Document:

EXHIBIT 4.10

THIS WARRANT AND THE SHARES OF STOCK OF POSITRON  CORPORATION  TO BE ISSUED UPON
ANY EXERCISE OF THIS WARRANT HAVE NOT BEEN AND WILL NOT BE  REGISTERED  WITH THE
SECURITIES AND EXCHANGE COMMISSION UNDER THE SECURITIES ACT OF 1933, AS AMENDED,
OR UNDER  ANY  STATE  SECURITIES  LAW AND ANY  SALE,  TRANSFER,  PLEDGE OR OTHER
DISPOSITION  THEREOF  MAY BE MADE ONLY (I) IN A  REGISTRATION  UNDER SAID ACT OR
(II) IF AN  EXEMPTION  FROM  REGISTRATION  UNDER SAID ACT AND  APPLICABLE  STATE
SECURITIES  LAWS IS AVAILABLE AND THE COMPANY HAS RECEIVED AN OPINION OF COUNSEL
TO THAT EFFECT REASONABLY SATISFACTORY TO IT.

                              POSITRON CORPORATION

                          COMMON STOCK PURCHASE WARRANT
                  TO PURCHASE 3,000,000 SHARES OF COMMON STOCK
                             OF POSITRON CORPORATION

                       This Warrant Expires June 15, 2009

Warrant No. 99-1                                                3,000,000 Shares

      THIS CERTIFIES that,  subject to the terms and conditions herein set forth
in this  warrant,  GARY H. BROOKS (the  "Holder")  is entitled to purchase  from
Positron Corporation, a Texas corporation ("Company"),  at any time or from time
to time during the Exercise  Period (defined in Section 12 below) and subject to
the provisions  regarding  Exercise of Warrant (as set forth in Section 6 below)
the  number of fully  paid and  non-assessable  shares  of  common  stock of the
Company (the "Shares") as provided  herein upon surrender of this Warrant at the
principal  office of the  Company,  and, at the  election  of the  Holder,  upon
payment of the purchase price at said office in cash or by cashier's check or by
the wire transfer of funds in a dollar amount equal to the purchase price of the
Shares for which the consideration is being given.

      This Warrant shall be  exercisable  for that number of Shares as set forth
above,  in minimum  units of  100,000  shares.

      1.    PURCHASE PRICE. Subject to adjustment as hereinafter  provided,  the
purchase  price of one  share of  Common  Stock  (or such  securities  as may be
substituted for one share of Common Stock pursuant to the provisions hereinafter
set forth) (the "Warrant Price") shall be Thirty Cents ($0.30).

      2.    ADJUSTMENT  OF WARRANT  PRICE AND  NUMBER OF SHARES.  The number and
kind of  securities  issuable upon the exercise of this Warrant shall be subject
to adjustment from time to time upon the happening of certain events as follows:

                                      -1-
<PAGE>

            (a)   ADJUSTMENT FOR DIVIDENDS IN STOCK.  If at any time on or after
the date  hereof,  the holders of the Common Stock of the Company (or any shares
of stock or other  securities at the time  receivable  upon the exercise of this
Warrant)  shall have  received,  or, on or after the  record  date fixed for the
determination of eligible  stockholders,  shall have become entitled to receive,
without  payment  therefor,  other or additional  stock of the Company by way of
dividend  (other than as provided for in Section  2(b) below),  then and in each
such case,  upon the exercise of this  Warrant,  the Holder shall be entitled to
receive,  in addition to the number of shares of Common  Stock  receivable,  and
without  payment of any additional  consideration  therefor,  the amount of such
other or  additional  stock of the Company which the Holder would receive on the
date of such  exercise  had it been the holder of record of such Common Stock on
the date  hereof and had  thereafter,  during the period from the date hereof to
and including the date of such  exercise,  retained such shares and/or all other
additional  stock  receivable  by it as  aforesaid  during such period and given
effect to all adjustments called for during such period by this Section 2.

