Comparison of multileaf collimation and shield alloy blocks on an irregular target volume

Multileaf collimation (MLC) is a crucial component dynamic conformal radiotherapy and can be used as a replacement for conventional blocks. The most appropriate volumetric approach for the lesion's shape is achieved by MLC by conforming the prescribed dose to the critical structure or normal tissue dose. In this study, the edge effects of dose profiles on an irregular radiation field obtained by MLC and shield alloy blocks drawn by a water-phantom system were compared. We used a SL25 linac machine with MLC consisting of 40 pairs of opposing leaves and conventional alloy block shielding on a water phantom system. We found no significant edge effect difference between MLC and conventional shielding, but MLC showed clear advantages over conventional blocks in terms of time-saving, repeatability, and reliability.