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                                                                    EXHIBIT 10.4

                                    EXHIBIT G

                               SECURITY AGREEMENT

     This Security Agreement (this "AGREEMENT") is made as of September 30,
2005, by ImaRx Therapeutics, Inc., a Delaware corporation (the "COMPANY"), in
favor of Abbott Laboratories, an Illinois corporation ("HOLDER").

                                     RECITAL

     Holder and the Company have executed a Secured Promissory Note (a "NOTE")
in connection with the closing of the transactions set forth in that certain
Asset Purchase Agreement dated as of September 30, 2005, between the Company and
Holder (the "ASSET PURCHASE AGREEMENT"). Pursuant to the terms of the Asset
Purchase Agreement, the Company is required to execute and deliver this
Agreement for the purpose of granting Holder a security interest in certain of
the Company's assets.

                                    AGREEMENT

     NOW, THEREFORE, in consideration of the representations, warranties and
covenants herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
hereby agree as follows.

     1. Capitalized Terms. Capitalized terms not defined herein shall have the
meanings given such terms in the Note.

     2. Grant of Security Interest. To secure the complete and timely
satisfaction of all Obligations, the Company hereby grants to Holder a security
interest (with power of sale, to the extent permitted by law or such other
security interests as may exist as of the date of this Agreement, upon the
occurrence of an Event of Default in all of the Company's right, title and
interest in and to all of the collateral set forth on attached Exhibit A (the
"COLLATERAL").

     3. Perfection of Security Interests. At any time and from time to time, the
Company will execute, file, and record any notice, financing statement, or other
instrument, reasonably necessary to create, continue, or perfect the security
interest granted by this Agreement or to enable Holder to exercise or enforce
its rights under this Agreement.

     4. Term. The term of this Agreement will extend until all Obligations under
the Note have been indefeasibly paid in full, as reasonably determined by the
parties, at which time the Company and any of its duly appointed officers is
hereby authorized to file any termination statement under the Uniform Commercial
Code in effect in any jurisdiction to terminate the financing statements that
evidence the security interest in the Collateral created by this Agreement and
the Note.

     5. Rights and Remedies Upon Default. Beginning on the date on which any
Event of Default shall have occurred, and while such Event of Default is
continuing:

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          (a) Holder may exercise, in addition to all other rights and remedies
granted to it under this Agreement, all rights and remedies of a secured party
under the Uniform Commercial Code.

          (b) The Company hereby waives presentment, demand, protest or any
notice (to the maximum extent permitted by applicable law) of any kind in
connection with this Agreement or any Collateral.

          (c) The Company shall, at the request of Holder, assemble the
Collateral at such place or places as may be reasonably designated by Holder.

          (d) Holder may, in its sole discretion, in its name or in the name of
the Company or otherwise, demand, sue for, collect or receive any money or
property at any time payable or receivable on account of or in exchange for any
of the Collateral, but shall be under no obligation to do so.

          (e) Holder may, upon ten (10) days' prior written notice to the
Company of the time and place (which notice the Company hereby agrees is
commercially reasonable notification for purposes hereof), with respect to the
Collateral or any part thereof which shall then be or shall thereafter come into
the possession, custody or control of Holder, sell lease, assign or otherwise
dispose of all or any part of such Collateral, at such place or places as Holder
deems best, and for cash or for credit or for future delivery (without thereby
assuming any credit risk), at public or private sale, without demand of
performance or notice of intention to effect any such disposition or of the time
or place thereof (except such notice as is required above or by applicable
statute and cannot be waived), and Holder or anyone else may be the purchaser,
lessee, assignee or recipient of any or all of the Collateral so disposed of at
any public sale (or, to the extent permitted by law, at any private sale) and
thereafter hold the same absolutely, free from any claim or right of whatsoever
kind, including any right or equity of redemption (statutory or otherwise), of
the Company, any such demand, notice and right or equity being hereby expressly
waived and released. Holder may, without notice or publication, adjourn any
public or private sale or cause the same to be adjourned from time to time by
announcement at the time and place fixed for the sale, and such sale may be made
at any time or place to which the sale may be so adjourned.

