bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐265: Calibration of EBT2 Film Using the Microtek ScanMaker 9800XL Plus Flatbed Scanner with a Modified One Red‐Channel After Three‐Channel Method
Authors: Chang L 
Published: July 2016

Purpose:In this study, we propose a technique to accurately calibrate the film using the Microtek ScanMaker 9800XL plus flatbed scanner following the “one red‐channel after three‐channel method” [Chang et al., Med. Phys. 42, 5838–5847 (2015)], which would be modified for this application.Methods:Following the PDD method, 6‐MV photon beams of two different MUs were delivered to eight EBT2 films (four films for each MU), where each film was tightly sandwiched in a 30‐cm cubic polystyrene phantom and parallel to the beam central axis. Before and after irradiation, all films were scanned through the Microtek 9800XL plus scanner, and the pixel values for red, green, and blue channels were extracted along the beam central axis on the film and fitted to the corresponding depth doses. Before performing the “one red‐channel after three‐channel method”, the irradiated film image first needs to be modified with a template matrix, which was generated through the pre‐scanned background images. The calibrated results were compared with the traditional one red‐channel method based on the net optical density.Results:Without using the template matrix, the three channel method cannot be correctly performed, since the pixel values did not follow the rational fitting form. Through our proposed method, the differences between the fitted dose and the delivered dose were within 2%, while that of the traditional one red channel method would be higher than 3%.Conclusion:We proposed a new technique that the one‐red channel after three‐channel method can be applied to the films scanned on a Microtek 9800XL plus scanner, and in this way, the calibration accuracy was improved. This method could also be used for other brand scanner to improve the calibration accuracy.MOST No. 104‐2221‐E‐214‐014
SU‐F‐T‐268: A Feasibility Study of Independent Dose Verification for Vero4DRT
Authors: Yamashita M , Takahashi R , Kokubo M , Takayama K , Tanabe H , Sueoka M , Ishii M , Okuuchi N , Iwamoto Y , Tachibana H 
Published: July 2016

Purpose:Vero4DRT (Mitsubishi Heavy Industries Ltd.) has been released for a few years. The treatment planning system (TPS) of Vero4DRT is dedicated, so the measurement is the only method of dose verification. There have been no reports of independent dose verification using Clarksonbased algorithm for Vero4DRT. An independent dose verification software program of the general‐purpose linac using a modified Clarkson‐based algorithm was modified for Vero4DRT. In this study, we evaluated the accuracy of independent dose verification program and the feasibility of the secondary check for Vero4DRT.Methods:iPlan (Brainlab AG) was used as the TPS. PencilBeam Convolution was used for dose calculation algorithm of IMRT and X‐ray Voxel Monte Carlo was used for the others. Simple MU Analysis (SMU, Triangle Products, Japan) was used as the independent dose verification software program in which CT‐based dose calculation was performed using a modified Clarkson‐based algorithm. In this study, 120 patients’ treatment plans were collected in our institute. The treatments were performed using the conventional irradiation for lung and prostate, SBRT for lung and Step and shoot IMRT for prostate. Comparison in dose between the TPS and the SMU was done and confidence limits (CLs, Mean ± 2SD %) were compared to those from the general‐purpose linac.Results:As the results of the CLs, the conventional irradiation (lung, prostate), SBRT (lung) and IMRT (prostate) show 2.2 ± 3.5% (CL of the general‐purpose linac: 2.4 ± 5.3%), 1.1 ± 1.7% (−0.3 ± 2.0%), 4.8 ± 3.7% (5.4 ± 5.3%) and −0.5 ± 2.5% (−0.1 ± 3.6%), respectively. The CLs for Vero4DRT show similar results to that for the general‐purpose linac.Conclusion:The independent dose verification for the new linac is clinically available as a secondary check and we performed the check with the similar tolerance level of the general‐purpose linac.This research is partially supported by Japan Agency for Medical Research and Development (AMED)
SU‐F‐T‐269: Preliminary Experience of Kuwait Cancer Control Center (KCCC) On IMRT Treatment Planning and Pre‐Treatment Verification
Authors: Sethuraman TKR , Sherif M , Subramanian N , Zoueil O , Mirza K 
Published: July 2016

