Tangential Beam Research Articles

Thermal neutrons effect on improvement of electrical properties at CIGS thin film derived by sol-gel dip coating technique

The thermal neutron effect on the copper indium gallium (di)selenide thin film synthesized by the sol-gel dip-coating technique has explained the novel use of this film under extreme conditions (such as neutron irradiation fields). The thin film samples were treated by using the reactor neutrons to obtain the optimum neutron treatment for the determination of the variations in the structural characteristics. The gamma filter system has provided the evaluation of the high thermal neutron flux effect on the thin film samples by using the tangential beam tube of ITU TRIGA Mark–II reactor. The influence of the neutron effect on the electrical and optical features was explained by the rise of selenium amount in the thin film. The neutron-treated thin film samples (at 50 at. % Se) had a significant effect on the lowest electrical resistivity depending on the increase of the film density. The equivalent gamma dose of the neutron-treated thin film was determined as a 0.024 Gy dose level for neutron irradiation. The neutron treatment was significant to evaluate the decrease in the sheet resistivity of the thin film at this dose level. The neutron dose has led to a slight decrease in the optical band gap as the result of the thermal and epithermal neutrons' effects on the thin film.

Long-Term Results of Two Novel Weekly High Dose Palliative Radiotherapy Schedules in Un-Resectable or Metastatic Breast Cancers: Should We Clinically Chase Statistical Significance?

<h3>Purpose/Objective(s)</h3> In a developing country like India, large fungating breast cancers are not uncommon. This causes much deterioration in the quality of life attributed to the pain, growth of maggots, bleeding and discharge from the tumor. Surgery is often not feasible, and chemotherapy hardly brings any response in such aggressive lesions. Our initial results were presented in the last two consecutive ASTRO conferences. Our first paper showed the feasibility and safety of extreme hypo-fractionated radiotherapy (8 Gy weekly x 5 fractions) while the second one compared the toxicity and response outcomes of 40 Gy (8 Gy weekly x 5 fractions) versus 24 Gy (8 Gy x 3). This paper presents the long-term local control and survival rates between the two groups. <h3>Materials/Methods</h3> A total of 54 patients were enrolled in the study. 24 patients received 5 fractions of weekly 8 Gy to the involved breast, while 30 patients received 3 fractions of the same dose. Early and late toxicities were assessed using RTOG toxicity criteria and Harvard 4-point cosmesis respectively. All patients were planned with tangential photon beams, ensuring that the lungs and the heart are outside our treatment field. <h3>Results</h3> Out of the fifty-four patients, 45 (83%) patients were upfront metastatic, while the remaining were unresectable post-neoadjuvant chemotherapy. Thirty-eight (70%) of the patients were hormone receptor-negative, 23 (42%) patients were Her 2 Neu positive which were almost equally distributed between both arms. Overall, 44 patients (81%) had extensive skin involvement including ulcerations, fungating mass, extensive peud' orange and satellite nodules. All these patients were treated with bolus over the skin. The median largest size was 8cm (3.3cm-16cm). 25 patients (46%) succumbed to their disease, within a year of treatment, as expected in such an aggressive cohort. As reported earlier, 52% of the patients had greater than grade 2 dermatitis in the 40 Gy arm versus none of the patients who had dermatitis grade 2 or above in the 24 Gy arm (p=0.051). Again, as reported earlier, the cosmesis was significantly worse in the 40 Gy arm with 25 % of patients reporting fair or poor cosmesis as compared to none in the 24 Gy arm (p=0.052). Nine (37%) progressed in the 40 Gy arm, versus 16 (53%) in the 24 Gy arm with a median progression-free survival of 11.3months versus 13.6 months, favoring the arm with 40 Gy (p=0.04). There was a trend to increased overall survival in the 40 Gy arm (25 months versus 18 months), although this was not statistically significant (p=0.5). <h3>Conclusion</h3> This unique study compares two novel high doses of palliative radiotherapy for fungating, unresectable and chemo-resistant malignancies of the breast. The 24 Gy regimen can be safely used, with minimal concerns of toxicity and cosmesis. Although the toxicities and deterioration of cosmesis were higher for the 40 Gy arm, the statistically significant local disease control may warrant the use of this higher dose which may be individualized based on the size and nature of the lesion.

