It has always been the aim of radiotherapy to conform high dose volume to the target. Normal practice was to use rectangular beams with limited use of blocking. Inevitably, some normal tissue was unnecessarily irradiated to high doses. Improved levels of conformation can be achieved by positioning shaped alloy blocks in the beam and, automatically, with a feature on the accelerator known as multi-leaf collimators (MLC). Here, the beam can be shaped under computer control by sliding a series of 1 cm-wide leaves into the beam.
By minimizing the amount of normal tissue irradiated to high dose, it may be possible to deliver higher doses to the target, thereby improving tumour control without increasing morbidity.
Was this article helpful?