Clinical implementation of dynamic multileaf collimation for compensated bladder treatments.
OBJECTIVE
To describe the clinical implementation of dynamic multileaf collimation (DMLC). Custom compensated four-field treatments of carcinoma of the bladder have been used as a simple test site for the introduction of intensity modulated radiotherapy.


METHODS
Compensating intensity modulations are calculated from computed tomography (CT) data, accounting for scattered, as well as primary 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-time electronic portal imaging.


RESULTS
Seven patients have been treated using DMLC. The technique improves dose homogeneity within the target volume, reducing high dose areas and compensating 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 site for DMLC in an extremely busy clinic.
Budgell
G J
GJ
North Western Medical Physics, Christie Hospital NHS Trust, Wilmslow Road, Withington, M20 4BX, Manchester, UK.
Mott
J H
JH
Logue
J P
JP
Hounsell
A R
AR
D002277:Carcinoma / Q000175:diagnosis / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D019047:Phantoms, Imaging; D011379:Prognosis; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods*; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*