Benchmarking EGSnrc in the kilovoltage energy range against experimental measurements of charged particle backscatter coefficients

Ali, Elsayed; Rogers, D. W. O.

doi:10.1088/0031-9155/53/6/002

Cited by 50 publications

(41 citation statements)

References 55 publications

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“…Monte Carlo simulations Simulated photon spectra for the Pantak beams used in this investigation were derived from a model utilising BEAMnrc and EGSnrc [5][6][7][8]. Spectra were simulated at 30 and 130 cm from the target focal spot for each of the beams generated with the filter inserts 4-8.…”

Section: Hvl Determinationmentioning

confidence: 99%

The variation of HVL with focal spot to chamber distance as a function of beam quality for the Pantak Therapax 150 X-ray unit and the implications on dose to water determination using the IPEMB code of practice

Baines

Sim

2014

Australas Phys Eng Sci Med

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Using a Pantak Therapax SXT 150 system HVL values for clinical beams generated with filters 4-8, were determined as a function of FCD (30-130 cm). Aluminium absorbers were placed midway between the focus and chamber with collimation to define both narrow and broad beam geometries. For filters 4-7 with broad beam geometry the HVL initially decreases as the FCD is increased from 30 cm and then increases as the FCD approaches 130 cm. In contrast filter 8 exhibits a reduction in HVL with increasing FCD attributed to the decreasing influence of absorber scatter. With narrow beam geometry the HVL of filter 4 increases as the FCD is increased. For other filters the HVL variation is similar to that for the broader beam albeit that for a given FCD the HVL is smaller, a consequence of reduced absorber scatter. Monte Carlo BEAMnrc simulations of filter 4-8 beams demonstrated a quality dependent air attenuation effect associated with an increase in HVL for lower quality beams with increasing FCD. Thus for the beams investigated in this work the variation of HVL with FCD can be interpreted in terms of the competing influences of absorber scatter, which tends to decrease the measured HVL, and a quality dependent in air attenuation that tends to increase the HVL with increasing FCD. In terms of an absorbed dose determination it is shown that changes of HVL with FCD resulted in variations of D w,z = 0 < ±0.5 %.

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Section: Hvl Determinationmentioning

confidence: 99%

The variation of HVL with focal spot to chamber distance as a function of beam quality for the Pantak Therapax 150 X-ray unit and the implications on dose to water determination using the IPEMB code of practice

Baines

Sim

2014

Australas Phys Eng Sci Med

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“…While the dose for megavoltage beams can be calculated with high accuracy using analytical methods, 24 the dose for kilovoltage beams can be accurately calculated with the Monte Carlo (MC) method, 25,26 and this strategy was employed here.…”

