The result is that patients only receive a high radiation dose where they need it and healthy tissue is preserved.
The problem with IMRT so far, however, is that it becomes increasingly difficult to verify that patients receive the prescribed dose of radiation. "IMRT prescriptions are based on very complex computer simulations, so it is important to validate these simulations by verifying exactly how much radiation is reaching the patient and where it is landing," says Aleksandar Jaksic, INVORAD project coordinator at Ireland's Tyndall National Institute.
INVORAD developed two sensors, a silicon diode and a p-channel metal-oxide semiconductor field-effect transistor (MOSFET), to do just that. "Several features, such as miniature size, response to types of radiation involved in radiotherapy, compatibility with microprocessors that enables real-time read-out and low cost, make these semiconductor sensors eminently suitable for the intended application," says Jaksic.
The diode sensor system is arranged in a series of modules containing 1069 individual diodes that can pick up incoming radiation.
"These diodes need to be very small and while there are commercial packaged diodes out there we needed diodes in bare die form with some novel properties so we developed the diodes ourselves, here at the Tyndall Institute," says Jaksic.
The arrays are extremely accurate and can track radiation at micro-Gray resolution over millimetres of spatial resolution.
These are then linked to a read-out unit and a PC with dedicated software. The read-out unit is based on ASIC (Application Specific Integrated Circuit) and mic