mergers, consolidations, share
exchanges,  recapitalizations,  reorganizations,  business combinations or other
similar  events  or  sales  of  assets.

          4.3.4     Deferral in Certain Circumstances.  In any case in which the
                    ---------------------------------
provisions  of  this  Section  4.3 shall require that an adjustment shall become
effective  immediately  after  a


                                      -4-
<PAGE>
record  date  of  an  event,  the Company may defer until the occurrence of such
event  issuing  to  the Holder of the Note, converted after such record date and
before  the  occurrence of such event, the shares of capital stock issuable upon
such  conversion  by reason of the adjustment required by such event and issuing
to  such  Holder  only the shares of capital stock issuable upon such conversion
before  giving  effect  to such adjustments; provided, however, that the Company
shall  deliver  to such Holder an appropriate instrument or due bills evidencing
such  holder's  right  to  receive  such  additional  shares.

          4.3.5     Notice  of  Adjustment  of  Conversion  Price.  Whenever the
                    ---------------------------------------------
Conversion  Price  is adjusted as herein provided: (i) the Company shall compute
the  adjusted  Conversion  Price  in  accordance with this Section 4.3 and shall
prepare  a  certificate  signed  by  the  Chief Financial Officer of the Company
setting forth the adjusted Conversion Price and showing in reasonable detail the
facts  upon which such adjustment is based, and such certificate shall forthwith
be  filed  at each office or agency maintained for such purpose of conversion of
the  Note; and (ii) a notice stating that the Conversion Price has been adjusted
and  setting  forth the adjusted Conversion Price shall forthwith be prepared by
the  Company, and as soon as practicable after it is prepared, such notice shall
be  mailed  by  the  Company  at  its expense to the Holder at the Holder's last
addresses  as  it  shall  appear  in  the  Company's  records.

     4.4  Conversion  Procedure.
          ---------------------

          4.4.1     Notice  of  Conversion.  In  order  to convert this Note (in
                    ----------------------
whole or in part) into full shares of Series D Preferred Stock, the Holder shall
surrender  the  Note,  duly endorsed, by either overnight courier or by hand, to
the  principal  office  of  the  Company,  and  shall  give  written notice (the
"Conversion  Notice")  by  facsimile (with the original of such notice forwarded
 ------------------
with  the  foregoing  courier)  to  the  Company at such office that the Company
elects  to  convert the amount specified therein, which such notice and election
shall be irrevocable by the Holder; provided however, that the Company shall not
be  obligated  to  issue  certificates  evidencing  the  shares  of the Series D
Preferred  Stock issuable upon such conversion unless either the Note evidencing
the  principal  amount  is  delivered  to  the Company as provided above, or the
Holder  notifies  the  Company  that  such  Note(s)  have  been  lost, stolen or
destroyed  and  promptly  executes  an  agreement reasonably satisfactory to the
Company  to  indemnify the Company from any loss incurred by its connection with
such  Note(s).

          4.4.2     Delivery  of  Stock  Certificates  Upon  receipt  of  such
                    ---------------------------------
Conversion Notice, the Company shall immediately verify the Holder's calculation
of  the  conversion  rate  and  shall use its best efforts to cause its transfer
agent  to  issue  and  deliver  as  promptly as practical to the Company of such
Note(s),  or after receipt of such agreement and indemnification, to such Holder
of  Note(s)  at  the address of the Holder, or to its designee, a certificate or
certificates  for  the number of shares of Series D Preferred Stock to which the
Holder shall be entitled, together with a Note or Notes for the principal amount
of  Notes  not submitted for conversion.  The issuance of such certificates upon
conversion  of this Note shall be made without charge to the Holder of this Note
for any issuance tax in respect thereof or other cost incurred by the Company in
connection  with  such  conversion  and  the  related  issuance  of the Series D
Preferred  Stock.  Upon  the conversion of this Note, the Company shall take all
such  actions  as  are  necessary in order to insure that the Series D Preferred
Stock issuable with respect to such conversion shall be validly issued and fully
paid.


                                      -5-
<PAGE>
          4.4.3     Effect  of  Conversion  The  date  on  which  the Conversion
                    ----------------------
Notice is given shall be deemed to be the date the Company received by facsimile
the  Conversion Notice, and the person or persons entitled to receive the shares
of  Series  D Preferred Stock issuable upon such conversion shall be treated for
all  purposes  as  the  record  holder  or  holders  of  such shares of Series D
Preferred  Stock on such date.  No fractional shares of Series D Preferred Stock
shall  be  issued  upon conversion of this Note.  In lieu of the Company issuing
any  fractional  shares  to  the  Holder  upon  the conversion of this Note, the
Company  shall pay to the Holder the amount of outstanding principal that is not
converted  because  its conversion would require fractional shares, such payment
to  be in the form as provided below.  Upon conversion of this Note, the Company
shall be forever released from all of its obligations and liabilities under this
Note,  except  that the Company shall be obligated to pay the Holder, within ten
(10)  days after the date of such conversion, any interest accrued and unpaid or
unconverted  to  and  including  the  date  of  such  conversion,  and  no more.

