bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐108: An Investigation of Cerenkov Light Production in the Exradin W1 Scintillator Under Various Measurement Conditions
Authors: Simiele E , Culberson W 
Published: June 2015

Purpose:To investigate the effects of depth, fiber‐optic cable bends, and incident radiation angle on Cerenkov production in the Standard Imaging Exradin W1.Methods:Measurements were completed using a Varian Clinac 21EX linear accelerator with an Exradin W1 scintillator as well as a cable‐only scintillator (no scintillation material) to isolate the Cerenkov signal. The effects of cable bend radius and location were investigated by bending the fiber‐optic cable into a circle with radii ranging from 1.0 to 10.8 cm and positioning the center of the coil at distances ranging from 10.0 to 175.0 cm from the photodiode. The effects of depth and incident radiation angle were investigated by performing measurements in water at depths ranging from 1.0 cm to 25.0 cm and angles ranging from 0° to 80°. Eclipse treatment‐planning software was utilized to ensure a consistent dose was delivered to the W1 regardless of depth or angle.Results:Measured signal in both channels of the cable‐only scintillator decreased as the bend radius decreased and as the distance between the bend and photodiode increased. A fiber bend of 1.0 cm radius produced a 17.1% decrease in the green channel response in the cable‐only scintillator. The effect of depth was less severe; a maximum increase of 6.6% in the green channel response was observed at a depth of 25.0 cm in the W1. In the angular dependence investigation, the signal in both channels of the W1 peaked at an angle of 40°; which is in agreement with the nominal Cerenkov emission angle of 45°.Conclusion:The green channel response in the W1 (mainly Cerenkov signal) varied with depth, fiber‐optic cable bends, and incident radiation angle. Fully characterizing Cerenkov production is essential to ensure it is properly accounted for in scintillator measurements.Research funding and materials received by Standard Imaging, Inc. (Middleton WI)
SU‐E‐T‐132: Assess the Shielding of Secondary Neutrons From Patient Collimator in Proton Therapy Considering Secondary Photons Generated in the Shielding Process with Monte Carlo Simulation
Authors: Yamanaka M , Takashina M , Kurosu K , Moskvin V , Das I , Koizumi M 
Published: June 2015

Purpose:In this study we present Monte Carlo based evaluation of the shielding effect for secondary neutrons from patient collimator, and secondary photons emitted in the process of neutron shielding by combination of moderator and boron‐10 placed around patient collimator.Methods:The PHITS Monte Carlo Simulation radiation transport code was used to simulate the proton beam (Ep = 64 to 93 MeV) from a proton therapy facility. In this study, moderators (water, polyethylene and paraffin) and boron (pure 1⁰B) were placed around patient collimator in this order. The rate of moderator and boron thicknesses was changed fixing the total thickness at 3cm. The secondary neutron and photons doses were evaluated as the ambient dose equivalent per absorbed dose [H*(10)/D].Results:The secondary neutrons are shielded more effectively by combination moderators and boron. The most effective combination of shielding neutrons is the polyethylene of 2.4 cm thick and the boron of 0.6 cm thick and the maximum reduction rate is 47.3 %. The H*(10)/D of secondary photons in the control case is less than that of neutrons by two orders of magnitude and the maximum increase of secondary photons is 1.0 µSv/Gy with the polyethylene of 2.8 cm thick and the boron of 0.2 cm thick.Conclusion:The combination of moderators and boron is beneficial for shielding secondary neutrons. Both the secondary photons of control and those emitted in the shielding neutrons are very lower than the secondary neutrons and photon has low RBE in comparison with neutron. Therefore the secondary photons can be ignored in the shielding neutrons.This work was supported by JSPS Core‐to‐Core Program (No.23003).This work was supported by JSPS Core‐to‐Core Program (No.23003).
SU‐E‐T‐195: Commissioning the Neutron Production of a Varian TrueBeam Linac
Authors: Irazola L , Brualla L , Rosello J , Terron JA , Sanchez‐Nieto B , Bedogni R , Sanchez‐Doblado F 
Published: June 2015

