bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐109: An Investigation of Including Variable Relative Biological Effectiveness in Intensity Modulated Proton Therapy Planning Optimization for Head and Neck Cancer Patients
Authors: Cao W , Zaghian M , Randeniya K , Lim G , Titt U , Mohan R 
Published: June 2015

Purpose:The current practice of considering the relative biological effectiveness (RBE) of protons in intensity modulated proton therapy (IMPT) planning is to use a generic RBE value of 1.1. However, RBE is indeed a variable depending on the dose per fraction, the linear energy transfer, tissue parameters, etc. In this study, we investigate the impact of using variable RBE based optimization (vRBE‐OPT) on IMPT dose distributions compared by conventional fixed RBE based optimization (fRBE‐OPT).Methods:Proton plans of three head and neck cancer patients were included for our study. In order to calculate variable RBE, tissue specific parameters were obtained from the literature and dose averaged LET values were calculated by Monte Carlo simulations. Biological effects were calculated using the linear quadratic model and they were utilized in the variable RBE based optimization. We used a Polak‐Ribiere conjugate gradient algorithm to solve the model. In fixed RBE based optimization, we used conventional physical dose optimization to optimize doses weighted by 1.1. IMPT plans for each patient were optimized by both methods (vRBE‐OPT and fRBE‐OPT). Both variable and fixed RBE weighted dose distributions were calculated for both methods and compared by dosimetric measures.Results:The variable RBE weighted dose distributions were more homogenous within the targets, compared with the fixed RBE weighted dose distributions for the plans created by vRBE‐OPT. We observed that there were noticeable deviations between variable and fixed RBE weighted dose distributions if the plan were optimized by fRBE‐OPT. For organs at risk sparing, dose distributions from both methods were comparable.Conclusion:Biological dose based optimization rather than conventional physical dose based optimization in IMPT planning may bring benefit in improved tumor control when evaluating biologically equivalent dose, without sacrificing OAR sparing, for head and neck cancer patients.The research is supported in part by National Institutes of Health Grant No. 2U19CA021239‐35.
SU‐E‐T‐115: Analysis of Patient Specific QA for VMAT by Disease Site and Planning‐Delivery System Using the ScandiDos Delta4 Phantom
Authors: Giaddui T , Hardin M , Keller J , Kremmel E , Fu M , Peng C , Doyle L , Yu Y , Xiao Y , Harrison A 
Published: June 2015

Purpose:To evaluate patient specific quality assurance (PSQA) for the delivery of volumetric modulated arc therapy (VMAT) by disease site. To compare planning‐delivery system (PDS) PSQA pass rates in a dual vendor institution.Methods:PSQA is performed for VMAT plans using a ScandiDos Delta4 phantom. Verification plans are calculated using Varian Eclipse and Elekta Monaco treatment planning systems (TPS) for patients treated using Varian Truebeam and Elekta linear accelerators respectively. Individual arcs are delivered to the Delta4 phantoms and assessed using the gamma index pass criterion(3% Dose Deviation(DD%), 3mm Distance to Agreement(DTA),10% dose threshold and 90% gamma index).Results:A total of 287 VMAT plans and 680 arcs were analyzed. The passing rates for VMAT QA plans were 95% and 98% for head/neck and pelvis/prostate plans respectively, and 100% for chest/abdomen, spine, lung Stereotactic Body Radiotherapy (SBRT) and Stereotactic Radiosurgery(SRS) plans. Average gamma indices were: (99 ± 2) % for pelvis/prostate, chest/abdomen and lung SBRT plans, (97 ± 4) % for head and neck plans and (98 ± 3) % for spine plans. The average DD% and DTA pass rates ranged from 82% to 90% and 98% to 99% respectively for plans in different disease sites. Paired t‐test analysis (two tails) indicated no significant differences in the gamma indices between plans delivered using different PDS; the P values were: 0.08, 0.45, and 0.94 for lung SBRT, head/neck and pelvis/prostate plans respectively. The statistical power for comparing PDS in different disease sites with an alpha of 0.05 is 1.Conclusion:The Gamma indices based on 3% DD%, 3 mm DTA and 10% dose threshold for the VMAT QA plans in all disease sites were well above 90%, suggesting the possibility of using a more stringent PSQA criterion. No significant differences were observed in the QA of VMAT plans delivered using different PDS.
SU‐E‐T‐117: Analysis of the ArcCHECK Dosimetry Gamma Failure Using the 3DVH System
Authors: Cho S , Choi W , Lee H , Yoon J , Lee E , Park K , Keum K 
Published: June 2015

