Beam Delivery Using Passive Scattering *

2018 ◽  
pp. 137-167
Author(s):  
Roelf Slopsema
Keyword(s):  
Beam Delivery ◽  
Passive Scattering

scholarly journals Dosimetric Comparison of Passive Scattering and Active Scanning Proton Therapy Techniques Using GATE Simulation

2021 ◽  
Author(s):  
Ali Asadi ◽  
Azadeh Akhavanallaf ◽  
Seyed Abolfazl Hosseini ◽  
Naser Vosoughi ◽  
Habib Zaidi
Keyword(s):  
Proton Beam ◽  
Proton Therapy ◽  
Dose Volume Histogram ◽  
Dose Ratio ◽  
Entrance Dose ◽  
Dose Volume ◽  
Active Scanning ◽  
The Difference ◽  
Beam Delivery ◽  
Passive Scattering

Abstract Background: In this study, two proton beam delivery designs, i.e. passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo (MC) particle transport code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements.Method: A water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120-235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including Bragg peak width (BPW50), peak position, range, peak-to-entrance dose ratio, and dose volume histogram have been analyzed under the same conditions. Furthermore, the clinical test cases introduced by AAPM TG-119 were simulated in both beam delivery modes to compare the relevant clinical values obtained from Dose Volume Histogram (DVH) analysis. Results: The parametric comparison in the water phantom between the two techniques revealed that the value of peak-to-entrance dose ratio in PSPT is considerably higher than that from PBS by a factor of 8%. In addition, the BPW50 in PSPT was increased by a factor of 7% compared to the corresponding value obtained from PBS model. TG-119 phantom simulations showed that the difference of PTV mean dose between PBS and PSPT techniques are up to 1.8 % while the difference of max dose to organ at risks (OARs) exceeds 50%. Conclusion: The results demonstrated that the active scanning proton therapy systems was superior in adapting to the target volume, better dose painting, and lower out-of-field dose compared to passive scattering design.

scholarly journals Adaptive planning based on single beam optimization in passive scattering carbon ion radiotherapy for patients with pancreatic cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yang Li ◽  
Yoshiki Kubota ◽  
Masahiko Okamoto ◽  
Shintaro Shiba ◽  
Shohei Okazaki ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Carbon Ion Radiotherapy ◽  
Adaptive Planning ◽  
Carbon Ion ◽  
Single Beam ◽  
Original Plan ◽  
Image Registration Algorithm ◽  
Passive Scattering ◽  
Accumulated Dose ◽  
Dose Difference

Abstract Background Daily anatomical deviations may distort the dose distribution in carbon ion radiotherapy (CIRT), which may cause treatment failure. Therefore, this study aimed to perform re-planning to maintain the dose coverage in patients with pancreatic cancer with passive scattering CIRT. Methods Eight patients with pancreatic cancer and 95 daily computed tomography (CT) sets were examined. Two types of adaptive plans based on new range compensators (RCs) (AP-1) and initial RCs (AP-2) were generated. In AP-2, each beam was optimized by manually adjusting the range shifter thickness and spread-out Bragg peak size to make dose reduction by < 3% of the original plan. Doses of the original plan with bone matching (BM) and tumor matching (TM) were examined for comparison. We calculated the accumulated dose using the contour and intensity-based deformable image registration algorithm. The dosimetric differences in respect to the original plan were compared between methods. Results Using TM and BM, mean ± standard deviations of daily CTV V95 (%) difference from the original plan was − 5.1 ± 6.2 and − 8.8 ± 8.8, respectively, but 1.2 ± 3.4 in AP-1 and − 0.5 ± 2.1 in AP-2 (P < 0.001). AP-1 and AP-2 enabled to maintain a satisfactory accumulated dose in all patients. The dose difference was 1.2 ± 2.8, − 2,1 ± 1.7, − 7.1 ± 5.2, and − 16.5 ± 15.0 for AP-1, AP-2, TM, and BM, respectively. However, AP-2 caused a dose increase in the duodenum, especially in the left–right beam. Conclusions The possible dose deterioration should be considered when performing the BM, even TM. Re-planning based on single beam optimization in passive scattering CIRT seems an effective and safe method of ensuring the treatment robustness in pancreatic cancer. Further study is necessary to spare healthy tissues, especially the duodenum.

scholarly journals Geometrical Scaling of Antiresonant Hollow-Core Fibers for Mid-Infrared Beam Delivery

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 420
Author(s):  
Ang Deng ◽  
Wonkeun Chang
Keyword(s):  
Structural Parameters ◽  
Transmission Band ◽  
Confinement Loss ◽  
Hollow Core ◽  
Core Size ◽  
Core Diameter ◽  
Mid Infrared ◽  
The Core ◽  
Tubular Type ◽  
Beam Delivery

We numerically investigate the effect of scaling two key structural parameters in antiresonant hollow-core fibers—dielectric wall thickness of the cladding elements and core size—in view of low-loss mid-infrared beam delivery. We demonstrate that there exists an additional resonance-like loss peak in the long-wavelength limit of the first transmission band in antiresonant hollow-core fibers. We also find that the confinement loss in tubular-type hollow-core fibers depends strongly on the core size, where the degree of the dependence varies with the cladding tube size. The loss scales with the core diameter to the power of approximately −5.4 for commonly used tubular-type hollow-core fiber designs.

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