Section: Methodsmentioning

confidence: 99%

Modality comparison for small animal radiotherapy: A simulation study

et al. 2013

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Purpose: Small animal radiation therapy has advanced significantly in recent years. Whereas in the past dose was delivered using a single beam and a lead shield for sparing of healthy tissue, conformal doses can be now delivered using more complex dedicated small animal radiotherapy systems with image guidance. The goal of this paper is to investigate dose distributions for three small animal radiation treatment modalities. Methods: This paper presents a comparison of dose distributions generated by the three approachesa single-field irradiator with a 200 kV beam and no image guidance, a small animal image-guided conformal system based on a modified microCT scanner with a 120 kV beam developed at Stanford University, and a dedicated conformal system, SARRP, using a 220 kV beam developed at Johns Hopkins University. The authors present a comparison of treatment plans for the three modalities using two cases: a mouse with a subcutaneous tumor and a mouse with a spontaneous lung tumor. A 5 Gy target dose was calculated using the EGSnrc Monte Carlo codes. Results: All treatment modalities generated similar dose distributions for the subcutaneous tumor case, with the highest mean dose to the ipsilateral lung and bones in the single-field plan (0.4 and 0.4 Gy) compared to the microCT (0.1 and 0.2 Gy) and SARRP (0.1 and 0.3 Gy) plans. The lung case demonstrated that due to the nine-beam arrangements in the conformal plans, the mean doses to the ipsilateral lung, spinal cord, and bones were significantly lower in the microCT plan (2.0, 0.4, and 1.9 Gy) and the SARRP plan (1.5, 0.5, and 1.8 Gy) than in single-field irradiator plan (4.5, 3.8, and 3.3 Gy). Similarly, the mean doses to the contralateral lung and the heart were lowest in the microCT plan (1.5 and 2.0 Gy), followed by the SARRP plan (1.7 and 2.2 Gy), and they were highest in the single-field plan (2.5 and 2.4 Gy). For both cases, dose uniformity was greatest in the single-field irradiator plan followed by the SARRP plan due to the sensitivity of the lower energy microCT beam to target heterogeneities and image noise. Conclusions:The two treatment planning examples demonstrate that modern small animal radiotherapy techniques employing image guidance, variable collimation, and multiple beam angles deliver superior dose distributions to small animal tumors as compared to conventional treatments using a single-field irradiator. For deep-seated mouse tumors, however, higher-energy conformal radiotherapy could result in higher doses to critical organs compared to lower-energy conformal radiotherapy. Treatment planning optimization for small animal radiotherapy should therefore be developed to take full advantage of the novel conformal systems.

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“…Unfortunately, the multiple-scattering process is not yet implemented and consequently it is not possible to estimate the backscattering coefficients with GEANT4. Accurate knowledge of the energy and angular distributions of keV charged particles is possible with the EGSnrc (Electron Gamma Shower) Monte Carlo code [72]. This code includes sophisticated low-energy physics comparable with PENELOPE.…”

Section: Backscattered Positronsmentioning

confidence: 99%

“…However, this background is clearly overestimated because the energy loss of the positron crossing the carbon foil is not taken into account. An estimation of the mean energy loss [74] [72] gives values of the order of few hundred eV that are significantly larger than the initial positron energy E 0 = 10 eV.…”

Section: Positron Backscattering From the Sio 2 Targetmentioning

confidence: 99%

Positronium portal into hidden sector: a new experiment to search for mirror dark matter

et al. 2010

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The understanding of the origin of dark matter has great importance for cosmology and particle physics. Several interesting extensions of the standard model dealing with solution of this problem motivate the concept of hidden sectors consisting of SU (3) C × SU (2) L × U (1) Y singlet fields. Among these models, the mirror matter model is certainly one of the most interesting. The model explains the origin of parity violation in weak interactions, it could also explain the baryon asymmetry of the Universe and provide a natural ground for the explanation of dark matter. The mirror matter could have a portal to our world through photon-mirror photon mixing (ε). This mixing would lead to orthopositronium (o − Ps) to mirror orthopositronium oscillations, the experimental signature of which is the apparently invisible decay of o − Ps. In this paper, we describe an experiment to search for the decay o − Ps → invisible in vacuum by using a pulsed slow positron beam and a massive 4π BGO crystal calorimeter. The developed high efficiency positron tagging system, the low calorimeter energy threshold and high hermiticity allow the expected sensitivity in mixing strength to be ε ≃ 10 −9 , which is more than one order of magnitude below the current Big Bang Nucleosynthesis limit and in a region of parameter space of great theoretical and phenomenological interest. The vacuum experiment with such sensitivity is particularly timely in light of the recent DAMA/LIBRA observations of the annual modulation signal consistent with a mirror type dark matter interpretation.

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Benchmarking EGSnrc in the kilovoltage energy range against experimental measurements of charged particle backscatter coefficients

Cited by 50 publications

References 55 publications

The variation of HVL with focal spot to chamber distance as a function of beam quality for the Pantak Therapax 150 X-ray unit and the implications on dose to water determination using the IPEMB code of practice

The variation of HVL with focal spot to chamber distance as a function of beam quality for the Pantak Therapax 150 X-ray unit and the implications on dose to water determination using the IPEMB code of practice

Modality comparison for small animal radiotherapy: A simulation study

Positronium portal into hidden sector: a new experiment to search for mirror dark matter

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