Purpose:To evaluate gamma analysis failure for the VMAT patient specific QA using ArcCHECK cylindrical phantom. The 3DVH system(Sun Nuclear, FL) was used to analyze the dose difference statistic between measured dose and treatment planning system calculated dose.Methods:Four case of gamma analysis failure were selected retrospectively. Our institution gamma analysis indexes were absolute dose, 3%/3mm and 90%pass rate in the ArcCHECK dosimetry. The collapsed cone convolution superposition (CCCS) dose calculation algorithm for VMAT was used. Dose delivery was performed with Elekta Agility. The A1SL(standard imaging, WI) and cavity plug were used for point dose measurement. Delivery QA plans and images were used for 3DVH Reference data instead of patient plan and image. The measured data of ‘.txt’ file was used for comparison at diodes to acquire a global dose level. The,.acml’ file was used for AC‐PDP and to calculated point dose.Results:The global dose of 3DVH was calculated as 1.10 Gy, 1.13, 1.01 and 0.2 Gy respectively. The global dose of 0.2 Gy case was induced by distance discrepancy. The TPS calculated point dose of was 2.33 Gy to 2.77 Gy and 3DVH calculated dose was 2.33 Gy to 2.68 Gy. The maximum dose differences were −2.83% and −3.1% for TPS vs. measured dose and TPS vs. 3DVH calculated respectively in the same case. The difference between measured and 3DVH was 0.1% in that case. The 3DVH gamma pass rate was 98% to 99.7%.Conclusion:We found the TPS calculation error by 3DVH calculation using ArcCHECK measured dose. It seemed that our CCCS algorithm RTP system over estimated at the central region and underestimated scattering at the peripheral diode detector point. The relative gamma analysis and point dose measurement would be recommended for VMAT DQA in the gamma failure case of ArcCHECK dosimetry.
SU‐E‐T‐119: Analysis the Efficacy of Different Radiotherapy Methods and Failure Mode in No‐Metastasis Esophageal Squamous Cell Carcinoma
Authors: Yankun C , Zhihui T , Runxiao L , Shen W 
Published: June 2015

Purpose:To evaluate the curative effect of radio (chemo) therapy and mode of treatment failure in no‐metastasis and lesion length ≤ 5.0cm esophageal squamous cell carcinoma (ESCC).Methods:There were 158 eligible patients were retrospectively analyzed, to analysis the curative effect of radio (chemo) therapy, prognosis factors, toxicity and prognostic index model.Results:To all patients the 1, 3, 5 overall survival rate were 83.54%, 52.53%, 32.58%, the local recurrence rate were 15.08%, 33.60% and 38.14%; distant metastasis rate were 10.64%, 25.21% and 36.06%; tumor specific survival rate were 76.64%, 54.07% and 44.51%. Multivariate analysis showed that patients with ECOG grade (χ2=13.945, P=0.000), short‐term effect (χ2=19.360, P=0.000) and different radiotherapy methods (χ2=9.866, P=0.002) as the independent prognostic factors. Prognostic index model showed that the survival rate was significantly higher in the lower value of PI group than in the larger value of PI group (χ2=49.19, P=0.0000). In our whole group, there were simple locoregional recurrence (LR) 40 cases (25.3%), simple Distant metastasis (DM) 31 cases (19.6%), LR and DM in 14 cases (8.9%) after treatment. The chi‐square test showed that there were no significant difference in the incidence of Elective Nodal Irradiation (ENI )and Involved Field Irradiation (IFI) patients with LR and DM ( χ2=2.363, 2.950, P=0.124, 0.085).Conclusion:Radio (chemo) therapy has a good curative effect in no‐metastasis and lesion length ≤ 5.0cm ESCC patients.
SU‐E‐T‐139: Automated Daily EPID Exit Dose Analysis Uncovers Treatment Variations
Authors: Olch A 
Published: June 2015

