Document:

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 NOTE
     PURCHASE  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

$300,000.00                                                       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 (the "Holder"), the sum of Three Hundred Thousand dollars
                             ------
($300,000),  or such lesser amount as shall then equal the outstanding principal
amount  hereof on the terms and conditions set forth hereinafter.  The principal
hereof  and any unpaid accrued interest hereon, as set forth below, shall be due
and  payable  on  the  earlier to occur of (i) _______, 2006 (two years from the
date of this Note, the "Maturity Date") or (ii) when declared due and payable by
                        -------------
the  Holder  upon  the  occurrence  of  an  Event of Default (as defined below).
Commencing  on  the  Maturity Date, all principal and accrued interest hereunder
shall  be  payable  upon demand.  Payment for all amounts due hereunder shall be
made  by  mail  to  the registered address of the Holder.  All numbers expressed
herein  as  "$"  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.  Except  as  otherwise  defined  herein,  each
               -----------
capitalized  term  used herein shall have the meaning assigned to it in the Note
Purchase Agreement dated as of May 21, 2004 (the "Purchase Agreement").  As used
                                                  ------------------
in  this  Note, the following terms, unless the context otherwise requires, have
the  following  meanings:

                                      -1-
<PAGE>
                    (a)  "Business  Day"  shall  mean a day other than Saturday,
                          -------------
Sunday  or  a  public  holiday  under  the  laws  of  the  State  of  Texas.

                    (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
                          --------------
Company and Holder, 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.

          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:

                    (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,

                                      -2-
<PAGE>
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 Purchase 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  C 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 C 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.

     4.2  Conversion  Price.  The  Conversion  Price  (the  "Conversion  Price")
applicable  per  share  of  Series C 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 C Preferred Stock outstanding is
increased  by  a stock dividend payable in shares of Series C Preferred Stock or
by  a  subdivision  or  split-up  of  shares  of Series C Preferred Stock, then,
following the record date for the determination of holders of Series C 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

                                      -3-
<PAGE>
Series  C  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 C Preferred Stock outstanding is decreased by a combination
of  the  outstanding shares of Series C Preferred Stock into a smaller number of
shares of Series C 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 C 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 C 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  C 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  C 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  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

                                      -4-
<PAGE>
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 C 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 C
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 C 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 C
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 C Preferred
Stock issuable with respect to such conversion shall be validly issued and fully
paid.

          4.4.4     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  C Preferred Stock issuable upon such conversion shall be treated for
all  purposes  as  the  record  holder  or  holders  of  such shares of Series C
Preferred  Stock  on such date. No fractional shares of Series C 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

                                      -5-
<PAGE>
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 C Preferred Stock, reserve and keep
available  out of its authorized but unissued shares of Series C Preferred Stock
solely  for  the  purpose of effecting the conversion of the Note such number of
its  shares of Series C 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  C  Preferred  Stock  into  Common  Stock in accordance with its
Articles.  If  at any relevant time the number of authorized but unissued shares
of  Series  C  Preferred  Stock  (and  shares  of  Common  Stock for issuance on
conversion  of  such Series C 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 C Preferred Stock (and shares of its Common Stock for issuance
on

                                      -6-
<PAGE>
conversion  of  such Series C 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.  Transfer  of this Note or the Series C Preferred Stock and Common Stock
------
issuable  upon  conversion thereof shall only be made in accordance with Section
4.7 and 4.8 of the Purchase Agreement.  All transferees of this Note agree to be
bound  by  the  obligations set forth under Sections 1.6, 1.7 and Section 4 (and
related  definitions)  of the Purchase Agreement, which Sections are incorporate
herein  by  reference.  In  connection  with  any such transfer, such transferee
shall  sign  an acknowledgment stating that it will become bound by the terms of
such  sections  Purchase  Agreement.  Holder  understands  and  agrees that each
certificate  held  by  Holder  representing  Series C 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 NOTE PURCHASE 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  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

                                      -7-
<PAGE>
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 C 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.

                  [Remainder of page intentionally left blank]

                                      -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 C 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>SECURITY AGREEMENT
                      ($700,000 Aggregate Principal Notes)

     This  Security  Agreement  (this "Agreement") is made as of May 21, 2004 by
                                       ---------
and  between  Positron Corporation, a Texas corporation (the "Debtor"), in favor
                                                              ------
of  IMAGIN  Diagnostic  Centers,  Inc., its successors and assigns (the "Secured
                                                                         -------
Party").
-----

                                R E C I T A L S :
                                - - - - - - - -

     WHEREAS, the Debtor and Secured Party are parties to a Loan Agreement dated
May  21,  2004,  wherein  Secured  Party  agreed  to loan Debtor $1,300,000 (the
"IMAGIN  Credit  Facility");
 ------------------------

