bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐240: EPID‐Based Quality Assurance for Dosimetric Credentialing
Authors: Miri N , Lehmann J , Vial P , Greer P 
Published: July 2016

Purpose:We propose a novel dosimetric audit method for clinical trials using EPID measurements at each center and a standardized EPID to dose conversion algorithm. The aim of this work is to investigate the applicability of the EPID method to different linear accelerator, EPID and treatment planning system (TPS) combinations.Methods:Combination of delivery and planning systems were three Varian linacs including one Pinnacle and two Eclipse TPS and, two ELEKTA linacs including one Pinnacle and one Monaco TPS. All Varian linacs had the same EPID structure and similarly for the ELEKTA linacs. Initially, dose response of the EPIDs was investigated by acquiring integrated pixel value (IPV) of the central area of 10 cm2 images versus MUs, 5‐400 MU. Then, the EPID to dose conversion was investigated for different system combinations. Square field size images, 2, 3, 4, 6, 10, 15, 20, 25 cm2 acquired by all systems were converted to dose at isocenter of a virtual flat phantom then the dose was compared to the corresponding TPS dose.Results:All EPIDs showed a relatively linear behavior versus MU except at low MUs which showed irregularities probably due to initial inaccuracies of irradiation. Furthermore, for all the EPID models, the model predicted TPS dose with a mean dose difference percentage of 1.3. However the model showed a few inaccuracies for ELEKTA EPID images at field sizes larger than 20 cm2.Conclusion:The EPIDs demonstrated similar behavior versus MU and the model was relatively accurate for all the systems. Therefore, the model could be employed as a global dosimetric method to audit clinical trials.Funding has been provided from Department of Radiation Oncology, TROG Cancer Research and the University of Newcastle. Narges Miri is a recipient of a University of Newcastle postgraduate scholarship.
SU‐F‐T‐243: Major Risks in Radiotherapy. A Review Based On Risk Analysis Literature
Authors: López‐Tarjuelo J , Bouché‐Babiloni A , Morillo‐Macías V , Guasp‐Tortajada M , Iglesias‐Montenegro N , Monasor‐Denia P , Ferrer‐Albiach C 
Published: July 2016

Purpose:We present a literature review of risk analyses in radiotherapy to highlight the most reported risks and facilitate the spread of this valuable information so that professionals can be aware of these major threats before performing their own studies.Methods:We considered studies with at least an estimation of the probability of occurrence of an adverse event (O) and its associated severity (S). They cover external beam radiotherapy, brachytherapy, intraoperative radiotherapy, and stereotactic techniques. We selected only the works containing a detailed ranked series of elements or failure modes and focused on the first fully reported quartile as much. Afterward, we sorted the risk elements according to a regular radiotherapy procedure so that the resulting groups were cited in several works and be ranked in this way.Results:29 references published between 2007 and February 2016 were studied. Publication trend has been generally rising. The most employed analysis has been the Failure mode and effect analysis (FMEA). Among references, we selected 20 works listing 258 ranked risk elements. They were sorted into 31 groups appearing at least in two different works. 11 groups appeared in at least 5 references and 5 groups did it in 7 or more papers. These last sets of risks where choosing another set of images or plan for planning or treating, errors related with contours, errors in patient positioning for treatment, human mistakes when programming treatments, and planning errors.Conclusion:There is a sufficient amount and variety of references for identifying which failure modes or elements should be addressed in a radiotherapy department before attempting a specific analysis. FMEA prevailed, but other studies such as “risk matrix” or “occurrence × severity” analyses can also lead professionals’ efforts. Risk associated with human actions ranks very high; therefore, they should be automated or at least peer‐reviewed.
SU‐F‐T‐251: The Quality Assurance for the Heavy Patient Load Department in the Developing Country: The Primary Experience of An Entire Workflow QA Process Management in Radiotherapy
Authors: Xie J , Wang J , Peng J , Chen J , Hu W 
Published: July 2016