Comparison of Dose Calculation Algorithms for Accelerated Partial Breast Intensity Modulated Radiation Therapy

<h3>Purpose/Objective(s)</h3> Accelerated partial breast irradiation (APBI) using intensity modulated radiation therapy (IMRT) has been introduced recently as an alternative treatment to whole breast irradiation for early-stage breast cancer after lumpectomy. Plan dose volume constraints for IMRT APBI are complex, requiring a more conformal and homogenous dose distribution compared to traditional tangential beam based whole breast planning. Anisotropic Analytical Algorithm (AAA) has been widely used for photon dose calculation. An Advanced Dose Calculation algorithm (AXB) is known to achieve comparable accuracy to Monte Carlo (MC) algorithm, the golden standard dose calculation, in heterogeneous media. However, the clinical assessment of AXB has been lacking. As a preliminary study, we investigated the dosimetric differences between the AAA, AXB and MC calculations on APBI IMRT. <h3>Materials/Methods</h3> Six patients with left breast cancer who previously received APBI IMRT were analyzed for this study. All patients received 30 Gy in 5 fractions with a multi beam IMRT technique using AAA 15.6 in the planning system. The following dose volume constraints were used for acceptable plan criteria based on the APBI IMRT Florence trial and all 6 cases previously treated met these criteria: For target (lumpectomy PTV), V28.5 Gy=100%, maximum dose to target < = 105% and V105% <= 2%. For critical organs, uninvolved breast with V15 Gy < 25%, ipsilateral lung volume with V10 Gy < 20%, contralateral breast maximal dose < 1 Gy, heart with V3 Gy < 10%. For a dosimetric comparison, plans were generated with AXB 15.6, reporting dose to medium, for each corresponding AAA plan by re-optimizing with the same dose constraints. After that, AXB plans were re-calculated with MC algorithm using XVMC and compared to AXB. <h3>Results</h3> The re-calculated plans using AXB for the same monitor units with an identical beam setup from AAA plans did not meet the acceptable dose volume criteria. For re-optimized plans with AXB, target conformity index, V28.5Gy and critical organs met the criteria but maximum dose and V105% were still higher than AAA plans (107-110% vs. 104-105.5% for max dose; <i>p</i>=0.02, 2.5- 5.0% vs. 0-2% for V105; <i>p</i> <0.001). The plan comparison between AXB and MC calculations showed similarity in dose distributions and hotspot area, and minimum difference in dose volume histogram. <h3>Conclusion</h3> The present data is the first report to assess the AXB for APBI IMRT. All 6 plans needed the re-optimization for AXB from plans with AAA to comply with the dose volume constraints. However hot spot size was better with AAA plans. MC calculation confirmed the dose distribution and hot spot area produced by AXB. Therefore, the clinical use of AXB for APBI IMRT will need careful evaluation due to a discrepancy in dose distributions and hot spot sizes between AAA and AXB calculations.

Three-dimensional conformal radiotherapy breast cancer planning: An evaluation study comparing two techniques using homemade phantom

Anthropomorphic phantoms, which can provide equivalent human tissue densities, are one of the best solutions for verifying the quality of radiotherapy treatment plans produced by treatment planning systems. The goal of this work was to develop and fabricate a breast phantom to estimate radiation doses to the breast, lung, and surface using radiochromic films (EBT3) for basically two techniques of three-dimensional conformal radiotherapy (3D-CRT) treatment planning. Thirty-two acrylic slices were used to construct the phantom. Cork and Teflon were used to mimic the lung and bone, respectively. Four slots were drilled for dosimetry purposes to allow access to the areas of ionization chamber installation. Both wedged and open of two tangential beams techniques were applied. With a mean deviation of 1.02 ± 1.1, the variation between estimated point doses and measurements using the three ionization chambers ranged from 2.9 to 1.4%. Using 0, 5 and 10 mm boluses, the mean percentage doses on the target surface were 54.7, 88.6 and 91.7% of the prescribed dose (PD), respectively. The homemade phantom was appropriate for conducting quality control (QC) tests for 3D-CRT planning techniques for breast radiotherapy.

A study of skin marker alignment using different diamond-shaped light fields for prone breast external-beam radiation therapy.

For breast cancer patients treated in the prone position with tangential fields, a diamond-shaped light field (DSLF) can be used to align with corresponding skin markers for image-guided radiation therapy (IGRT). This study evaluates and compares the benefits of different DSLF setups. Seventy-one patients who underwent daily tangential kilovoltage (kV) IGRT were categorized retrospectively into four groups: (1) DSLF field size (FS)=10×10cm2 , gantry angle=90° (right breast)/270° (left breast), with the same isocenter as treatment tangential beams; (2) same as group 1, except DSLF FS=4×4cm2 ; (3) DSLF FS=4×4-6×8cm2 , gantry angle=tangential treatment beam, off-isocenter so that the DSLF was at the approximate breast center; and (4) No-DSLF. We compared their total setup time (including any DSLF/marker-based alignment and IGRT) and relative kV-based couch shift corrections. For groups 1-3, DSLF-only dose distributions (excluding kV-based correction) were simulated by reversely shifting the couch positions from the computed tomography plans, which were assumed equivalent to the delivered dose when both DSLF and IGRT were used. For patient groups 1-4, the average daily setup time was 2.6, 2.5, 5.0, and 8.3min, respectively. Their mean and standard deviations of daily kV-based couch shifts were 0.64±0.4, 0.68±0.3, 0.8±0.6, and 1.0±0.6cm. The average target dose changes after excluding kV-IGRT for groups 1-3 were-0.2%, -0.1%, and +0.4%, respectively, whereas DSLF-1 was most efficient in sparing heart and chest wall, DSLF-2 had lowest lung Dmax ; and DSLF-3 maintained the highest target coverage at the cost of highest OAR dose. In general, the use of DSLF greatly reduces patient setup time and may result in smaller IGRT corrections. If IGRT is limited, different DSLF setups yield different target coverage and OAR dose sparing. Our findings will help DSLF setup optimization in the prone breast treatment setting.

