Characteristics of a novel treatment system for linear accelerator–based stereotactic radiosurgery

The purpose of this study is to characterize the dosimetric properties and accuracy of a novel treatment platform (Edge radiosurgery system) for localizing and treating patients with frameless, image-guided stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). Initial measurements of various components of the system, such as a comprehensive assessment of the dosimetric properties of the flattening filter-free (FFF) beams for both high definition (HD120) MLC and conical cone-based treatment, positioning accuracy and beam attenuation of a six degree of freedom (6DoF) couch, treatment head leakage test, and integrated end-to-end accuracy tests, have been performed. The end-to-end test of the system was performed by CT imaging a phantom and registering hidden targets on the treatment couch to determine the localization accuracy of the optical surface monitoring system (OSMS), cone-beam CT (CBCT), and MV imaging systems, as well as the radiation isocenter targeting accuracy. The deviations between the percent depth-dose curves acquired on the new linac-based system (Edge), and the previously published machine with FFF beams (TrueBeam) beyond Dmax were within 1.0% for both energies. The maximum deviation of output factors between the Edge and TrueBeam was 1.6%. The optimized dosimetric leaf gap values, which were fitted using Eclipse dose calculations and measurements based on representative spine radiosurgery plans, were 0.700 mm and 1.000 mm, respectively. For the conical cones, 6X FFF has sharper penumbra ranging from 1.2–1.8 mm (80%-20%) and 1.9–3.8 mm (90%-10%) relative to 10X FFF, which has 1.2–2.2mm and 2.3–5.1mm, respectively. The relative attenuation measurements of the couch for PA, PA (rails-in), oblique, oblique (rails-out), oblique (rails-in) were: -2.0%, -2.5%, -15.6%, -2.5%, -5.0% for 6X FFF and -1.4%, -1.5%, -12.2%, -2.5%, -5.0% for 10X FFF, respectively, with a slight decrease in attenuation versus field size. The systematic deviation between the OSMS and CBCT was -0.4 ± 0.2 mm, 0.1± 0.3mm, and 0.0 ± 0.1 mm in the vertical, longitudinal, and lateral directions. The mean values and standard deviations of the average deviation and maximum deviation of the daily Winston-Lutz tests over three months are 0.20 ± 0.03 mm and 0.66 ± 0.18 mm, respectively. Initial testing of this novel system demonstrates the technology to be highly accurate and suitable for frameless, linac-based SRS and SBRT treatment

Assessment of dredging impact on hydrodynamics of Surma River using hydrodynamic model: HEC-RAS approach

Surma River is the main source of fresh water in the South-Eastern region of Bangladesh. Every year, huge amounts of sediment loads are coming from upstream, which are settling down on the Surma River bed, hindering the safe passage of flow that contributes to the change in the hydrodynamic of the river. Recently, dredging has been done in the Sunamganj area to increase the navigability of the river. In this study, the hydrodynamics of the Surma River has been investigated to check the impact of dredging with the help of HEC-RAS. Flood frequency analyses have been done for 5, 10, 25, 50, and 100 years return periods, and a comparison of water level, velocity, and discharge has been done before and after dredging. Before dredging the water level, the flow path was very high, and velocity was low, but after dredging the water level, the flow path decreases and velocity increased. Discharge also decreases after dredging in the six stations, which are located in the dredged area, and the values are 1,375.41, 1,374.31, 1,373.73, 1,369.7, 1,373.11, and 1,372.08 m3/s. Before dredging, the values are 1,669.62, 1,665.53, 1,664.69, 1,658.12, 1,624.23, and 1,383.98 m3/s. HIGHLIGHTS Dredging causes huge funding. If it is not done in the proper place, then it is a wastage of money. My research focuses on the assessment of dredging.; Many researchers have done 1D modeling of the Surma River. But the impact assessment of dredging has not been done earlier.; This model is very innovative by which exact dredging location can be found, and its impact can be analyzed and the predication of flood can also be determined.

Generation and verification of QFix kVue Calypso-compatible couch top model for a dedicated stereotactic linear accelerator with FFF beams

This study details the generation, verification, and implementation of a treatment planning system (TPS) couch top model for patient support system used in conjunction with a dedicated stereotactic linear accelerator. Couch top model was created within the TPS using CT simulation images of the kVue Calpyso-compatible couchtop (with rails). Verification measurements were compared to TPS dose prediction for different energies (6 MV FFF and 10 MV FFF) and rail configurations (rails in and rails out) using: 1) central axis point-dose measurements with pinpoint chamber in water-equivalent phantom at 42 gantry angles for various field sizes (2 × 2 cm², 4 × 4 cm², 10 × 10 cm²); and 2) Gafchromic EBT3 film parallel to beam in acrylic slab to assess changes in surface and percent depth doses in PA geometry. To assess sensitivity of delivered dose to variations in patient lateral position, measurements at central axis using the pinpoint chamber geometry were taken at lateral couch displacements of 2, 5, and 10 mm for 6 MV FFF. The maximum percent difference for point-dose measurements was 3.24% (6 MV FFF) and 2.30% (10 MV FFF). The average percent difference for point-dose measurements was less than 1.10% for all beam energies and rail geometries. The maximum percent difference between calculated and measured dose can be as large as 13.0% if no couch model is used for dose calculation. The presence of the couch structures also impacts surface dose and PDD, which was evaluated with Gafchromic film measurements. The upstream shift in the depth of dose maximum (dmax) was found to be 10.5 mm for 6 MV FFF and 5.5 mm for 10 MV FFF for \u27Rails In\u27 configuration. Transmission of the treatment beam through the couch results in an increase in surface dose (absolute percentage) of approximately 50% for both photon energies (6 MV FFF and 10MV FFF). The largest sensitivity to lateral shifts occurred at the lateral boundary of the rail structures. The mean magnitude (standard deviation) of the deviation between shifted and centered measurements over all field sizes tested was 0.61% (0.61%) for 2 mm shifts, 0.46% (0.67%) for 5 mm shifts, and 0.86% (1.46%) for 10 mm shifts