     WHEREAS,  the  Debtor  and  Secured  Party are parties to that certain Note
Purchase  Agreement dated May 21, 2004, wherein Secured Party agreed to purchase
and  Debtor agreed to sell Secured Convertible Promissory Notes in the principal
amounts  of  $300,000  and  $400,000  (collectively,  the  "Notes");
                                                            -----

     WHEREAS,  the  Debtor and Secured Party desire to enter into this Agreement
pursuant  to which the Debtor grants to Secured Party a security interest in the
Collateral  (as  that  term  is  hereinafter  defined) to secure the payment and
performance  by  the  Debtor  of  its  obligations  under  the  Notes;

     NOW,  THEREFORE,  in  consideration  of  the  purchase  of the Notes by the
Secured  Party  and for other good and valuable consideration, the Debtor hereby
agrees  with  the  Secured  Party  as  follows:

                               A G R E E M E N T :
                               - - - - - - - - -

     1.   Grant of Security Interest.
          --------------------------

          (a)  To  secure the Debtor's full and timely performance of all of the
Debtor's  indebtedness,  liabilities  and other obligations to the Secured Party
pursuant  to  this  Agreement  and  the  Notes  (including,  without limitation,
Debtor's  obligation  to  timely  pay  the  principal  amount  of the Notes, all
interest  accrued  thereon,  all fees and all other amounts payable by Debtor to
the Secured Party thereunder or in connection therewith, whether now existing or
hereafter  arising,  and  whether  due or to become due, absolute or contingent,
liquidated or unliquidated, determined or undetermined) (the "Obligations"), the
                                                              -----------
Debtor  hereby  pledges,  assigns,  transfers, hypothecates and sets over to the
Secured  Party,  and hereby grants to the Secured Party a security interest (the
"Security  Interest")  in,  all of Debtor's right, title and interest in, to and
 ------------------
under  the  property described on Exhibit A hereto, wherever located and whether
 -                                ---------
now existing or owned or hereafter acquired or arising (the "Collateral"), until
                                                             ----------
such  Obligations  are  paid  in  full.

          (b)  Anything herein to the contrary notwithstanding, (i) Debtor shall
remain  liable  under  any contracts, agreements and other documents included in
the  Collateral,  to the

<PAGE>
extent  set  forth  therein,  to  perform  all  of  its  duties  and obligations
thereunder  to  the same extent as if this Agreement had not been executed, (ii)
the  exercise  by Secured Party of any of the rights hereunder shall not release
Debtor  from  any  of its duties or obligations under such contracts, agreements
and  other  documents  included in the Collateral, and (iii) Secured Party shall
not  have  any obligation or liability under any contracts, agreements and other
documents  included  in  the  Collateral  by reason of this Agreement, nor shall
Secured Party be obligated to perform any of the obligations or duties of Debtor
thereunder  or  to  take  any  action  to  collect or enforce any such contract,
agreement  or  other  document  included  in the Collateral hereunder; provided,
however,  that Secured Party may perform such obligations or duties of Debtor if
such  have  not  been  timely performed by Debtor, and if Secured Party performs
such  obligations  or  duties,  Debtor  shall pay to Secured Party on demand all
reasonable  expenses  incurred  by  Secured  Party  in  connection  with  such
performance,  and  such  obligation shall constitute Obligations secured by this
Agreement.

          (c)  This Agreement shall create a continuing security interest in the
Collateral.

     2.   Representations and Warranties.  Debtor represents and warrants to the
          ------------------------------
Secured  Party  that:

          (a)  Debtor's  chief  executive office and principal place of business
is  located  at  the  address  set forth in Schedule 1; Debtor's jurisdiction of
                                            ----------
organization  is  set  forth  in Schedule 1; Debtor's exact legal name is as set
                                 ----------
forth in the first paragraph of this Agreement; all other locations where Debtor
conducts  business  or  Collateral  is kept are set forth in Schedule 1; and all
                                                             ----------
trade  names and fictitious names under which Debtor at any time in the past has
conducted  or  presently  conducts  its  business  operations  are  set forth in
Schedule  1.
-----------

          (b)  Other than Permitted Liens, Debtor is the sole and complete owner
of  the  Collateral,  free  from  any  mortgage, deed of trust, pledge, security
interest, assignment, deposit arrangement, charge or encumbrance, lien, or other
type  of  preferential  arrangement  (a  "Lien"),  and  (ii) Debtor's grant of a
                                          ----
security  interest  in  the  Collateral under this Agreement, upon filing of the
financing  statement(s) in the office(s) of the Texas Secretary of State creates
a  perfected  first  priority  security  interest  in  the  Collateral.

