Tangential Beam Research Articles

Understanding and modeling human-AI interaction of artificial intelligence tool in radiation oncology clinic using deep neural network: a feasibility study using three year prospective data

Objective.Artificial intelligence (AI) based treatment planning tools are being implemented in clinic. However, human interactions with such AI tools are rarely analyzed. This study aims to comprehend human planner's interaction with the AI planning tool and incorporate the analysis to improve the existing AI tool.Approach.An in-house AI tool for whole breast radiation therapy planning was deployed in our institution since 2019, among which 522 patients were included in this study. The AI tool automatically generates fluence maps of the tangential beams to create anAI plan. Human planner makes fluence edits deemed necessary and after attending physician approval for treatment, it is recorded asfinal plan. Manual modification value maps were collected, which is the difference between theAI-planand thefinal plan. Subsequently, a human-AI interaction (HAI) model using full scale connected U-Net was trained to learn such interactions and perform plan enhancements. The trained HAI model automatically modifies theAI planto generate AI-modified plans (AI-m plan), simulating human editing. Its performance was evaluated against originalAI-planandfinal plan. Main results. AI-m planshowed statistically significant improvement in hotspot control over theAI plan, with an average of 25.2cc volume reduction in breast V105% (p= 0.011) and 0.805% decrease in Dmax (p< .001). It also maintained the same planning target volume (PTV) coverage as thefinal plan, demonstrating the model has captured the clinic focus of improving PTV hot spots without degrading coverage.Significance.The proposed HAI model has demonstrated capability of further enhancing theAI planvia modeling human-AI tool interactions. This study shows analysis of human interaction with the AI planning tool is a significant step to improve the AI tool.

Comparison of Lung and Contralateral Scattered Breast Dose between Field-in-Field and Wedge Techniques in Patients with Early Breast Cancer

Purpose: This study aims to evaluate the dosimetric result of the Field-In-Field (FIF) plans compared with Tangential Wedged Beams (TWB) plans for whole breast radiotherapy of patients. Materials and Methods: In this survey, we entered fifty patients with breast-conserving surgery and postoperative whole-breast radiotherapy. FIF and a TWB plan were made for each patient to compare dosimetric outcomes. Results: The Homogeneity Index (HI) and Conformity Index (CI) were specified for the evaluation of Planning Target Volume (PTV). The mean dose of the ipsilateral lung and contra-lateral breast for the evaluation of organs at risk dose were used. The FIF plans had significantly lower HI (p &lt; 0.01) and CI (p &lt; 0.01) than those of the TWB plans. It means in the dosimetric comparisons of the PTV, the FIF plans were better than the TWB plans. The V10lung (31.152vs. 32.72%, p &lt; 0.01), V20lung (25.6064vs. 26.6%, p &lt; 0.01) V30lung (17.4% vs. 18.4%, p &lt; 0.01) were lower with the FIF plans compared with those of the TWB plans, with statistical significance. The FIF plans had a lower mean dose for the lung than those of TWB plans (1225.48 vs. 1670.32 cGy) but no statistical significance (p=0.06). The mean dose in the contra-lateral of the breast in FIF plans was lower than in TWB plans (61.666 vs. 163.45 cGy), with statistical significance (p &lt; 0.01). Conclusion: The FIF plans increased the dose homogeneity, and conformity of the target volume for the whole-breast irradiation compared with the TWB plans. Moreover, the doses of organs at risk (ipsilateral lung and contralateral breast) were reduced with FIF plans.

Core density profile control by energetic ion anisotropy in LHD

Electron and impurity ion density profiles have been controlled by using tangential and perpendicular neutral beams for plasma heating in a stellarator/heliotron for the first time. Reduced anisotropy of stored energy for energetic ion En⊥/Enǁ has resulted in an inward electron and impurity transport, forming a core electron density peaking. Increased anisotropy leads to a flat or hollowed electron density profile with an impurity exhaust in a core region [Yoshinuma et al., Nucl. Fusion 49, 062002 (2009)]. A high confinement state of particles in LHD has yet to be achieved, except for a temporal state of an electron density peaking created by a pellet injection. As a pioneering and crucial research result, the operation of energetic ion anisotropy by neutral beams has newly demonstrated that the direction of the radial transport of bulk and impurity ions can be controlled. At the same time, the overall plasma performance rises in neutron flux and stored energy. On the other hand, the increase in the anisotropy flattens the density profile. This new finding holds promise for a control knob of nuclear fusion reactors to enhance fusion power output.

