bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐136: Assessment of Seasonal Linear Accelerator Output Variations and Associated Impacts
Authors: Bartolac S , Letourneau D 
Published: June 2015

Purpose:Application of process control theory in quality assurance programs promises to allow earlier identification of problems and potentially better quality in delivery than traditional paradigms based primarily on tolerances and action levels. The purpose of this project was to characterize underlying seasonal variations in linear accelerator output that can be used to improve performance or trigger preemptive maintenance.Methods:Review of runtime plots of daily (6 MV) output data acquired using in house ion chamber based devices over three years and for fifteen linear accelerators of varying make and model were evaluated. Shifts in output due to known interventions with the machines were subtracted from the data to model an uncorrected scenario for each linear accelerator. Observable linear trends were also removed from the data prior to evaluation of periodic variations.Results:Runtime plots of output revealed sinusoidal, seasonal variations that were consistent across all units, irrespective of manufacturer, model or age of machine. The average amplitude of the variation was on the order of 1%. Peak and minimum variations were found to correspond to early April and September, respectively. Approximately 48% of output adjustments made over the period examined were potentially avoidable if baseline levels had corresponded to the mean output, rather than to points near a peak or valley. Linear trends were observed for three of the fifteen units, with annual increases in output ranging from 2–3%.Conclusion:Characterization of cyclical seasonal trends allows for better separation of potentially innate accelerator behaviour from other behaviours (e.g. linear trends) that may be better described as true out of control states (i.e. non‐stochastic deviations from otherwise expected behavior) and could indicate service requirements. Results also pointed to an optimal setpoint for accelerators such that output of machines is maintained within set tolerances and interventions are required less frequently.
SU‐E‐T‐140: Automated Daily Patient Treatment Chart Checks Using Data Mining System
Authors: Dhabaan A , Jiang X , Schreibmann E , Elder E 
Published: June 2015

Purpose:The aim of this study is the use of data mining techniques to establish an automated daily chart check. This automated technique increases the likelihood of error capture before subsequent treatment delivery, allowing the delivery of the prescribed treatment course with high confidence level. Furthermore, the scope of inspected parameters expands compared to that able to be performed manually.Methods:Considering the significant number of parameters that are checked, performing chart check manually has a number of shortfalls such as human error, comparison of incorrect field and inability to verify MLC shape and leaves positions. Developing a computer‐driven automatic chart checkers eliminates human error, improves the accuracy and the frequency of the process, shortens the time of error discovery and correction, increases the number of parameters that are checked, allows inspection of parameters that are impossible to check manually and reduces the time the physicist need to spend to check a chart. This work will utilizes in house data mining framework (RT Metrix) to establish this QA function. The system utilize ARIA data base to verify the treatment delivery by comparing the plan record in ARIA to record verification which is the delivery parameters. Acceptable tolerances were defined in the software. If the delivery variation from the tolerance is minor then the system will show a warning flag but if the variation is major the system will flag the delivery as failed.Results:This system has been developed, tested, compared to ARIA Chart QA and is currently able to check parameters that routinely checked by the clinical physicist.Conclusion:The automated chart check system is feasible and offers great potential in the improvement of patient delivery quality assurance. The system can be developed further to include more QA functions.
SU‐E‐T‐142: Automatic Linac Log File: Analysis and Reporting
Authors: Gainey M , Rothe T 
Published: June 2015

