bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐574: Novel Chance‐Constrained Optimization in Intensity‐Modulated Proton Therapy Planning to Account for Range and Patient Setup Uncertainties
Authors: An Y , Liang J , Liu W 
Published: June 2015

Purpose:We propose to apply a probabilistic framework, namely chanceconstrained optimization, in the intensity‐modulated proton therapy (IMPT) planning subject to range and patient setup uncertainties. The purpose is to hedge against the influence of uncertainties and improve robustness of treatment plans.Methods:IMPT plans were generated for a typical prostate patient. Nine dose distributions are computed — the nominal one and one each for ±5mm setup uncertainties along three cardinal axes and for ±3.5% range uncertainty. These nine dose distributions are supplied to the solver CPLEX as chance constraints to explicitly control plan robustness under these representative uncertainty scenarios with certain probability. This probability is determined by the tolerance level. We make the chance‐constrained model tractable by converting it to a mixed integer optimization problem. The quality of plans derived from this method is evaluated using dose‐volume histogram (DVH) indices such as tumor dose homogeneity (D5% – D95%) and coverage (D95%) and normal tissue sparing like V70 of rectum, V65, and V40 of bladder. We also compare the results from this novel method with the conventional PTV‐based method to further demonstrate its effectivenessResults:Our model can yield clinically acceptable plans within 50 seconds. The chance‐constrained optimization produces IMPT plans with comparable target coverage, better target dose homogeneity, and better normal tissue sparing compared to the PTV‐based optimization [D95% CTV: 67.9 vs 68.7 (Gy), D5% – D95% CTV: 11.9 vs 18 (Gy), V70 rectum: 0.0 % vs 0.33%, V65 bladder: 2.17% vs 9.33%, V40 bladder: 8.83% vs 21.83%]. It also simultaneously makes the plan more robust [Width of DVH band at D50%: 2.0 vs 10.0 (Gy)]. The tolerance level may be varied to control the tradeoff between plan robustness and quality.Conclusion:The chance‐constrained optimization generates superior IMPT plan compared to the PTV‐based optimization with explicit control of plan robustness.NIH/NCI K25CA168984, Eagles Cancer Research Career Development, The Lawrence W. and Marilyn W. Matteson Fund for Cancer Research, Mayo ASU Seed Grant, and The Kemper Marley Foundation.
SU‐E‐T‐576: Obesity as a Factor in Prostate Cancer Treatment Modality and Outcomes
Authors: Njeh C , Stankowski R , Liang H , Kahana B 
Published: June 2015

Purpose:Prostate cancer is the most frequently diagnosed malignancy in American males. To date, no single study has examined the effect of obesity on the outcomes of all three treatment modalities in a single population. We examined the relationship between obesity and prostate cancer treatment decisions as well as outcomes.Methods:We conducted a retrospective observational cohort study of the patients treated for prostate cancer with curative intent between January 1998 and December 2010. Wilcoxon ranksum and Chi‐Square tests were used to analyze the association between treatment mode and body mass index (BMI). Cox proportional Hazards models adjusted for risk category, age, and androgen deprivation therapy (ADT) were performed to evaluate the effects of BMI on overall, disease‐free, biochemical recurrence‐free, incontinence‐free, and impotence‐free survival.Results:A total of 1681 patients were included in the analysis, including 338 that received BT, 439 that received EBRT, and 904 that received RP. When BMI was assessed as a continuous variable, median BMI was higher in patients treated with BT (29.4) than in those treated with EBRT (28.8) or RP (28.9) (P = 0.0677, Wilcoxon rank‐sum test). After stratifying BMI into two groups (BMI < 29.4 or ≥ 29.4), Chi‐Square test showed that the treatment mode was significantly related to BMI where the proportion of high BMI individuals undergoing was 50.9% for BT, 42.4% for EBRT, and 43.2% for RP (P = 0.0309). Cox proportional hazards modeling was used to assess the relationship between BMI and survival outcomes. For patients receiving EBRT, BMI was a significant risk factor for incontinence‐free survival where HR for incontinence in the lower BMI group was 0.515 (95% CI 0.307–0.865, P = 0.0121).Conclusion:BMI appears to be related to prostate cancer treatment decisions, High BMI (≥ 29.4) is associated with poorer incontinence‐free survival for EBRT.This study was supported by a grant from the Marshfield Clinic Research Foundation
SU‐E‐T‐577: Obliquity Factor and Surface Dose in Proton Beam Therapy
Authors: Das I , Andersen A , Coutinho L 
Published: June 2015

