Clinical implementation of dynamic multileaf collimation for compensated bladder treatments

Background and purpose: To describe the clinical implementation of dynamic multileaf collimation (DMLC). Custom compensated four-field treatments of c arcinoma of the bladder have been used as a simple test site for the introd uction of intensity modulated radiotherapy. Materials and Methods: Compensating intensity modulations are calculated fr om computed tomography (CT) data, accounting for scattered, as well as prim ary radiation. Modulations are converted to multileaf collimator (MLC) leaf and jaw settings for dynamic delivery on a linear accelerator. A full dose calculation is carried out, accounting for dynamic leaf and jaw motion and transmission through these components. Before treatment, a test run of the delivery is performed and an absolute dose measurement made in a water or solid water phantom. Treatments are verified by in vivo diode measurements and real-rime electronic portal imaging. Results: Seven patients have been treated using DMLC. The technique improve s dose homogeneity within the target volume, reducing high dose areas and c ompensating for loss of scatter at the beam edge. A typical total treatment time is 20 min. Conclusions: Compensated bladder treatments have proven an effective test s ite for DMLC in an extremely busy clinic. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.