Purpose:To implement an entire workflow quality assurance (QA) process in the radiotherapy department and to reduce the error rates of radiotherapy based on the entire workflow management in the developing country.Methods:The entire workflow QA process management starts from patient registration to the end of last treatment including all steps through the entire radiotherapy process. Error rate of chartcheck is used to evaluate the the entire workflow QA process. Two to three qualified senior medical physicists checked the documents before the first treatment fraction of every patient. Random check of the treatment history during treatment was also performed. A total of around 6000 patients treatment data before and after implementing the entire workflow QA process were compared from May, 2014 to December, 2015.Results:A systemic checklist was established. It mainly includes patient's registration, treatment plan QA, information exporting to OIS(Oncology Information System), documents of treatment QAand QA of the treatment history. The error rate derived from the chart check decreases from 1.7% to 0.9% after our the entire workflow QA process. All checked errors before the first treatment fraction were corrected as soon as oncologist re‐confirmed them and reinforce staff training was accordingly followed to prevent those errors.Conclusion:The entire workflow QA process improved the safety, quality of radiotherapy in our department and we consider that our QA experience can be applicable for the heavily‐loaded radiotherapy departments in developing country.
SU‐F‐T‐263: Dosimetric Characteristics of the Cine Acquisition Mode of An A‐Si EPID
Authors: Bawazeer O , Sarasanandarajah S , Herath S , Kron T , Deb P 
Published: July 2016

Purpose:To investigate the dosimetric characteristics of Varian a‐Si‐500 electronic portal imaging device (EPID) operated in cine mode particularly considering linearity with delivered dose, dose rate, field size, phantom thickness, MLC speed and common IMRT fields.Methods:The EPID that attached to a Varian Clinac 21iX linear accelerator, was irradiated with 6 and 18 MV using 600 MU/min. Image acquisition is controlled by the IAS3 software, Trigger delay was 6 ms, BeamOnDelay and FrameStartDelay were zero. Different frame rates were utilized. Cine mode response was calculated using MATLAB as summation of mean pixel values in a region of interest of the acquired images. The performance of cine mode was compared to integrated mode and dose measurements in water using CC13 ionization chamber.Results:Figure1 illustrates that cine mode has nonlinear response for small MU, when delivering 10 MU was about 0.5 and 0.64 for 6 and 18 MV respectively. This is because the missing acquired images that were calculated around four images missing in each delivery. With the increase MU the response became linear and comparable with integrated mode and ionization chamber within 2%. Figure 2 shows that cine mode has comparable response with integrated mode and ionization chamber within 2% with changing dose rate for 10 MU delivered. This indicates that the dose rate change has no effect on nonlinearity of cine mode response. Except nonlinearity, cine mode is well matched to integrated mode response within 2% for field size, phantom thickness, MLC speed dependences.Conclusion:Cine mode has similar dosimetric characteristics to integrated mode with open and IMRT fields, and the main limitation with cine mode is missing images. Therefore, the calibration of EPID images with this mode should be run with large MU, and when IMRT verification field has low MU, the correction for missing images are required.
SU‐F‐T‐271: Comparing IMRT QA Pass Rates Before and After MLC Calibration
Authors: Mazza A , Perrin D , Fontenot J 
Published: July 2016

Purpose:To compare IMRT QA pass rates before and after an in‐house MLC leaf calibration procedure.Methods:The MLC leaves and backup jaws on four Elekta linear accelerators with MLCi2 heads were calibrated using the EPID‐based RIT Hancock Test as the means for evaluation. The MLCs were considered to be successfully calibrated when they could pass the Hancock Test with criteria of 1 mm jaw position tolerance, and 1 mm leaf position tolerance. IMRT QA results were collected pre‐ and postcalibration and analyzed using gamma analysis with 3%/3mm DTA criteria. AAPM TG‐119 test plans were also compared pre‐ and post‐calibration, at both 2%/2mm DTA and 3%/3mm DTA.Results:A weighted average was performed on the results for all four linear accelerators. The pre‐calibration IMRT QA pass rate was 98.3 ± 0.1%, compared with the post‐calibration pass rate of 98.5 ± 0.1%. The TG‐119 test plan results showed more of an improvement, particularly at the 2%/2mm criteria. The averaged results were 89.1% pre and 96.1% post for the C‐shape plan, 94.8% pre and 97.1% post for the multi‐target plan, 98.6% pre and 99.7% post for the prostate plan, 94.7% pre and 94.8% post for the head/neck plan.Conclusion:The patient QA results did not show statistically significant improvement at the 3%/3mm DTA criteria after the MLC calibration procedure. However, the TG‐119 test cases did show significant improvement at the 2%/2mm level.
SU‐F‐T‐283: A Novel Device to Enable Portal Dosimetry for Flattening Filter Free Beams
Authors: Faught A , Wu Q , Adamson J 
Published: July 2016