            (b)   ADJUSTMENT  FOR  CHANGES  IN  COMMON  STOCK.  In the  event of
changes in the  outstanding  Common Stock of the Company by reason of split-ups,
recapitalizations,  reclassifications,  mergers, consolidations, combinations or
exchanges of shares, separations,  reorganizations,  liquidations,  or the like,
the number and class of shares  available under the Warrant in the aggregate and
the Warrant Price shall be correspondingly adjusted by the Board of Directors of
the Company.  The  adjustment  shall be such as will give the Holder on exercise
for the same aggregate Warrant Price the total number, class, and kind of shares
as the Holder would have owned had the Warrant been exercised prior to the event
and had the Holder continued to hold such shares until after the event requiring
adjustment.

      3.    NO FRACTIONAL  SHARES.  No fractional shares of Common Stock will be
issued in connection with any  subscription  under this Warrant.  In lieu of any
fractional shares which would otherwise be issuable,  the Company shall pay cash
equal to the product of such fraction multiplied by the fair market value of one
share of Common Stock on the date of exercise as determined in good faith by the
Company's Board of Directors.

      4.    NO STOCKHOLDER  RIGHTS. This Warrant shall not entitle its holder to
any of the rights of a stockholder of the Company prior to its exercise.

      5.    RESERVATION OF STOCK.  The Company  covenants that during the period
this Warrant is  exercisable,  the Company will reserve from its  authorized and
unissued Common Stock a sufficient  number of shares to provide for the issuance
of Common Stock upon the exercise of this Warrant.  The Company  agrees that its
issuance of this Warrant shall constitute full authority to its officers who are
charged with the duty of executing  stock  certificates to execute and issue the
necessary  certificates  for shares of Common  Stock upon the  exercise  of this
Warrant.

      6.    EXERCISE  OF  WARRANT;  REPURCHASE  RIGHT.  Subject to the terms and
conditions  hereof,  this  Warrant may be  exercised  by the holder  hereof then
registered  on the books of the  Company  any time on or after  granting  of the
Warrant,  subject  however to the Company's  right to repurchase  any portion of
this  Warrant,  and/or any  portion of any stock  issued  upon  exercise  of the
Warrant ("Repurchase Right"), as of a date 90 days following termination for any
reason

                                      -2-
<PAGE>

or for no reason of the  employment  by the Company of the initial  holder.  The
Company's Repurchase Right shall lapse as follows:  immediately upon issuance as
to 750,000 shares; as to an additional 187,500 shares on September 15, 1999; and
as to an additional  187,500  shares  quarterly  thereafter  until the Company's
Repurchase  Right shall have lapsed as to all shares.  Subject to the foregoing,
this Warrant may be exercised by the Holder or its registered  assigns, in whole
or in part and in minimum  units of 100,000  shares,  by the  surrender  of this
Warrant at the principal office of the Company,  together with the attached form
of subscription  duly executed,  accompanied by payment in full of the amount of
the Warrant Price in the form described in this Warrant.  Upon partial  exercise
of this  Warrant,  a new  warrant  or  warrants  containing  the  same  date and
provisions  as this  Warrant  shall be issued by the  Company to the  registered
holder  for the  number of shares of Common  Stock  with  respect  to which this
Warrant  shall not have been  exercised.  A Warrant shall be deemed to have been
exercised  immediately  prior  to the  close  of  business  on the  date  of its
surrender for exercise as provided above, and the person entitled to receive the
shares of Common  Stock  issuable  upon such  exercise  shall be treated for all
purposes  as the holder of such  shares of record as of the close of business on
such date. As promptly as  practicable  on or after such date, the Company shall
issue and deliver to the person or persons  entitled  to receive  the shares,  a
certificate  or  certificates  for the  number of full  shares  of Common  Stock
issuable  upon such  exercise,  together  with cash in lieu of any fraction of a
share as provided above.

      7.    CERTIFICATE OF ADJUSTMENT. Whenever the Warrant Price is adjusted as
provided in Section 2, the Company shall  promptly  deliver to the record holder
of this Warrant a  certificate  of an officer of the Company  setting  forth the
relevant  Warrant  Price or number of shares after such  adjustment  and setting
forth a brief statement of the facts requiring such adjustment.