          (c)  For  the  purpose  of  this  Agreement "Permitted Liens" mean the
                                                       ---------------
following:

               (i)  the  security  interests granted pursuant to this Agreement;

               (ii)  liens  for  taxes  assessments  or  governmental charges or
               claims  (a)  for  amounts not yet overdue or (b) for amounts that
               are overdue and that (inthe case of any such amounts overdue for
               a  period  in  excess  of  five days) are being contested in good
               faith by appropriate proceedings, so long as (A) such reserves or
               other  appropriate  provisions,  if  any, as shall be required by
               generally  accepted  accounting principles (GAAP) shall have been
               made for any such contested amounts and (B) in the case of a lien
               with  respect  to  any  portion  of  the Collateral, such contest
               proceedings

                                      -2-
<PAGE>
               conclusively  operate  to  stay  the  sale  of any portion of the
               Collateral  on  account  of  such  lien;

               (iii)  liens  incurred or deposits made in the ordinary course of
               business  in  connection with workers' compensation, unemployment
               insurance  and  other  types  of social security or to secure the
               performance  of  tenders,  statutory  obligations,  bids, leases,
               government  contracts,  trade  contracts,  performance  and
               return-of-money bonds and other similar obligations (exclusive of
               obligations  for  the  payment  of borrowed money), so long as no
               foreclosure, sale or similar proceedings have been commenced with
               respect  to  any  portion  of  the Collateral on account thereof;

               (iv) any attachment or judgment lien not constituting an Event of
               Default;

               (v)  leases  or  subleases  granted  to  third  parties  and  not
               interfering  in any material respect with the ordinary conduct of
               the  business  of  Debtor  or  any  of  its  subsidiaries;

               (vi)  liens arising from filing UCC financing statements relating
               solely  to  equipment  leases;

               (vii)  liens  in favor of customs and revenue authorities arising
               as  a  matter  of  law  to  secure  payment  of customs duties in
               connection  with  the  importation  of  goods;  and

               (viii)  security  interests granted in connection with the IMAGIN
               credit  facility.

               "UCC"  shall  mean the Uniform Commercial Code, as in effect from
time  to time, of the State of Texas or of any other state the laws of which are
required  as  a  result  thereof  to  be applied in connection with the issue of
perfection  of  security  interests.

     3.   Covenants.  From  and  after  the  date  of  this  Agreement until the
          ---------
Obligations  are  paid  in  full:

          (a)  Limitations  on  Liens.  With  the  exception of liens created in
               ----------------------
connection with the IMAGIN Credit Facility, the Debtor will not create, incur or
permit  to  exist,  will defend the Collateral against, and will take such other
action  as  is  necessary  to remove, any lien or claim on or to the Collateral.
The  Debtor  shall  do and perform all reasonable acts that may be necessary and
appropriate  to  maintain,  preserve and protect the Collateral, and will defend
the  right,  title  and  interest  of  the  Secured  Party  in and to any of the
Collateral  against  the  claims  and  demands  of  all other persons.  With the
exception  of financing statements filed pursuant to the IMAGIN Credit Facility,
no  financing  statements  or  other  notices of security interests covering any
Collateral  or  any  proceeds thereof are currently on file in any public office
and  the  Debtor shall not authorize any party (other than the Secured Party) to
file  a financing statement in any public office before the Obligations are paid
in  full.

                                      -3-
<PAGE>
          (b)  Financing  Statements,  Etc.  Debtor shall execute and deliver to
               ---------------------------
the  Secured  Party  upon  the  request of the Secured Party as soon as possible
after  the  closing  of  the  transactions contemplated hereby and Debtor hereby
authorizes  the  Secured  Party to file (with or without Debtor's signature), at
any  time  and  from  time  to  time  thereafter,  all  financing  statements,
assignments,  continuation financing statements, termination statements, account
control  agreements,  and  other  documents  and  instruments, including but not
limited to filings with the relevant patent, trademark and copyright authorities
in  connection  with  notice  of  the  Secured Party's interest in the Company's
intellectual property and rights, in form reasonably satisfactory to the Secured
Party,  and  take  all other action, as Secured Party may reasonably request, to
perfect  and  continue  perfected, maintain the priority of or provide notice of
the  security  interest of Secured Party in the Collateral and to accomplish the
purposes  of  this  Agreement.  Debtor  will  cooperate  with  Secured  Party in
obtaining  control (as defined in the Uniform Commercial Code, as enacted in the
State  of  Texas  and  amended  from  time  to  time (the "Code")) of Collateral
                                                           ----
consisting of deposit accounts, investment property, letter of credit rights and
electronic  chatter paper.  Debtor will join with Secured Party in notifying any
third  party  who  has  possession of any Collateral of Secured Party's security
interest  therein  and  obtaining an acknowledgment from the third party that is
holding the Collateral for the benefit of Secured Party.  Debtor will not create
any  chattel  paper  without placing a legend on the chattel paper acceptable to
Secured  Party  indicating  that  Secured  Party  has a security interest in the
chattel  paper.