Observation of energetic ion anisotropy using neutron diagnostics in the Large Helical Device

Energetic ion anisotropy was observed by tangential sightline compact neutron energy spectrometers (CNESs) in tangential neutral beam heated deuterium plasmas in Large Helical Device. Significant upper and lower energy shifts in D–D neutron energy from 2.45 MeV were measured according to the beam ion injection directions and CNES sightline using a conventional liquid scintillation detector with the unfolding technique and a novel Cs2LiYCl6:Ce with a 7Li-enrichment (CLYC7) scintillation detector without unfolding. The observed neutron energy spectrum was compared with that predicted by a numerical simulation based on orbit following models. Numerical simulation revealed that the Doppler shift in D–D neutron energy results from energetic ion anisotropy.

A Concept for a Multipurpose Time-of-Flight Neutron Reflectometer at Compact Neutron Sources

The design of a time-of-flight neutron reflectometer proposed for the new generation of compact neutron sources is presented. The reflectometer offers the possibility to use spin-polarized neutrons. The reflectometer design presented here takes advantage of a cold neutron source and uses neutrons with wavelengths in the range of 2–15 Å for the unpolarized mode. In general, due to tight spatial restrictions and the need to avoid moving parts inside the beam channel, a multi-channel collimator guide and reflective neutron guide are used for the first section of the instrument. This enables definition of the desired wavelength band and easy selection of one out of three different Q-resolutions. A low background for the collimator system and the reflectometer is ensured by employing a tangential beam channel and an in-channel sapphire filter. The second section is the time-of-flight (TOF) system, which uses a double-disk neutron chopper followed by polarization elements, the sample environment and the neutron detector system. Monte Carlo simulations and neutron beamline intensity measurements are presented. The design considerations are adoptable for neutron sources where space is limited and sections of the instrument are in a high-radiation environment.

Does Breast Surgery Type Alter Incidental Axillary Irradiation? A Dosimetric Analysis of the "Sentinel Envahi et Randomisation du Curage" SERC Trial.

An incidental axillary dose of adjuvant radiotherapy using tangential beams is usually given after breast-conserving surgery for breast cancer. The goal of this sub-study was to evaluate this incidental dose in the setting of post-mastectomy radiotherapy (PMRT) according to two different radiotherapy techniques. Patients participating in a randomized SERC trial who received PMRT in a single center were included. We collected the incidental axillary dose delivered to the Berg level 1 using different dosimetric parameters and compared two techniques using Student's t-test: three-dimensional conformal radiotherapy (3D-CRT) and volumetric arc therapy (VMAT). We analyzed radiotherapy plans from 52 patients who received PMRT from 2012 to 2021. The mean dose delivered to the Berg level 1 was 37.2 Gy. It was significantly higher with VMAT than with 3D-CRT-43.6 Gy (SD = 3.1 Gy) versus 34.8 Gy (SD = 8.6 Gy) p < 0.001. Eighty-four percent of the Berg level 1 was covered by 40 Gy isodose in the VMAT group versus 55.5% in the 3D-CRT group p < 0.001. On the Berg level 1, PMRT gives a dose at least equivalent to the one given by post-breast-conserving surgery radiotherapy, making it possible to limit completion axillary lymph node dissections in select pN1a patients treated with a mastectomy. Modern radiotherapy techniques like VMAT tend to increase this incidental dose.

Design of Neutron Activation and Radiography Facilities Based on DD Generator

Design and simulation of radiation facility using deuterium-deuterium (DD) neutron generator for neutron activation analysis (NAA) and radiography have been conducted by PHITS 3.30. A cylindrical DD neutron tube (E = 2.45 MeV isotropic, 5 x 109/s) flux is surrounded by high-density polyethylene blocks which serve as the moderator. Within the moderator there are several cavities to perform neutron activation experiments. A 90 cm long beam tube is installed either radially or tangentially for radiography purposes. Monte Carlo simulations then calculate the thermal flux inside the cavities and on the end of the beam tube. The biggest thermal flux obtained in the activation chambers is about 1.95 x 109/(cm2.s) in the cavity closest to the source center. Radial beam tube delivers thermal flux of 7.86 x 103/(cm2.s), while tangential beam tube transports 1.86 x 103/(cm2.s). Although the thermal flux in the radial beam tube is higher, the fast neutron flux is also higher, about 9.60 x 103/(cm2.s). Tangential beam tube configuration can decrease fast neutron flux to only 2.00 x 102/(cm2.s). This result can serve as a preliminary study for the commisioning of radiation facilities based on compact, low-power neutron source.