Purpose:Varian's electronic portal imaging device (EPID) based portal dosimetry tool is a popular and effective means of performing IMRT QA. EPIDs for older models of the TrueBeam accelerator utilize a 40cmx30cm Image Detection Unit (IDU) that saturates at the center for standard source to imager distances with high dose rate flattening filter free (FFF) beams. This makes portal dosimetry not possible and an alternative means of IMRT QA necessary. We developed a filter that would attenuate the beam to a dose rate measureable by the IDU for portal dosimetry IMRT QA.Methods:Multipurpose 304 stainless steel plates were placed on an accessory tray to attenuate the beam. Profiles of an open field measured on the IDU were acquired with varying number of plates to assess the thickness needed to reduce the maximum dose rates of 6XFFF and 10XFFF beams to measurable levels. A new portal dose image prediction (PDIP) model was commissioned based on open field measurements with plates in position, and a modified beam profile was input to portal dosimetry calibration at the console to empirically correct for attenuation and scatter. The portal dosimetry tool was used to assess agreement between predicted and measured doses for open 25×25cm2 fields and intensity modulated fields using 6XFFF and 10XFFF beams.Results:Thicknesses of 2.5cm and 3.8cm of steel were required to reduce the highest dose rates to a measureable level for 6XFFF and 10XFFF, respectively. Gamma analysis using a 3%/3mm relative criterion with the filter in place and using the new PDIP model resulted in 98.2% and 93.6% of pixels passing while intensity modulated fields showed passing rates of 98.2% and 99.0%.Conclusion:Use of the filter allows for portal dosimetry to be used for IMRT QA of FFF plans in place of purchasing a second option for IMRT QA.
SU‐F‐T‐247: Collision Risks in a Modern Radiation Oncology Department: An Efficient Approach to Failure Modes and Effects Analysis
Authors: Schubert L , Westerly D , Vinogradskiy Y , Aldridge J , Fisher C , Liu A 
Published: July 2016

Purpose:Collisions between treatment equipment and patients are potentially catastrophic. Modern technology now commonly involves automated remote motion during imaging and treatment, yet a systematic assessment to identify and mitigate collision risks has yet to be performed. Failure modes and effects analysis (FMEA) is a method of risk assessment that has been increasingly used in healthcare, yet can be resource intensive. This work presents an efficient approach to FMEA to identify collision risks and implement practical interventions within a modern radiation therapy department.Methods:Potential collisions (e.g. failure modes) were assessed for all treatment and simulation rooms by teams consisting of physicists, therapists, and radiation oncologists. Failure modes were grouped into classes according to similar characteristics. A single group meeting was held to identify implementable interventions for the highest priority classes of failure modes.Results:A total of 60 unique failure modes were identified by 6 different teams of physicists, therapists, and radiation oncologists. Failure modes were grouped into four main classes: specific patient setups, automated equipment motion, manual equipment motion, and actions in QA or service mode. Two of these classes, unusual patient setups and automated machine motion, were identified as being high priority in terms severity of consequence and addressability by interventions. The two highest risk classes consisted of 33 failure modes (55% of the total). In a single one hour group meeting, 6 interventions were identified. Those interventions addressed 100% of the high risk classes of failure modes (55% of all failure modes identified).Conclusion:A class‐based approach to FMEA was developed to efficiently identify collision risks and implement interventions in a modern radiation oncology department. Failure modes and interventions will be listed, and a comparison of this approach against traditional FMEA methods will be presented.
SU‐F‐T‐291: Development of Physician‐Driven, Clinically‐Relevant Pass/fail Criteria for a DVH‐Based IMRT Patient Specific QA Program
Authors: Price A , Lawrence M , Das S , Rankine L 
Published: July 2016