          (c)  Indemnification.  The  Debtor  will  defend,  indemnify  and hold
               ---------------
harmless  the  Secured Party against any and all liabilities, costs and expenses
(including,  without limitation, legal fees and expenses):  (i) with respect to,
or resulting from, any delay in paying, any and all excise, sales or other taxes
which  may  be  payable  or  determined to be payable with respect to any of the
Collateral, (ii) with respect to, or resulting from, any delay in complying with
any  law,  rule, regulation or order of any governmental authority applicable to
any  of  the  Collateral  or  (iii)  in  connection with any of the transactions
contemplated  by  this  Agreement.

          (d)  Maintenance  of  Records.  The  Debtor will keep and maintain, at
               ------------------------
its  own  expense,  complete  and  satisfactory  records  of  the  Collateral.

          (e)  Inspection  Rights.  The  Secured  Party  shall  have full access
               ------------------
during  normal  business  hours,  and  upon  reasonable prior notice, to all the
books,  correspondence  and  other  records  of  the  Debtor  relating  to  the
Collateral.  The  Secured  Party or its representatives may examine such records
and  make  photocopies or otherwise take extracts from such records.  The Debtor
shall  render  to  the Secured Party, at the Debtor's expense, such clerical and
other  assistance  as may be reasonably requested with regard to the exercise of
its  rights  pursuant  to  this  paragraph.

          (f)  Compliance  with  Laws.  The  Debtor  will comply in all material
               ----------------------
respects  with  all  laws,  rules,  regulations  and  orders of any governmental
authority  applicable  to  any part of the Collateral or to the operation of the
Debtor's  business; provided, however, that the Debtor may contest any such law,
rule,  regulation  or  order  in  any  reasonable  manner which does not, in the
reasonable opinion of the Debtor, adversely affect the Secured Party's rights or
the  priority  of  its  liens  on  the  Collateral.

                                      -4-
<PAGE>
          (g)  Payment  of  Obligations.  The  Debtor will pay promptly when due
               ------------------------
all  taxes,  assessments  and  governmental  charges  or levies imposed upon the
Collateral  or  with  respect  to  any of its income or profits derived from the
Collateral,  as  well  as all claims of any kind (including, without limitation,
claims  for  labor,  materials  and  supplies)  against  or  with respect to the
Collateral,  except that no such charge need be paid if (i) the validity of such
charge  is  being  contested in good faith by appropriate proceedings, (ii) such
proceedings  do  not involve any material danger of the sale, forfeiture or loss
of any of the Collateral or any interest in the Collateral and (iii) such charge
is  adequately  reserved  against  on  the  Debtor's  books  in  accordance with
generally  accepted  accounting  principles.

          (h)  Limitations  on  Dispositions of Collateral.  The Debtor will not
               -------------------------------------------
sell, transfer, lease or otherwise dispose of any of the Collateral, or attempt,
offer  or  contract  to  do  so,  other  than in the ordinary course of Debtor's
business.

          (i)  Change  of  Location.  Debtor shall give prompt written notice to
               --------------------
Secured  Party  (and  in any event not later than thirty (30) days following any
change  described  below in this subsection) of:  (i) any change in the location
of  Debtor's  chief  executive  office  or principal place of business, (ii) any
change  in  the locations set forth in Schedule 1; (iii) any change in its name,
                                       ----------
(iv) any changes in its identity or structure in any manner which might make any
financing  statement filed hereunder incorrect or misleading; and (v) any change
in  its  jurisdiction of organization; provided that Debtor shall not locate any
Collateral outside of the United States nor shall Debtor change its jurisdiction
of  organization  to  a  jurisdiction  outside  of  the  United  States.

          (j)  Insurance.  Debtor  shall  carry  and  maintain in full force and
               ---------
effect,  at  its  own expense and with financially sound and reputable insurance
companies,  insurance  with respect to the Collateral in such amounts, with such
deductibles  and  covering  such  risks  as  is customarily carried by companies
engaged  in  the same or similar businesses and owning similar properties in the
localities  where  Debtor  operates.

          (k)  Corporate  Existence.  Debtor  shall  maintain  and  preserve its
               --------------------
corporate  existence,  its  rights  to  transact  business and all other rights,
franchises  and  privileges  necessary  or desirable in the normal course of its
business  and  operations  and  the  ownership  of  the  Collateral,  except  in
connection  with  any  transactions  expressly  permitted  by  the  Notes.

