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IMRT planning and delivery incorporating daily dose from mega‐voltage cone‐beam computed tomography imaging
Author(s) -
Miften Moyed,
Gayou Olivier,
Reitz Bodo,
Fuhrer Russell,
Leicher Brian,
Parda David S.
Publication year - 2007
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 - 10.1118/1.2779127
Subject(s) - cone beam computed tomography , medicine , nuclear medicine , radiation treatment planning , rectum , image guided radiation therapy , radiation therapy , medical imaging , dosimetry , prostate cancer , prostate , radiology , computed tomography , cancer , surgery
The technology of online mega‐voltage cone‐beam (CB) computed tomography (MV‐CBCT) imaging is currently used in many institutions to generate a 3D anatomical dataset of a patient in treatment position. It utilizes an accelerator therapy beam, delivered with 200° gantry rotation, and captured by an electronic portal imager to account for organ motion and setup variations. Although the patient dose exposure from a single volumetric MV‐CBCT imaging procedure is comparable to that from standard double‐exposure orthogonal portal images, daily image localization procedures can result in a significant dose increase to healthy tissue. A technique to incorporate the daily dose, from a MV‐CBCT imaging procedure, in the IMRT treatment planning optimization process was developed. A composite IMRT plan incorporating the total dose from the CB was optimized with the objective of ensuring uniform target coverage while sparing the surrounding normal tissue. One head and neck cancer patient and four prostate cancer patients were planned and treated using this technique. Dosimetric results from the prostate IMRT plans optimized with or without CB showed similar target coverage and comparable sparing of bladder and rectum volumes. Average mean doses were higher by 1.6 ± 1.0 Gy for the bladder and comparable for the rectum ( − 0.3 ± 1.4 Gy ) . In addition, an average mean dose increase of 1.9 ± 0.8 Gy in the femoral heads and 1.7 ± 0.6 Gy in irradiated tissue was observed. However, the V 65 and V 70 values for bladder and rectum were lower by 2.3 ± 1.5 % and 2.4 ± 2.1 % indicating better volume sparing at high doses with the optimized plans incorporating CB. For the head and neck case, identical target coverage was achieved, while a comparable sparing of the brain stem, optic chiasm, and optic nerves was observed. The technique of optimized planning incorporating doses from daily online MV‐CBCT procedures provides an alternative method for imaging IMRT patients. It allows for daily treatment modifications where other volumetric tomographic imaging techniques may not be feasible and/or available and where accurate patient localization with a high degree of precision is required.