The Dosimetric Study of Static MLC Based Electronic Tissue Compensation using In-house Leaf Sequencing Software

摘要

In the traditional external beam radiotherapy, most treatments are delivered with radiation beams that are of uniform intensity across the field. This beam when incident on an irregular surface gives rise to unacceptable non-uniformity of dose within target volume or causes excessive irradiation of sensitive structures1. Many techniques have been devised including the use of wedged filters and tissue compensators to modify the intensity profile to produce more uniform composite dose distributions. Multileaf Collimator (MLC) also played a vital role in this aspect. In this study we explored the feasibility of using Static MLC for the Electronic Tissue Compensation (ETC) with In-house leaf sequencing software. In the "stop and shoot" method of achieving beam intensity modulation, a field is divided into a set of subfields each of which are irradiated with uniform beam intensity levels. Usually the fluence profile for each beam, provided by the inverse treatment planning software program is normalized into a specified number of intensity levels. The leaf sequencing software then generates the multileaf collimator (MLC) leaf position sequence required to produce the fluence profile.