Purpose:End to end QA for IMRT/VMAT is time consuming. Automated linac log file analysis and recalculation of daily recorded fluence, and hence dose, distribution bring this closer.Methods:Matlab (R2014b, Mathworks) software was written to read in and analyse IMRT/VMAT trajectory log files (TrueBeam 1.5, Varian Medical Systems) overnight, and are archived on a backed‐up network drive (figure). A summary report (PDF) is sent by email to the duty linac physicist. A structured summary report (PDF) for each patient is automatically updated for embedding into the R&V system (Mosaiq 2.5, Elekta AG). The report contains cross‐referenced hyperlinks to ease navigation between treatment fractions. Gamma analysis can be performed on planned (DICOM RTPlan) and treated (trajectory log) fluence distributions. Trajectory log files can be converted into RTPlan files for dose distribution calculation (Eclipse, AAA10.0.28, VMS).Results:All leaf positions are within +/−0.10mm: 57% within +/−0.01mm; 89% within 0.05mm. Mean leaf position deviation is 0.02mm. Gantry angle variations lie in the range −0.1 to 0.3 degrees, mean 0.04 degrees. Fluence verification shows excellent agreement between planned and treated fluence. Agreement between planned and treated dose distribution, the derived from log files, is very good.Conclusion:Automated log file analysis is a valuable tool for the busy physicist, enabling potential treated fluence distribution errors to be quickly identified. In the near future we will correlate trajectory log analysis with routine IMRT/VMAT QA analysis. This has the potential to reduce, but not eliminate, the QA workload.
SU‐E‐T‐145: Beam Characteristics of Flattening Filter Free Beams Including Low Dose Rate Setting
Authors: Uehara K , Ogata T , Nakayama M , Shinji T , Nishimura H , Masutani T , Ishihara T , Ejima Y , Sasaki R 
Published: June 2015

Purpose:In commissioning of volumetric modulated arc therapy (VMAT), it is necessary to evaluate the beam characteristics of various dose rate settings with potential to use. The aim of this study is to evaluate the beam characteristics of flattened and flattening filter free (FFF) including low dose rate setting.Methods:We used a Varian TrueBeam with Millennium 120 MLC. Both 6 and 10 MV beams with or without flattening filter were used for this study. To evaluate low‐dose rate FFF beams, specially‐designed leaf sequence files control out‐of‐field MLC leaf pair at constant dose rate ranging from 80 to 400 MU/min. For dose rate from 80 MU/min to the maximum usable value of all energies, beam output were measured using ionization chamber (CC04, IBA). The ionization chamber was inserted into water equivalent phantom (RT3000‐New, R‐tech), and the phantom was set with SAD of 100cm. The beam profiles were performed using the 2D diode array (Profiler2, Sun Nuclear). The SSD was set to 90cm and a combined 30cmx30cmx9cm phantom which consisted of solid water slabs was put on the device. All measurement were made using 100MU irradiation for 10cmx10cm jaw‐defined field size with a gantry angle of 0°.Results:In all energies, the dose rate dependences with beam output and variation coefficient were within 0.2% and 0.07%, respectively. The flatness and symmetry exhibited small variations (flatness ≤0.1 point and symmetry≤0.3 point at absolute difference).Conclusion:We had studied the characteristics of flattened and FFF beam over the 80 MU/min. Our results indicated that the beam output and profiles of FFF of TrueBeam linac were highly stable at low dose rate setting.
SU‐E‐T‐148: Benchmarks and Pre‐Treatment Reviews: A Study of Quality Assurance Effectiveness
Authors: Lowenstein J , Nguyen H , Roll J , Walsh A , Tailor A , Followill D 
Published: June 2015