The effect of pressure anisotropy on 3-D MHD stability for low magnetic field LHD equilibria

The magnetohydrodynamic stability of plasmas with an anisotropic pressure component is analysed for a low magnetic field configuration of the large helical device. Magnetic equilibria are calculated by the anisotropic Neumann inverse moments equilibrium code, an extension of the three-dimensional variational moments equilibrium code. A modified version of the bi-Maxwellian is used to model the anisotropic particle velocity distribution. Magnetohydrodynamic stability calculations for the $n=1$ mode family are carried out by TERPSICHORE, which has been expanded by the Kruskal–Oberman energy principle. For on-axis particle deposition, the growth rate and plasma displacement show that the parallel dominant plasmas are significantly more stable than isotropic or perpendicular dominant plasmas. For off-axis particle deposition, the growth rate and the Mercier criterion in the peripheral region $\rho =0.9$ , show that low field (LF) deposition perpendicular dominant plasmas are most unstable. For the most realistic off-axis deposition profile, it is found that parallel dominant plasmas are most stable for LF deposition, while perpendicular dominant plasmas are most stable for high field deposition. We conclude that, under low magnetic field conditions in the large helical device, tangential neutral beam injection heating has a stabilising influence on the plasma.

Energetic passing particle-driven instabilities and their impact on discharge evolution in KSTAR

An experimental study is conducted on the onset and evolution characteristics of energetic particle-driven instabilities in Korea Superconducting Tokamak Advanced Research (KSTAR) with dominant tangential neutral beam injection (NBI). A scan of NBI beam energy shows the evanescence of the sawtooth crash and the concomitant onset of the strong passing particle-driven low-frequency fishbone instability. A quantitative analysis shows that the safety factor (q)-profile in the core region is clamped by a balance between the depletion of energetic passing particles by the fishbone instability and their external replenishment. Two synchronized chirping modes with distinct toroidal mode numbers (n = 1 and n = 5) supersede the fishbone instability after a self-organized q-profile is attained. An analysis shows that the n = 1 mode is likely to be a high-frequency beta-induced Alfvén eigenmode fishbone branch, while the n = 5 mode is an energetic particle mode (EPM). A dynamic system analysis of the synchronized EPM (S-EPM) shows that a stable S-EPM cycle can exist when the coupling between the two modes involved is insignificant. The potential impact of such EPMs on the establishment of a burning plasma scenario with a flat core q-profile is briefly discussed.

Near-Surface Dose Correlates With Moist Desquamation and Unplanned Reconstructive Surgery in Patients With Implant-Based Reconstruction Receiving Postmastectomy Radiation Therapy

Postmastectomy radiation therapy (PMRT) reduces disease recurrence in appropriately selected patients but may compromise implant-based reconstruction. We investigated whether near-surface dose correlates with radiation-related toxic effects in these patients. Patients receiving PMRT at a single institution from 2016 to 2019 were retrospectively reviewed. Patient demographics and treatment information were collected. Three near-surface structures were retrospectively generated, bound by the chest wall tangent beam as well as the skin surface and the skin-3 mm contour (SR3), skin surface and skin-5 mm contour (SR5), or skin-5 and skin-10 mm contours. Dosimetric analysis of these near-surface contours was performed in 2 Gy intervals. Univariate and multivariate analyses were used to identify predictors of moist desquamation, grade 2+ chest wall pain, use of opiate pain medication, unplanned reconstructive surgery, and implant failure. Logistic regression for each outcome and near-surface contour was performed for receiver-operator area under the curve (AUC) analysis and the Youden J Statistic was used to determine the optimal threshold for each dosimetric parameter. Of 126 patients reviewed, 109 met the study's eligibility criteria. Median follow-up was 2.3 years. Twenty-five patients (23%) underwent unplanned reconstructive surgery, and 10 (9.2%) experienced implant failure. Among clinical variables, low body mass index and history of smoking predicted unplanned surgery on univariate and multivariate analyses, and moist desquamation predicted grade 2+ chest wall pain. The top dosimetric parameters by AUC for moist desquamation, grade 2+ chest wall pain, use of opiates, unplanned reconstructive surgery, and implant failure were SR5 D10 cc (AUC=0.701, optimal threshold 57.8 Gy, P < .001), SR3 D10 cc (AUC=0.600, optimal threshold 56.8 Gy, P=.079), SR5 D10 cc (AUC=0.642, optimal threshold 57.3 Gy, P=.041), SR3 V44 Gy (AUC=0.711, optimal threshold 81%, P=.001), and SR3 V44 Gy (AUC=0.688, optimal threshold 82%, P=.052), respectively. Near-surface dose correlates with moist desquamation and unplanned reconstructive surgery after PMRT. Further evaluation of prospective optimization of dosimetric parameters related to SR3 and SR5 should be considered.