          (l)  Further Identification of Collateral.  The Debtor will furnish to
               ------------------------------------
the Secured Party from time to time statements and schedules further identifying
and  describing  the  Collateral  and  such other reports in connection with the
Collateral  as  the  Secured  Party  may  reasonably  request, all in reasonable
detail.

     4.   Secured  Party's  Appointment  as  Attorney-in-Fact.
          ---------------------------------------------------

          (a)  Powers.  The  Debtor  hereby  appoints  the Secured Party and any
               ------
officer  or  agent of the Secured Party, with full power of substitution, as its
attorney-in-fact  with  full irrevocable power and authority in the place of the
Debtor and in the name of the Debtor or their own name, from time to time in the
Secured  Party's  discretion  so long as an Event of Default has occurred and is
continuing, for the purpose of carrying out the terms of this Agreement, to take

                                      -5-
<PAGE>
any  appropriate  action and to execute any instrument which may be necessary or
desirable  to  accomplish  the purposes of this Agreement.  Without limiting the
foregoing,  so  long  as an Event of Default has occurred and is continuing, the
Secured  Party  shall  have the right, without notice to, or the consent of, the
Debtor,  to  do  any  of  the  following  on  the  Debtor's  behalf:

                    (i)  to pay or discharge any taxes or liens levied or placed
               on  or  threatened  against  the  Collateral;

                    (ii) to direct any party liable for any payment under any of
               the  Collateral  to make payment of any and all amounts due or to
               become  due  thereunder  directly  to the Secured Party or as the
               Secured  Party  directs;

                    (iii)  to ask for or demand, collect, and receive payment of
               and receipt for, any payments due or to become due at any time in
               respect  of  or  arising  out  of  any  Collateral;

                    (iv)  to  commence  and  prosecute  any  suits,  actions  or
               proceedings  at  law  or  in  equity  in  any  court of competent
               jurisdiction  to  enforce any right in respect of any Collateral;

                    (v) to defend any suit, action or proceeding brought against
               the  Debtor  with  respect  to  any  Collateral;

                    (vi)  to  settle,  compromise  or adjust any suit, action or
               proceeding  described  in  subsection  (v) above and to give such
               discharges  or  releases  in  connection therewith as the Secured
               Party  may  deem  appropriate;

                    (vii)  to assign and/or license any patent right included in
               the  Collateral  of  Debtor  (along  with  the  goodwill  of  the
               business,  if  any,  to  which  any  such patent right pertains),
               throughout  the world for such term or terms, on such conditions,
               and  in  such  manner,  as  the  Secured  Party shall in its sole
               discretion  determine;  and

                    (viii)  generally,  to  sell,  transfer, pledge and make any
               agreement  with  respect  to  or  otherwise  deal with any of the
               Collateral  and  to  take,  at the Secured Party's option and the
               Debtor's  expense,  any  actions  which  the  Secured Party deems
               necessary to protect, preserve or realize upon the Collateral and
               the  Secured  Party's lien on the Collateral and to carry out the
               intent  of  this Agreement, in each case to the same extent as if
               the  Secured  Party  was the absolute owner of the Collateral for
               all  purposes.

The  Debtor hereby ratifies whatever actions the Secured Party shall lawfully do
or  cause  to be done in accordance with this Section 4.  This power of attorney
shall  be  a  power  coupled  with  an  interest  and  shall  be  irrevocable.

          (b)  No  Duty  on  Secured  Party's Part.  The powers conferred on the
               -----------------------------------
Secured  Party  by  this  Section  4  are  solely to protect the Secured Party's
interests  in  the  Collateral and shall not impose any duty upon it to exercise
any  such  powers.  The  Secured Party and its

                                      -6-
<PAGE>
officers,  directors,  employees  or  agents  shall,  in  the absence of willful
misconduct  or gross negligence, not be responsible to the Debtor for any act or
failure  to  act  pursuant  to  this  Section 4.

     5.   Event of Default.  Any of the following events which shall occur or be
          ----------------
continuing shall constitute an "Event of Default," unless otherwise consented to
                                ----------------
in  writing  by  the  Secured  Party:

          (a)  Any  event, constituting an "Event of Default," as such terms are
defined  in  Section  3  of  the  Notes.

          (b)  Any  representation  or warranty by Debtor under or in connection
with  this  Agreement shall prove to have been incorrect in any material respect
when  made  or  deemed  made.

          (c)  Debtor  shall  fail to perform or observe in any material respect
any  other  term, covenant or agreement contained in this Agreement or the Notes
on  its  part  to  be  performed  or  observed and any such failure shall remain
unremedied  for  a  period  of  15  days  from  the  date  of  such  failure.

          (d)  Any  material  impairment  in  the value of the Collateral (other
than  normal  depreciation)  or  the priority of Secured Party's Lien hereunder.

          (e)  Any  levy  upon,  seizure or attachment of any of the Collateral.

