AMERICAN SHARED HOSPITAL SERVICES INCREASES ITS EQUITY INVESTMENT IN STILL RIVER SYSTEMS, DEVELOPER OF THE CLINATRON 250 PROTON BEAM RADIATION THERAPY DEVICE San Francisco, CA

AMERICAN SHARED HOSPITAL SERVICES

INCREASES ITS EQUITY INVESTMENT IN STILL RIVER SYSTEMS,

DEVELOPER OF THE CLINATRON 250 PROTON BEAM RADIATION THERAPY DEVICE

San Francisco, CA, September 10, 2007 AMERICAN SHARED HOSPITAL SERVICES (AMEX,PCX:AMS), a

leading provider of turnkey technology solutions for advanced radiosurgical and radiation therapy

services, announced today that it has increased its equity interest in privately owned Still River

Systems, Inc., Littleton, Massachusetts, developer of the Clinatron 250 proton beam radiation

therapy (PBRT) device, with the purchase of an additional $617,000 of Still River convertible

In April 2006, AMS purchased $2 million of Still River convertible preferred stock and an option to

acquire two Clinatron 250 PBRT systems. AMS has contracted to place both of these devices, and

expects to commence lease agreements with Tufts-NEMC and M. D. Anderson Cancer Center Orlando for

the Still River PBRT systems in 2009, subject to the receipt of FDA clearance. AMS currently is

negotiating contracts for additional PBRT systems.

The Clinatron 250 device under development by Still River Systems is a single-treatment-room PBRT

system incorporating proprietary technology which may dramatically reduce the cost of implementing

this Medicare-approved therapy.

Today, more than half of the approximately one million new cancer patients diagnosed annually in

the United States alone receive some form of radiation therapy. Because proton beam radiation

therapy is widely regarded as the optimal radiation treatment for a wide variety of cancers, PBRT

is expected to capture a significant share of this market as the technology becomes more widely

available over the next few years. We see tremendous growth potential in Still River Systems

cost-effective PBRT device, especially when coupled with AMS s innovative financing programs. Our

investment in Still River Systems positions AMS to take full advantage of this next major advance

in radiation oncology, said Ernest A. Bates, M.D., Chairman and CEO of AMS.

American Shared Hospital Services provides turnkey technology solutions for advanced radiosurgical

and radiation therapy services. AMS is the world leader in providing Gamma Knife radiosurgery

services, a non-invasive treatment for malignant and benign brain tumors, vascular malformations

and trigeminal neuralgia (facial pain). The Company also offers the latest IGRT and IMRT systems,

as well as its proprietary Operating Room for the 21st Century concept. Through its equity

investment in Still River Systems, AMS also plans to complement these services with the Clinatron

250 proton beam radiation therapy (PBRT) system, which has not yet been approved by the FDA.

Safe Harbor Statement

This press release may be deemed to contain certain forward-looking statements with respect to the

financial condition, results of operations and future plans of American Shared Hospital Services,

which involve risks and uncertainties including, but not limited to, the risks of the Gamma Knife

business, the risks of developing its IMRT and The Operating Room for the 21st Century

programs, and the risks of investing in a development-stage company, Still River Systems, Inc.,

without a proven product. Further information on potential factors that could affect the financial

condition, results of operations and future plans of American Shared Hospital Services is included

in the filings of the Company with the Securities and Exchange Commission, including the Company s

Annual Report on Form 10-K and 10-K/A for the

year ended December 31, 2006, Form 10-Q for the three months ended March 31, 2007, Form 10-Q for

the three months ended June 30, 2007, and the definitive Proxy Statement for the Annual Meeting of

Shareholders held on June 14, 2007.