      8.    COMPLIANCE WITH  SECURITIES  ACT. The Holder,  by acceptance of this
Warrant,  agrees that this  Warrant and the shares of Common  Stock to be issued
upon its exercise (or shares of any security into which such Common Stock may be
converted)  (the "Shares") are being acquired for investment and that the Holder
will not offer,  sell,  or  otherwise  dispose of this Warrant and any shares of
Common  Stock to be issued upon its  exercise  (or shares of any  security  into
which such Common Stock may be converted) except under  circumstances which will
not  result in a  violation  of the  Securities  Act of 1933,  as  amended  (the
"Securities  Act").  Upon exercise of this Warrant,  the holder hereof shall, if
requested  by the  Company,  confirm  in  writing  its  investment  purpose  and
acceptance of the restrictions on transfer of the Shares.

      9.    SUBDIVISION OF WARRANT. At the request of the holder of this Warrant
in  connection  with a transfer or exercise of a portion of the Warrant and upon
surrender of this  Warrant for such  purpose to the Company,  the Company at its
expense  (except for any transfer tax payable)  will issue in exchange  therefor
warrants  of like  tenor and date  representing  in the  aggregate  the right to
purchase  such number of shares of such Common Stock as shall be  designated  by
such holder at the time of such surrender; provided, however, that the Company's
obligations to subdivide  securities  under this Section shall be subject to and
conditioned  upon the compliance of any such  subdivision  with applicable state
securities laws and with the Securities Act.

      10.   LOSS, THEFT, DESTRUCTION,  OR MUTILATION OF WARRANT. Upon receipt by
the  Company  of  evidence  reasonably  satisfactory  to it of the loss,  theft,
destruction,  or mutilation of this

                                      -3-
<PAGE>

Warrant,  and in the  case of loss,  theft,  or  destruction,  of  indemnity  or
security  reasonably  satisfactory to it and reimbursement to the Company of all
reasonable  expenses  incidental  thereto,  in the case of mutilation,  and upon
surrender and  cancellation  of this Warrant the Company will make and deliver a
new  Warrant  of like tenor and dates as of such  cancellation,  in lieu of this
Warrant.

      11.   MISCELLANEOUS.  This  Warrant  shall be  governed by the laws of the
State of Texas. The headings in this Warrant are for purposes of convenience and
reference  only,  and shall not be deemed to  constitute a part of this Warrant.
Neither this Warrant nor any term included may be changed,  waived,  discharged,
or terminated  orally but only by an instrument in writing signed by the Company
and the Holder.  All notices  and other  communications  from the Company to the
Holder  shall  be by  telecopy  or  expedited  courier  service  to the  address
furnished to the Company in writing by the last holder of this Warrant who shall
have  furnished  an address to the  Company in  writing.  This  Warrant has been
issued pursuant to a Warrant  Purchase  Agreement dated as of June 15, 1999, the
terms of which, including certain repurchase provisions, are incorporated herein
by reference.  A copy of such Warrant Purchase Agreement may be inspected at the
office of the Company during normal business hours.

      12.   EXERCISE   PERIOD.   The  Exercise  Period  shall  mean  the  period
commencing on the date hereof and ending on June 15, 2009.

      ISSUED this 15th day of June, 1999.

                                            POSITRON CORPORATION

                                            By: /s/ S. Lewis Meyer
                                               ---------------------------------
                                            Its: Chairman

ATTEST:

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

                                      -4-
<PAGE>

                               FORM OF ASSIGNMENT
                              POSITRON CORPORATION

      FOR VALUE RECEIVED the undersigned registered owner of this warrant hereby
sells, assigns, and transfers unto the Assignee named below all of the rights of
the undersigned  under the within Warrant,  with respect to the number of shares
of Common Stock set forth below.

             Name of Assignee:

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

             Address:

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

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

             Number of Shares

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

and does hereby  irrevocably  constitute and appoint  __________________________
Attorney to make such transfer on the books of POSITRON  CORPORATION  maintained
for the purpose, with full power of substitution in the premises.