Comparison of Dosimetric Parameters and Clinical Outcomes in Inversely Planned Intensity-Modulated Radiotherapy (IMRT) and Field-in-Field Forward Planned IMRT for the Treatment of Breast Cancer.

IntroductionRadiotherapy has been an important component of the multimodality approach to breast cancer treatment. Newer techniques like three-dimensional radiotherapy had led to better dose distribution over the target volume, with tissue inhomogeneity corrections. To improve the uniformity in dose distribution, a newer technique of intensity modulation was developed, namely, intensity-modulated radiotherapy (IMRT). The present study was designed to compare inverse planned IMRT (IP IMRT) and field-in-field forward planned IMRT (FP IMRT) in patients with breast cancer receiving post-modified radical mastectomy (MRM) adjuvant radiotherapy in terms of dosimetric parameters and clinical outcomes.Materials and methodsFifty patients with breast cancer who have undergone MRM and need adjuvant radiotherapy were randomly assigned in a 1:1 ratio into two groups (25 each) of IP IMRT and FP IMRT techniques. The prescribed dose was 50 Gy in 25 fractions over five weeks. In IP IMRT, five to seven tangential beams were used for the chest wall, nodal volumes were placed at suitable angles with beam optimization, and calculation was carried out by the analytical anisotropic algorithm. For FP IMRT, two opposing tangential fields were created in such a way to achieve uniform dose distribution to the planning target volume (PTV), minimizing hot spot regions, and limiting dose to the ipsilateral lung and contralateral breast. Multiple subfields were manually designed to boost the area not included in the dose cloud. The dosimetric parameters were compared for PTV, lungs, heart, left anterior descending coronary artery (LAD), opposite breast, and esophagus.ResultsThe dosimetric parameters in terms of PTV are better for IP IMRT plans compared to FP IMRT plans (V95%: 92.3% vs 75.2%, p = 0.0001; D90%: 47.4 Gy vs 42.9 Gy, p = 0.0001; D95%: 44.9 Gy vs 37.1, p = 0.0004). The ipsilateral lung (V10Gy: 71.9% vs 41%, p = 0.00001; V20Gy: 42.14% vs 36.35%, p = 0.03; V40Gy: 17.31% vs 26.95%, p = 0.00004; Dmean: 20.91 Gy vs 17.88 Gy, p = 0.01) and contralateral lung (V5Gy: 31.8% vs 0.1%, p < 0.00001; V10Gy: 6.2% vs 0.08%, p = 0.0001) received statistically significant lesser doses in terms of low dose parameters in FP IMRT. In the heart, the dosimetric parameter V5 was significantly lower for FP IMRT (61.7% vs 9.7%, p = 0.00001) along with Dmean (10.92 Gy vs 4.01 Gy, p = 0.001). Similarly, LAD parameters showed comparable high dose volumes (V40Gy: 21.02% vs 16.26%; p = 0.29) in both groups and a trend toward reduction in mean dose (17.1% vs 9.2%; p = 0.05) in FP IMRT group, although low dose volumes were higher in IP IMRT group. In contralateral breast, doses in smaller volumes were better for FP IMRT plans (V0.5Gy: 59.7% vs 43.8%, p = 0.01; V0.6Gy: 54.07% vs 37.6%, p = 0.007; V1Gy: 40.9% vs 22.1%, p = 0.001; V2Gy: 28.7% vs 9.4%, p = 0.00003; V5Gy: 12.07% vs 4.2%, p = 0.0001). In esophagus, statistically significant lower doses were seen only in terms of Dmean (10.29 Gy vs 5.1 Gy; p = 0.03) with FP IMRT. No significant difference in terms of skin reactions and dysphagia was seen in both the groups.ConclusionBoth IP IMRT and FP IMRT techniques have advantages and disadvantages, and the superiority of one technique over another cannot be established in this study. The decision for choosing one technique over another can also be based on various patient-related factors weighing the risk of loco-regional recurrences to that of manifesting radiation-induced sequelae.