Purpose:To determine the impact benchmarks and pre‐treatment reviews have on improving the quality of submitted clinical trial data.Methods:Benchmarks are used to evaluate a site's ability to develop a treatment that meets a specific protocol's treatment guidelines prior to placing their first patient on the protocol. A pre‐treatment review is an actual patient placed on the protocol in which the dosimetry and contour volumes are evaluated to be per protocol guidelines prior to allowing the beginning of the treatment. A key component of these QA mechanisms is that sites are provided timely feedback to educate them on how to plan per the protocol and prevent protocol deviations on patients accrued to a protocol. For both benchmarks and pre‐treatment reviews a dose volume analysis (DVA) was performed using MIM softwareTM. For pre‐treatment reviews a volume contour evaluation was also performed.Results:IROC Houston performed a QA effectiveness analysis of a protocol which required both benchmarks and pre‐treatment reviews. In 70 percent of the patient cases submitted, the benchmark played an effective role in assuring that the pre‐treatment review of the cases met protocol requirements. The 35 percent of sites failing the benchmark subsequently modified there planning technique to pass the benchmark before being allowed to submit a patient for pre‐treatment review. However, in 30 percent of the submitted cases the pre‐treatment review failed where the majority (71 percent) failed the DVA. 20 percent of sites submitting patients failed to correct their dose volume discrepancies indicated by the benchmark case.Conclusion:Benchmark cases and pre‐treatment reviews can be an effective QA tool to educate sites on protocol guidelines and to minimize deviations. Without the benchmark cases it is possible that 65 percent of the cases undergoing a pre‐treatment review would have failed to meet the protocols requirements.Support: U24‐CA‐180803
SU‐E‐T‐150: Brachytherapy QA Employing a High Resolution Liquid Filled Ionisation Chamber Array: Initial Experience and Limitations
Authors: Gainey M , Kollefrath M , Bruggmoser G 
Published: June 2015

Purpose:Verifying a complex 3D brachytherapy dose distribution by measurement is non‐trivial. Ideally a photon detector array should be independent of energy and angle, have high spatial resolution and be robust for routine clinical use.Methods:An iridium‐192 source was used. A PMMA jig was constructed comprising an outer slab and a central insert with eight milled channels for 1.33mm (outer diameter) steel needles, see figure. All calculations were performed using an empty CT study reconstructing eight virtual needles (QA‐CT), using the v2 source model (Elekta AG, Sweden). A high resolution liquid filled ionisation chamber array SRS1000, together with Verisoft software v6.0 (PTW Freiburg, Germany), was used to perform measurements of plans of increasing complexity to evaluate its suitability for device‐ and patient‐specific QA. The dimension of backscatter material was investigated. The patient plan dwell time distribution was entered manually into the QA‐CT and the dose distribution was calculated.Results:Our measurements indicate that the array is independent of energy and angle. The resulting measured dose values are linearly interpolated to 2025 values. Shifts of 1mm of the entire needle are readily detectable. Individual dwell position shifts (2.5mm) are also readily measurable. Moreover a dwell time increase of 1 second both in the edge and central region are detectable.Conclusion:The high resolution SRS1000 array is a powerful instrument for brachytherapy QA enabling 977 simultaneous measurements to be performed. Our measurements suggest 60mm of RW3 backscatter material upstream and downstream are sufficient. Local percentage difference analysis is useful for device based QA, normalized relative percentage difference is arguably better for patient specific QA. Automated transfer of patient plan dwell time distribution to the QA plan is required to enable a comprehensive patient QA study to be performed. Moreover the described measurement technique can be used for commissioning new brachytherapy applicators.
SU‐E‐T‐151: Breathing Synchronized Delivery (BSD) Planning for RapicArc Treatment
Authors: Lu W , Chen M , Jiang S 
Published: June 2015

Purpose:To propose a workflow for breathing synchronized delivery (BSD) planning for RapicArc treatment.Methods:The workflow includes three stages: screening/simulation, planning, and delivery. In the screening/simulation stage, a 4D CT with the corresponding breathing pattern is acquired for each of the selected patients, who are able to follow their own breathing pattern. In the planning stage, one breathing phase is chosen as the reference, and contours are delineated on the reference image. Deformation maps to other phases are performed along with contour propagation. Based on the control points of the initial 3D plan for the reference phase and the respiration trace, the correlation with respiration phases, the leaf sequence and gantry angles is determined. The beamlet matrices are calculated with the corresponding breathing phase and deformed to the reference phase. Using the 4D dose evaluation tool and the original 3D plan DVHs criteria, the leaf sequence is further optimized to meet the planning objectives and the machine constraints. In the delivery stage, the patients are instructed to follow the programmed breathing patterns of their own, and all other parts are the same as the conventional Rapid‐Arc delivery.Results:Our plan analysis is based on comparison of the 3D plan with a static target (SD), 3D plan with motion delivery (MD), and the BSD plan. Cyclic motion of range 0 cm to 3 cm was simulated for phantoms and lung CT. The gain of the BSD plan over MD is significant and concordant for both simulation and lung 4DCT, indicating the benefits of 4D planning.Conclusion:Our study shows that the BSD plan can approach the SD plan quality. However, such BSD scheme relies on the patient being able to follow the same breathing curve that is used in the planning stage during radiation delivery.Funded by Varian Medical Systems.
SU‐E‐T‐154: Calculation of Tissue Dose Point Kernels Using GATE Monte Carlo Simulation Toolkit to Compare with Water Dose Point Kernel
Authors: Khazaee M , Asl A Kamali , Geramifar P 
Published: June 2015