Dated:
      ----------------------

                                               ---------------------------------
                                               Name of Warrant Holder

                                               ---------------------------------
                                               Signature

Witness:
        --------------------

<PAGE>

                                SUBSCRIPTION FORM
                              POSITRON CORPORATION

                 (To be executed only upon exercise of Warrant)

      The undersigned  registered  owner of this Warrant  irrevocably  exercises
this  Warrant  for and  purchases  ________________  of the  number of shares of
Common Stock of POSITRON CORPORATION purchasable with this Warrant, and herewith
makes  payment  therefor,  all at the  price  and on the  terms  and  conditions
specified in this Warrant.

Dated:
      ---------------------

                                        ----------------------------------------
                                        Signature of Registered Owner

                                        ----------------------------------------
                                        Street Address

                                        ----------------------------------------
                                        City                State    Zip CodeEXHIBIT 4.11

                           WARRANT PURCHASE AGREEMENT

      THIS WARRANT PURCHASE AGREEMENT (the "Agreement") is made and entered into
this  15th  day of  June,  1999 by and  between  POSITRON  CORPORATION,  a Texas
corporation (the "Company") and S. LEWIS MEYER (the "Investor").

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

      WHEREAS, the Company desires to issue to Investor and the Investor desires
to purchase  from the Company a warrant (the  "Warrant")  to purchase  1,500,000
shares  of the  Company's  common  stock  (the  "Shares")  all on the  terms and
conditions  hereinafter  provided.  The  Warrant  and the Shares  are  hereafter
collectively referred to as the "Securities".

      NOW, THEREFORE, IT IS AGREED AS FOLLOWS:

      1.    ISSUANCE  OF  WARRANT;  REPURCHASE  RIGHT.  For a purchase  price of
$0.0067 per warrant (the "Per Warrant Purchase Price") representing an aggregate
purchase  price of $10,000  ("Aggregate  Purchase  Price")  payable in cash upon
execution hereof, the Company agrees to issue to Investor the Warrant,  the form
of which is  attached  hereto as Exhibit A. The  Company  reserves to itself the
right  to  repurchase  any  portion  of the  Warrant  issued  pursuant  to  this
Agreement,  and the right to  repurchase  any stock issued upon  exercise of any
portion of the  Warrant  ("Repurchase  Right"),  as of a date 90 days  following
termination  for  any  reason  or for no  reason  of  Investor's  service  to or
affiliation  with the Company.  The price of repurchase will be equal to the Per
Warrant  Purchase  Price  regarding  any  portion of the  Warrant  that  remains
unexercised  at the time the Company  exercises  its  Repurchase  Right,  or the
purchase price of the underlying  stock (i.e. the exercise price of the Warrant)
regarding any portion of the Warrant that has already been exercised at the time
the Company  exercises its Repurchase Right. The Repurchase Right shall lapse as
follows:  immediately  upon issuance as to 375,000  shares;  as to an additional
93,750  shares on September  15, 1999;  and as to an  additional  93,750  shares
quarterly  thereafter until the Company's  Repurchase Right shall have lapsed as
to all shares.

      2.    INVESTOR REPRESENTATIONS. Investor hereby represents and warrants to
the Company as follows:

            (a)   The Investor  understands  that:  (i)The offer and sale of the
Securities  by the  Company  to  Investor  has not  been  registered  under  the
Securities Act of 1933 (the "Securities  Act"), in reliance on an exemption from
such  registration   available  under  the  Securities  Act  and  rules  adopted
thereunder;  (ii)The  Investor  must hold the  Warrant  indefinitely  unless the
Securities are  subsequently  registered  under the Securities Act and qualified
under

<PAGE>

applicable state securities laws, or unless an exemption from such  registration
and qualification is available.

            (b)   The Investor is acquiring  the  Securities  for his or her own
account, for investment,  and not with a view to any sale or distribution of any
interest therein.

