A simple backprojection algorithm for 3D in vivo EPID dosimetry of IMRT treatments

Journal Article · Wed Jul 15 04:00:00 EDT 2009 · Medical Physics

DOI:https://doi.org/10.1118/1.3148482· OSTI ID:22100573

Wendling, Markus; McDermott, Leah N.; Mans, Anton; Sonke, Jan-Jakob; Herk, Marcel van; Mijnheer, Ben J. ^[1]

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1. Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands)

Treatment plans are usually designed, optimized, and evaluated based on the total 3D dose distribution, motivating a total 3D dose verification. The purpose of this study was to develop a 2D transmission-dosimetry method using an electronic portal imaging device (EPID) into a simple 3D method that provides 3D dose information. In the new method, the dose is reconstructed within the patient volume in multiple planes parallel to the EPID for each gantry angle. By summing the 3D dose grids of all beams, the 3D dose distribution for the total treatment fraction is obtained. The algorithm uses patient contours from the planning CT scan but does not include tissue inhomogeneity corrections. The 3D EPID dosimetry method was tested for IMRT fractions of a prostate, a rectum, and a head-and-neck cancer patient. Planned and in vivo-measured dose distributions were within 2% at the dose prescription point. Within the 50% isodose surface of the prescribed dose, at least 97% of points were in agreement, evaluated with a 3D {gamma} method with criteria of 3% of the prescribed dose and 0.3 cm. Full 3D dose reconstruction on a 0.1x0.1x0.1 cm{sup 3} grid and 3D {gamma} evaluation took less than 15 min for one fraction on a standard PC. The method allows in vivo determination of 3D dose-volume parameters that are common in clinical practice. The authors conclude that their EPID dosimetry method is an accurate and fast tool for in vivo dose verification of IMRT plans in 3D. Their approach is independent of the treatment planning system and provides a practical safety net for radiotherapy.

• OSTI ID: 22100573
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 7 Vol. 36; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
ALGORITHMS
CAT SCANNING
DOSIMETRY
HEAD
IMAGE PROCESSING
IN VIVO
NECK
NEOPLASMS
PLANNING
PROSTATE
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
RECTUM
VERIFICATION