"Sequential Volumetric Modulated Arc Therapy (VMAT) Boost in Hy- brid Plan With Tangential Beams for Whole Breast Treatment: a Do- simetric Study "

"Purpose: Whole breast radiation therapy (WBRT) with a boost to the tumor bed following con-servative primary surgery in women with breast cancer (BC) plays a central role in reducing local recurrences and mortality. Volumetric modulated arc therapy (VMAT) technique has been shown to allow better dose conformation with low dose levels to organs at risk (OARs), compared to static fields three-dimensional Conformal Radiotherapy (3D-CRT). The aim of this study was to evaluate the feasibility and dosimetric advantages of sequential boost (SB), administered with VMAT tech-nique in hybrid plans with tangential beams for whole breast treatment. Material and methods: BC patients undergoing adjuvant RT from June to October 2020 were selected. ESTRO guidelines for the Clinical Target Volume (CTV) delineation were used. Total delivered dose was 60-66 Gy; 50 Gy in 2 Gy daily fractions for whole breast and 10-16 in 2 Gy daily fractions Gy to tumor bed was 10-16 Gy in 2 Gy daily fractions. Results: The analysis included 31 patients with BC treated with adjuvant RT following con-servative surgery. Hybrid treatment plans characterized by a 3D-CRT plan using tangential medi-olateral and lateromedial fields for the irradiation of the whole breast Planning Target Volume (PTV) and a sequential VMAT plan with 2 coplanar arches for boost PTV irradiation were gener-ated. Dosimetric analysis resulted in homogeneous target volumes coverage and OARs constraints compliance. As regarding to organs at risks (OARs), contralateral breast, ipsi- and contralateral lung and heart constraints values were analysed. Conclusions: In the frame BC RT, this dosimetric study showed that hybrid plans performed with 3D-CRT and VMAT techniques are feasible in terms of dosimetric outcomes. "

Collective Thomson scattering diagnostic with in situ calibration system for velocity space analysis in large helical device.

A collective Thomson scattering (CTS) diagnostic with a ±3 GHz band around a 77 GHz gyrotron probe beam was developed to measure the velocity distribution of bulk and fast ions in high-temperature plasmas. We propose a new in situ calibration method for a CTS diagnostic system combined with a raytracing code. The method is applied in two situations for electron cyclotron emission in plasmas and in a CTS diagnostic with a modulated probe beam. Experimental results highlight the importance of refraction correction in probe and receive beams. The CTS spectrum is measured with the in situ calibrated CTS receiver and responds to fast ions originating from a tangential neutral beam with an energy of 170 keV and from a perpendicular beam with an energy of 60 keV, both in the large helical device. From a velocity space analysis model, the results elucidate the measured anisotropic CTS spectrum caused by fast ions. The calibration methods and analyses demonstrated here are essential for CTS, millimeter-wave diagnostics, and electron cyclotron heating required under fusion reactor conditions.

Dosimetric Impact of Inter-Fraction Variability in the Treatment of Breast Cancer: Towards New Criteria to Evaluate the Appropriateness of Online Adaptive Radiotherapy.

PurposeAs a discipline in its infancy, online adaptive RT (ART) needs new ontologies and ad hoc criteria to evaluate the appropriateness of its use in clinical practice. In this experience, we propose a predictive model able to quantify the dosimetric impact due to daily inter-fraction variability in a standard RT breast treatment, to identify in advance the treatment fractions where patients might benefit from an online ART approach.MethodsThe study was focused on right breast cancer patients treated using standard adjuvant RT on an artificial intelligence (AI)-based linear accelerator. Patients were treated with daily CBCT images and without online adaptation, prescribing 40.05 Gy in 15 fractions, with four IMRT tangential beams. ESTRO guidelines were followed for the delineation on planning CT (pCT) of organs at risk and targets. For each patient, all the CBCT images were rigidly aligned to pCT: CTV and PTV were manually re-contoured and the original treatment plan was recalculated. Various radiological parameters were measured on CBCT images, to quantify inter-fraction variability present in each RT fraction after the couch shifts compensation. The variation of these parameters was correlated with the variation of V95% of PTV (ΔV95%) using the Wilcoxon Mann–Whitney test. Fractions where ΔV95% > 2% were considered as adverse events. A logistic regression model was calculated considering the most significant parameter, and its performance was quantified with a receiver operating characteristic (ROC) curve.ResultsA total of 75 fractions on 5 patients were analyzed. The body variation between daily CBCT and pCT along the beam axis with the highest MU was identified as the best predictor (p = 0.002). The predictive model showed an area under ROC curve of 0.86 (95% CI, 0.82–0.99) with a sensitivity of 85.7% and a specificity of 83.8% at the best threshold, which was equal to 3 mm.ConclusionA novel strategy to identify treatment fractions that may benefit online ART was proposed. After image alignment, the measure of body difference between daily CBCT and pCT can be considered as an indirect estimator of V95% PTV variation: a difference larger than 3 mm will result in a V95% decrease larger than 2%. A larger number of observations is needed to confirm the results of this hypothesis-generating study.