     4.5  Notices  of  Record  Date,  etc.  In  the  event  of:
          -------------------------------

          4.5.1     Any  taking by the Company of a record of the holders of any
class  of  securities  of the Company for the purpose of determining the holders
thereof  who  are  entitled  to receive any dividend (other than a cash dividend
payable  out  of  earned  surplus at the same rate as that of the last such cash
dividend theretofore paid) or other distribution, or any right to subscribe for,
purchase  or  otherwise  acquire  any  shares of stock of any class or any other
securities  or  property,  or  to  receive  any  other  right;  or

          4.5.2     Any  capital  reorganization  of  the  Company,  any
reclassification  or recapitalization of the capital stock of the Company or any
transfer  of  all or substantially all of the assets of the Company to any other
person  or  any  consolidation  or  merger  involving  the  Company;  or

          4.5.3     Any  voluntary  or  involuntary  dissolution, liquidation or
winding-up  of  the  Company,

the Company will mail to the holder of this Note at least five (5) days prior to
the  earliest  date  specified  therein,  a  notice  specifying:

                    4.5.3.1   The  date  on which any such record is to be taken
for  the  purpose  of  such  dividend, distribution or right, and the amount and
character  of  such  dividend,  distribution  or  right;  and

                    4.5.3.2   The  date  on  which  any  such  reorganization,
reclassification,  transfer,  consolidation, merger, dissolution, liquidation or
winding-up  is  expected to become effective and the record date for determining
shareholders  entitled  to  vote  thereon.

     4.6  Notice  of  Prepayment.  The  Company shall mail to the holder of this
Note at least sixty (60) days prior to repayment of any principal due hereunder.

     4.7  Reservation  of  Stock  Issuable  Upon  Conversion  The Company shall,
prior to conversion of this Note into Series D Preferred Stock, reserve and keep
available  out of its authorized but unissued shares of Series D Preferred Stock
solely  for  the  purpose  of  effecting  the


                                      -6-
<PAGE>
conversion  of the Note such number of its shares of Series D Preferred Stock as
shall from time to time be sufficient to effect the conversion of the Note.  The
Company  shall at all times reserve and keep available out of its authorized but
unissued  Common Stock, such number of its duly authorized Common Stock as shall
be  sufficient  to  effect  the  conversion of the Series D Preferred Stock into
Common  Stock  in  accordance  with  its  Articles.  If at any relevant time the
number of authorized but unissued shares of Series D Preferred Stock (and shares
of  Common  Stock  for  issuance on conversion of such Series D Preferred Stock)
shall  not  be  sufficient  to  effect  the conversion of the entire outstanding
principal  amount  of  this Note, in addition to such other remedies as shall be
available  to  the  holder  of  this  Note,  the Company will use its reasonable
efforts  to forthwith take such corporate action as may be necessary to increase
its  authorized  but  unissued shares of Series D Preferred Stock (and shares of
its Common Stock for issuance on conversion of such Series D Preferred Stock) to
such  number  of  shares  as  shall  be  sufficient  for  such  purposes.

          5.   Assignment.  Subject to the restrictions on transfer described in
               ----------
Section  8  below,  the  rights and obligations of the Company and the Holder of
this  Note  shall  be  binding  upon and benefit the successors, assigns, heirs,
administrators  and  transferees  of  the  parties.

          6.   Waiver and Amendment.  Any provision of this Note may be amended,
               --------------------
waived  or  modified  (either  generally  or  in  a  particular instance, either
retroactively  or  prospectively,  and  either for a specified period of time or
indefinitely),  upon  the  written  consent  of  the  Company and of the Holder.

          7.   Waiver of Notice.  The Company hereby waives notice, presentment,
               ----------------
demand,  protest  and  notice  of  dishonor.

          8.   Transfer  of  this  Note  or  Securities  Issuable  on Conversion
               -----------------------------------------------------------------
Hereof.  The  offer,  sale  or other disposition of this Note or securities into
which  such  Note  may  be  converted,  shall  be subject to the restrictions on
transfer  set  forth  in Section 7.11 of the Loan Agreement.  Holder understands
and  agrees that each certificate held by Holder representing Series D Preferred
Stock  and  Common  Stock  issuable  upon  conversion of this Note, or any other
securities  issued in respect of this Note issuable upon conversion thereof upon
any  stock  split,  stock  dividend,  recapitalization, merger, consolidation or
similar  event,  shall  bear  the  following  legend  (in addition to any legend
required  under  applicable  federal  or  state  securities  laws):

     "THE  SHARES  REPRESENTED  BY  THIS  CERTIFICATE ARE RESTRICTED BY THE
     TERMS  OF,  AND  ARE SUBJECT TO RESTRICTIONS ON TRANSFER AND RIGHTS OF
     SALE  AS  PROVIDED  IN  A  LOAN  AGREEMENT BETWEEN THE COMPANY AND THE
     HOLDER HEREOF, OR ITS SUCCESSOR, A COPY OF WHICH IS AVAILABLE FROM THE
     COMPANY."