Purpose:The complexity of IMRT delivery requires pre‐treatment quality assurance and plan verification. KCCC has implemented IMRT clinically in few sites and will extend to all sites. Recently, our Varian linear accelerator and Eclipse planning system were upgraded from Millennium 80 to 120 Multileaf Collimator (MLC) and from v8.6 to 11.0 respectively. Our preliminary experience on the pre‐treatment quality assurance verification is discussed.Methods:Eight Breast, Three Prostate and One Hypopharynx cancer patients were planned with step and shoot IMRT. All breast cases were planned before the upgrade with 60% cases treated. The ICRU 83 recommendations were followed for the dose prescription and constraints to OAR for all cases. Point dose measurement was done with CIRS cylindrical phantom and PTW 0.125 cc ionization chamber. Measured dose was compared with calculated dose at the point of measurement. Map CHECK diode array phantom was used for the plan verification. Planned and measured doses were compared by applying gamma index of 3% (dose difference) / 3 mm DTA (average distance to agreement). For all cases, a plan is considered to be successful if more than 95% of the tested diodes pass the gamma test. A prostate case was chosen to compare the plan verification before and after the upgrade.Results:Point dose measurement results were in agreement with the calculated doses. The maximum deviation observed was 2.3%. The passing rate of average gamma index was measured higher than 97% for the plan verification of all cases. Similar result was observed for plan verification of the chosen prostate case before and after the upgrade.Conclusion:Our preliminary experience from the obtained results validates the accuracy of our QA process and provides confidence to extend IMRT to all sites in Kuwait.
SU‐F‐T‐277: Using Dose Weighted Mean Effective Depth to Improve Accuracy of Secondary MU Calculation for VMAT Plans
Authors: Qu H , Yu N , Qi P , Godley A , Xia P 
Published: July 2016

Purpose:In commercial secondary dose calculation system, an average effective depth is used to calculate the Monitor Units for an arc beam from the volumetric modulated arc (VMAT) plans. Typically, an arithmetic mean of the effective depths (AMED) of a VMAT arc beam is used, which may result in large MU discrepancy from that of the primary treatment planning system. This study is to demonstrate the use of a dose weighted mean effective depth (DWED) can improve accuracy of MU calculation for the secondary MU verification.Methods:In‐house scripts were written in the primary treatment planning system (TPS) to first convert a VMAT arc beam to a series of static step & shoot beams (every 4 degree). The computed dose and effective depth of each static beam were then used to obtain the dose weighted mean effective depth (DWED) for the VMAT beam. The DWED was used for the secondary MU calculation for VMAT plans. Six lung SBRT VMAT plans, eight head and neck VMAT plans and ten prostate VMAT plans that had > 5% MU deviations (failed MU verification) using the AMED method were recalculated with the DWED. For comparison, same number VMAT plans that had < 5% MU deviations (passed MU verification) using AMED method were also reevaluated with the dose weighted mean effective depth method.Results:For MU verification passed plans, the mean and standard deviation of MU differences between the TPS and the secondary calculation program were 2.2%±1.5% for the AMED and 2.1%±1.7% for the DMED method. For the failed plans, the mean and standard deviation of MU differences of TPS to the secondary calculation program were 9.9%±4.7% and 4.7%±2.6, respectively.Conclusion:The dose weighted mean effective depth improved MU calculation accuracy which can be used for the pre‐treatment MU verification of VMAT plans.
SU‐F‐T‐279: Impact of Beam Energy Drifts On IMRT Delivery Accuracy
Authors: Goddu S , Kamal G , Herman A , Edwards S , Yaddanapudi S , Oddiraju S , Cai B , Rangaraj D , Mutic S 
Published: July 2016

