The photon radiosurgery system (PRS) uses an NEC V25+ 16bit CISC microcontroller with an enhanced X86 instruction to control a beam of therapeutic radiation delivered to tumour sites. The control offered by the device allows clinicians to treat tumours with minimal damage to surrounding tissue. The PRS is a portable device that resembles a hypodermic needle and delivers x-ray photons to a controlled site. The system is linked to a monitor so the surgeon can make sure the right amount of radiation is being administered. Trials on the treatment of brain and skin tumours have taken place and the system is now being extended to the treatment of breast cancer. Professor Michael Baum treated the first UK breast cancer patient at Middlesex hospital in July and a second patient received treatment a few months later. Eighteen other women will be involved in the trial over the coming months. Baum's team will have to wait three to five years to find out if the patients are entirely clear of cancer. Baum remains optimistic that the system will replace conventional radiation treatment -- external radiation administered through a linear accelerator -- and describes his grandiose schemes for the future. "Conventional treatments are both costly and time consuming for the patient. Using a linear accelerator, current post-op radiation treatments take six weeks. It is labour intensive and difficult to get right. If this new system works, all the radiotherapy can be done at the same time the surgeon is removing the tumour, adding only about 20 minutes to the operation." Compared to the linear accelerator, the photon radiosurgery system is cheap -- at around a tenth of the cost and can be moved from hospital to hospital -- a great advantage in third world countries.