Purpose:the objective of this study was to assess utilizing water dose point kernel (DPK)instead of tissue dose point kernels in convolution algorithms.to the best of our knowledge, in providing 3D distribution of absorbed dose from a 3D distribution of the activity, the human body is considered equivalent to water. as a Result tissue variations are not considered in patient specific dosimetry.Methods:In this study Gate v7.0 was used to calculate tissue dose point kernel. the beta emitter radionuclides which have taken into consideration in this simulation include Y‐90, Lu‐177 and P‐32 which are commonly used in nuclear medicine. the comparison has been performed for dose point kernels of adipose, bone, breast, heart, intestine, kidney, liver, lung and spleen versus water dose point kernel.Results:In order to validate the simulation the Result of 90Y DPK in water were compared with published results of Papadimitroulas et al (Med. Phys., 2012). The results represented that the mean differences between water DPK and other soft tissues DPKs range between 0.6 % and 1.96% for 90Y, except for lung and bone, where the observed discrepancies are 6.3% and 12.19% respectively. The range of DPK difference for 32P is between 1.74% for breast and 18.85% for bone. For 177Lu, the highest difference belongs to bone which is equal to 16.91%. For other soft tissues the least discrepancy is observed in kidney with 1.68%.Conclusion:In all tissues except for lung and bone, the results of GATE for dose point kernel were comparable to water dose point kernel which demonstrates the appropriateness of applying water dose point kernel instead of soft tissues in the field of nuclear medicine.
SU‐E‐T‐159: Characteristics of Fiber‐Optic Radiation Sensor for Proton Therapeutic Beam
Authors: Son J , Kim M , Hwang U , Park J , Lim Y , Lee S , Park S , Yoon M , Shin D 
Published: June 2015

Purpose:A fiber‐optic radiation sensor using Cerenkov radiation has been widely studied for use as a dosimeter for proton therapeutic beam. Although the fiber‐optic radiation sensor has already been investigated for proton therapeutic, it has been examined relatively little work for clinical therapeutic proton beams. In this study, we evaluated characteristics of a fiber‐optic radiation sensor for clinical therapeutic proton beams. We experimentally evaluated dose‐rate dependence, dose response and energy dependence for the proton beam.Methods:A fiber‐optic radiation sensor was placed in a water phantom. Beams with energies of low, middle and high were used in the passively‐scattered proton therapeutic beam at the National Cancer Center in Korea. The sensor consists of two plastic optical fibers (POF). A reference POF and 2 cm longer POF were used to utilize the subtraction method for having sensitive volume. Each POF is optically coupled to the Multi‐Anode Photo Multiplier Tube (MAPMT) and the MAPMT signals are processed using National Instruments Data Acquisition System (NI‐DAQ). We were investigated dosimetric properties including dose‐rate dependence, dose response and energy dependence.Results:We have successfully evaluated characteristics of a fiber optic radiation sensor using Cerenkov radiation. The fiber‐optic radiation sensor showed the dose response linearity and low energy dependence. In addition, as the dose‐rate was increased, Cerenkov radiation increased linearly.Conclusion:We evaluated the basic characteristics of the fiber optic radiation sensor, the dosimetry tool, to raise the quality of proton therapy. Based on the research, we developed a real time dosimetry system of the optic fiber to confirm the real time beam position and energy for therapeutic proton pencil beam.
SU‐E‐T‐160: Characterization and Monitoring of Linear Accelerator Gantry Radiation Isocenter Motion
Authors: Letourneau D , Amin N , Wang K , Norrlinger B , Jaffray D , McNiven A 
Published: June 2015