Purpose:To evaluate a fully automated EPID exit dose system for its ability to detect daily treatment deviations including patient setup, delivery, and anatomy changes.Methods:PerFRACTION (Sun Nuclear Corporation) software is a system that uses integrated EPID images taken during patient treatment and automatically pulled from the Aria database and analyzed based on user‐defined comparisons. This was used to monitor 20 plans consisting of a total of 859 fields for 18 patients, for a total of 251 fractions. Nine VMAT, 5 IMRT, and 6 3D plans were monitored. The Gamma analysis was performed for each field within a plan, comparing the first fraction against each of the other fractions in each treatment course. A 2% dose difference, 1 mm distance‐to‐agreement, and 10% dose threshold was used. These tight tolerances were chosen to achieve a high sensitivity to treatment variations. The field passed if 93% of the pixels had a Gamma of 1 or less.Results:Twenty‐nine percent of the fields failed. The average plan passing rate was 92.5%.The average 3D plan passing rate was less than for VMAT or IMRT, 84%, vs. an average of 96.2%. When fields failed, an investigation revealed changes in patient anatomy or setup variations, often also leading to variations of transmission through immobilization devices.Conclusion:PerFRACTION is a fully automated system for determining daily changes in dose transmission through the patient that requires no effort other than for the imager panel to be deployed during treatment. A surprising number of fields failed the analysis and can be attributed to important treatment variations that would otherwise not be appreciated. Further study of inter‐fraction treatment variations is possible and warranted.Sun Nuclear Corporation provided a license to the software described.
SU‐E‐T‐141: Automated Dose Point Placement for Cervical Cancer Brachytherapy Using Tandem and Ovoid Applicators
Authors: Kang H , Padilla L , Hasan Y , Al‐Hallaq H 
Published: June 2015

Purpose:To develop a standalone application, which automatically and consistently calculates the coordinates of points A and H based solely on the implanted applicator geometry for cervical cancer HDR brachytherapy.Methods:Manchester point A and ABS point H are both located 2cm lateral from the central tandem plane. While both points are located 2cm above the cervical os, surrogates for the os differ. Point A is defined relative to the anatomical cervical os. Point H is defined relative to the intersection of the tandem with the superior aspects of the ovoids. The application takes an input text file generated by the treatment planning system (TPS, BrachyVision, Varian) that specifies the source geometries. It then outputs the 3D coordinates of points A and H in both the left and right directions. The algorithm was implemented and tested on 34 CT scans of 7 patients treated with HDR brachytherapy delivered using tandem and ovoids. A single experienced user retrospectively and manually placed points A and H on the CT scans, whose coordinates were used as the gold standard for the comparison to the automatically calculated points.Results:The automatically calculated coordinates of points A and H agree within 0.7mm with the gold standard. The averages and standard deviations of the 3D coordinate difference between points placed by the two methods are 0.3±0.1 and 0.4±0.1mm for points A and H, respectively. The maximum difference in 3D magnitude is 0.7mm.Conclusion:The algorithm consistently calculates dose point coordinates independently of the planner for cervical cancer brachytherapy treated with tandem and ovoids. Automated point placement based on the geometry of the implanted applicators agrees in sub‐millimeter with careful manual placements by an experienced user. This algorithm expedites the planning process and eliminates dependencies on either user input or TPS visualization tools.
SU‐E‐T‐143: Automatic PBS Treatment Planning for Prostate Cancer
Authors: Zhang J , Durci M , Wu H , Rosen L , Ding X 
Published: June 2015

Purpose:This study presents a novel idea of using automated planning technique for parallel‐opposed prostate plans with pencil beam scanning proton therapy.Methods:A random 5 clinical prostate patients treated with parallel‐opposed modulated‐scanning proton beam in our proton center were selected in this study. All of the 5 cases were re‐planned with in‐house developed python scripts integrated into RayStation 4.0 clinical version. This automatic tool was designed to perform patient DICOM data import, external structure contours, CT density assignment, prescription to PTV assignment, beam placement, optimization, and dose calculation.Results:The mean time to generate a complete treatment plan was 1 minute per plan. For the automatically generated plans, 5 out of 5 plans (100%) were deemed clinically acceptable by one experienced radiation oncologist. In addition, the automated plans were overall dosimetrically equivalent to the clinical plans when scored for target coverage, rectum and bladder dose. Mann‐Whitney U tests did not show significant dosimetric differences for normal tissue structures between the clinical and automated plans.Conclusion:We have developed a robust and automated method for fully inversed planned paralleled‐opposed prostate proton treatment planning. This efficient method can be readily integrated into clinical practice. The tool produces clinically acceptable plans using only manually contoured anatomic structures and simulation CT data set. We anticipate that this tool will not only improve patient access to high‐quality proton treatment by simplifying the planning process and will also reduce the effort and cost of incorporating more advanced planning into clinical practice in the near future.
SU‐E‐T‐144: Bayesian Inference of Local Relapse Data Using a Poisson‐Based Tumour Control Probability Model
Authors: La Russa D 
Published: June 2015