Purpose:The purpose of this work is the characterization of a new Varian TrueBeam™ facility in terms of neutron production, in order to estimate neutron equivalent dose in organs during radiotherapy treatments.Methods:The existing methodology [1] was used with the reference SRAMnd detector, calibrated in terms of thermal neutron fluence at the reference field operated by PTB (Physikalisch‐Technische‐Bundesanstalt) at the GeNF (Geesthacht‐Neutron‐Facility) with the GKSS reactor FRG‐1 [2]. Thermal neutron fluence for the 5 available possibilities was evaluated: 15 MV and 10&6 MV with and without Flattening Filter (FF and FFF, respectively). Irradiation conditions are as described in [3]. In addition, three different collimator‐MLC configurations were studied for 15 MV: (a) collimator of 10×10 cm2 and MLC fully retracted (reference), (b) field sizes of 20×20 cm2 and 10×10 cm2 for collimator and MLC respectively, and (c) collimator and MLC aperture of 10×10 cm2.Results:Thermal fluence rate at the “reference point” [3], as a consequence of the neutron production, obtained for (a) conformation in 15 MV is (1.45±0.11) x10⁴ n•cm2/MU. Configurations (b) and (c) gave fluences of 96.6% and 97.8% of the reference (a). Neutron production decreases up to 8.6% and 5.7% for the 10 MV FF and FFF beams, respectively. Finally, it decreases up to 2.8% and 0.1% for the 6 MV FF and FFF modes, respectively.Conclusion:This work evaluates thermal neutron production of Varian TrueBeam™ system for organ equivalent dose estimation. The small difference in collimator‐MLC configuration shows the universality of the methodology [3]. A decrease in this production is shown when decreasing energy from 15 to 10 MV and an almost negligible production was found for 6 MV. Moreover, a lower neutron contribution is observed for the FFF modes.[1]Phys Med Biol,2012;57:6167–6191.[2]Radiat Meas,2010;45:1513–1517.[3]Med Phys,2015;42:276–281.
SU‐E‐T‐205: Comparison of Dose‐Volume and Dose‐Mass 4D Inverse Optimization in NSCLC
Authors: Mihaylov I , Moros E 
Published: June 2015

Purpose:To compare dose‐volume (Dvh) and dose‐mass (Dmh) inverse treatment planning results, performed on time‐resolved (4D) CT scans for non‐small cell lung cancers (NSCLC), thereby accounting for the temporal variation in lung volume and mass.Methods:Ten NSCLC cases were retrospectively studied. The estimated range of tumor motion was in excess of 0.5 cm (0.7 cm to 1.8 cm) in at least one principal direction. For each case five phases, uniformly distributed over the breathing cycle, were chosen for planning. For each of the phases two IMRT plans, with Dvh and with Dmh quadratic objective cost function applied only for the organs at risk (OARs), were generated. Pure dose objective functions were used for the targets. The final dose in each case for each optimization scheme was achieved through a deformable dose accumulation over the five breathing phases. Plan quality of Dvh and Dmh optimization was evaluated by several dose indices (DIs), represented by the dose to certain volume of an OAR. Tallied DIs were cord1%, heart33%, lungs20%, lungs30%, and esophagus50%, as well as lung volumes encompassed by 20 Gy and 30 Gy isodose lines. Statistical significance in the differences among those indices was quantified with two‐tailed paired t‐tests with a significance level of 5%.Results:On average Dmh optimized plans outperformed the 4D Dvh optimized plans. The statistically significant dose reduction in cord DI1, heart DI33, esophagus DI50, lung DI20 and DI30 were 27.5%, 9.9%, 21.3%, 5.6%, and 14.7% respectively. Isovolumes of 20 Gy and 30 Gy differed by 9.6% and 6.7% respectively.Conclusions:The presented findings suggest that on average 4D Dmh optimized plans Result in better OAR sparing than 4D Dvh optimized plans. This is true for the majority of the tallied dosimetric endpoints, indicating that the potential sparing and its magnitude are patient specific.NIH
SU‐E‐T‐213: Comparison of Treatment Efficiency of Gamma Knife SRS Plans for Brain Metastases with Different Planning Methods
Authors: Feng Y , Huang Z , Lo S , Mayr N , Yuh W 
Published: June 2015

