<PAGE>

                                                                   Exhibit 10.29

THIS WARRANT AND THE SECURITIES THAT MAY BE ACQUIRED UPON EXERCISE OF THE
WARRANT HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED.
NEITHER THIS WARRANT NOR THE SECURITIES THAT MAY BE ACQUIRED UPON EXERCISE OF
THIS WARRANT MAY BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN THE
ABSENCE OF A REGISTRATION STATEMENT IN EFFECT UNDER SUCH ACT OR AN OPINION OF
COUNSEL SATISFACTORY TO ACUSPHERE THAT SUCH REGISTRATION IS NOT REQUIRED OR
UNLESS SOLD PURSUANT TO RULE 144 OR RULE 144A OF SUCH ACT.

THIS WARRANT AND THE SECURITIES THAT MAY BE ACQUIRED UPON EXERCISE OF THE
WARRANT ARE SUBJECT TO A CONVERTIBLE NOTE AND WARRANT PURCHASE AND SECURITIES
EXCHANGE AGREEMENT, DATED AS OF _________, 2003, AS AMENDED AND IN EFFECT FROM
TIME TO TIME, A COPY OF WHICH IS ON FILE AT THE PRINCIPAL PLACE OF BUSINESS OF
ACUSPHERE.

THIS WARRANT AND THE SECURITIES THAT MAY BE ACQUIRED UPON EXERCISE OF THE
WARRANT ARE SUBJECT TO A VOTING AGREEMENT (A COPY OF WHICH MAY BE OBTAINED FROM
ACUSPHERE), AS AMENDED FROM TIME TO TIME, AND BY ACCEPTING ANY INTEREST IN THIS
WARRANT OR SUCH SECURITIES THE PERSON ACCEPTING SUCH INTEREST SHALL BE DEEMED TO
AGREE TO AND SHALL BECOME BOUND BY ALL THE PROVISIONS OF SUCH VOTING AGREEMENT.

                                 ACUSPHERE, INC.

                                WARRANT AGREEMENT

                Exercise Amount: $ [20% of note principal amount]


Warrant No. ____                                                 _________, 2003

         ACUSPHERE, INC., a Delaware corporation (the "Company"), hereby
certifies that, for value received, [NAME] (hereinafter referred to as "Holder")
is entitled, subject to the terms and conditions set forth below, to purchase
from the Company the Warrant Number (as defined in Section 1.3 below) of fully
paid and non-assessable shares of the Warrant Class (as defined in Section 1.2
below), at a price per share equal to the Exercise Price (as defined in Section
1.2 below). The shares issuable upon exercise of this Warrant are hereinafter
referred to as the "Shares" and are subject to adjustment as hereinafter
provided.

         This Warrant is one of a series of warrants of like tenor
(collectively, the "Warrants" and each a "Warrant") issued by the Company
pursuant to and entitled to the benefits of that certain Convertible Promissory
Note and Warrant Purchase Agreement, dated as of _________, 2003, by and among
the Company and the several Investors listed in Exhibit A thereto (collectively,
the "Holders" and each a "Holder") (as the same may be amended from time to
time, the "Purchase Agreement"), and each Holder of this Warrant, by such
Holder's acceptance hereof, agrees to be bound by the provisions of the Purchase
Agreement, including without limitation the
<PAGE>
                                      -2-

amendment, waiver and exercise of remedies provisions set forth in Section 6.9
therein. This Warrant is being issued in conjunction with the issuance of one of
a series of 10% convertible promissory notes (collectively, the "Notes" and each
a "Notes") pursuant to the Purchase Agreement. Capitalized terms used herein but
not defined herein shall have the meanings ascribed to them in the Purchase
Agreement.

ARTICLE 1. EXERCISE.

         1.1 Method of Exercise. The Holder may exercise this Warrant in whole
or in part by delivering this Warrant together with a duly executed Notice of
Exercise in substantially the form attached as Appendix 1 hereto to the
principal office of the Company. Unless the Holder is exercising the conversion
right set forth in Section 1.4, the Holder shall also deliver to the Company
payment in full, in lawful money of the United States, for the aggregate
Exercise Price for the Shares being purchased. Any exercise of this Warrant in
connection with a Change of Control or an initial public offering of the
Company's equity securities may be conditioned upon the actual consummation of
such Change of Control or initial public offering.

