AccSys is an integrated design and manufacturing company specializing in the development, production, installation and servicing of ion linear accelerator (linac) systems using the radiofrequency quadrupole (RFQ) linac and drift-tube linac (DTL). Capabilities include: high power RF cavity amplifiers and amplifier systems operating in the UHF frequency range. ion linear accelerators for producing radioisotopes & neutrons for medical & industrial diagnostics. In May 2001, Hitachi, Ltd. acquired an eighty percent (80%) stake in AccSys Technology, Inc., (AccSys) to expand its proton beam therapy systems business. Hitachi will apply AccSyss ion linear accelerator (linac) technology to its in-house developed proton beam therapy system (PROBEAT) expected to enable Hitachi to aim for the top share in this market. Proton beam therapy is a new type of cancer treatment. It is a localized form of radiation therapy, in which a proton beam is directed solely at a tumor lying deep within the body in order to destroy the tumor. When a proton beam is used to treat a tumor, the side effects are minimal compared with those of a conventional electron beam and X-ray radiation therapy. This is because the proton beam has little effect on the surrounding healthy cells and only the cancerous cells are treated. Compared with surgical treatment and chemotherapy, the strain on the patient is much less. Proton beam therapy is drawing attention worldwide as a promising application for the treatment of a variety of difficult-to-treat diseases. In the United States, this therapy became widely accepted in 2000 following its approval for insurance coverage that year. It also appears likely that it will be accepted for insurance coverage in Europe and Japan in the near future.