Time-of-flight neutron rejection to improve prompt gamma imaging for proton range verification
| Autor: | Patricia Cambraia Lopes, Marco Pinto, D. Oxley, Dennis R. Schaart, Aleksandra Biegun, Peter Dendooven, Frank Verhaegen, Enrica Seravalli, Paulo Crespo, Ilaria Rinaldi, Katia Parodi |
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| Přispěvatelé: | KVI - Center for Advanced Radiation Technology, Research unit Medical Physics, Radiotherapie, RS: GROW - School for Oncology and Reproduction |
| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
Time Factors
Photon Proton Astrophysics::High Energy Astrophysical Phenomena Nuclear Theory Physics::Medical Physics Imaging phantom Collimated light 030218 nuclear medicine & medical imaging Nuclear physics COMPTON CAMERA 03 medical and health sciences 0302 clinical medicine POSITRON-EMISSION-TOMOGRAPHY Proton Therapy Radiology Nuclear Medicine and imaging Neutron ION THERAPY Radionuclide Imaging Nuclear Experiment MCNPX Neutrons Physics Range (particle radiation) Radiological and Ultrasound Technology Phantoms Imaging business.industry TREATMENT UNCERTAINTIES Gamma ray TOF-PET Radiotherapy Dosage Radiotherapy Computer-Assisted IRRADIATION Time of flight 030220 oncology & carcinogenesis Physics::Accelerator Physics SENSITIVITY Nuclear medicine business Monte Carlo Method SYSTEM RADIOTHERAPY |
| Zdroj: | Physics in Medicine and Biology, 57(20), 6429-6444. IOP PUBLISHING LTD Physics in Medicine and Biology, 57(20), 6429-6444. IOP Publishing Ltd. Physics in Medicine and Biology; Vol 57 Physics in Medicine and Biology |
| ISSN: | 0031-9155 |
| Popis: | Therapeutic proton and heavier ion beams generate prompt gamma photons that may escape from the patient. In principle, this allows for real-time, in situ monitoring of the treatment delivery, in particular, the hadron range within the patient, by imaging the emitted prompt gamma rays. Unfortunately, the neutrons simultaneously created with the prompt photons create a background that may obscure the prompt gamma signal. To enhance the accuracy of proton dose verification by prompt gamma imaging, we therefore propose a time-of-flight (TOF) technique to reject this neutron background, involving a shifting time window to account for the propagation of the protons through the patient. Time-resolved Monte Carlo simulations of the generation and transport of prompt gamma photons and neutrons upon irradiation of a PMMA phantom with 100, 150 and 200 MeV protons were performed using Geant4 (version 9.2.p02) and MCNPX (version 2.7.D). The influence of angular collimation and TOF selection on the prompt gamma and neutron longitudinal profiles is studied. Furthermore, the implications of the proton beam microstructure (characterized by the proton bunch width and repetition period) are investigated. The application of a shifting TOF window having a width of Delta TOFz = 1.0 ns appears to reduce the neutron background by more than 99%. Subsequent application of an energy threshold does not appear to sharpen the distal falloff of the prompt gamma profile but reduces the tail that is observed beyond the proton range. Investigations of the influence of the beam time structure show that TOF rejection of the neutron background is expected to be effective for typical therapeutic proton cyclotrons. |
| Databáze: | OpenAIRE |
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