         1.2 Warrant Class and Exercise Price.

                  (a) Upon the consummation of the earlier to occur of a Next
Equity Financing (as defined in the Notes), or a Negotiated Conversion (as
defined in the Notes), if any, "Warrant Class" shall mean shares of the same
class and series as the equity securities into which the Notes are automatically
converted in connection therewith, and "Exercise Price" shall mean an amount
equal to the conversion price per share at which such Notes are so converted.

                  (b) Prior to the consummation of the earlier to occur of a
Next Equity Financing or Negotiated Conversion, "Warrant Class" shall mean
shares of the Company's Series J-2 Convertible Preferred Stock, $.01 par value
per share (the "Series J-2 Preferred Stock"), and "Exercise Price" shall mean an
amount equal to the Original Series J Issue Price (as defined in the Company's
Twelfth Amended and Restated Certificate of Incorporation (as amended and in
effect from time to time, the "Charter")); provided, however, that, immediately
prior to the consummation of a Change of Control (as defined in the Company's
Charter), in connection with which the aggregate consideration to be paid or
payable to the Company and/or its stockholders is less than the sum of the
aggregate cumulative liquidation preference of the Company's preferred stock
then outstanding (excluding any shares of preferred stock issued or issuable
upon exercise of the Warrants), plus the aggregate principal amount outstanding
under all Notes then outstanding and all accrued and unpaid interest thereon,
"Exercise Price" shall mean an amount equal to 80% of the Original Series J
Issue Price. If the consideration received by the Company and/or its
stockholders in connection with such Change of Control is other than cash, its
value will be deemed to be its fair market value, as determined by the Company
and the Holders of Warrants representing at least a majority of the aggregate
Exercise Amount under all Warrants then outstanding (a "Warrant Majority") in a
manner reasonably consistent with Section 2.10(b) and Section 8 of ARTICLE
FOURTH of the Charter, or in such manner as the Company and such Holders of a
Warrant Majority may otherwise agree.

                  1.3 Warrant Number. The Warrant Number shall be determined as
follows:

                           N = A/E
<PAGE>
                                      -3-

                  Where:

                     N = The maximum number of shares of stock of the
                         Warrant Class that may be purchased upon exercise of
                         this Warrant.

                     A = The Exercise Amount

                     E = The Exercise Price

         1.4 Net Issue Exercise. In lieu of exercising this Warrant as specified
in Section 1.1, the Holder may convert this Warrant from time to time, in whole
or in part, without payment of any consideration, into a number of Shares
determined as follows:

                     X = Y(A-B)/A

                  Where:

                     X = The number of Shares to be issued to the Holder.

                     Y = The number of Shares with respect to which this Warrant
                         is being exercised.

                     A = The Fair Market Value of one Share.

                     B = The Exercise Price.

         1.5 Fair Market Value. The fair market value of a Share shall be
determined by the Company and the Holders of a Warrant Majority in a manner
reasonably consistent with Section 2.10(b) and Section 8 of ARTICLE FOURTH of
the Charter, or in such manner as the Company and such Holders of a Warrant
Majority may otherwise agree.

         1.6. Partial Exercise. This Warrant may be exercised in part, and the
Holder shall be entitled to receive a new warrant, which shall be dated as of
the date of this Warrant, covering the number of Shares in respect of which this
Warrant shall not have been exercised.

         1.7. Fractional Shares. No fractional Shares shall be issuable upon
exercise or conversion of the Warrant and the number of Shares to be issued
shall be rounded down to the nearest whole Share. In lieu of such fractional
shares, the Company will pay the cash value of such fraction.

         1.8. Issuance Date. The person or persons in whose name or names any
certificate representing Shares is issued hereunder shall be deemed to have
become the holder of record of the Shares represented thereby as at the close of
business on the date this Warrant is exercised with respect to such shares,
whether or not the transfer books of the Company shall be closed.