Modeling of beam ions loss and slowing down with Coulomb collisions in EAST

This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection (NBI)-generated fast ions due to Coulomb collisions in the equilibrium configuration of Experimental Advanced Superconducting Tokamak (EAST). This program is based on the weak equivalence of the Fokker–Planck equation under Rosenbluth MacDonald Judd (RMJ) potential and Stratonovich stochastic differential equation (SDE). The prompt loss with the LCFS boundary and the first wall (FW) boundary of the two co-current neutral injection beams are studied. Simulation results indicate that the loss behavior of fast ions using the FW boundary is very different from that of the LCFS boundary, especially for fast ions with a large gyration radius. According to our calculations, about 5.11% of fast ions generated by perpendicular injection drift out of the LCFS and then return inside the LCFS to be captured by the magnetic field. The prompt loss ratio of fast ions and the ratio of orbital types depend on the initial distribution of fast ions in the Pζ –Λ space. Under the effect of Coulomb collisions, the pitch-angle scattering and stochastic diffusion happens, which will cause more fast ion loss. For short time scales, among the particles lost due to collisions, the fraction of banana ions reaches 92.31% in the perpendicular beam and 58.65% in the tangential beam when the fraction of banana ions in the tangential beam is 3.4% of the total ions, which means that the effect of Coulomb collisions on banana fast ions is more significant. For long time scales, the additional fast ion loss caused by Coulomb collisions of tangential and perpendicular beams accounted for 16.21% and 25.05% of the total particles, respectively. We have also investigated the slowing down process of NBI fast ions.

Observation of significant Doppler shift in deuterium-deuterium neutron energy caused by neutral beam injection in the large helical device

The compact neutron emission spectrometer (CNES) having a tangential sightline was installed to observe a significant Doppler shift of the neutron energy due to the high-energy tangential neutral beam (NB) injections in the Large Helical Device (LHD) for understanding of the energy distribution of fast-ion. The CNES is based on a 1-inch diameter and 1-inch height EJ301 liquid scintillator coupled with a conventional 1-inch photomultiplier tube. The histogram of the integrated pulse signal (Qtotal) during different NBs heating phases measured by the CNES shows that the edge of Qtotal changes depending on NB directions. Using the simple derivative unfolding technique, the neutron energy spectra were unfolded from the measured Qtotal histogram. Peaks of the neutron energy shift to 2.0 MeV, 2.42 MeV, and 3.0 MeV according to the injection direction of NBs. The obtained neutron energy is almost consistent with the virgin deuterium-deuterium neutron energy evaluated by the simple two-body kinematics considering the sightline of CNES, NB injection angle, and NB injection energy.

Clinical evaluation of two AI models for automated breast cancer plan generation

BackgroundArtificial intelligence (AI) shows great potential to streamline the treatment planning process. However, its clinical adoption is slow due to the limited number of clinical evaluation studies and because often, the translation of the predicted dose distribution to a deliverable plan is lacking. This study evaluates two different, deliverable AI plans in terms of their clinical acceptability based on quantitative parameters and qualitative evaluation by four radiation oncologists.MethodsFor 20 left-sided node-negative breast cancer patients, treated with a prescribed dose of 40.05 Gy, using tangential beam intensity modulated radiotherapy, two model-based treatment plans were evaluated against the corresponding manual plan. The two models used were an in-house developed U-net model and a vendor-developed contextual atlas regression forest model (cARF). Radiation oncologists evaluated the clinical acceptability of each blinded plan and ranked plans according to preference. Furthermore, a comparison with the manual plan was made based on dose volume histogram parameters, clinical evaluation criteria and preparation time.ResultsThe U-net model resulted in a higher average and maximum dose to the PTV (median difference 0.37 Gy and 0.47 Gy respectively) and a slightly higher mean heart dose (MHD) (0.01 Gy). The cARF model led to higher average and maximum doses to the PTV (0.30 and 0.39 Gy respectively) and a slightly higher MHD (0.02 Gy) and mean lung dose (MLD, 0.04 Gy). The maximum MHD/MLD difference was ≤ 0.5 Gy for both AI plans. Regardless of these dose differences, 90–95% of the AI plans were considered clinically acceptable versus 90% of the manual plans. Preferences varied between the radiation oncologists. Plan preparation time was comparable between the U-net model and the manual plan (287 s vs 253 s) while the cARF model took longer (471 s). When only considering user interaction, plan generation time was 121 s for the cARF model and 137 s for the U-net model.ConclusionsTwo AI models were used to generate deliverable plans for breast cancer patients, in a time-efficient manner, requiring minimal user interaction. Although the AI plans resulted in slightly higher doses overall, radiation oncologists considered 90–95% of the AI plans clinically acceptable.