Purpose:According to TG‐40 percent‐depth‐dose (PDD) tolerance is ±2% but TG‐142 is ±1%. Now the question is, which one is relevant in IMRT era? The primary objective of this study is to evaluate dosimetric impact of beam‐energy‐drifts on IMRT‐delivery.Methods:Beam‐energy drifts were simulated by adjusting Linac's bending‐magnet‐current (BMC) followed by tuning the pulse‐forming network and adjusting gun‐current. PDD change of −0.6% and +1.2% were tested. Planar‐dosimetry measurements were performed using an ionization‐chamber‐array in solid‐water phantoms. Study includes 10‐head‐and‐neck and 3‐breast cancer patients. en‐face beam‐deliveries were also tested at 1.3cm and 5.3cm depths. Composite and single‐field dose‐distributions were compared against the plans to determine %Gamma pass‐rates (%GPRs). For plan dose comparisons, changes in %Gamma pass‐rates (cPGPRs) were computed/reported to exclude the differences between dose‐computation and delivery. Dose distributions of the drifted‐energies were compared against their baseline measurements to determine the% GPRs. A Gamma criteria of 3%/3mm was considered for plan‐dose comparisons while 3%/1mm used for measured dose intercomparisons.Results:For composite‐dose delivery, average cPGPRs were 0.41%±2.48% and −2.54%±3.65% for low‐energy (LE) and high‐energy (HE) drifts, respectively. For measured dose inter‐comparisons, the average%GPRs were 98.4%±2.2% (LE‐drift) and 95.8%±4.0 (HE‐drift). The average %GPR of 92.6%±4.3% was noted for the worst‐case scenario comparing LE‐drift to HE‐drift. All en‐face beams at 5.3 cm depth have cPGPRs within ±4% of the baseline‐energy measurements. However, greater variations were noted for 1.3cm depth. Average %GPRs for drifted energies were >99% at 5.3cm and >97% at 1.3cm depths. However, for the worst‐case scenario (LE‐drift to HE‐drift) these numbers dropped to 95.2% at 5.3cm and 93.1% at 1.3cm depths.Conclusion:The dosimetric impact of beam‐energy drifts was found to be within clinically acceptable tolerance. However, this study includes a single energy with limited range of PDD change. Further studies are on going and the results will be presented.Received funding from Varian Medical Systems, Palo Alto, CA
SU‐F‐T‐282: Quality Assurance for IMRT/VMAT QA Devices: Issues Affecting the Timing for ArcCHECK Recalibration
Authors: Steers J , Fraass B 
Published: July 2016

Purpose:To discuss several factors surrounding the decision on when to recalibrate the ArcCHECK device as well as present a simple and efficient monthly check to evaluate ArcCHECK calibrations.Methods:ArcCheck (Sun Nuclear) calibrations were evaluated monthly by measuring a 25×25cm2 field with 100 MU. Since ArcCHECK measurements are run on an almost nightly basis, such additional square field measurements are obtained with minimal additional effort. An in‐house MATLAB script compares two radial (y‐direction) profiles from the top/center of the new measurement relative to a baseline measurement acquired at the last device calibration. The program automatically generates PDF profile and percent difference comparisons for inspection. Recalibration is based on inspection of measurement profile shapes and percent differences from the baseline measurement.Results:The method presented here shows the utility of a simple monthly check for evaluating ArcCHECK calibrations, and in addition shows the importance of recalibrating after Linac beam steering. Our device required recalibration approximately every 8–10 months. However, for ease of scheduling, we propose a bi‐annual recalibration interval. Clinics with a lighter/heavier IMRT/VMAT QA case load may require different recalibration intervals, which are easily determined using the single‐field method presented. Analysis of additional square fields is also easily incorporated, if desired. We further illustrate the importance of array recalibration given that diode irradiation is not uniform over the entire device, with central diodes receiving more than 900 Gy over the course of 10 months and peripheral diodes receiving as little as 50 Gy (in our experience). Finally, we show that timely device recalibration decreases spread in clinical IMRT/VMAT QA gamma passing rates.Conclusion:Quality assurance for ArcCHECK array calibrations is important to ensure quality IMRT/VMAT QA comparisons. For many clinics, calibrations should be performed at least annually, if not more frequently, based on use of the proposed monthly check.
SU‐F‐T‐292: Imaging and Radiation Oncology Core (IROC) Houston QA Center's Anthropomorphic Phantom Program
Authors: Mehrens H , Lewis B , Lujano C , Nguyen T , Hernandez N , Alvarez P , Molineu A , Followill D 
Published: July 2016