         1.9. Expiration Date. This Warrant shall expire and be void thereafter
upon the earliest to occur of (a) the consummation of an initial public offering
of the Company's equity securities in which the underwriters advise the Holders
in writing that marketing factors require
<PAGE>
                                      -4-

that no warrants remain outstanding following the consummation of the initial
public offering, (b) the consummation of a Change of Control or (c) _________,
2008.

ARTICLE 2. ADJUSTMENTS TO THE SHARES.

         2.1 Stock Dividends, Splits, Etc. If the Company declares or pays a
dividend on the outstanding shares of the Warrant Class, payable in shares of
the Warrant Class, or other securities, or subdivides the outstanding Warrant
Class into a greater number of shares of the Warrant Class, then upon exercise
of this Warrant, for each Share acquired, Holder shall receive, without
additional cost to Holder, the total number and kind of securities to which
Holder would have been entitled had Holder owned the Shares of record as of the
date the dividend or subdivision occurred.

         2.2 Reclassification, Merger, Exchange or Substitution. Upon any
reclassification, exchange, substitution, merger, consolidation, reorganization
or other event that results in a change of the number and/or class of the
securities issuable upon exercise or conversion of this Warrant, Holder shall be
entitled to receive, upon exercise or conversion of this Warrant, the number and
kind of securities and property that Holder would have received for the Shares
if this Warrant had been exercised immediately before such reclassification,
exchange, substitution, merger, consolidation, reorganization or other event.
The Company or its successor shall promptly issue to Holder a new warrant of
like tenor for such new securities or other property. The new warrant shall
provide for adjustments which shall be as nearly equivalent as may be
practicable to the adjustments provided for in this Article 2 including, without
limitation, adjustments to the Exercise Price and to the number of securities or
property issuable upon exercise of the new warrant. The provisions of this
Section 2.2 shall similarly apply to successive reclassifications, exchanges,
substitutions, mergers, consolidations, reorganizations or other events.

         2.3 Adjustments for Combinations, Etc. If the outstanding shares of the
Warrant Class are combined or consolidated, by reclassification or otherwise,
into a lesser number of shares, the Exercise Price shall be proportionately
increased and the number of Shares issuable upon exercise or conversion of this
Warrant shall be proportionately decreased.

         2.4 No Impairment. The Company shall not, by amendment of the
Certificate or its by-laws or through a reorganization, transfer of assets,
consolidation, merger, dissolution, issue, or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed under this Warrant by the Company, but
shall at all times in good faith assist in carrying out of all the provisions of
this Article 2 and in taking all such action as may be necessary or appropriate
to protect Holder's rights under this Article 2 against impairment.

         2.5 Certificate as to Adjustments. Upon each adjustment of the Exercise
Price, number or class of Shares or other securities for which the Shares are
convertible or exchangeable, the Company at its expense shall promptly compute
such adjustment, and furnish Holder with a certificate of its chief financial
officer setting forth such adjustment and the facts upon which such adjustment
is based. The Company shall at any time and from time to time, upon written
request, furnish Holder with a certificate setting forth the Exercise Price,
number and class of Shares and conversion ratio in effect upon the date thereof
and the series of adjustments leading to such Exercise Price, number and class
of Shares and conversion ratio.
<PAGE>
                                      -5-

ARTICLE 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY.

         3.1 Representations and Warranties. The Company hereby represents and
warrants to, and agrees with, the Holder as follows:

                  (a) All Shares which may be issued upon the due exercise of
this Warrant, and all Common Stock or other securities, if any, issuable upon
due conversion of the Shares, shall, upon issuance, be duly authorized, validly
issued, fully paid and non-assessable, and free of any liens and encumbrances
except for restrictions on transfer provided for herein, any other agreement to
which the Company is a party, or under applicable federal and state securities
laws.

                  (b) The Company covenants that at such time as the Warrant
Class is determined, it shall promptly take all necessary corporate actions to
authorize and reserve and keep available out of its authorized and unissued
shares such number of shares of the Warrant Class, Common Stock and other
securities as will be sufficient to permit the exercise in full of this Warrant
and the conversion of the Shares into shares of Common Stock or such other
securities.