Purpose:To improve Gamma Knife SRS treatment efficiency for brain metastases and compare the differences of treatment time and radiobiological effects between two different planning methods of automatic filling and manual placement of shots with inverse planning.Methods:T1‐weighted MRI images with gadolinium contrast from five patients with a single brain metastatic‐lesion were used in this retrospective study. Among them, two were from primary breast cancer, two from primary melanoma cancer and one from primary prostate cancer. For each patient, two plans were generated in Leksell GammaPlan10.1.1 for radiosurgical treatment with a Leksell GammaKnife Perfexion machine: one with automatic filling, automatic sector configuration and inverse optimization (Method1); and the other with manual placement of shots, manual setup of collimator sizes, manual setup of sector blocking and inverse optimization (Method2). Dosimetric quality of the plans was evaluated with parameters of Coverage, Selectivity, Gradient‐Index and DVH. Beam‐on Time, Number‐of‐Shots and Tumor Control Probability(TCP) were compared for the two plans while keeping their dosimetric quality very similar. Relative reduction of Beam‐on Time and Number‐of‐Shots were calculated as the ratios among the two plans and used for quantitative analysis.Results:With very similar dosimetric and radiobiological plan quality, plans created with Method 2 had significantly reduced treatment time. Relative reduction of Beam‐on Time ranged from 20% to 51 % (median:29%,p=0.001), and reduction of Number‐of‐Shots ranged from 5% to 67% (median:40%,p=0.0002), respectively. Time of plan creation for Method1 and Method2 was similar, approximately 20 minutes, excluding the time for tumor delineation. TCP calculated for the tumors from differential DVHs did not show significant difference between the two plans (p=0.35).Conclusion:The method of manual setup combined with inverse optimization in LGP for treatment of brain metastatic lesions with the Perfexion can achieve significantly higher time efficiency without degrading treatment quality.
SU‐E‐T‐216: Comparison of Volumetrically Modulated Arc Therapy Treatment Using Flattening Filter Free Beams Vs. Flattened Beams for Partial Brain Irradiation
Authors: Yu S , Roa D , Hanna N , Sehgal V , Farol H , Kuo J , Daroui P , Ramsinghani N , Al‐Ghazi M 
Published: June 2015

Purpose:Flattening Filter Free (FFF) beams offer the potential for higher dose rates, short treatment time, and lower out of field dose. Therefore, the aim of this study was to investigate the dosimetric effects and out of field dose of Volumetric Modulated Arc Therapy (VMAT) plans using FFF vs Flattening Filtering (FF) beams for partial brain irradiation.Methods:Ten brain patients treated with a 6FF beam from a Truebeam STX were analyzed retrospectively for this study. These plans (46Gy at 2 Gy per fraction) were re‐optimized for 6FFF beams using the same dose constraints as the original plans. PTV coverage, PTV Dmax, total MUs, and mean dose to organs‐at‐risk (OAR) were evaluated. In addition, the out‐of‐field dose for 6FF and 6FFF plans for one patient was measured on an anthropomorphic phantom. TLDs were placed inside (central axis) and outside (surface) the phantom at distances ranging from 0.5 cm to 17 cm from the field edge. Paired T‐test was used for statistical analysis.Results:PTV coverage and PTV Dmax were comparable for the FF and FFF plans with 95.9% versus 95.6% and 111.2% versus 111.9%, respectively. Mean dose to the OARs were 3.7% less for FFF than FF plans (p<0.0001). Total MUs were, on average, 12.5% greater for FFF than FF plans with 481±55 MU (FFF) versus 429±50 MU (FF), p=0.0003. On average, the measured out of field dose was 24% less for FFF compared to FF, p<0.0001. A similar beam‐on time was observed for the FFF and FF treatment.Conclusion:It is beneficial to use 6FFF beams for regular fractionated brain VMAT treatments. VMAT treatment plans using FFF beams can achieve comparable PTV coverage but with more OAR sparing. The out of field dose is significant less with mean reduction of 24%.
SU‐E‐T‐218: Comprehensive Plan Integrity and Quality Check by Accessing Eclipse Planning Data Remotely Via a Novel Eclipse‐API Client‐Server Interface
Authors: Yang D , Wu Y , He G , Chang X , Olsen L , Mutic S 
Published: June 2015

