Design and development of motorized multileaf collimator for telecobalt unit.

A manual multileaf collimator developed for telecobalt unit was motorized to accomplish the easy movement of the leaves. The required field shaping using MLC could be achieved by either using template or display. The beam characteristics were investigated and then compared with those of customized blocks. The maximum interleaf leakage and the percentage of transmission measured at the depth of maximum ionization (0.5cm) were found to be 2.7% and 2.4%, respectively. The field shaping performed by the MLC was verified using film dosimetry. The comparative study of treatment plans of 3DCRT and IMRT between (60)Co beam and 6 MV beams was carried out. This MLC could be used as a substitute for conventional blocks in static fields, there by eliminating the effort and cost of fabricating customized blocks, the need for storage space for blocks and other practical difficulties during the process of the block making. It is also demonstrated that if a provision for IMRT delivery with MLC for (60)Co is made, could be a cost effective alternative to IMRT with 6 MV beam.