          9.   Notices.  Any  notice, request or other communication required or
               -------
permitted  hereunder  shall  be in writing and shall be deemed to have been duly
given  if  personally  delivered  or  if  sent  by nationally recognized courier
service  or  mailed  by  registered  or  certified mail, postage prepaid, to the
respective  addresses of the parties as set forth herein or if sent by facsimile
to  the respective facsimile numbers of the parties set forth herein.  Any party
hereto  may  by  notice so given change its address for future notice hereunder.
Notice  shall


                                      -7-
<PAGE>
conclusively be deemed to have been given and received when personally delivered
or three (3) Business Days after deposited in the mail or one Business Day after
sent  by  courier  or  upon confirmation of facsimile delivery in the manner set
forth  above.

          10.  Loss,  Theft or Destruction of Note.  Upon receipt by the Company
               -----------------------------------
of  evidence  reasonably satisfactory to it of the loss, theft or destruction of
this  Note  and  of  indemnity  or  security  reasonably satisfactory to it, the
Company  will  make  and deliver a new Note which shall carry the same rights to
interest  (unpaid and to accrue) carried by this Note, stating that such Note is
issued  in  replacement  of  this Note, making reference to the original date of
issuance  of  this  Note,  (and  any  successors  hereto)  and  dated as of such
cancellation,  in  lieu  of  this  Note.

          11.  Usury  Disclosure.  Regardless of any provision contained in this
               -----------------
Note,  it  is  expressly stipulated and agreed that the intent of the Holder and
the  Company is to comply at all times with all usury and other laws relating to
this  Note.  If  the  laws  of  the State of Texas would now or hereafter render
usurious,  or  are  revised,  repealed  or  judicially  interpreted as to render
usurious,  the  indebtedness evidenced by this Note, or if any prepayment by the
Company  results  in  the  Company's  having paid any interest in excess of that
permitted  by law, then it is the Holder's and the Company's express intent that
all  excess  amounts  theretofore  collected  by  the  Holder be credited to the
principal balance of this Note (or, if this Note has been paid in full, refunded
to  the Company), and the provisions of this Note immediately be deemed reformed
the  amounts  therefor  collectible  hereunder reduced, without the necessity of
execution of any new document, so as to comply with the then applicable law, but
so  as  to  permit  the  recovery  of  the  fullest  amount otherwise called for
hereunder.

          12.  No  Shareholder  Rights.  Nothing contained in this Note shall be
               -----------------------
construed as conferring upon the Holder or any other person the right to vote or
to  consent  or  to  receive  notice  as a shareholder in respect of meetings of
shareholders  for  the election of directors of the Company or any other matters
or  any  rights  whatsoever  as  a  shareholder  of  the  Company.

          13.  Impairment  of  Rights.  The Company shall not amend or otherwise
               ----------------------
modify  the terms of the Series D Preferred Stock without the written consent of
the  Holder.

          14.  Security.  This  Note  is  secured  pursuant  to the terms of the
               --------
Security  Agreement.

          15.  Governing Law.  This Agreement shall be governed by and construed
               -------------
in  accordance  with  the laws of the State of Texas, excluding that body of law
relating  to  conflict  of  laws.

          16.  Heading;  References.  All  headings  used  herein  are  used for
               --------------------
convenience  only  and  shall  not  be  used to construe or interpret this Note.
Except  as  otherwise  indicated,  all  references  herein  to Sections refer to
Sections  hereof.


                                      -8-
<PAGE>
     IN WITNESS WHEREOF, the Company has caused this Note to be issued as of the
date  first  set  forth  above.

COMPANY:                             POSITRON CORPORATION, a Texas corporation


                                     By:
                                        ----------------------------------------
                                            Gary H. Brooks, President

                                        Address:  1304 Langham Creek Drive, #300
                                                  Houston, Texas 77084
                                                  Facsimile:  281-492-2961


                                      -9-
<PAGE>
                              NOTICE OF CONVERSION
                              --------------------
                   (To Be Signed Only Upon Conversion of Note)


TO POSITRON CORPORATION

     The  undersigned,  the holder of the foregoing Note, hereby surrenders such
Note  for  conversion  into  ___  shares of Series D Preferred Stock of POSITRON
CORPORATION,  to  the extent of ________________________ dollars ($____________)
unpaid  principal  amount  of  such Note, and requests that the certificates for
such  shares  be  issued  in  the  name  of,  and  delivered  to,
_________________________________________,  whose  address  is
__________________________________________________.

     Dated:  ________________________.


                              --------------------------------------------------
                              (Signature must conform in all respects to name of
                              holder as specified on the face of the Note)

                              Address
                                          --------------------------------------

                                          --------------------------------------

                                          --------------------------------------


<PAGE>