          (f)  Any  loss, theft or substantial damage to, or destruction of, any
material  portion  of the Collateral (unless within 15 days after the occurrence
of  any  such  event, Debtor furnishes to Secured Party evidence satisfactory to
Secured  Party that the amount of any such loss, theft, damage to or destruction
of  the  Collateral  is  fully insured under policies naming Secured Party as an
additional  named  insured  or  loss  payee).

     6.   Performance  by  Secured Party of Debtor's Obligations.  If the Debtor
          ------------------------------------------------------
fails  to perform or comply with any of its agreements or covenants contained in
this  Agreement  and the Secured Party performs or complies, or otherwise causes
performance  or  compliance,  with such agreement or covenant in accordance with
the  terms  of this Agreement, then the reasonable expenses of the Secured Party
incurred  in  connection with such performance or compliance shall be payable by
the  Debtor  to  the  Secured  Party  on demand and shall constitute Obligations
secured  by  this  Agreement.

     7.   Remedies.  If  an Event of Default has occurred and is continuing, the
          --------
Secured Party may exercise, in addition to all other rights and remedies granted
to it in this Agreement and in any other instrument or agreement relating to the
Obligations,  all rights and remedies of a secured party under the Code or other
applicable  law.  Without  limiting  the  foregoing,  the Secured Party, without
demand  of  performance  or other demand, presentment, protest, advertisement or
notice  of any kind (except any notice required by law) to or upon the Debtor or
any other person (all of which demands, defenses, advertisements and notices are
hereby  waived),  may  in  such  circumstances collect, receive, appropriate and
realize  upon any or all of the Collateral, and/or may sell, lease, assign, give
an option or options to purchase, or otherwise

                                      -7-
<PAGE>
dispose  of  and  deliver any or all of the Collateral (or contract to do any of
the  foregoing), in one or more parcels at a public or private sale or sales, at
any  exchange,  broker's board or office of Secured Party or elsewhere upon such
terms  and  conditions  as  the Secured Party may deem advisable, for cash or on
credit or for future delivery without assumption of any credit risk. The Secured
Party shall have the right upon any such public sale or sales and, to the extent
permitted  by  law,  upon any such private sale or sales, to purchase all or any
part of the Collateral so sold, free of any right or equity of redemption in the
Debtor,  which  right  or  equity  is  hereby  waived  or released to the extent
permitted  by  law.  The  Secured Party shall apply the net proceeds of any such
collection,  recovery,  receipt,  appropriation,  realization  or  sale,  after
deducting  all  reasonable  expenses  incurred therein or in connection with the
care  or  safekeeping  of  any  of  the Collateral or in any way relating to the
Collateral  or  the rights of the Secured Party under this Agreement (including,
without  limitation,  reasonable attorneys' fees and expenses) to the payment in
whole  or  in part of the Obligations, and only after such application and after
the  payment  by the Secured Party of any other amount required by any provision
of  law,  need the Secured Party account for the surplus, if any, to the Debtor.
To the extent permitted by applicable law, the Debtor waives all claims, damages
and demands it may acquire against the Secured Party arising out of the exercise
by the Secured Party of any of its rights hereunder. If any notice of a proposed
sale  or  other  disposition of Collateral shall be required by law, such notice
shall  be  deemed  reasonable  and proper if given at least five (5) days before
such  sale  or  other  disposition.  The  Debtor  shall  remain  liable  for any
deficiency  if  the  proceeds of any sale or other disposition of the Collateral
are  insufficient  to  pay the Obligations and the fees and disbursements of any
attorneys  employed  by  the  Secured  Party  to  collect  such  deficiency.

     8.   Limitation  on  Duties Regarding Preservation of Collateral.  The sole
          -----------------------------------------------------------
duty  of  the  Secured  Party  with  respect  to  the  custody,  safekeeping and
preservation  of  the  Collateral, under the Code or otherwise, shall be to deal
with it in the same manner as such Secured Party deals with similar property for
its  own account.  Neither the Secured Party nor any of its directors, officers,
employees  or  agents  shall be liable for failure to demand, collect or realize
upon  all or any part of the Collateral or for any delay in doing so or shall be
under  any  obligation  to  sell or otherwise dispose of any Collateral upon the
request  of  the  Debtor  or  otherwise.

     9.   Powers  Coupled  with  an  Interest.  All  authorizations and agencies
          -----------------------------------
contained  in  this  Agreement  with  respect the Collateral are irrevocable and
powers  coupled  with  an  interest.