Purpose:It is desirable to seamlessly and remotely access treatment plan data in Eclipse in order to allow sequential treatment planning and quality assurance automation, e.g. automatic plan quality check and comprehensive plan integrity check. The manual DICOM export function and the native Eclipse SQL interface cannot fully support the needs. Therefore we have developed a procedure and computer programs to enable access of Eclipse planning data remotely, and directly from Eclipse server, via Eclipse API, so to support such clinical software applications requiring advanced mathematics and extensive computation.Methods:A novel client‐server interface was developed to allow external software programs to remotely and seamlessly access the Eclipse planning data using Eclipse‐API from outside the Eclipse workstations. Remote (client) programs send requests as network socket messages to the server program running on an Eclipse workstation, and the server program uses Eclipse‐API functions to access planning data, and sends data back to the client programs.Results:The Eclipse‐API client‐server interface were implemented and successfully tested in clinical settings. Comprehensive plan integrity and quality check programs, which were previously supporting Pinnacle TPS only, have been extended to support Eclipse and are executable on any network computer in the department independent of Eclipse installation. Advanced plan check features, e.g. IMRT optimization structure overlapping check, on‐the‐fly derivation of new structures in planning quality check, that were previously not possible in C# programs via Eclipse‐API, have now been implemented, allowed by the inclusion of advanced mathematics packages e.g. MATLAB in the external programs.Conclusion:The new Eclipse‐API client‐server interface has enabled Eclipse data to be accessed remotely and seamlessly. It has the potential to significantly improve the comprehensiveness of third party software programs based on Eclipse‐API for both clinical and research purposes, and would be useful to extend the Eclipse / ARIA ecosystem.This work was partially funded by Varian Medical System
SU‐E‐T‐228: Coupling Database Search with Atlas‐Based Segmentation: Application to Esophageal Delineation
Authors: Schreibmann E , Elder E 
Published: June 2015

Purpose:Atlas segmentation is a popular method of warping a pre‐segmented template to a new patient anatomy, however for anatomy in the thorax and abdomen large inter‐patient variations exists, and a single template does not provide the required clinical accuracy. With the proposed method the CT dataset to be segmented is matched to a similar case in a database of pre‐segmented templates.Method:The key aspect of the approach is to search in a database of images and associated segmentations for a case with similar anatomy. A set of 29 previous cases have been pre‐registered to a common reference and cropped to the esophageal region to construct a compact representation of the database through quantification with a principal component analysis algorithm that is designed to find similar cases by direct comparison of the eigenvectors for ranking database cases according to the similarity with the query case. Once a similar case at image level is identified in the database, an affine registration is performed to transfer the pre‐segmentations from the database to the images to be segmented.Results:The algorithm was applied for segmenting the esophageal region on 12 test cases and the conformity between the atlas and manual segmentations were measured using the Dice coefficient and the Euclidian distance. Dice coefficients ranged between (0.60, 0.87) with mean of 0.78 and standard deviation of 0.09. Mean distance ranged between (0.18,1.66) mm mean of 0.82 mm, SD of 0.51. Once registered to the database, searching in the database takes seconds as it does not compare the images directly but just the components of the PCA vectors, adding little overhead to the overall delineation algorithm.Conclusions:Selection of a similar atlas from a database can be achieved with little computational overhead by using a PCA‐based similarity metric as demonstrated for esophageal segmentation.
SU‐E‐T‐239: Design and Evaluation of a Nozzle Shielding System in Passively Scattered Proton Therapy
Authors: Wroe A , McAuley G , Slater J 
Published: June 2015

Purpose:To design, implement and evaluate a shielding system that will reduce out‐of‐field dose experienced by the patient and associated electronic systems in passively scattered proton therapy treatment.Methods:A multi‐stage neutron shielding system was retrofitted to the Gantry 1 treatment nozzle at Loma Linda University Medical Center. The system uses multiple borated polyethylene plates staged after the primary beam modifying devices to attenuate and absorb neutrons produced by such devices. This arrangement locates increasing levels of shielding between the sources of secondary particles in the nozzle and the patient. Additionally, the design of this shielding structure allows it to be easily retrofitted to an existing proton nozzle system without impacting design or treatment beam characteristics. The effectiveness of the shielding was evaluated both through experimental measurements and Geant4 Monte Carlo simulations.Results:Measurements were completed with Landauer Luxel+ dosimeters that use optically stimulated luminescence and CR‐39 to detect fast neutrons, thermal neutrons, protons, photons and beta particles. Measurements of a 250 MeV proton beam indicated that the shielding system reduced out‐of‐field dose to the patient by almost half with dose equivalent values at 50 and 40 cm from the field edge decreasing from 0.965 and 1.262 mSv/Gy to 0.596 and 0.777 mSv/Gy respectively. The installation of the multi‐stage shielding system also reduced dose equivalent experienced by electronic systems installed in the treatment room by up to 80%. Geant4 simulations were also used to evaluate the neutron fluence at various positions in the treatment room as well as provide information on microdosimetry spectra within the patient and treatment room.Conclusion:The shielding system described above proved to be an effective an inexpensive method of reducing out‐of‐field doses to the patient and electronic systems and can be easily retrofitted to existing passive scattering nozzles.
SU‐E‐T‐245: Detection of the Photon Target Damage in Varian Linac Based On Periodical Quality Assurance Measurements
Authors: Gao S , Balter P , Wang X , Sadagopan R , Pollard J 
Published: June 2015

