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Titolo:
Photon scatter in portal images: Accuracy of a fluence based pencil beam superposition algorithm
Autore:
McCurdy, BMC; Pistorius, S;
Indirizzi:
CancCare Manitoba, Dept Phys Med, Winnipeg, MB R3E 0V9, Canada CancCare Manitoba Winnipeg MB Canada R3E 0V9 Winnipeg, MB R3E 0V9, Canada Univ Manitoba, Dept Phys, Winnipeg, MB R3T 2N2, Canada Univ Manitoba Winnipeg MB Canada R3T 2N2 ys, Winnipeg, MB R3T 2N2, Canada Univ Manitoba, Dept Phys & Radiol, Winnipeg, MB R3T 2N2, Canada Univ Manitoba Winnipeg MB Canada R3T 2N2 ol, Winnipeg, MB R3T 2N2, Canada
Titolo Testata:
MEDICAL PHYSICS
fascicolo: 5, volume: 27, anno: 2000,
pagine: 913 - 922
SICI:
0094-2405(200005)27:5<913:PSIPIA>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
EXIT DOSE MEASUREMENTS; IMAGING DEVICE; CONVOLUTION/SUPERPOSITION METHOD; DOSIMETRY; VERIFICATION; RADIOTHERAPY; QUALITY; DISTRIBUTIONS; EPIDS;
Keywords:
portal imaging; predicting portal images; pencil beam algorithm; treatment verification;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Life Sciences
Citazioni:
33
Recensione:
Indirizzi per estratti:
Indirizzo: McCurdy, BMC CancCare Manitoba, Dept Phys Med, 100 Olivia St, Winnipeg, MBR3E 0V9, Canada CancCare Manitoba 100 Olivia St Winnipeg MB Canada R3E 0V9da
Citazione:
B.M.C. McCurdy e S. Pistorius, "Photon scatter in portal images: Accuracy of a fluence based pencil beam superposition algorithm", MED PHYS, 27(5), 2000, pp. 913-922

Abstract

The accuracy of a pencil beam algorithm to predict scattered photon fluence into portal imaging systems was studied, A data base of pencil beam kernels describing scattered photon fluence behind homogeneous water slabs (1-50cm thick) at various air gap distances (0-100 cm) was generated using the EGS Monte Carlo code. Scatter kernels were partitioned according to particle history: singly-scattered, multiply-scattered, and bremsstrahlung and positron annihilation photons. Mean energy and mean angle with respect to the incident photon pencil beam were also scored. This data allows fluence, mean energy, and mean angular data for each history type to be predicted usingthe pencil beam algorithm. Pencil beam algorithm predictions for 6 and 24 MV incident photon beams were compared against full Monte Carlo simulationsfor several inhomogeneous phantoms, including approximations to a lateral neck, and a mediastinum treatment. The accuracy of predicted scattered photon fluence, mean energy, and mean angle was investigated as a function of air gap, field size, photon history, incident beam resolution, and phantom geometry. Maximum errors in mean energies were 0.65 and 0.25 MeV for the higher and lower energy spectra, respectively, and 15 degrees for mean angles. The ability of the pencil beam algorithm to predict scatter fluence decreases with decreasing air Sap, with the largest error for each phantom occurring at the exit surface. The maximum predictive error was found to be 6.9% with respect to the total fluence on the central axis. By maintaining even a small air Sap (similar to 10 cm), the error in predicted scatter fluence may be kept under 3% for the phantoms and beam energies studied here. It isconcluded that this pencil beam algorithm is sufficiently accurate (using International Commission on Radiation Units and Measurements Report No, 24 guidelines for absorbed dose) over the majority of clinically relevant air gaps, for further investigation in a portal dose prediction algorithm. (C) 2000 American Association of Physicists in Medicine.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 13/07/20 alle ore 16:40:48