Purpose:To describe the results of IROC Houston's international and domestic end‐to‐end QA phantom irradiations.Methods:IROC Houston has anthropomorphic lung, liver, head and neck, prostate, SRS and spine phantoms that are used for credentialing and quality assurance purposes. The phantoms include structures that closely mimic targets and organs at risk and are made from tissue equivalent materials: high impact polystyrene, solid water, cork and acrylic. Motion tables are used to mimic breathing motion for some lung and liver phantoms. Dose is measured with TLD and radiochromic film in various planes within the target of the phantoms.Results:The most common phantom requested is the head and neck followed by the lung phantom. The head and neck phantom was sent to 800 domestic and 148 international sites between 2011 and 2015, with average pass rates of 89% and 92%, respectively. During the past five years, a general upward trend exists regarding demand for the lung phantom for both international and domestic sites with international sites more than tripling from 5 (2011) to 16 (2015) and domestic sites doubling from 66 (2011) to 152 (2015). The pass rate for lung phantoms has been consistent from year to year despite this large increase in the number of phantoms irradiated with an average pass rate of 85% (domestic) and 95% (international) sites. The percentage of lung phantoms used in combination with motions tables increased from 38% to 79% over the 5 year time span.Conclusion:The number of domestic and international sites irradiating the head and neck and lung phantoms continues to increase and the pass rates remained constant. These end‐to‐end QA tests continue to be a crucial part of clinical trial credentialing and institution quality assurance.This investigation was supported by IROC grant CA180803 awarded by the NCI.
SU‐F‐T‐295: MLCs Performance and Patient‐Specific IMRT QA Using Log File Analysis
Authors: Osman A , Maalej N , Jayesh K , Abdel‐Rahman W 
Published: July 2016

Purpose:To analyze the performance of the multi‐leaf collimators (MLCs) from the log files recorded during the intensity modulated radiotherapy (IMRT) treatment and to construct the relative fluence maps and do the gamma analysis to compare the planned and executed MLCs movement.Methods:We developed a program to extract and analyze the data from dynamic log files (dynalog files) generated from sliding window IMRT delivery treatments. The program extracts the planned and executed (actual or delivered) MLCs movement, calculates and compares the relative planned and executed fluences. The fluence maps were used to perform the gamma analysis (with 3% dose difference and 3 mm distance to agreement) for 3 IMR patients. We compared our gamma analysis results with those obtained from portal dose image prediction (PDIP) algorithm performed using the EPID.Results:For 3 different IMRT patient treatments, the maximum difference between the planned and the executed MCLs positions was 1.2 mm. The gamma analysis results of the planned and delivered fluences were in good agreement with the gamma analysis from portal dosimetry. The maximum difference for number of pixels passing the gamma criteria (3%/3mm) was 0.19% with respect to portal dosimetry results.Conclusion:MLC log files can be used to verify the performance of the MLCs. Patientspecific IMRT QA based on MLC movement log files gives similar results to EPID dosimetry results. This promising method for patient‐specific IMRT QA is fast, does not require dose measurements in a phantom, can be done before the treatment and for every fraction, and significantly reduces the IMRT workload.The author would like to thank King Fahd University of petroleum and Minerals for the support.
SU‐F‐T‐302: Implementation of the RadCalc Image Analysis Tool for IMRT QA
Authors: Soldner A , Fitzherbert C , Zhou F , Hand C 
Published: July 2016

Purpose:To assess RadCalc as a means for analyzing fluence maps of IMRT QA patient plans. Eclipse generated fluence maps were compared to RadCalc fluence maps generated from both Eclipse parameters and from dynalog trajectory files.Methods:Six IMRT plans consisting of fifty individual fields were compared both field‐by‐field and as composite plans. These plans were exported from Eclipse to RadCalc. Each plan was then delivered in QA mode on a Varian Clinac iX, while recording and saving the dynalog trajectory files. These files were then imported into RadCalc, providing three sources of generating fluence maps: Eclipse, RadCalc, and dynalog files. Using the image analysis tool in RadCalc, a gamma analysis was then performed as a point‐by‐point comparison for each IMRT field. The Eclipse fluence map was used as the baseline for each comparison.Results:Based on the manufacturer's recommendations, all fields were normalized to the maximum pixel value within each Eclipse field. All data was analyzed using a gamma index of 3mm/3% with passing criteria of 90%. For both dynalog analysis and RadCalc fluence analysis, 48/50 created fluence maps passed at greater than 90% when compared with the Eclipse baseline. In analyzing the composite of each of the six patients’ plans, all plans passed over 90%.Conclusion:Using the dynalog trajectory files in combination with RadCalc Version 6.3 image analysis is a promising metric for verifying IMRT QA passing rates. Notably, if a field failed, it did so for both dynalog and RadCalc compared to Eclipse. This suggests RadCalc can accurately simulate fluence maps, with similar results to dynalog comparisons. Limitations within the RadCalc software were discovered in the analytical process such as pixel resolution and the inability to set minimum threshold values. Comparisons could be extended to include dose map and distance to agreement analysis by expanding software capabilities.
SU‐F‐T‐303: Quantification of MLC Positioning Accuracy in VMAT Delivery of Head and Neck Cancer Treatment
Authors: Li X , Yang F 
Published: July 2016