Purpose:The purpose of this project is to develop a robust method of parameter estimation for a Poisson‐based TCP model using Bayesian inference.Methods:Bayesian inference was performed using the PyMC3 probabilistic programming framework written in Python. A Poisson‐based TCP regression model that accounts for clonogen proliferation was fit to observed rates of local relapse as a function of equivalent dose in 2 Gy fractions for a population of 623 stage‐I non‐small‐cell lung cancer patients. The Slice Markov Chain Monte Carlo sampling algorithm was used to sample the posterior distributions, and was initiated using the maximum of the posterior distributions found by optimization. The calculation of TCP with each sample step required integration over the free parameter α, which was performed using an adaptive 24‐point Gauss‐Legendre quadrature. Convergence was verified via inspection of the trace plot and posterior distribution for each of the fit parameters, as well as with comparisons of the most probable parameter values with their respective maximum likelihood estimates.Results:Posterior distributions for α, the standard deviation of α (σ), the average tumour cell‐doubling time (Td), and the repopulation delay time (Tk), were generated assuming α/β = 10 Gy, and a fixed clonogen density of 10⁷ cm−3. Posterior predictive plots generated from samples from these posterior distributions are in excellent agreement with the observed rates of local relapse used in the Bayesian inference. The most probable values of the model parameters also agree well with maximum likelihood estimates.Conclusion:A robust method of performing Bayesian inference of TCP data using a complex TCP model has been established.
SU‐E‐T‐149: Brachytherapy Patient Specific Quality Assurance for a HDR Vaginal Cylinder Case
Authors: Barbiere J , Napoli J , Ndlovu A 
Published: June 2015

Purpose:Commonly Ir‐192 HDR treatment planning system commissioning is only based on a single absolute measurement of source activity supplemented by tabulated parameters for multiple factors without independent verification that the planned distribution corresponds to the actual delivered dose. The purpose on this work is to present a methodology using Gafchromic film with a statistically valid calibration curve that can be used to validate clinical HDR vaginal cylinder cases by comparing the calculated plan dose distribution in a plane with the corresponding measured planar dose.Methods:A vaginal cylinder plan was created with Oncentra treatment planning system. The 3D dose matrix was exported to a Varian Eclipse work station for convenient extraction of a 2D coronal dose plane corresponding to the film position. The plan was delivered with a sheet of Gafchromic EBT3 film positioned 1mm from the catheter using an Ir‐192 Nucletron HDR source. The film was then digitized with an Epson 10000 XL color scanner. Film analysis is performed with MatLab imaging toolbox. A density to dose calibration curve was created using TG43 formalism for a single dwell position exposure at over 100 points for statistical accuracy. The plan and measured film dose planes were registered using a known dwell position relative to four film marks. The plan delivered 500 cGy to points 2 cm from the sources.Results:The distance to agreement of the 500 cGy isodose between the plan and film measurement laterally was 0.5 mm but can be as much as 1.5 mm superior and inferior. The difference between the computed plan dose and film measurement was calculated per pixel. The greatest errors up to 50 cGy are near the apex.Conclusion:The methodology presented will be useful to implement more comprehensive quality assurance to verify patient‐specific dose distributions
SU‐E‐T‐156: Can Sr‐90 Check Sources Replace Co‐60 Measurements for Monitoring of Reference Chamber Stability?
Authors: McEwen M , Miksys N , Niven D 
Published: June 2015