     10.  No  Waiver;  Cumulative  Remedies.  The Secured Party shall not by any
          ---------------------------------
act  (except  by  a written instrument pursuant to Section 11(a) hereof), delay,
indulgence,  omission  or otherwise be deemed to have waived any right or remedy
hereunder  or to have acquiesced in any default under the Notes or in any breach
of  any  of the terms and conditions of this Agreement.  No failure to exercise,
nor  any delay in exercising, on the part of the Secured Party, any right, power
or  privilege hereunder shall operate as a waiver thereof.  No single or partial
exercise  of any right, power or privilege hereunder shall preclude any other or
further exercise thereof or the exercise of any other right, power or privilege.
A waiver by the Secured Party of any right or remedy under this Agreement on any
one  occasion  shall  not be construed as a bar to any right or remedy which the
Secured  Party  would otherwise have on any subsequent occasion.  The rights and
remedies  provided  in this Agreement are cumulative, may be exercised singly or
concurrently  and  are  not exclusive of any rights or remedies provided by law.

                                      -8-
<PAGE>
     11.  Miscellaneous.
          -------------

          (a)  Amendments  and  Waivers.  Any  term  of  this  Agreement  may be
               ------------------------
amended with the written consent of the Debtor and Secured Party.  Any amendment
or  waiver  effected in accordance with this Section 11(a) shall be binding upon
the  parties  and  their  respective  successors  and  assigns.

          (b)  Transfer;  Successors  and  Assigns.  The terms and conditions of
               -----------------------------------
this  Agreement  shall be binding upon the Debtor and its successors and assigns
and  inure  to  the benefit of the Secured Party and its successors and assigns.
Nothing  in  this  Agreement, express or implied, is intended to confer upon any
party  other  than the parties hereto or their respective successors and assigns
any  rights,  remedies,  obligations  or  liabilities under or by reason of this
Agreement,  except  as  expressly  provided  in  this  Agreement.

          (c)  Governing  Law.  This  Agreement  and  all  acts and transactions
               --------------
pursuant  hereto  and  the rights and obligations of the parties hereto shall be
governed,  construed and interpreted in accordance with the laws of the State of
Texas,  without  giving  effect  to  principles  of  conflicts  of  law.

          (d)  Counterparts;  Facsimile  Signatures.  This  Agreement  may  be
               ------------------------------------
executed  in two or more counterparts, each of which shall be deemed an original
and  all  of which together shall constitute one instrument.  This Agreement may
be  executed  by  facsimile  signatures.

          (e)  Titles  and  Subtitles.  The  titles  and  subtitles used in this
               ----------------------
Agreement  are  used  for  convenience  only  and  are  not  to be considered in
construing  or  interpreting  this  Agreement.

          (f)  Notices.  Any  notice  required  or  permitted  by this Agreement
               -------
shall  be in writing and shall be deemed sufficient upon receipt, when delivered
personally  or by courier, overnight delivery service or confirmed facsimile, or
forty-eight  (48)  hours  after being deposited in the U.S. mail as certified or
registered  mail with postage prepaid (airmail if sent internationally), if such
notice  is  addressed  to  the  party  to be notified at such party's address or
facsimile  number  as  set  forth  below, or as subsequently modified by written
notice.

          (g)  Severability.  If  one  or  more provisions of this Agreement are
               ------------
held  to be unenforceable under applicable law, the parties agree to renegotiate
such provision in good faith, in order to maintain the economic position enjoyed
by  each  party  as  close  as  possible  to  that  under the provision rendered
unenforceable.  In  the event that the parties cannot reach a mutually agreeable
and enforceable replacement for such provision, then (i) such provision shall be
excluded  from  this  Agreement,  (ii)  the  balance  of  the Agreement shall be
interpreted  as  if such provision were so excluded and (iii) the balance of the
Agreement  shall  be  enforceable  in  accordance  with  its  terms.

          (h)  Entire  Agreement.  This Agreement, and the documents referred to
               -----------------
herein  constitute the entire agreement between the parties hereto pertaining to
the  subject  matter  hereof,  and  any and all other written or oral agreements
existing between the parties hereto concerning such subject matter are expressly
canceled.

                                      -9-
<PAGE>
          (i)  Code  Definitions.  All  terms  defined  in  the Code and as used
               -----------------
herein  shall  have  the same definitions herein as specified therein; provided,
however,  that  the term "instrument" shall be such term as defined in Article 9
of  the  Code  rather  than  Article  3  of  the  Code.

     The Debtor and Secured Party have caused this Agreement to be duly executed
and  delivered  as  of  the  date  first  above  written.

                              DEBTOR:

                              POSITRON  CORPORATION

                              By:  /s/ Gary H. Brooks
                                 --------------------
                                   Name:  Gary H. Brooks
                                   Its:  President

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

                              SECURED PARTY:

                              IMAGIN Diagnostic Centers, Inc.