     6. Release of Security Interest. Upon the indefeasible payment in full of
the Obligations, Holder will execute and deliver to the Company all deeds,
assignments and other instruments, and will take such other actions, as may be
necessary or proper to re-vest in the Company full title to the Collateral,
subject to any disposition which may have been made by Holder pursuant to this
Agreement.

     7. Certain Restrictions. The Company agrees that until the Obligations have
been indefeasibly paid in full, the Company will not sell or assign its interest
in, or grant any license under, other than in the ordinary course of business in
consultation with Holder, the Collateral, or enter into any other agreement with
respect to the Collateral that is inconsistent with the Company's obligations
under this Agreement, without the prior written consent of Holder; provided,
however, that the Company may assign the Collateral to an Affiliate if the
Company fully guarantees such Affiliate's performance of all of the Company's
obligations hereunder.


                                        2

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The Company further agrees that it will not take any action, or permit any
action to be taken by others subject to its control, including licensees, or
fail to take any action (solely with respect to any Collateral that are
registered patents or registered trademarks), which would affect the validity or
enforcement of the rights transferred to Holder under this Agreement. Further,
the Company covenants and agrees that, until the Obligations hereunder have been
indefeasibly paid in full, the Company will preserve and maintain the Collateral
in good working condition and will protect the Collateral against spoilage,
deterioration and any other wasting.

     8. Expenses. All expenses incurred in connection with the performance by
the Company and Holder of any of the agreements set forth in this Agreement will
be borne by the Company. All fees, costs and expenses, of whatever kind or
nature, including reasonable attorneys' and paralegals' fees and legal expenses,
incurred by Holder in connection with the filing or recording of any documents
(including all taxes in connection therewith) in public offices, the payment or
discharge of any taxes, counsel fees, maintenance fees, encumbrances or
otherwise in protecting, maintaining or preserving the Collateral will be borne
by and paid by the Company.

     9. Severability. The provisions of this Agreement are severable, and if any
clause or provision is held invalid and unenforceable in whole or in part in any
jurisdiction, then such invalidity or unenforceability will affect only such
clause or provision, or part of such clause or provision, in such jurisdiction,
and will not in any manner affect such clause or provision in any other
jurisdiction, or any other clause or provision of this Agreement in any
jurisdiction.

     10. Modification. This Agreement cannot be altered, amended or modified in
any way, except as specifically provided in writing and signed by the Company
and Holder.

     11. Binding Effect; Benefits. This Agreement will be binding upon the
Company and its successors and permitted assigns, and will inure to the benefit
of Holder, its successors, nominees and assigns.

     12. Governing Law. This Agreement shall be governed in all respects by the
internal laws of the State of Delaware, excluding that body of law relating to
conflict of laws and choice of law.

     13. Headings. Paragraph headings used in this Agreement are for convenience
only and will not modify the provisions that they precede.

                            [Signature pages follow.]


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     IN WITNESS WHEREOF, the undersigned has caused this Security Agreement to
be duly executed by its officer thereunto duly authorized as of the first date
written above.

                                        COMPANY:

                                        IMARX THERAPEUTICS, INC.


                                        By: /s/ Evan Unger
                                            ------------------------------------
                                        Name: Evan Unger
                                        Its: President and CEO


                                        HOLDER:

                                        ABBOTT LABORATORIES


                                        By: /s/ Sean Murphy
                                            ------------------------------------
                                        Name: Sean E. Murphy
                                        Its: Vice President, Global Licensing/
                                             New Business Development


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                                    EXHIBIT A

                                   COLLATERAL

     The Collateral consists of all of ImaRx Therapeutics, Inc.'s (the
"COMPANY") right, title and interest in and to the Purchased Assets (as defined
in the Asset Purchase Agreement) transferred to the Company by Abbott
Laboratories, an Illinois corporation ("ABBOTT"), pursuant to that certain Asset
Purchase Agreement (the "ASSET PURCHASE AGREEMENT") dated as of September 30,
2005, between the Company and Abbott, and any written data or research related
to the Purchased Assets or developments and improvements in the intellectual
property included in the Purchased Assets created by the Company subsequent to
the closing of the sale of such Purchased Assets to the Company.