Purpose:To determine the best dosimetric metric measured by our routine QA devices for diagnosing photon target failure on a Varian C‐series linac.Methods:We have retrospectively reviewed and analyzed the dosimetry data from a Varian linac with a target degradation that was undiagnosed for one year. A failure in the daily QA symmetry tests was the first indication of an issue. The beam was steered back to a symmetric shape and water scans indicated the beam energy had changed but stayed within the manufacturer's specifications and agreed reasonably with our treatment planning system data. After the problem was identified and the target was replaced, we retrospectively analyzed our QA data including diagonals normalized flatness (F_DN) from the daily device (DQA3), profiles from an ionization chamber array (IC Profiler), as well as profiles and PDDs from a 3D water Scanner (3DS). These metrics were cross‐compared to determine which was the best early indicator of target degradation.Results:A 3% change in FDN measured by the DQA3 was found to be an early indicator of target degradation. It is more sensitive than changes in output, symmetry, flatness or PDD. All beam shape metrics (flatness at dmax and 10 cm depth, and F_DN) indicated an energy increase while the PDD indicated an energy decrease. This disagreement between the beam‐shape based energy metrics (F_DN and flatness) and PDD based energy metric may indicate target failure as opposed to an energy change resulting from changes in the incident electron energy.Conclusion:Photon target degradation has been identified as a failure mode for linacs. The manufacturer's test for this condition is highly invasive and requires machine down time. We have demonstrated that the condition could be caught early based upon data acquired during routine QA activities, such as the F_DN.
SU‐E‐T‐249: Determining the Sensitivity of Beam Profile Parameters for Detecting Energy Changes in Flattening Filter‐Free Beams
Authors: Mooney K , Yaddanapudi S , Mutic S , Goddu S 
Published: June 2015

Purpose:To identify the beam profile parameters that can be used to detect energy changes in a flattening filter‐free photon beams.Methods:Flattening filter‐free beam profiles (inline, crossline, and diagonals) were measured for multiple field sizes (25×25cm and 10×10cm) at 6MV on a clinical system (Truebeam, Varian Medical Systems Palo Alto CA). Profiles were acquired for baseline energy and detuned beams by changing the bending magnet current (BMC), above and below baseline. The following profile parameters were measured: flatness (off‐axis ratio at 80% of field size), symmetry, uniformity, slope, and the off‐axis ratio (OAR) at several off‐axis distances. Tolerance values were determined from repeated measurements. Each parameter was evaluated for sensitivity to the induced beam changes, and the minimum detectable BMC change was calculated for each parameter by calculating the change in BMC that would Result in a change in the parameter above the measurement tolerance.Results:Tolerance values for the parameters were‐Flatness≤0.1%; Symmetry≤0.4%; Uniformity≤0.01%; Slope≤ 0.001%/mm. The measurements made with a field size of 25cm and a depth of d=1.5cm showed the greatest sensitivity to bending magnet current variations. Uniformity had the highest sensitivity, able to detect a change in BMC of BMC=0.02A. The OARs and slope were sensitive to the magnitude and direction of BMC change. The sensitivity in the flatness parameter was BMC=0.04A; slope was sensitive to BMC=0.05A. The sensitivity decreased for OARs measured closer to central axis‐BMC(8cm)=0.23A; BMC(5cm)=0.47A; BMC(2cm)=1.35A. Symmetry was not sensitive to changes in BMC.Conclusion:These tests allow for better QA of FFF beams by setting tolerance levels to beam parameter baseline values which reflect variations in machine calibration. Uniformity is most sensitive to BMC changes, while OARs provide information about magnitude and direction of miscalibration.Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.