Search This Blog

Monday, March 10, 2008

Custom blocks

Custom blocks used for shielding critical structures in the treatment of MV photon beams must be diverging.

THEY ARE NOT KEPT TO CLOSE TO THE PATIENT SKIN BECAUSE THAT WOULD INCREASE THE ELECTRON CONTAMINATION REACHING THE PATIENT

However, also consider this: Another reason not to keep it close to the patient is that if the block is closer to the patient, the larger size and weight of the block needes to shield the same volume will be a disadvantage. This occurs due to the beam divergence.

On the other hand, the transmission penumbra would be larger for a larger block to skin distance. A block to skin distance of about 15 to 20 cm is a good compromise for positioning custom blocks in patient treatment.

1 comment:

  1. The accuracy of a custom block can be checked using the simulator light field and the simulator film with the blocking area marked on it.

    ReplyDelete