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Inverse‐planned modulated‐arc total‐body irradiation
Author(s) -
Kirby Neil,
Held Mareike,
Morin Olivier,
Fogh Shan,
Pouliot Jean
Publication year - 2012
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 - 10.1118/1.4705366
Subject(s) - imaging phantom , ionization chamber , nuclear medicine , radiation treatment planning , quality assurance , electromagnetic shielding , dosimetry , dose profile , total body irradiation , linear particle accelerator , materials science , biomedical engineering , radiation therapy , medicine , optics , beam (structure) , physics , radiology , ionization , surgery , ion , external quality assessment , pathology , quantum mechanics , chemotherapy , cyclophosphamide , composite material
Purpose: To develop a simple and robust method for inverse‐planned total‐body irradiation (TBI) that is more comfortable and has better dose homogeneity than the conventional forward‐planned techniques and that can be delivered in a standard‐sized treatment vault.Methods: Modulated‐arc TBI (MATBI) utilizes an arc of static open‐field beams to irradiate patients as they lay on a stationary couch beneath the gantry, with cerrobend blocks suspended over organs at risk to provide shielding. Prior to treatment, full‐body computed tomography (CT) images are acquired of each patient and imported into the PINNACLE 3 planning system, which modulates the monitor units for the open‐field beams to optimize the body dose uniformity. The volume of the body within 10% of the prescription dose, V(±10), is used as a metric to evaluate the dose uniformity. For comparison to MATBI, the dose distribution of a conventional forward‐planned treatment is also calculated. Quality assurance measurements are acquired before treatment by delivering the plans to a phantom and during treatment with an ionization chamber inside a buildup block, placed between the patient's ankles.Results: For MATBI, the achieved values of V(±10) were 75.8%, 90.2%, 84.6%, and 79.8% compared to 60.3%, 77.4%, 65.6%, and 68.5% for the conventional TBI technique, respectively. The pretreatment ion chamber measurements in the phantom had an average error of 1.2%. Those acquired during treatment had larger errors, with most points being within 3% of predictions.Conclusions: MATBI provides better dose uniformity and comfort than the conventional forward‐planned TBI techniques. In addition, the technique can be implemented on most linacs, in standard‐sized vaults, without the use of a translating couch.