            (c)   The Investor has such  knowledge  and  experience in financial
and business  matters as to be capable of evaluating  the merits and risks of an
investment  in the  Securities,  and the  Investor is able to bear the  economic
risks of such an investment.

            (d)   All  statements  made,  and  information  furnished,   by  the
Investor in this certificate and all other information furnished by the Investor
to the Company, are true and complete, to the best of the Investor's knowledge.

      3.    RESTRICTIONS ON TRANSFER. The Investor agrees that:

            (a)   The Investor  will not attempt to transfer the  Securities  in
violation of the restrictions set forth in this Agreement.

            (b)   The  Company  may note such  restrictions  on  transfer in its
records and refuse to recognize any transfer  which  violates this  agreement or
for which the Company has not received an acceptable  opinion of counsel stating
that such transfer will not violate such restrictions.

            (c)   One or more legends  indicating a lack of  registration  under
the Securities Act and a lack of qualification  under state securities laws will
be imprinted on the  Securities.  One such legend  shall read  substantially  as
follows:

      THE SECURITIES  HAVE NOT BEEN  REGISTERED WITH THE SECURITIES AND EXCHANGE
COMMISSION UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND ANY SALE, TRANSFER,
PLEDGE OR OTHER DISPOSITION THEREOF MAY BE MADE ONLY (i) IN A REGISTRATION UNDER
SAID ACT OR (ii) IF AN EXEMPTION FROM  REGISTRATION  UNDER SAID ACT IS AVAILABLE
AND THE  COMPANY HAS  RECEIVED  AN OPINION OF COUNSEL TO THAT EFFECT  REASONABLY
SATISFACTORY TO IT.

      4.    BINDING ON SUCCESSORS; INDEMNIFICATION. The Investor agrees that the
above  representations  and warranties are binding on the Investor's  successors
and assigns  and are made for the  benefit of the Company and any other  persons
who may become liable for  violations of federal or state  securities  laws as a
result of the falsity of any of the  Investor's  representations  or warranties.
The Investor  agrees to indemnify,  defend,  and hold harmless such persons from
any liability arising from the falsity of any of the Investor's  representations
or warranties or from the breach of any covenant of Investor contained herein.

      5.    REGISTRATION  RIGHTS.  The Company  hereby  grants to  Investor  the
following registration rights with respect to the Shares:

            (a)   Definitions.

                                      -2-
<PAGE>

            "Commission"  shall mean the Securities  and Exchange  Commission or
any other federal  agency at the time  administering  the Securities Act of 1933
(the "Securities Act").

            "Register," "registered," and "registration" refer to a registration
effected by preparing and filing a registration statement in compliance with the
Securities Act of 1933, and the declaration or ordering of the  effectiveness of
such registration statement.

            "Registration  Expenses"  shall mean all  expenses  incurred  by the
Company in compliance with the provisions of this Section 5, including,  without
limitation,  all  registration  and filing  fees,  printing  expenses,  fees and
disbursements  of counsel for the Company,  blue sky fees and expenses,  and the
expenses of any special audits incident to or required by any such  registration
(but excluding the compensation of regular employees of the Company, which shall
be paid in any event by the Company).

            "Selling Expenses" shall mean all underwriting discounts and selling
commissions  applicable to the sale of Shares and all fees and  disbursements of
counsel to Investor.

            "Shares" means the shares of the Company's common stock  exercisable
upon  exercise of the Warrant and any common stock  issued with respect  thereto
(e.g. upon a stock split or stock dividend.

            "Investor"  means  the  person  set forth  above  and any  permitted
assignee.

            (b)   COMPANY REGISTRATION.

                  (i)   NOTICE OF  REGISTRATION.  If, at any time after the date
hereof, the Company shall determine to register any of its securities either for
its own account or the account of a security holder or holders  exercising their
respective demand registration rights, other than a registration relating solely
to employee  benefit plans,  or a registration  relating  solely to a Commission
Rule 145 transaction,  or a registration on any registration form which does not
permit secondary sales, the Company will:

            a)    promptly give to Investor  written notice thereof (which shall
include a list of the  jurisdictions  in which the Company intends to attempt to
qualify such securities  under the applicable blue sky or other state securities
laws); and

            b)    include in such  registration  (and any related  qualification
under  blue sky  laws or other  compliance),  and in any  underwriting  involved
therein,  all the Shares  specified in a written  request or  requests,  made by
Investor  within  fifteen (15) days after receipt of the written notice from the
Company  described in this clause (i),  except as set forth in Section  5(b)(ii)
below.