                              By:  /s/ Cynthia R. Jordan
                                 -----------------------
                                   Name: Cynthia R. Jordan
                                   Its: Chief Executive Officer

                              Address:  1835 Yonge St., Suite 500
                                        Toronto, Ontario, Canada M4S 1XB
                                        Facsimile:  416-646-8750

                                      -10-
<PAGE>
                                    EXHIBIT A
                                    ---------

     The  Collateral shall consist of all right, title and interest of Debtor in
all  of  its  assets,  including  but  not  limited  to  the  following:

     (i)   all  accounts,  accounts  receivable,  contract  rights,  rights  to
payment, chattel paper, electronic chattel paper, commercial tort claims, letter
of credit rights and proceeds of letters of credit, documents, securities, money
and  instruments,  and  investment  property, whether held directly or through a
securities  intermediary,  and  other  obligations  of  any kind owed to Debtor,
however  evidenced;

     (ii)  all  deposits  and  deposit  accounts with any bank, savings and loan
association,  credit  union  or  like  organization,  and  all funds and amounts
therein,  and  whether  or  not  held in trust, or in custody or safekeeping, or
otherwise  restricted  or  designated  for  a  particular  purpose;

     (iii)  all  inventory,  including,  without  limitation, all materials, raw
materials,  parts,  components,  work  in progress, finished goods, merchandise,
supplies,  and  all  other  goods  which  are  held  for  sale,  lease  or other
disposition  or  furnished  under  contracts  of service or consumed in Debtor's
business, including, without limitation, those held for display or demonstration
or  out  on  lease  or  consignment;

     (iv)  all  equipment,  including,  without  limitation,  all  machinery,
furniture,  furnishings,  fixtures,  trade  fixtures, tools, parts and supplies,
automobiles, trucks, tractors and other vehicles, appliances, computer and other
electronic  data  processing  equipment  and  other  office  equipment, computer
programs  and related data processing software, and all additions substitutions,
replacements,  parts,  accessories,  and  accessions  to  and for the foregoing;

     (v)   all  general  intangibles  and  other  personal  property  of Debtor,
including, without limitation, (A) all tax and other refunds, rebates or credits
of  every  kind  and  nature  to  which  Debtor  is  now or hereafter may become
entitled;  (B)  all intellectual property and all worldwide rights and interests
therein  of  any  type  or  description,  including,  without  limitation,  all
inventions  and  discoveries,  patents  and  patent applications, copyrights and
applications  for  copyright  (together with the underlying works of authorship)
whether  or  not  registered, together with any renewals and extensions thereof,
trademarks,  service marks and trade names, and applications for registration of
such  trademarks,  service  marks  and trade names, domain names, trade secrets,
trade  dress,  trade  styles,  logos,  other  source  of  business  identifiers,
mask-works,  mask-work  registrations,  mask-work  applications,  software,
confidential  and proprietary information, customer lists, other license rights,
advertising  materials,  operating  manuals,  methods,  processes,  know-how,
algorithms,  formulae,  databases,  quality control procedures, product, service
and technical specifications, operating, production and quality control manuals,
sales  literature,  drawings,  specifications,  blue  prints,  descriptions,
inventions,  name  plates and catalogs, and the entire goodwill of or associated
with  the  businesses  now  or  hereafter conducted by Debtor connected with and
symbolized  by any of the aforementioned properties and assets, and all licenses
relating  to  any  of  the  foregoing,  all  reissuance,  continuations  and
continuations-in-part  of  the  foregoing,  all  other  rights  derived  from or
associated  with  the foregoing, including the right to sue and recover for past
infringement,  and  all  income  and  royalties  with  respect  thereto;

                                    EXHIBIT A
                                      -1-
<PAGE>
(C)  all  good will, choses in action and causes of action; (D) all interests in
limited  and  general  partnerships and limited liability companies; and (E) all
indemnity  agreements,  guaranties,  insurance  policies,  insurance claims, and
other  contractual,  equitable  and  legal  rights  of  whatever kind or nature;

     (vi)  all  books,  records  and  other  written,  electronic  or  other
documentation  in  whatever  form maintained by or for Debtor in connection with
the  ownership  of  its  assets  or the conduct of its business or evidencing or
containing  information  relating  to  the  Collateral;  and

     (vii)  all  products  and  proceeds,  including  insurance  proceeds,  and
supporting  obligations  of  any  and  all  of  the  foregoing.

                                    EXHIBIT A
                                      -2-
<PAGE>
                                   SCHEDULE 1
                                   ----------

Business Address:            1304 Langham Creek Drive #300, Houston, Texas 77084
----------------

Incorporated:                Texas
------------

Other Places of Business:         N/A
------------------------   ------------------------------

Other Business Names:             N/A
--------------------       ------------------------------

                                   SCHEDULE 1
                                      -1-
<PAGE>

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