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Custom step wedge blocking using dynamic multileaf collimation for parametrial pelvic boost irradiation following brachytherapy for carcinoma of the cervix
Author(s) -
Popple Richard A.,
Kim Robert Y.,
Pareek Prem,
Duan Jun,
Shen Sui,
Brezovich Ivan A.
Publication year - 2003
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1604511
Subject(s) - brachytherapy , parametrial , collimated light , cervix , nuclear medicine , medicine , dosimetry , pelvis , radiation therapy , biomedical engineering , radiology , cervical cancer , optics , cervical carcinoma , physics , cancer , laser
Carcinoma of the cervix is typically treated with a combination of intracavitary brachytherapy and external beam radiation. The external beam dose is delivered with whole pelvis fields followed by split fields that protect midline organs at risk (bladder and rectum) while treating the parametria. Three approaches have been developed to shield midline structures: a simple rectangular block, a block customized to a single brachytherapy isodose line, and a step wedge filter constructed to conform to multiple brachytherapy isodose lines. A customized step wedge filter has the potential to produce a more homogeneous dose distribution but has not achieved widespread use due to labor intensive construction. We have developed a simple, novel method to produce a custom midline step wedge using dynamic multileaf collimation (dMLC). A comparison of film measurements in a phantom with the dose calculated by a commercial treatment planning system demonstrated agreement within 3% or 3 mm. The technique requires delivery times comparable to conventional techniques.