                  (ii)  UNDERWRITING.  If the  registration of which the Company
gives notice is for a registered public offering involving an underwriting:  the
Company shall so advise Investor as part of the written notice given pursuant to
Section  5(b)  hereof.  In such event,  the right of  Investor  to  registration
pursuant to this Section 5 shall be conditioned upon Investor's participation in
such underwriting and the inclusion of Investor's Shares in the underwriting to

                                      -3-
<PAGE>

the extent  provided  herein.  Investor shall  (together  with the Company,  its
directors and officers, and any other shareholders distributing their securities
through such  underwriting)  enter into an  underwriting  agreement in customary
form with the  underwriter  or  underwriters  selected for  underwriting  by the
Company.

      Notwithstanding  any other provision of this Section 5, if the underwriter
determines  that marketing  factors require a limitation on the number of shares
to be  underwritten,  the  underwriter  may exclude from such  registration  and
underwriting  some or all of the Shares which would  otherwise  be  underwritten
pursuant hereto.  Any securities so excluded shall be apportioned pro rata among
Investor and any other  shareholders  distributing their securities through such
underwriting  according to the total amount of securities  otherwise entitled to
be included therein owned by such  shareholders or in such other  proportions as
shall mutually be agreed upon.

      If  Investor  disapproves  of the terms of any such  underwriting,  it may
elect  to  withdraw   therefrom  by  written  notice  to  the  Company  and  the
underwriter.  Any Shares excluded or withdrawn from such  underwriting  shall be
withdrawn from such registration.

      The Company shall bear all  Registration  Expenses  incurred in connection
with any  registration,  qualification and compliance by the Company pursuant to
this Section  5(b).  All Selling  Expenses  shall be borne by the holders of the
securities so registered  pro rata on the basis of the number of their shares so
registered.

                  (iii) REGISTRATION  PROCEDURES.  In the  case of  registration
effected  by the  Company  pursuant to this  Agreement,  the  Company  will keep
Investor  advised in writing as to the initiation of registration  and as to the
completion thereof. At its expense, the Company will:

                        a)    keep such  registration  effective for a period of
one year or until  Investor  has  completed  the  distribution  described in the
registration statement relating thereto, whichever first occurs;

                        b)    furnish  such  number  of  prospectuses  and other
documents incident thereto as Investor from time to time may reasonably request;
and

                        c)    use its best  efforts to  register  or qualify the
Shares under the securities or blue sky laws of such  jurisdictions  as Investor
may  request;  provided,  however,  that the Company  shall not be  obligated to
register or qualify  such  Shares in any  particular  jurisdiction  in which the
Company would be required to execute a general  consent to service of process in
order to effect such  registration,  qualification,  or  compliance,  unless the
Company is already subject to service in such  jurisdiction and except as may be
required by the Securities Act or applicable rules or regulations thereunder.

                        d)    Notify  the  holder  of  Shares  covered  by  such
registration  statement  at any  time  when a  prospectus  relating  thereto  is
required to be delivered under the Act of the happening of any event as a result
of which the  prospectus  included in such  registration  statement,  as then in
effect,  includes  an untrue  statement  of a material  fact or omits to state a
material fact required to be stated  therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing.

                                      -4-
<PAGE>

            (c)   INDEMNIFICATION.