Study of Alfvén eigenmode stability in Quasi-Poloidal Stellarator (QPS) plasma using a Landau closure model

The aim of this study is to analyze the linear stability of Alfvén eigenmodes (AE) in the QPS device heated by a tangential neutral beam injector (NBI). The analysis is performed using the gyro-fluid code FAR3d, that solves the reduced MHD equations for the thermal plasma coupled with moments of the kinetic equation for the energetic particles (EP). The AE stability is calculated in several operational regimes of the tangential NBI: EP β between 0.001 and 0.1, EP energy between 12 and 180 keV and different radial locations of the beam. The analysis is performed for vacuum and finite β equilibria as well as QPS configurations with two and three periods. The EP β threshold in the vacuum case is 0.001 and the AE frequency is lower as the energy of the EP population decreases. Toroidal Alfvén eigenmodes with f = 80–120 kHz and elliptical AE between f = 120–350 kHz are triggered between the middle-outer plasma region (). The AE stability improves in the simulations with finite β equilibria and three period configurations with respect to the vacuum case with two periods because the continuum gaps are slender, leading to a higher threshold of the EP β, above 0.03 for the AEs triggered by the helical mode families. Helical effects are not strong enough to destabilize Helical Alfvén eigenmodes, the AEs with the largest growth rates are triggered by the n = 1 and n = 2 toroidal families.

Abstract P1-10-15: Concious sparing of contralateral thyroid lobe in Ca Breast patients receiving post mastectomy radiotherapy by IMRT technique – A single institution dosimetric study

Abstract Purpose/Objective(s): The purpose of this paper is to report the dosimetric effects of conscious sparing of contralateral lobe of thyroid gland in carcinoma breast patient receiving locoregional radiation by tangential beam Intensity Modulated radiotherapy technique. Materials/Methods: Treatment plans of 20 Ca Breast patients, who received post mastectomy adjuvant locoregional radiotherapy, were evaluated. Since October 2021 we adopted a department protocol of conscious sparing of contralateral thyroid in breast radiotherapy. 10 of these had conscious sparing of contralateral thyroid (group A) whereas 10 of old plans were evaluated when C/L thyroid were not given constraints &amp; are being passively spared due to location on contralateral/non treatment side of neck (group B). Treatment planning was done using tangential beam (6 MV) IMRT in Eclipse 13.7 TPS in all of these patients. All of these patients received treatment to chest wall &amp; SCF. RTOG contouring guidelines were followed in all the patients. Prescription Dose was 40Gy in 15# for both groups. The best treatment plans were selected ensuring 95% PTV dose coverage and acceptable dose to OARs. Uniform contouring, plan optimization &amp; evaluation protocols were followed for all of these patients. Results: The mean thyroid volume in group A is 4.30cc &amp; in group B is 3.99cc which is not statistically different (P value -0.639) The mean dose of thyroid in group A is 7.98Gy whereas in group B it is 17.00Gy which is spastically significant (P value – 0.000003). Comparison of mean dose to contralateral lobe (in Gy) between the two groups Groups No. Mean ± SD ‘t’ value P value Thyroid dose with constraint 10 7.98±1.46 -6.702, df=18 0.000003* Thyroid dose without constraint 10 17.00±3.99 Unpaired ‘t’ test applied. P value = 0.000003, Significant Conclusion: OARs present on contralateral side are passively spared due to the location. This often results in a tendency of not actively prescribing constraints to these. This study emphasizes that conscious sparing of contralateral Thyroid lobe can further reduce the dose to significant levels. This reduction can preserve thyroid function further. Further clinical trials are required to corroborate this dosimetric gain with clinical thyroid function preservation. Citation Format: Manish Chomal, Minaal Iyer, Ananth Kalimurthy, Joshua Sahay, Sushanta Banik. Concious sparing of contralateral thyroid lobe in Ca Breast patients receiving post mastectomy radiotherapy by IMRT technique – A single institution dosimetric study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-10-15.