         3.2 Notice of Certain Events. In the event of (a) any taking by the
Company of a record of the holders of any class of securities for the purpose of
determining the holders thereof who are entitled to receive any dividend or
other distribution, (b) an initial public offering of the Company's equity
securities in which the underwriters advise the Holders in writing that
marketing factors require that no warrants remain outstanding following the
consummation of the initial public offering, (c) any reclassification of the
capital stock of the Company, capital reorganization of the Company,
consolidation or merger involving the Company, or sale or conveyance of all or
substantially all of its assets, or any Change of Control, or (c) any voluntary
or involuntary dissolution, liquidation or winding-up of the Company, then and
in each such event the Company will mail or cause to be mailed to the Holder a
notice specifying (i) the date on which any such record is to be taken for the
purpose of such dividend, distribution or right, and stating the amount and
character of such dividend, distribution or right, or (ii) the date on which any
such initial public offering, reclassification, reorganization, consolidation,
merger, sale or conveyance, Change of Control, dissolution, liquidation or
winding-up is to take place, and the time, if any is to be fixed, as of which
the holders of record in respect of such event are to be determined. Such notice
shall be mailed as soon as practicable, but in any event no less than ten (10)
days prior to the date specified in such notice on which any such action is to
be taken.

ARTICLE 4. MISCELLANEOUS.

         4.1. No Rights as Shareholder. This Warrant shall not entitle the
Holder to any of the rights of a shareholder of the Company except upon exercise
in accordance with the terms hereof.

         4.2. Legends. The Shares (and the securities issuable, directly or
indirectly, upon conversion of the Shares, if any) shall be imprinted with a
legend in substantially the following form:
<PAGE>
                                      -6-

         "THESE SHARES AND THE SECURITIES THAT MAY BE ACQUIRED UPON CONVERSION
         OF THESE SHARES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
         1933, AS AMENDED. NEITHER THESE SHARES NOR THE SECURITIES THAT MAY BE
         ACQUIRED UPON CONVERSION OF THESE SHARES MAY BE SOLD, OFFERED FOR SALE,
         PLEDGED OR HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT IN
         EFFECT UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO
         ACUSPHERE THAT SUCH REGISTRATION IS NOT REQUIRED OR UNLESS SOLD
         PURSUANT TO RULE 144 OR RULE 144A OF SUCH ACT.

         THESE SHARES AND THE SECURITIES THAT MAY BE ACQUIRED UPON CONVERSION OF
         THESE SHARES ARE SUBJECT TO A CONVERTIBLE NOTE AND WARRANT PURCHASE AND
         SECURITIES EXCHANGE AGREEMENT, DATED AS OF __________, 2003, AS AMENDED
         AND IN EFFECT FROM TIME TO TIME, A COPY OF WHICH IS ON FILE AT THE
         PRINCIPAL PLACE OF BUSINESS OF ACUSPHERE.

         THESE SHARES AND THE SECURITIES THAT MAY BE ACQUIRED UPON CONVERSION OF
         THESE SHARES ARE SUBJECT TO A VOTING AGREEMENT (A COPY OF WHICH MAY BE
         OBTAINED FROM ACUSPHERE), AS AMENDED FROM TIME TO TIME, AND BY
         ACCEPTING ANY INTEREST IN THESE SHARES OR SUCH SECURITIES THE PERSON
         ACCEPTING SUCH INTEREST SHALL BE DEEMED TO AGREE TO AND SHALL BECOME
         BOUND BY ALL THE PROVISIONS OF SUCH VOTING AGREEMENT."

         4.3. Waiver by Holder. No waiver of any obligation of the Company under
this Warrant shall be effective unless it is in a writing signed in accordance
with the amendment, waiver and exercise of remedies provisions set forth in
Section 6.9 of the Purchase Agreement. A waiver by the Holder of, or delay or
omission on the part of the Holder in exercising, any right or remedy under this
Warrant on any occasion shall not be a bar to exercise of the same right or
remedy on any subsequent occasion or of any other right or remedy at any time.