Comparison of Dosimetric Parameters of Three- Dimensional Conformal Radiotherapy and Intensity- Modulated Radiotherapy in Breast Cancer Patients Undergoing Adjuvant Radiotherapy after Modified Radical Mastectomy

Introduction Adjuvant radiotherapy has an important role in preventing locoregional recurrences. But radiation-induced late sequelae have become an important area of concern. The ideal postmastectomy radiotherapy technique is an area of controversy. The present study was designed to compare two widely practiced conformal techniques, three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT), in terms of dosimetry. Material and Methods A total of 50 postmodified radical mastectomy patients were selected and were randomized to treatment either by 3DCRT or IMRT technique. Two opposing tangential beams were used in 3DCRT plans whereas five to seven tangential beams were used for IMRT plans. The prescribed dose was 50 Gy in 25 fractions over 5 weeks. The dosimetric parameters were compared for planning target volume (PTV), lungs, heart, and left ventricle, opposite breast and esophagus. Results The dosimetric parameters of PTV in terms of D95%, D90%, D50%, and Dmean showed no significant difference among both techniques. The IMRT technique had significantly better mean values of Dnear-min/D98% (45.56 vs. 37.92 Gy; p = 0.01) and Dnear-max/D2% (51.47 vs. 53.65 Gy; p &lt; 0.001). Also, conformity index (1.07 vs. 1.29; p = 0.004) and homogeneity index (0.22 vs. 0.46; p = 0.003) were significantly better in IMRT arm. The dosimetric parameters of ipsilateral lung were significantly higher in IMRT arm in terms of mean dose (19.92 vs. 14.69 Gy; p &lt; 0.001) and low/medium dose regions (V5, V10, V13, V15, V20; p &lt; 0.05). However, high-dose regions (V40) were significantly higher in 3DCRT arm (15.57 vs. 19.89 Gy; p = 0.02). In contralateral lung also, mean dose was significantly higher in IMRT technique (3.63 vs. 0.53 Gy; p &lt; 0.0001) along with low-dose regions (V5, V10, V13, V15; p &lt; 0.05) while V20 was comparable between both the arms. In left-sided patients, the heart dose favored 3DCRT technique in terms of mean dose (17.33 vs. 8.51 Gy; p = 0.003), low/medium dose regions (V5, V10, V20; p &lt; 0.05), and doses to partial/whole volumes (D33, D67, D100). But the high-dose regions (V25, V30, V40) were comparable between both the arms. The dosimetry of left ventricle also showed significantly lesser values of mean dose and V5 in 3DCRT technique (p &lt; 0.0001). The opposite breast also showed higher mean dose with IMRT technique (2.60 vs. 1.47 Gy; p = 0.009) along with higher V5 (11.60 vs. 3.83 Gy; p = 0.001). The dosimetric parameters of esophagus showed higher mean dose in IMRT technique (10.04 vs. 3.24 Gy; p &lt; 0.0001) but the high-dose regions V35 and V50 were comparable between both the arms. Conclusion A clear advantage could not be demonstrated with any of the techniques. The IMRT technique led to more conformal and homogenous dose distribution with reduction in high-dose regions in ipsilateral lung while the 3DCRT technique showed lesser mean dose to organs at risk (OARs). The exposure of large volumes of OARs to low doses in IMRT technique may translate to increased long-term radiation-induced complications. The shortcomings of 3DCRT technique can be overcome by using multiple subfields within tangential fields.