A dose planning study for cardiac and lung dose sparing techniques in left breast cancer radiotherapy: Can free breathing helical tomotherapy be considered as an alternative for deep inspiration breath hold?

To investigate the possibility to be able to offer left sided breast cancer patients, not suitable for DIBH, an organ at risk saving treatment. Twenty patients receiving radiotherapy for left breast cancer in DIBH were enrolled in the study. Planning CT scans were acquired in the same supine treatment position in FB and DIBH. 3DCRT_DIBH plans were designed and optimized using two parallel opposed tangent beams (with some additional segments) for the breast and chest wall and anterior-posterior fields for regional lymph nodes irradiation. Additionally, FB helical tomotherapy plans were optimized to minimize heart and lung dose. All forty plans were optimized with at least 95% of the total CTV covered by the 95% of prescribed dose of 50Gy in 25 fractions. HT_FB plans showed significantly better dose homogeneity and conformity compared to the 3DCRT_DIBH specially for regional nodal irradiation. The heart mean dose was almost comparable in 3DCRT_DIBH and HT_FB while the volume (%) of the heart receiving 25Gy had a statistically significant reduction from 7.90±3.33 in 3DCRT_DIBH to 0.88±0.66 in HT_FB. HT_FB was also more effective in left descending artery (LAD) mean dose reduction about 100% from 30.83±9.2Gy to 9.7±3.1. The ipsilateral lung volume receiving 20Gy has a further reduction of 43 % in HT_FB compared with 3DCRT_DIBH. For low dose comparison, 3DCRT_DIBH was superior for contralateral organ sparing compared to the HT_FB due to the limited angle for dose delivery. For patients who cannot be a candidate for DIBH for any reason, HT in free breathing may be a good alternative and provides heart and ipsilateral lung dose sparing, however with the cost of increased dose to contralateral breast and lung.

Excitation of toroidal Alfvén eigenmodes with counter-current NBI in the TCV tokamak

In Tokamak á Configuration Variable (TCV), unstable modes excited by resonant interaction between the shear Alfvèn waves in continuum gaps and energetic particles have been observed in scenarios with neutral beam injection (NBI). TCV is a middle-size device () equipped with a , tangential neutral beam injector. In this paper the phenomenology of modes excited with on-axis NBI is presented. The Alfvènic nature of the modes has been confirmed investigating their sensitivity against plasma parameters such as NBI energy, toroidal magnetic field, and cross-checking with the predictions from linear kinetic stability code. The mode radial profile is estimated using electron cyclotron emission measurement and agrees well with modelling results. In addition, the fast particle distribution function has been modelled using TRANSP/NUBEAM code. Even with counter-current NBI (leading to higher losses), the drive from the resonant particles is sufficient for the mode excitation. An ad-hoc additional diffusion model allows to estimate the fast particle transport, modifying the fast particle gradient at the mode location and matching the neutron rates.

Development of an upgraded motional Stark effect diagnostic system on EAST tokamak

A new multi-channel motional Stark effect (MSE) diagnostic system has been developed on the upgraded EAST tokamak, which was installed on the port C to observe a tangential neutral beam. A telecentric imaging lens was deployed to ensure uniform illumination from the core to the boundary. A square fiber head which contained 23 fiber bundles was mounted to this imaging lens; each fiber bundle contained 19 fibers and two of them were assigned to CXRS and BES spectrometer, respectively. The angle tuning method was used for matching the Doppler shift of the σ component’s wavelength which was caused by the beam voltage. At the present stage, the MSE system only contains ten channels that would be extended to 23 channels in the future, covering a measurement range from R = 1.8 to R = 2.27 m with a temporal resolution of 10 ms and a spatial resolution of 3 cm. The polarization angle-constrained q profiles and current density profiles were reconstructed with EFIT equilibrium reconstructions. In the sawtooth discharges, the q = 1 surface position was validated by the ECE signals, which further verified the rationality of the MSE measurement.

