title: Dose reconstruction for intensity-modulated radiation therapy using a non-iterative method and portal dose image.
abstract: A straightforward and accurate method was developed to verify the delivery of intensity-modulated radiation therapy (IMRT) and to reconstruct the dose in a patient. The method is based on a computational algorithm that linearly describes the physical relationship between beamlets and dose-scoring voxels in a patient and the dose image from an electronic portal imaging device (EPID). The relationship is expressed in the form of dose response functions (responses) that are quantified using Monte Carlo (MC) particle transport techniques. From the dose information measured by the EPID the received patient dose is reconstructed by inversely solving the algorithm. The unique and novel non-iterative feature of this algorithm sets it apart from many existing dose reconstruction methods in the literature. This study presents the algorithm in detail and validates it experimentally for open and IMRT fields. Responses were first calculated for each beamlet of the selected fields by MC simulation. In-phantom and exit film dosimetry were performed on a flat phantom. Using the calculated responses and the algorithm, the exit film dose was used to inversely reconstruct the in-phantom dose, which was then compared with the measured in-phantom dose. The dose comparison in the phantom for all irradiated fields showed a pass rate of higher than 90% dose points given the criteria of dose difference of 3% and distance to agreement of 3 mm.
authors: Radiation Oncology, Cooper University Hospital, Robert Wood Johnson School of Medicine, Camden, NJ 08103, USA.
authors: Inhwan Jason
authors: IJ
authors: Yeo
authors: Jae Won
authors: JW
authors: Jung
authors: Meng
authors: M
authors: Chew
authors: Jong Oh
authors: JO
authors: Kim
authors: Brian
authors: B
authors: Wang
authors: Steven
authors: S
authors: Dibiase
authors: Yunping
authors: Y
authors: Zhu
authors: Dohyung
authors: D
authors: Lee
mesh_terms: D000465:Algorithms; D006801:Humans; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results