Purpose:To derive and implement physician driven metrics for dose volume histogram (DVH)‐based patient specific quality assurance (QA) for prostate radiation therapy based on clinically relevant deviations.Methods:An observership study presented 3 radiation oncology physicians from our institution with a series of artificial DVH‐based IMRT QA results, each generated by introducing iteratively larger perturbations from a planned DVH (from our pool of 20 real patient plans) to portions of the bladder, rectum, and planning target volume (PTV) DVHs. Physician responses were quantified by recording acceptable deviations from both in‐house defined clinical goals (e.g. V70Gy < 10cc for rectum, mean dose for bladder) and other accepted dosimetric indices from the literature . The newly defined DVH criteria were used to evaluate 14 clinical IMRT plans measured using ArcCHECK and processed using 3DVH (Sun Nuclear Corporation, Melbourne, FL), all of which passed the standard 3%/3mm 2D‐Γ comparison at >90% (absolute dose). In addition, 4 intentionally perturbed plans were measured, all with close to 90% 2D‐Γ passing rates (relative dose). We compared physician derived constraints against 2D‐Γ results to establish the relationship with an accepted IMRT QA metric.Results:Of the 14 clinical patients measured, 7 were flagged for physician review (i.e. did not pass physician‐derived DVH constraints). The rectum and bladder ΔD0.1cc constraint was the root cause of 5/7 of these QA failures. Of the 4 perturbed plans, 3/4 patients failed multiple DVH criteria in the bladder and rectum. Observership results from one physician‐derived metric (PTV ΔD0.1cc) were found to be too strict and excluded from analysis.Conclusion:We derived clinically relevant physician driven criteria for DVH‐based patient specific QA at our institution. In N=14 patient plans, implementation of these criteria reduced the need for physician review of patient QA results by 50%. Further refinement of PTV D0.1cc constraint is needed.Partially funded by Sun Nuclear Corporation research agreement.
SU‐F‐T‐293: Experimental Comparisons of Ionization Chambers with Different Volumes for CyberKnife Delivery Quality Assurance
Authors: Nakayama M , Munetomo Y , Ogata T , Uehara K , Tsudou S , Nishimura H , Mayahara H , Sasaki R 
Published: July 2016

Purpose:To evaluate the practicality use of ionization chambers with different volumes for delivery quality assurance of CyberKnife plans,Methods:Dosimetric measurements with a spherical solid water phantom and three ionization chambers with volumes of 0.13, 0.04, and 0.01 cm3 (IBA CC13, CC04, and CC01, respectively) were performed for various CyberKnife clinical treatment plans including both isocentric and nonisocentric delivery. For each chamber, the ion recombination correction factors <I>Ks</I> were calculated using the Jaffe plot method and twovoltage method at a 10‐cm depth for a 60‐mm collimator field in a water phantom. The polarity correction factors <I>Kpol</I> were determined for 5–60‐mm collimator fields in same experimental setup. The measured doses were compared to the doses for the detectors calculated using a treatment planning system.Results:The differences in the <I>Ks</I> between the Jaffe plot method and two‐voltage method were −0.12, −0.02, and 0.89% for CC13, CC04, and CC01, respectively. The changes in <I>Kpol</I> for the different field sizes were 0.2, 0.3, and 0.8% for CC13, CC04, and CC01, respectively. The measured doses for CC04 and CC01 were within 3% of the calculated doses for the clinical treatment plans with isocentric delivery with collimator fields greater than 12.5 mm. Those for CC13 had differences of over 3% for the plans with isocentric delivery with collimator fields less than 15 mm. The differences for the isocentric plans were similar to those for the single beam plans. The measured doses for each chamber were within 3% of the calculated doses for the non‐isocentric plans except for that with a PTV volume less than 1.0 cm3.Conclusion:Although there are some limitations, the ionization chamber with a smaller volume is a better detector for verification of the CyberKnife plans owing to the high spatial resolution.
SU‐F‐T‐294: The Analysis of Gamma Criteria for Delta4 Dosimetry Using Statistical Process Control
Authors: Cho S , Ahn S , Kim J , Park K , Choi W , Lee H , Lee E , Yoon J , Keum K 
Published: July 2016