Purpose:To characterize the motion of the radiation isocenter, over time, as a function of gantry rotation for multiple linear accelerators (linacs). Two semi‐automated image‐based quality control (QC) test workflows were designed to achieve this goal.Methods:The full QC‐test workflow for motion characterization consisted of acquiring 16 megavoltage images at 8 gantry angles of a ball‐bearing suspended off the end of the couch. Performance constancy was assessed using a shortened QC‐test workflow which consisted of imaging a cube phantom placed on the couch (5 images at 4 gantry angles). Both workflows use an image processing algorithm to determine the field center and phantom position on each image and computed radiation isocenter motion as a function of gantry angle. Motion was characterized for 9 linacs of same model and performance monitored for 2 months on 3 linacs.Results:The maximum isocenter motion determined with the full‐workflow for 9 linacs was within 0.38–0.79 mm. The shortened‐workflow usually agreed within 0.1 mm with the full‐workflow and the time required for these methods was about 4 and 15 min, respectively. For all linacs, the isocenter motion perpendicular to the gantry rotation plane followed a consistent pattern with maximum amplitude of 0.36–0.59 mm. In the gantry rotation plane, the variation among linacs was higher and the beam axis described a circle of up to 0.6 mm radius around the gantry axis of rotation (2 linacs). The radiation isocenter motion was stable as a function of time for the monitored linacs and was within ±0.1 mm of the average.Conclusion:Radiation isocenter motion parallel and perpendicular to the gantry rotation plane was characterized. In the gantry rotation plane, beam spot positioning adjustment might be used to reduce the observed radiation isocenter motion. A shortened‐workflow was designed and enables performance monitoring over time.
SU‐E‐T‐164: Characterization of Breast Deformation During Accuboost TM Treatment
Authors: Garcia‐Cobian J , Liu F 
Published: June 2015

Purpose:During treatment using AccuboostTM (Advanced Radiation Therapy, Tyngsboro, MA) applicators the breast is compressed between two paddles in order to immobilize it. This causes the breast tissue to expand. The purpose of this study was to analyze the nature of this deformation.Methods:CT scans of a breast phantom (Computerized Imaging Reference Systems, Norfolk, VA) were acquired at different compressions in the cranial‐caudal (CC) direction. These were performed by placing the phantom between two plates whose position is controlled by a manual crank. The phantom masses were contoured in order to simulate the clips placed after surgery. For all scans the mean distance between the masses was computed. Additionally, deformable registration was performed between two scans using the Velocity software (Varian Medical Systems, Palo Alto, CA) to assess the shifts of each of these masses.Results:As the compression increases so does the average distance between the masses. The relationship between deformation and compression is not linear. Additionally, the largest displacements are in the direction of compression. The mean shift is 1.8mm. The shifts in the RT‐LT direction and ANT‐POST direction are 1.1 mm and 0.7 mm respectivelyConclusion:When treating patients the clips shift their position as a Result of the plate compression. For CC compressions this is not a problem if they shift their position primarily in the superior‐inferior direction. The problem of not being able to cover all clips (target area) can arise when they shift position on a plane perpendicular to the patient. For clips which are already near the chest wall, care should be exercised not to compress the breast in such a way as to move those clips out of the treatable area.These preliminary results show a larger shift in the RT‐LT direction than the ANT‐POST one. Further research will seek to either confirm or infirm this.