Test the waters

WATER HAS SIMILAR properties to some human tissue in the way that it scatters and absorbs radiation. This is why radiotherapy physicists use large tanks filled with water when testing linear accelerators, or linacs – complex machines used to deliver radiotherapy at The Royal Marsden. During quality assurance checks and machine commissioning, radiation is passed through the tank to allow the measurement of its effects. As well as being cheap and readily available, water allows the physicist to move a detector around in the tank to measure the amount of radiation in different places. The green lasers are used to precisely set up the water tank, as well as to align the patient on the linac bed prior to radiotherapy. Find out more about the work of our radiotherapy physicists on page 18.