Purpose:To evaluate the sensitivity of gamma criteria for patient‐specific volumetric modulated arc therapy(VMAT) quality assurance of the Delta4 dosimetry program using the statistical process control(SPC) methodology.Methods:The authors selected 20 patient‐specific VMAT QA cases which were undertaken MapCHECK and ArcCHECK with gamma pass rate better than 97%. The QAs data were collected Delta4 Phantom+ and Elekta Agility six megavolts without using an angle incrementer. The gamma index(GI) were calculated in 2D planes with normalizing deviation to local dose(local gamma). The sensitivity of the GI methodology using criterion of 3%/3mm, 3%/2mm and 2%/3mm was analyzed with using process acceptability indices. We used local confidence(LC) level, the upper control limit(UCL) and lower control limit(LCL) of I‐MR chart for process capability index(Cp) and a process acceptability index (Cpk).Results:The lower local confidence levels of 3%/3mm, 3%/2mm and 2%/3mm were 92.0%, 83.6% and 78.8% respectively. All of the calculated Cp and Cpk values that used LC level were under 1.0 in this study. The calculated LCLs of I‐MR charts were 89.5%, 79.0% and 70.5% respectively. These values were higher than 1.0 which means good quality of QA. For the generally used lower limit of 90%, we acquired over 1.3 of Cp value for the gamma index of 3%/3mm and lower than 1.0 in the rest of GI.Conclusion:We applied SPC methodology to evaluate the sensitivity of gamma criteria and could see the lower control limits of VMAT QA for the Delta 4 dosimetry and could see that Delta 4 phantom+ dosimetry more affected by the position error and the I‐MR chart derived values are more suitable for establishing lower limits.Acknowledgement: This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (No. 2015R1D1A1A01060463)
SU‐F‐T‐323: A Post‐Mastectomy Radiation Therapy Dose Distribution Study Using Nanodots and Films
Authors: Qian X , Vaidya K , Puckett L , Souri S , Chen Y , Cao Y , Jamshidi A , Lee L , Klein E , Diaz F 
Published: July 2016

Purpose:In post‐mastectomy radiation therapy (RT), skin dose must be accurately estimated to assess skin reactions such as erythema, desquamation and necrosis. Planning systems cannot always provide accurate dosimetry for target volumes distal to skin. Therefore, in‐vivo dosimetry is necessary. A female anthropomorphic phantom was used with optically stimulated luminescence dosimeters (nanoDots) to measure dose to chest wall skin. In addition, EBT2 films was employed to measure dose to left lung and heart in post‐mastectomy RT.Methods:Films and nanoDots were calibrated under full buildup conditions at 100cm SAD for 6MV photons. Five pieces of films were placed between slabs of Rando phantom to assess dose to left lung and heart. Two layers of 0.5cm thick bolus were used to cover the whole left chest. Six pairs of nanoDots were placed at medical and lateral aspects on the bolus surface, between the 0.5cm bolus layers, and under the bolus. Three control nanoDots were placed on chest wall to quantify imaging dose. The phantom was CT scanned with all dosimeters in place, and treatment planning was performed with tangential fields (200cGy). All dosimeters were contoured on CT and dose was extracted. NanoDots were read using nanoDot reader and films were scanned using film scanner. The measured and calculated doses were tabulated.Results:Dose to 12 nanoDots were evaluated. Dose variance for surface nanoDots were +3.8%, +2.7%, −5% and −9.8%. Those at lateral positions, with greater beam obliquity had larger variance than the medial positions. A similar trend was observed for other nanoDots (Table1). Point doses from films for heart and the left lung were 112.7cGy and 108.7cGy, with +10.2% and +9.04% deviation from calculated values, respectively.Conclusion:Dosimetry provided by the advanced planning system was verified using NanoDots and films. Both nanoDots and films provided good estimation of dose distribution in post‐mastectomy RT.