Effects of respiratory motion on dose uniformity with a charged particle scanning method

A three-dimensional spot-scanning technique for radiotherapy with protons is being developed at the Paul Scherrer Institute. As part of the effort to optimize the design and ensure clinically useful dose distributions, a computer simulation of the dose deposition in the presence of respiratory motio...

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Bibliographic Details
Published in:Physics in medicine & biology 1992-01, Vol.37 (1), p.223-234
Main Authors: Phillips, M H, Pedroni, E, Blattmann, H, Boehringer, T, Coray, A, Scheib, S
Format: Article
Language:English
Subjects:
Biological and medical sciences
Computer Simulation
Humans
Medical sciences
Movement - physiology
Protons
Radiotherapy Dosage
Radiotherapy, High-Energy
Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
Respiration - physiology
Technology. Biomaterials. Equipments. Material. Instrumentation
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Summary:A three-dimensional spot-scanning technique for radiotherapy with protons is being developed at the Paul Scherrer Institute. As part of the effort to optimize the design and ensure clinically useful dose distributions, a computer simulation of the dose deposition in the presence of respiratory motion was performed. Preliminary experiments have characterized the proton beam and the scanning procedure. Using these parameters, the computer program calculated the dose within a uniform volume of water in the presence of respiratory motion. Respiration amplitude, respiration period, respiration direction, number of fractions, size and position of the beamspots and rescanning multiplicity were systematically varied and the effect on the dose distribution determined. The dose uniformity is very dependent on the direction of the respiration relative to the three independent beam scanning directions. The dose uniformity decreases with increasing respiration amplitude, but has little response to changes in respiration frequency. Rescanning the volume, such as with fractionation, improves the dose uniformity roughly as the square root of the number of fractions. Broad, Gaussian beams result in better dose uniformity than narrow, sharply delineated ones, but produce slower dose fall-off at the edges of the scanned volume. Results of this work are being incorporated into the design of the system.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/37/1/016