Effects of nuclear interactions on energy and stopping power in proton beam dosimetry

Laitano, R.F.; Rosetti, M.; Frisoni, M.

doi:10.1016/0168-9002(96)00421-4

Cited by 22 publications

(22 citation statements)

References 13 publications

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“…Further, nuclear interactions can play a significant role and secondary particles have to be tracked. Nuclear interaction products contribute significantly to ionization chamber response in particular in high energy beams (> 100 MeV) (Laitano et al 1996). The monitor chamber detects the energy loss that corresponds to the entrance region of a SOBP where the influence of nuclear interactions on dose is in general more pronounced than in the peak region (Paganetti 2002).…”

Section: Resultsmentioning

confidence: 99%

Monte Carlo calculations for absolute dosimetry to determine machine outputs for proton therapy fields

Paganetti¹

2006

Phys. Med. Biol.

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The prescribed dose in radiation therapy has to be converted into machine monitor units for patient treatment. This is done routinely for each spread-out Bragg peak (SOBP) field either by calibration measurements, by using analytical algorithms or by relying on empirical data. At the Northeast Proton Therapy Center, a monitor unit corresponds to a fixed amount of charge collected in a segmented transmission ionization chamber inside the treatment head. The goal of this work was to use a detailed Monte Carlo model of the treatment head to calculate the dose delivered to the patient as a function of ionization chamber reading, i.e. to yield absolute dose in patients in terms of machine monitor units. The results show excellent agreement with measurements. For 50 SOBP fields considered in this study, the mean absolute difference between the experimental and the calculated value is 1.5%, where ~50% of the fields agree within 1%. This is within the uncertainties of the data. The Monte Carlo method has advantages over analytical algorithms because it takes into account scattered and secondary radiation, does not rely on empirical parameters, and provides a tool to study the influence of parts of the treatment head on the ionization chamber reading. Compared to experimental methods the Monte Carlo method has the advantage of being able to verify the dose in the patient geometry.

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Section: Resultsmentioning

confidence: 99%

Monte Carlo calculations for absolute dosimetry to determine machine outputs for proton therapy fields

Paganetti¹

2006

Phys. Med. Biol.

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“…The effects of nuclear interactions on the dose distribution have been presented by other investigators. 20,21 However, the effect of nuclear secondaries on the activity distribution has not been reported in detail yet. The radioisotopic images suggest that a library of accurate cross sections over a range of energies needs to be developed for neutron-and protoninduced reactions on the elements in tissue.…”

Section: B Nuclear Secondaries and The Production Of 14 Omentioning

confidence: 99%

“…8 Since then the radioactivity induced in tissues by photon, [8][9][10] proton, 11,12 neutron, 13 pion, [14][15][16] and heavy-ion radiotherapy beams [17][18][19] has been investigated. This induced activity has been studied as a source of patient dose, 11,20,21 as a means of determining elemental tissue composition, 10,11,13 and for determining dose distributions. 14,15,17,[22][23][24][25][26][27][28][29][30][31] In vivo dose localization by imaging positron-emitting nuclei is considered essential for light-ion, and radioactive-ion beam therapy.…”

Section: Introductionmentioning

confidence: 99%

On‐line monitoring of radiotherapy beams: Experimental results with proton beams

et al. 1999

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Proton radiotherapy is a powerful tool in the local control of cancer. The advantages of proton radiotherapy over gamma-ray therapy arise from the phenomenon known as the Bragg peak. This phenomenon enables large doses to be delivered to well-defined volumes while sparing surrounding healthy tissue. To fully realize the potential of this technique the location of the high-dose volume must be controlled very accurately. An imaging system was designed and tested to monitor the positron-emitting activity created by the beam as a means of verifying the beam's range, monitoring dose, and determining tissue composition. The prototype imaging system consists of 12 pairs of cylindrical BGO detectors shielded in lead. Each crystal was 1.9 cm in diameter, 5.0 cm long, and separated by 0.5 cm from other detectors in the row. These are arranged in two rows, 60 cm apart, with the proton beam and tissue phantoms half-way between and parallel to the detector rows. Experiments were conducted with 150 MeV continuous and macro-pulsed proton beams which had beam currents ranging from 0.14 nA to 1.75 nA. The production and decay of short-lived isotopes, 15O and 14O, was studied using 1 min irradiations with a continuous beam. These isotopes provide a significant signal on short time scales, making on-line imaging possible. Macro-pulsed beams, having a period of 10 s, were used to study on-line imaging and the production and decay of long-lived isotopes, 13N, 11C, and 18F. Decay data were acquired and on-line images were obtained between beam pulses and indicate that range verification is possible, for a 150 MeV beam, after one beam pulse, to within the 1.2 cm resolution limit of the imaging system. The dose delivered to the patient may also be monitored by observing the increase in the number of coincidence events detected between successive beam pulses. Over 80% of the initial positron-emitting activity is from 15O while the remainder is primarily 11C, 13N, 14O with traces of 18F, and 10C. Radioisotopic imaging may also be performed along the beam path by fitting decay data collected after the treatment is complete. Using this technique, it is shown that variations in elemental composition in inhomogenous treatment volumes may be identified and used to locate anatomic landmarks. Radioisotopic imaging also reveals that 14O is created well beyond the Bragg peak, apparently by secondary neutrons.

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“…The relative importance of the two depends on the application. 1,4,7 For instance, beam line design is relatively insensitive to the nuclear model. Although plenty of nuclear interactions occur in the beam line, very few nuclear secondaries reach the patient because of their large angles and short ranges.…”

Section: Introductionmentioning

confidence: 99%

Test of GEANT3 and GEANT4 nuclear models for 160 MeV protons stopping in

Paganetti

Gottschalk

2003

Medical Physics

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Monte Carlo simulations are used for many problems in proton radiation therapy, some of which are sensitive to the nuclear interaction model. The available models have been little tested in the regime of interest, namely in their ability to predict the secondary particle yield, including their angle and energy, when 70-250 MeV protons stop in various materials. The present study provides one such test in carbon, complementing a previous one in copper. Using a multilayer Faraday cup we have measured the projected range distribution of charged nuclear secondaries from 160 MeV protons stopping in polyethylene (CH2). To test the popular GEANT Monte Carlo we have simulated the experiment with GEANT3 using the "Gheisha" (default) and "Fluka" models and with GEANT4.5 using the "low-energy" and "precompound" models. The GEANT3/Fluka and GEANT4/precompound simulations agree moderately well with the observed range distribution. The data are given in a convenient form for testing other Monte Carlo programs.

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Effects of nuclear interactions on energy and stopping power in proton beam dosimetry

Cited by 22 publications

References 13 publications

Monte Carlo calculations for absolute dosimetry to determine machine outputs for proton therapy fields

Monte Carlo calculations for absolute dosimetry to determine machine outputs for proton therapy fields

On‐line monitoring of radiotherapy beams: Experimental results with proton beams

Test of GEANT3 and GEANT4 nuclear models for 160 MeV protons stopping in

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