         4.4. Notice. Any notice required or permitted under this Warrant shall
be given in the manner set forth in the Purchase Agreement.

         4.5. Severability. In the event any one or more of the provisions of
this Warrant shall for any reason be held to be invalid, illegal or
unenforceable, in whole or in part or in any respect, or in the event that any
one or more of the provisions of this Warrant operate or would prospectively
operate to invalidate this Warrant, then and in any such event, such
provision(s) only shall be deemed null and void and shall not affect any other
provision of this Warrant and the remaining provisions of this Warrant shall
remain operative and in full force and effect and in no way shall be affected,
prejudiced, or disturbed thereby.

         4.6. Governing Law. This Warrant shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
<PAGE>
                                      -7-

         IN WITNESS WHEREOF, the Company has caused this Warrant to be executed
as an instrument under seal by its duly authorized representative as of the date
first above written.

Dated:  April  __, 2003               ACUSPHERE, INC.


(Corporate Seal)                      By: _______________________________
                                      Name: _____________________________
Attest:                               Title: ____________________________

____________________________
<PAGE>
                                                                      APPENDIX 1

                                 ACUSPHERE, INC.

                               NOTICE OF EXERCISE

         1. The undersigned hereby elects to purchase _____ Warrant Shares
pursuant to Section 1.1 of the attached Warrant, and tenders herewith payment of
the Exercise Price of such shares in full.

         1. The undersigned hereby elects to convert the attached Warrant into
Shares in the manner specified in Section 1.4 of the attached Warrant. This
conversion is exercised with respect to _______________ Warrant Shares.

         [Strike paragraph that does not apply.]

         2. Please issue a certificate or certificates representing said shares
in the name of the undersigned or in such other name as is specified below:

                _________________________________
                (Name)
                _________________________________

                _________________________________
                (Address)

         3. The undersigned represents it is acquiring the shares solely for its
own account and not as a nominee for any other party and not with a view toward
the resale or distribution thereof except in compliance with applicable
securities laws.


                                         ____________________________
                                         (Signature)

                                         ____________________________
                                         (Date)
<PAGE>
                           SCHEDULE OF WARRANTHOLDERS

<TABLE>
<CAPTION>
INVESTOR:                                                                       NUMBER OF SHARES ISSUABLE UPON EXERCISE OF WARRANTS:
<S>                                                                             <C>
Thomas Weisel Capital Partners, L.P.                                                             854,703

TWP CEO Founders' Circle (AI), L.P.                                                               19,747

TWP CEO Founders' Circle (QP), L.P.                                                               72,146

Thomas Weisel Capital Partners (Dutch), L.P.                                                      19,996

Thomas Weisel Capital Partners (Dutch II), L.P.                                                   19,996

Thomas Weisel Capital Partners Employee Fund, L.P.                                                 6,792

MVI Medical Venture Investments Limited                                                          203,662

Diamond Capital Management Inc. (as Investment Advisor for the Retirement                        141,377

Program Plan for Employees of Union Carbide Corporation and its Participating

Subsidiary Companies)

Alta V Limited Partnership                                                                       241,175

Customs House Partners                                                                             2,534

Polaris Venture Partners, L.P.                                                                   209,105

Polaris Venture Partners Founders' Fund, L.P.                                                     12,510

Audax Private Equity Fund, L.P.                                                                  164,449

Audax Co-Invest, L.P.                                                                             13,771

Audax Trust Co-Invest, L.P.                                                                           33

BancBoston Ventures, Inc.                                                                        151,743

Private Equity Portfolio Fund II, LLC                                                             57,613

Bank of America Ventures                                                                         370,871

BA Venture Partners II                                                                            41,208

Technology Funding Partners III, L.P.                                                             84,229

Technology Fund Venture Partners V, an Aggressive Growth Fund, L.P.                               53,885

DeBar Investment Partnership LLP                                                                   3,394

Dintersmith Family Partnership                                                                     1,656

Robert S. Langer                                                                                   2,898

David Norman                                                                                       8,003

TOTAL:                                                                                         2,757,495
</TABLE>