Purpose:To determine the ultimate precision of a system for monitoring reference‐class ion chamber stability using a commercial Sr‐90 check source.Methods:A detailed investigation of a commercial Sr‐90 check source (PTW48002) was carried out using a series of Farmer‐type ionization chambers. Investigations included: positioning repeatability (angular variation as chamber is rotated in source, variation in ionization current with vertical alignment); chamber settling; short and long term repeatabilityResults:i) Measurement precision – the ionization current was typically 10 pA, and therefore a high‐precision electrometer is required to prevent electrometer noise/resolution/leakage biaising the results. ii) Chamber settling ‐ the chamber response stabilizes after approximately 10 minutes, which is longer than reported for linac beams and is likely due to the low doserate of the source.iii) The measured response depended at the 1 % level on the orientation of the chamber with respect to the source. However, consistent positioning resulted in repeatability at the 0.05 % level. Care was also required to ensure that the chamber was consistently positioned vertically with respect to the source. The sensitivity to vertical position was found to be > 1 % per mm.iv)With a uniform procedure the long‐term (> 6 month) repeatability was found to be better than 0.1 % for multiple chamber types and potentially a precision of 0.05 % is achievable.Conclusion:A Sr‐90 check source is easy to use and is a viable alternative to Co‐60 for monitoring reference chamber stability.
SU‐E‐T‐162: Characterization of a New Oblong Cone for Use with the Intraoperative Mobetron Unit
Authors: Cantley J , Colussi V 
Published: June 2015

Purpose:To evaluate the dosimetric characteristics of a new flat 7 cm × 12 cm oblong cone for intraoperative radiation therapy (IORT) procedures.Methods:Percent depth dose (PDD) curves and profile measurements at dose depths of D100, D90, D80, D50, and D30 were measured using a parallel‐plate ion chamber and a 3‐D water tank Blue phantom II (iba) for the three energies (6, 9, and 12 MeV) available with the new generation Mobetron 2000. In addition, PDD curves and profiles were made with Gafchromic EBT3 films in solid water phantom. H&D curves were created for each energy for absolute calibration. The films were analyzed using the RIT image analysis software and then compared with the ion chamber results. Output values were obtained by normalizing the dose/MU at D100 at the clinical axis of the oblong cone by the dose/MU at D100 for the flat 10cm cylindrical standard cone using ion chamber measurements.Results:Ion chamber results show that the PDDs from the flat oblong cone, at the clinical axis, match with the PDDs for its “cylindrical brother” 7cm flat cone. These PDDs are comparable with those from the 10cm standard cone. The D100 coincides for all three energies. The cone output factors for the oblong cone are 1.07 for all energies. Ion chamber profiles measurements and film analysis show that the use of flat oblong cone with the 6 and 9 MeV energiesResultin horns of approximately 12% and 8%, respectively. Conversely, 12 MeV profiles show loss of flatness near the field edge.Conclusion:The potential advantage of the oblong cones is the elimination of the well‐known difficulties of electron field matching, both dosimetrically and in clinical setup.
SU‐E‐T‐167: Characterization of In‐House Plastic Scintillator Detectors Array for Radiation Therapy
Authors: Zhu T , Liu H , Dimofte A , Darafsheh A , Lin H , Kassaee A , Finlay J , Both S 
Published: June 2015

Purpose:To characterize basic performance of plastic scintillator detectors (PSD) array designed for dosimetry of radiation therapy.Methods:An in‐house PSD array has been developed by placing single point PSD into customized 2D holder. Each point PSD is a plastic scintillating fiber‐based detector designed for highly accurate measurement of small radiotherapy fields used in patient plan verification and machine commissioning and QA procedures. A parallel fiber without PSD is used for Cerenkov separation by subtracting from PSD readings. Cerenkov separation was confirmed by optical spectroscopy. Alternative Cerenkov separation approaches are also investigated. The optical signal was converted to electronic signal with a photodiode and then subsequently amplified. We measured its dosimetry performance, including percentage depth dose and output factor, and compared with reference ion chamber measurements. The PSD array is then placed along the radiation beam for multiple point dose measurement, representing subsets of PDD measurements, or perpendicular to the beam for profile measurements.Results:The dosimetry results of PSD point measurements agree well with reference ion chamber measurements. For percentage depth dose, the maximal differences between PSD and ion chamber results are 3.5% and 2.7% for 6MV and 15MV beams, respectively. For the output factors, PSD measurements are within 3% from ion chamber results. PDD and profile measurement with PSD array are also performed.Conclusions:The current design of multichannel PSD array is feasible for the dosimetry measurement in radiation therapy. Dose distribution along or perpendicular to the beam path could be measured. It might as well be used as range verification in proton therapy.A PS hollow fiber detector will be investigated to eliminate the Cerenkov radiation effect so that all 32 channels can be used.