First observations of confined fast ions in MAST Upgrade with an upgraded neutron camera

Spherical tokamaks are key to the successful design of operating scenarios of future fusion reactors in the areas of divertor physics, neutral beam current drive and fast ion physics. MAST Upgrade, which has successfully concluded its first experimental campaign, was specifically designed to address the role of the radial gradient of the fast ion distribution in driving the excitation of magneto-hydrodynamic (MHD) instabilities, such as toroidal Alfvén eigenmodes, fish-bones and long-lived mode, thanks to its two tangential neutral beam injection systems, one on the equatorial plane and one that is vertically shifted 65 cm above the equatorial plane. To study the fast ion dynamics in the presence of such instabilities, as well as of sawteeth and neo-classical tearing modes, several fast ion diagnostics were upgraded and new ones added. Among them, the MAST prototype neutron camera (NC) has been upgraded to six, equatorial sight-lines. The first observations of the confined fast ion behavior with the upgraded NC in a wide range of plasma scenarios characterized by on-axis and/or off-axis heating and different MHD instabilities are presented here. The observations presented in this study confirm previous results on MAST but with a higher level of detail and highlight new physics observations unique to the MAST Upgrade. The results presented here confirm the improved performance of the NC Upgrade, which thus becomes one of the key elements, in combination with the rich set of fast ion diagnostics available on the MAST Upgrade, for a more constrained modeling of the fast ion dynamics in fusion reactor relevant scenarios.

Radiation-Associated Cardiotoxicity during Breast Cancer Treatment with Ionizing Radiation

Introduction: Breast cancer is the most common cancer in women. The treatment of breast carcinoma has advanced in the last decade and nowadays there are treatment protocols for all stages of the disease. Depending on the histopathology and stage breast cancer is treated with surgery, chemotherapy and radiotherapy. Regarding radiation, the field of irradiation includes the chest wall in patients with mastectomy, or the breast glandular tissue in patients with conserving surgical approaches. It is often treated with radiation therapy with two opposing tangential fields, and when indicated supraclavicular lymph nodes have to be irradiated. In this case an additional anterior field is applied. The tangential as well as the other radiation beams have a potential damaging effect on the healthy surrounding tissues, particularly over the heart in the left breast irradiation and in the lungs as well. Material and Methods: The study included 25 patients with left breast carcinoma, all post surgery, treated with radiation therapy, with the Elekta accelerator at our department. For academic purpose the treatment plans were generated following two methods. The first one with two tangential opposite beams plus a supraclavicular beam. In this method the angles of the tangential internal and external create an angle that is equal to 180&#730 {310&#730& 130&#730}; no further changes were made to the beam geometry. Even though this is not the best option from the dose distribution point of view, it is still the most applied method, probably because of the semplicity of it. For each patient, a second plan was generated using two opposite tangential beams plus the supraclavicular beam. The angles of the internal and external beam were changed from 1&#730to 3&#730, depending on the surface of the body, so that the resulting angle was 180&#730± 3&#730 {310&#730± 3&#730& 130&#730± 3&#730} with the aim to adapt the beam geometry as much as possible to the shape of the thoracic wall and to spare the OAR-s. Results and Discussion: The data show that the dose in the organs at risk, in terms of dose percentage, is lower when the angles of the beams are changed with 1&#730-3&#730, compared to the classic method where the internal and external angles equal 180&#730. This dose is not only non-negligible but significant; for every angle change from 1&#730to 3&#730, there is a significant reduction in the integral dose in the radiated volume, expressed in percentage, up to 5%. Conclusion: In most centers, the radiation treatment of breast is realized with two tangential opposite beams, which usually are mirror beams, or in other words, the internal and external beam angles create an angle of 180&#730 {α + β = 180&#730}. This is a simple method, which provides a good dose distribution, but leaves a relatively high dose in the organs at risk. This study shows the difference in the dose percentage in the heart and lung when the beam angles are changed adapting to the anatomy of the patient. Reducing these doses allows for better overall treatment and less longtime toxicity, particularly for the heart tissues.