                  (i)   The Company will  indemnify  the  Investor,  each of its
officers,  directors and  partners,  and each person  controlling  such Investor
within the  meaning of Section 15 of the  Securities  Act or the 1934 Act,  with
respect to which  registration,  qualification  or compliance  has been effected
pursuant to this Agreement,  and each  underwriter,  if any, and each person who
controls any underwriter  within the meaning of Section 15 of the Securities Act
or the 1934 Act, against all expenses,  claims,  losses,  damages or liabilities
(or actions in respect  thereof),  including  any of the  foregoing  incurred in
settlement of any litigation,  commenced or threatened,  arising out of or based
on any untrue  statement  (or  alleged  untrue  statement)  of a  material  fact
contained in any registration statement,  prospectus, offering circular or other
document,  or  any  amendment  or  supplement  thereto,  incident  to  any  such
registration,  qualification or compliance, or based on any omission (or alleged
omission)  to state  therein a material  fact  required to be stated  therein or
necessary to make the statements  therein,  in the light of the circumstances in
which they were made,  not  misleading,  or any  violation by the Company of the
Securities Act, or the 1934 Act, or any rule or regulation promulgated under the
Securities  Act,  or the 1934 Act,  or under any state  securities  law or under
common law,  applicable to the Company in connection with any such registration,
qualification or compliance,  and the Company will reimburse the Investor,  each
of its  officers,  directors  and  partners,  and each  person  controlling  the
Investor,   each  such  underwriter  and  each  person  who  controls  any  such
underwriter,  for any legal and any other expenses reasonably incurred,  as such
expenses are incurred, in connection with investigating,  preparing or defending
any such claim, loss, damage, liability or action;  provided,  however, that the
Company will not be liable (i) for amounts paid in  settlement of any such loss,
claim,  damage,  liability or action if such settlement is effected  without the
consent of the Company  (which consent shall not be  unreasonably  withheld) and
(ii) in any such case to the extent that any such claim, loss, damage, liability
or expense  arises out of or is based on any untrue  statement  or  omission  or
alleged  untrue  statement or omission,  made in reliance upon and in conformity
with written information furnished to the Company by an instrument duly executed
by the Investor, controlling person or underwriter and stated to be specifically
for use therein.

                  (ii)  The  Investor  will,  if Shares held by the Investor are
included  in the  securities  as to which such  registration,  qualification  or
compliance is being effected,  indemnify the Company,  each of its directors and
officers, each underwriter,  if any, of the Company's securities covered by such
a  registration  statement,  each  person  who  controls  the  Company  or  such
underwriter  within the meaning of Section 15 of the  Securities Act against all
claims,  losses, damages and liabilities (or actions in respect thereof) arising
out of or based on any untrue  statement  (or  alleged  untrue  statement)  of a
material fact contained in any such registration statement, prospectus, offering
circular or other  document,  or any  omission  (or alleged  omission)  to state
therein a material fact  required to be stated  therein or necessary to make the
statements  therein  not  misleading,  and  will  reimburse  the  Company,  such
directors,  officers, persons,  underwriters or control persons for any legal or
any other  expenses  reasonably  incurred in connection  with  investigating  or
defending any such claim, loss, damage, liability or action, in each case to the
extent,  but only to the extent,  that such untrue  statement (or alleged untrue
statement)  or  omission  (or  alleged  omission)  is made in such  registration
statement,  prospectus, offering circular or other document in reliance upon and
in conformity with written

                                      -5-
<PAGE>

information  furnished  to the  Company by an  instrument  duly  executed by the
Investor  and stated to be  specifically  for use therein.  Notwithstanding  the
foregoing,  the liability of the Investor under this subsection  shall not apply
to amounts paid in  settlement  of any such loss,  claim,  damage,  liability or
action if such settlement is effected without the consent of the Investor (which
consent  shall not be  unreasonably  withheld),  and (ii) shall be limited in an
amount equal to the  aggregate  net proceeds of the shares sold by the Investor,
except  to the  extent  such  liability  arises  out of or is based  on  willful
misconduct by the Investor.