Dosimetric Effects of a Commercial Breast Board Patient Support System

Aim: In prone breast treatments, a carbon fiber support device resides under the contralateral breast. Tangent beams are designed to encompass the treated breast and these often pass through the board at a shallow angle, resulting in significant attenuation. Our planners account for this attenuation by adding field-in-field dose to the deep part of the breast, through the board. Concern was raised about how accurate the treatment delivery is when the inherent uncertainties of patients’ positions are accounted for. Furthermore, transmission measurements are usually carried out perpendicular to the board, a non-clinical situation. The goal of this study is to evaluate the dosimetric effect of the board and the robustness of the plan to positional uncertainty. Materials and Methods: Twenty-two breast patients treated on a commercial prone breast board between 2017 and 2020 were selected for this retrospective study. To evaluate the board’s attenuation, we compared the plans with the board removed from the dose calculation. To quantify the robustness of this technique, we moved the beam isocenter with respect to the patient and board. Results: Our results showed that when the breast board is removed from a plan which was designed to account for the board attenuation, the average point dose increases by 7.48%, with a maximum of 22%. Comparing results with a mixed Analysis of Variance (ANOVA) and a least-square means analysis, our robustness evaluation indicates that anterior shifts at every magnitude (1 mm through 5 mm) make a significant difference in all dose statistics (D95, max, 95% prescription coverage and homogeneity index) investigated. In/out and right/left shifts resulted in an insignificant change in dose statistics. Conclusion: Prone breast boards can add significant dosimetric uncertainty into the treatment delivery process. Accounting for plan robustness in the design of the plan is highly recommended. A prone breast board design with support moved away from the beam path is warranted.

Neutron energy spectrum measurement using CLYC7-based compact neutron emission spectrometer in the Large Helical Device

Tangential compact neutron emission spectrometer (CNES) based on the Cs2LiYCl6:Ce with 7Li-enrichment (CLYC7) scintillator is newly installed in the Large Helical Device (LHD). Measurement of neutron energy spectrum was performed using CNES in tangential neutral beam (NB) heated deuterium plasma discharges. The Doppler shift of neutron energy according to the direction of tangential NB injection has been obtained. When the fast ions moving away from the CNES, lower shifted neutron energy is obtained, whereas the upper shifted neutron energy is obtained when the fast ions moving toward the CNES. The obtained neutron energy is almost consistent with the virgin deuterium-deuterium neutron energy evaluated by the simple two-body kinematic calculation.

Effects of resonant magnetic perturbations on neutral beam heating in a tokamak

The effects of resonant magnetic perturbations (RMPs) on tangential neutral beam heating in the EAST tokamak are studied numerically. RMPs with linear resistive magnetohydrodynamics response are used in the modeling. A variety of representing configurations of RMP coil currents are examined, and their effects on the neutral beam injection (NBI) heating efficiency are compared, in order to find a parameter window where deleterious effects of RMPs on NBI heating efficiency are minimized. It is found that the internal redistribution of fast ions by RMPs induces local accumulation of fast ions, resulting in higher local fast ion pressure than the case without RMPs. It is also found that the toroidal phasing of the RMP with respect to the fast ion source has slight effects on the steady-state radial profile of fast ions. The dependence of fast ion loss fraction on the RMP up-down phase difference shows a similar behavior as the dependence of the radial width of chaotic magnetic field on the phase difference. A statistical method of identifying resonances between RMPs and lost fast ions is proposed, and the results indicate that some resonances between RMPs and lost passing particles may be of non-integer fractional order, rather than the usual integer order.

Combined proton–photon treatment for breast cancer

Objective. Proton therapy remains a limited resource due to gantry size and its cost. Recently, a new design without a gantry has been suggested. It may enable combined proton–photon therapy (CPPT) in conventional bunkers and allow the widespread use of protons. In this work, we explore this concept for breast cancer. Methods. The treatment room consists of a LINAC for intensity modulated radiation therapy (IMRT), a fixed proton beamline (FBL) with beam scanning and a motorized couch for treatments in lying positions with accurate patient setup. Thereby, proton and photon beams are delivered in the same fraction. Treatment planning is performed by simultaneously optimizing IMRT and IMPT plans based on the cumulative dose. The concept is investigated for three breast cancers where the goal is to minimize mean dose to the heart and lung while delivering 40.05 Gy in 15 fractions to the PTV with a SIB of 48 Gy to the tumor bed. The probabilistic approach is applied to mitigate the sensitivity to range uncertainties. Results. CPPT is particularly advantageous for irradiating concave target volumes that wrap around a curved chest wall. There, protons may deliver dose to the peripheral and medial parts of the target volume including lymph nodes. Thereby, the mean dose in normal tissues is reduced compared to single-modality IMRT. However, tangential photon beams may treat parts of the target volume near the interface to the lung. To ensure target coverage for range undershoot in an IMPT plan, proton beams have to deliberately overshoot into the lung tissue—a problem that can be mitigated via the photon component which ensures plan conformity and robustness. Conclusion. CPPT using an FBL may represent a realistic approach to make protons available to more patients. In addition, CPPT may generally improve treatment quality compared to both single-modality proton and photon treatments.

Calculation of dose rates in loss of coolant accident due to double ended rupture of the experimental tangential irradiation beam tube of MTR reactor.