Investigation of the synergistic effects of ICRF + NBI heating in EAST plasma discharges

Following an upgrade of the neutral beam injection (NBI) system, obvious synergy between combined NBI and ion cyclotron resonance frequency (ICRF) heating was observed in recent experiments conducted at EAST. To investigate the effects of beam-ions accelerated by radiofrequency (RF) wave, analyses are performed by using TRANSP code based on the experimental results. The calculated results argue that only a small fraction of the ICRF power is absorbed by the beam ions in the ICRF + NBI synergistic heating of the (H)D plasma. To enhance the beam–RF interactions in synergistic heating and achieve high plasma performance of EAST, different experimental conditions, including multiple injection powers and diverse beam injection options, were explored. Beam injected fast ions are passing particles, trapped particles observed when synergy heating between ICRF and NBI. In particular, by varying the injection direction of the beam ions it was observed that more tangential beam yields better synergy in comparison with more perpendicular beam. The neutron emission rate of D–D fusion in tokamaks is improved and less fast ion loss is produced with tangential NBI + ICRF heating. Also, the effect of the ratio P ICRF/P NBI on ICRF + NBI combined heating is demonstrated, the higher power boosts the fusion enhancement. The study of the performed synergistic heating provides an important reference for the subsequent combined NBI + ICRF heating experiments on EAST.

Effects of external kink and fishbone-like modes on energetic particle transport in tokamak plasmas

Transport and loss of beam injected energetic particles (EPs) due to three-dimensional perturbations, associated with the external kink (XK) instability and fishbone-like mode (FLM), are numerically investigated utilizing the guiding center following code ORBIT for static toroidal plasmas in HL-2A. The perturbation structure for the XK is computed by the MARS-F code and then mapped to the Boozer coordinates as defined in ORBIT. The simulation shows that the EP profile experiences a significant change in the middle of the plasma column, when the XK-induced radial magnetic field perturbation amplitude, normalized by the equilibrium field, exceeds a threshold value of about . The EP transport is found to be dominated by a diffusion process instead of convection. Furthermore, by scanning the perturbation frequency as a free parameter while maintaining the XK mode structure (thus mimicking the FLM as observed in DIII-D and JT-60U tokamaks), redistribution and loss of EPs are found to be substantially enhanced due to strong resonances between the FLM and EPs, when the mode frequency exceeds a threshold value of ∼2 kHz for the case considered. For either XK or FLM, the response of passing EPs to the perturbation is dominant due to the assumed tangential neutral beam injection. Most lost EPs due to these instabilities are initially passing particles but are eventually lost through trapped orbits.

DOSIMETRIC ANALYSIS OF INCIDENTALAXILLARY IRRADIATION IN BREAST CANCER USING TANGENTIAL FIELDS TREATED BY 3DCRT TECHNIQUE

Introduction Radiotherapy is an important aspect of treatment for multimodality approach in cancer breast. Inclusion of axillary nodes in radiotherapy tangential elds remains a long-standing controversial issue. It is considered that axillary nodes receive incidental radiation through tangential beams of chest-wall. The benet of decreasing regional recurrences with axillary nodal irradiation needs to be weighed against the risk of chronic lymphedema and its impact on quality of life. The following study was done to analyze the incidental dose received to axillary region and whether the addition of radiotherapy to axillary region will be useful. Material and methods Twenty post Modied Radical Mastectomy (MRM) patients who had received adjuvant radiotherapy from 2018-2021were retrospectively selected. Planning was a done with Field in Field–Forward planned–3DCRT with mono-isocentric technique. Dose prescribed was 50Gy/25 fractions. Axillary Lymph nodes were contoured according to RTOG guidelines. Various parameters of PTV(V95,D90, D95, Dmax, Dmean, Homogeneity Index(HI), Conformity Index (CI), Volume of PTV), Axillary Lymph nodes I, II, III and SCF (Dmean,V95, V90, Volume) and BMI were evaluated. Correlation was done among these parameters and Statistical analysis was done using Pearson-Correlation coefcient. Results The mean dose to axillary Lymph node level I, II, III were 45.75Gy, 31.80Gy and 25.83Gy respectively. The V90% and V95% of Axillary level–III also received a dose of 32.97Gy and 22.73Gy respectively. The combined volume of I and II received a mean dose of 40.85Gy and all three levels received 39.44.Gy. There is a weak correlation of SCF dosimetry with axillary nodal volumes although PTV volumes and BMI had positive correlation with axillary lymph nodal irradiation. ConclusionAxillary levels I and II received substantial amount of incidental radiation by the tangential eld 3DCRT technique. Our small sample size may have impacted a more detailed analysis of the correlation among variables. However more prospective clinical studies addressing this issue may help in understanding the risks versus benets of axillary lymph nodal irradiation.