Purpose:Knowing MLC leaf positioning error over the course of treatment would be valuable for treatment planning, QA design, and patient safety. The objective of the current study was to quantify the MLC positioning accuracy for VMAT delivery of head and neck treatment plans.Methods:A total of 837 MLC log files were collected from 14 head and neck cancer patients undergoing full arc VMAT treatment on one Varian Trilogy machine. The actual and planned leaf gaps were extracted from the retrieved MLC log files. For a given patient, the leaf gap error percentage (LGEP), defined as the ratio of the actual leaf gap over the planned, was evaluated for each leaf pair at all the gantry angles recorded over the course of the treatment. Statistics describing the distribution of the largest LGEP (LLGEP) of the 60 leaf pairs including the maximum, minimum, mean, Kurtosis, and skewness were evaluated.Results:For the 14 studied patients, their PTV located at tonsil, base of tongue, larynx, supraglottis, nasal cavity, and thyroid gland with volume ranging from 72.0 cm3 to 602.0 cm3. The identified LLGEP differed between patients. It ranged from 183.9% to 457.7% with a mean of 368.6%. For the majority of the patients, the LLGEP distributions peaked at non‐zero positions and showed no obvious dependence on gantry rotations. Kurtosis and skewness, with minimum/maximum of 66.6/217.9 and 6.5/12.6, respectively, suggested relatively more peaked while right‐skewed leaf error distribution pattern.Conclusion:The results indicate pattern of MLC leaf gap error differs between patients of lesion located at similar anatomic site. Understanding the systemic mechanisms underlying these observed error patterns necessitates examining more patient‐specific plan parameters in a large patient cohort setting.
SU‐F‐T‐306: Validation of Mobius 3D and FX for Elekta Linear Accelerators
Authors: Nelson C , Garcia M , Calderon E , Kirsner S 
Published: July 2016

Purpose:Log file based IMRT and VMAT QA is a system that analyzes treatment log files and uses delivery parameters to compute the dose to the patient/phantom. This system was previously commissioned for Varian machines, the purpose of this work is to describe the process for commissioning Mobius for use with Elekta machines.Methods:Twelve IMRT and VMAT plans (6×) were planned and delivered and dose was measured using MapCheck, the results were compared to that computed by Mobius. For 10x and 18x, plans were generated, copied to a phantom and delivered, the dose was measured using a single ion chamber. The difference in measured dose to computed dose (Mobius) was used to adjust the dynamic leaf gap (DLG) in Mobius to achieve optimal agreement between measurements, Mobius and treatment plans.Results:For the measured dose comparison, the average 3%/3mm gamma 97.1% of pixels passed criteria using MapCheck where Mobius computed 96.9% of voxels passing. For 10×, a DLG of −5.5 was determined to achieve optimal results for TPS and measured ion chamber data with an average 0.1% difference and −1.7% respectively. For 18×, a DLG of −3 was determined to achieve optimal results from the TPS and measured data with an average of −0.7% and −1.4% difference on average from a set of IMRT and VMAT plans. The 6x data needed no DLG correction to arrive at agreement with the TPS and the MapCheck measured data.Conclusion:We have validated with measurements for IMRT and VMAT cases the use of Mobius FX with Elekta treatment machines for IMRT and VMAT QA. For 6×, no adjustments to the DLG were required to obtain good results utilizing Mobius whereas for 10× and 18×, the DLG had to be adjusted to obtain optimum agreement with measured data and our TPS.