                  (iii) Each  party  entitled  to  indemnification   under  this
Section 5(d) (the  "Indemnified  Party") shall give notice to the party required
to  provide  indemnification  (the  "Indemnifying  Party")  promptly  after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought,  and shall  permit the  Indemnifying  Party to assume the defense of any
such claim or any litigation resulting therefrom,  provided that counsel for the
Indemnifying  Party,  who shall conduct the defense of such claim or litigation,
shall  be  approved  by  the   Indemnified   Party  (whose  approval  shall  not
unreasonably  be withheld),  and the  Indemnified  Party may participate in such
defense at such party's  expense,  and provided  further that the failure of any
Indemnified  Party to give  notice as  provided  herein  shall not  relieve  the
Indemnifying  Party of its obligations under this Agreement except to the extent
that  the  failure  to  give  such  notice  is  materially   prejudicial  to  an
Indemnifying  Party's ability to defend such action and provided  further,  that
the  Indemnifying  Party  shall not assume the  defense  for matters as to which
there is a conflict of interest or separate and  different  defenses,  but shall
pay the fees and expenses of one separate  counsel  retained by the  Indemnified
Party in the event of such conflict of interest.  No Indemnifying  Party, in the
defense of any such claim or litigation,  shall, except with the consent of each
Indemnified Party, consent to entry of any judgment or enter into any settlement
which  does not  include  as an  unconditional  term  thereof  the giving by the
claimant or plaintiff to such Indemnified  Party of a release from all liability
in respect to such claim or litigation.

                  (iv)  If the indemnification provided for in this Section 5(d)
is held by a court of competent jurisdiction to be unavailable to an indemnified
party with respect to any loss, liability, claim, damage, or expense referred to
therein,  then the Indemnifying  Party, in lieu of indemnifying such Indemnified
Party  hereunder,  shall  contribute  to the  amount  paid  or  payable  by such
Indemnified Party as a result of such loss, liability, claim, damage, or expense
in such  proportion  as is  appropriate  to reflect  the  relative  fault of the
Indemnifying  Party on the one hand and of the Indemnified Party on the other in
connection  with  the  statements  or  omissions  that  resulted  in such  loss,
liability,  claim,  damage,  or expense as well as any other relevant  equitable
considerations.  The  relative  fault  of  the  Indemnifying  Party  and  of the
Indemnified  Party shall be  determined  by reference  to,  among other  things,
whether  the  untrue or  alleged  untrue  statement  of a  material  fact or the
omission  to state a  material  fact  relates  to  information  supplied  by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge,  access to  information,  and  opportunity to correct or prevent such
statement or omission.

                  (v)   The  obligations  of the Company and the Investor  under
this Section 5(d) shall  survive the  completion  of any offering of Shares in a
registration statement under this Section 5 and otherwise.

                                      -6-
<PAGE>

                  (vi)  INFORMATION BY INVESTOR. The Investor of Shares included
in any  registration  shall  furnish to the Company such  information  regarding
Investor,  the Shares held by it and the distribution  proposed by such Investor
as the Company  may  reasonably  request in writing  and as shall be  reasonably
required  in  connection  with any  registration,  qualification  or  compliance
referred to in this Agreement.

                  (vii) TRANSFER OF REGISTRATION RIGHTS. The rights to cause the
Company to register  securities  granted Holders under Section 5 may be assigned
to a transferee  or assignee in  connection  with any transfer or  assignment of
Shares by a Holder provided that: (i) such transfer may otherwise be effected in
accordance with applicable  securities laws and (ii) such assignee or transferee
becomes a party to this  Agreement  and  assumes all of the  obligations  of the
transferring Holder under Section 5.

      6.    GOVERNING LAW. This Agreement  shall be governed by and construed in
accordance with the laws of the State of Texas.

      7.    COUNTERPARTS.  This  Agreement  may be  executed  in any  number  of
counterparts,  each of which  shall be an  original,  but all of which  together
shall constitute one instrument.

      IN WITNESS  WHEREOF,  the  undersigned  purchasers of  securities  and the
Company have executed this Agreement as of the day and year first above written.

                                            POSITRON CORPORATION

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

                                            INVESTOR

                                            /s/ S. Lewis Meyer
                                            ------------------------------------
                                                      S. Lewis Meyer

                                      -7-

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