A MTR reactor is an open water pool reactor type. The water pool serves as a shield from radioactive radiations. The most serious accident in this type of reactor is the Loss of Coolant Accident (LOCA) due to rupture either of a primary coolant pipe or of any experimental beam tube. In the present work it has been assumed that pool water drains out due to double ended rupture of the tangential irradiation beam tube (TIC) which has a diameter 150 mm. For an operating power level of 22 MW, the equilibrium core would enter into melting conditions if the pool drain time is less than one hour. It was also assumed that Emergency Core Cooling System (chimney water injection system and siphon effect breaker were not working. The reactor interiors have been modeled using the Monte Carlo N-Particle Transport code MCNPX 2.7.0. The source term has been determined using the ORIGEN-2 code. The doses and dose rates calculations in different places of operator (as phantom of Tissue-Equivalent Material) inside of the reactor building were determined by using Monte Carlo N-Particle Transport (MCNPX).The results show that the dose rate in the control room would be 5.24557 SV/h, the dose rate in the reactor hall above the pools on the gate would be7.20137 SV/h and the dose rate in the Emergency control room would be 2.68239 SV/h. Those dose rates are extremely high and would lead to fatal doses in short time.

Calculation of dose rates in loss of coolant accident due to double ended rupture of the experimental tangential irradiation beam tube of MTR reactor

The doses and dose rates following a LOCA in MTR reactor have been studied. A MTR reactor is an open pool type. The water pool serves as a shield from radioactive radiations.The most serious accident in this type of reactor is the Loss of Coolant Accident (LOCA) due to rupture either of a primary coolant pipe or of any experimental beam tube. In the present work it has been assumed that pool water drains out due to double ended rupture of the tangential irradiation beam tube (TIC) which has a diameter 150 mm. For an operating power level of 22 MW, the equilibrium core will enter into melting conditions if the pool drain time is less than 1 h.It was also assumed that Emergency Core Cooling System (chimney water injection system and siphon effect breaker) were not working. Therefore, conservatively a severe damage (∼80%) is expected to occur to the core, either by a core uncover situation following extended boiling operation, or by a core covered situation with extended boiling.The reactor interiors have been modeled using the Monte Carlo N-Particle Transport code MCNPX 2.7.0. The source term has been determined using the ORIGEN-2 code. The doses and dose rates calculations in different places of operator (as phantom of Tissue-Equivalent Material) inside of the reactor building were determined by using Monte Carlo N-Particle Transport (MCNPX). The results show that the dose rate in the control room is 5.24 Sv/h, the dose rate in the reactor hall above the pools on the gate is 7.20Sv/h and the dose rate in the Emergency control room is 2.68Sv/h. Those dose rates are extremely high and would lead to fatal doses in short time.

Breast Tangent Beam Energy, Surgical Bed-to-Skin Distance and Local Recurrence After Breast-Conserving Treatment

Higher energy (>6 MV) photons reduce dose inhomogeneity with breast tangent beams, thereby reducing late breast toxicity, but skin and superficial tissue sparing by higher energy beams raises concerns about local recurrence (LR) risk. This study aimed to determine whether beam energy and surgical bed-to-skin distance affect LR. This population-based study included newly diagnosed invasive breast cancers without skin involvement (pT1-4a, any-N, M0) treated with breast-conserving surgery and adjuvant whole breast radiation therapy without bolus or beam spoilers. The primary endpoint was the cumulative incidence of LR (CILR). Multivariable analysis (MVA) included mean beam energy, age, T-stage, nodal status, overall stage, lymphovascular invasion (LVI), grade, margin status, extensive intraductal component (EIC), breast cancer subtype, hormone therapy, and chemotherapy. In a subgroup with contoured surgical beds, another MVA included surgical bed-to-skin distance. The cohort consisted of 10,083 women treated from 2002 to 2011: 327 with 4 MV, 6006 with 6 MV, 2083 with >6 to 10 MV, and 1667 with >10 MV tangents. The median follow-up time was 11.1 years. The 10-year CILR was 3.1% (95% confidence interval [CI], 1.6-5.4) with 4 MV, 2.8% (2.4-3.3) with 6 MV, 4.2% (3.4-5.3) with >6 to 10 MV, and 2.6% (1.9-3.5) with >10 MV. On MVA of the entire cohort, LR risk was increased with positive margins, LVI, EIC, and lack of hormone therapy, but was not associated with beam energy (hazard ratio [HR], 1.01; 95% CI, 0.96-1.05; P=.8). On MVA of 3359 patients with contoured surgical beds, LR risk was not associated with surgical bed-to-skin distance (HR, 1.00; 95% CI, 0.99-1.02; P=.8). Use of higher breast tangent beam energies is not associated with increased risk of LR, including in cases with surgical beds that are close to the skin.