TomoTherapy Incorporated (NASDAQ:TTPY) is entering the proton therapy business through a collaboration with scientists at California's Lawrence Livermore National Laboratory (LLNL). The makers of the TomoTherapy® Hi-Art® treatment system have agreed to fund continued development of a revolutionary accelerator that it expects will form the basis of a compact, low-cost proton therapy system. The system, which uses dielectric wall accelerator (DWA) technology, is the result of defense-related research and, with further development, has the potential to bring proton therapy into the medical mainstream. LLNL has worked to develop the technology with the UC Davis Cancer Center, which helped finance the early development of the DWA as a proton accelerator for cancer treatment.

It is acknowledged that proton beams are fundamentally superior to x-rays for radiation therapy and that high cost is the reason why only a fraction of a percent of all cancer patients are treated with proton therapy. If the collaboration is successful, TomoTherapy expects to provide DWA-based proton therapy systems for less than $20 million and that these units would be installed in existing radiation therapy facilities. Proton therapy is currently provided only within large, dedicated facilities, typically costing more than $100 million to establish. At this time there are only 25 such facilities worldwide, with six operational in the United States, including one at UC Davis that treats only ocular malignancies.

TomoTherapy co-founders Dr. Thomas ?Rock? Mackie and Paul Reckwerdt have spearheaded the relationship with LLNL that led to the collaboration. Reckwerdt will oversee the project.

Said Dr. Fred Robertson, TomoTherapy CEO, ?It is an honor for us to be chosen as a partner by Lawrence Livermore to commercialize this groundbreaking technology. Because proton therapy clearly has advantages for many cancer sufferers, it is an ideal complement to the TomoTherapy Hi-Art treatment system, which is being embraced by hospitals and cancer centers for its own distinct advantages.?

?We are excited about the possibility of applying this new technology to the field of cancer therapy and look forward to working with TomoTherapy and the UC Davis Cancer Center to make proton therapy widely available as a treatment option,? said LLNL's George Caporaso, the lead scientist on the Compact Proton Therapy Accelerator. ?This technology has grown out of work to develop compact high current accelerators as flash x-ray radiography sources for Nuclear Weapons Stockpile Stewardship.?

Dr. Ralph deVere White, director of the UC Davis Cancer Center and associate dean for Cancer Programs at UC Davis, said the research partnership of UC Davis Cancer Center and Lawrence Livermore National Laboratory, has fulfilled the mission for which it was created: to deliver translational research to advance health. ?With TomoTherapy, we are aiming to deliver the world's most sophisticated way of delivering radiation therapy."

About the DWA

A dielectric wall accelerator (DWA) is distinct from current proton accelerator technology in that energies of at least 200 MeV are expected to be achieved with a light ceramic-based structure approximately two meters in length, instead of with cyclotron or synchrotron devices several meters in diameter and weighing up to several hundred tons. It is intended that the DWA will be mounted on a gantry that rotates about the patient and directs radiation at the tumor?very similar to the configuration of the current TomoTherapy Hi-Art treatment system. A feature of DWA technology is that radiation will be produced in rapid pulses, creating small ?spots? of dose throughout the tumor. This enables a technique known as intensity-modulated proton therapy (IMPT), which is currently performed at only one facility in the world.

TomoTherapy has agreed to initially fund the development of a prototype of the DWA in order to test components and component integration. Subsequent development phases will include fabrication of a full-scale DWA and integration with state-of-the-art image guidance and patient positioning systems. A clinical prototype will first be installed and tested at the UC Davis Cancer Center, which has been a key driving force behind the effort to bring DWA technology to the medical industry.

About TomoTherapy Incorporated

TomoTherapy Incorporated has developed, manufactures and sells the TomoTherapy® Hi-Art® treatment system, an advanced radiation therapy system for the treatment of a wide variety of cancers. The Hi-Art treatment system combines integrated CT imaging with conformal radiation therapy to deliver sophisticated radiation treatments with speed and precision while reducing radiation exposure to surrounding healthy tissue. The company completed its initial public offering in May 2007 and its stock is traded on the NASDAQ Global Market under the symbol TTPY. To learn more about TomoTherapy, please visit our Web site at www.TomoTherapy.com.

About Lawrence Livermore National Laboratory

Founded in 1952, Lawrence Livermore National Laboratory has a mission to ensure national security and to apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.

About UC Davis Cancer Center

UC Davis Cancer Center, a program of the University of California, Davis, is the nation's 61st National Cancer Institute center. Its research program includes more than 280 scientists on three campuses: the UC Davis Health System in Sacramento, Calif., UC Davis in Davis, Calif., and Lawrence Livermore National Laboratory in Livermore, Calif. It is the first major cancer center to form a formal research partnership with a national laboratory. It is the only NCI center serving inland Northern California, a region of more than 6 million people.

Forward-Looking Statements

Statements in this release regarding future business, plans, events, expectations, products and other similar matters, including but not limited to statements using the terms ?can? and ?expect? constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements contained in this press release are subject to risks and uncertainties that could cause actual results to differ materially from those anticipated, including but not limited to risks inherent in the development and commercialization of new technology and products, and the other risks listed from time to time in TomoTherapy's filings with the U.S. Securities and Exchange Commission, which by this reference are incorporated herein. These forward-looking statements represent TomoTherapy's judgments as of the date of this press release. TomoTherapy assumes no obligation to update or revise the forward-looking statements in this release because of new information, future events or otherwise.

©2007 TomoTherapy Incorporated. All rights reserved. TomoTherapy, the TomoTherapy logo and Hi-Art are among trademarks or registered trademarks of TomoTherapy Incorporated.

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