Purpose:The advantage of lower skin dose in proton beam may be diminished creating radiation related sequalae usually seen with photon and electron beams. This study evaluates the surface dose as a complex function of beam parameters but more importantly the effect of beam angle.Methods:Surface dose in proton beam depends on the beam energy, source to surface distance, the air gap between snout and surface, field size, material thickness in front of surface, atomic number of the medium, beam angle and type of nozzle (ie double scattering, (DS), uniform scanning (US) or pencil beam scanning (PBS). Obliquity factor (OF) is defined as ratio of surface dose in 0° to beam angle Θ. Measurements were made in water phantom at various beam angles using very small microdiamond that has shown favorable beam characteristics for high, medium and low proton energy. Depth dose measurements were performed in the central axis of the beam in each respective gantry angle.Results:It is observed that surface dose is energy dependent but more predominantly on the SOBP. It is found that as SSD increases, surface dose decreases. In general, SSD, and air gap has limited impact in clinical proton range. High energy has higher surface dose and so the beam angle. The OF rises with beam angle. Compared to OF of 1.0 at 0° beam angle, the value is 1.5, 1.6, 1,7 for small, medium and large range respectively for 60 degree angle.Conclusion:It is advised that just like range and SOBP, surface dose should be clearly understood and a method to reduce the surface dose should be employed. Obliquity factor is a critical parameter that should be accounted in proton beam therapy and a perpendicular beam should be used to reduce surface dose.
SU‐E‐T‐583: Operated Left Breast and Chest Wall Radiotherapy: A Dosimetric Comparison Between 3DCRT,IMRT and VMAT
Authors: Sarkar B , Roy S , Munshi A , Pradhan A 
Published: June 2015

Purpose:To evaluate the comparative dosimetric efficacy between field and field 3DCRT(FnF), multiple field Intensity modulated radiotherapy (SnS IMRT) and, partial arc volumetric modulated arc therapy (VMAT) in case of post operative left side breast and chest wall irradiation.Methods:CT study set of fifteen post‐operative left breast and chest wall patient was tested for a treatment plan of 50Gy in 25 fraction using partial arc VMAT, SnSIMRT and tangential beam 3DCRT . 3DCRT FnF gantry angle was ranging for left medial tangential 290±170 and Lt lateral tangential l14°±120. For IMRT four fixed beam at gantry angle G1300 G1100 G3000 and G3300 was used, in case of insufficient dose another beam G1500 was added. In case of partial arc VMAT, lateral tangential arc G1300‐G1000 and medial tangential arc G2800‐G3100. Inverse optimization was opted to cover at least 95%PTV by 95% prescription dose (RxD) and a strong weightage on reduction of heart and lung dose. PTV coverage was evaluated for it's clinically acceptability depending on the tumor spatial location and its quadrant. Out of the three plans, any one was used for the actual patient treatment.Results:Dosimetric analysis done for breast PTV, left lung, heart and the opposite breast. PTV mean dose and maximum dose was 5129.8±214.8cGy, 4749.0±329.7cGy, 5024.6±73.4cGy and 5855.2±510.7cGy, 5340.7±146.1cGy, 5347.2±196.8cGy for FnF, VMAT and IMRT respectively. Ipsilateral lung volume receiving 20Gy and 5Gy was 23.6±9.5cGy and 32.7±10.3cGy for FnF, 18.6±8.7cGy and 38.8±15.2cGy for VMAT and 25.7±9.6cGy and 50.7±8.4cGy for IMRT respectively. Heart mean and 2cc dose was 867.9±456.7cGy and 5038.5±184.3cGy for FnF, 532.6±263cGy and 3632.1±990.6 for VMAT, 711±229.9cGy and 4421±463.7cGy for IMRT respectively. VMAT shows minimum contralateral breast dose 168±113.8cGy.Conclusion:VMAT shows a better tumor conformity, minimum heart, ipsilateral lung and opposite breast dose. Cardiac Toxicity and risk of contralateral breast cancer can be reduce using VMAT.
SU‐E‐T‐587: Optimal Volumetric Modulated Arc Radiotherapy Treatment Planning Technique for Multiple Brain Metastases with Increasing Number of Arcs
Authors: Keeling V , Hossain S , Hildebrand K , Ahmad S , Larson D , Sahgal A , Ma L 
Published: June 2015

Purpose:To show improvements in dose conformity and normal brain tissue sparing using an optimal planning technique (OPT) against clinically acceptable planning technique (CAP) in the treatment of multiple brain metastases.Methods:A standardized international benchmark case with12 intracranial tumors was planned using two different VMAT optimization methods. Plans were split into four groups with 3, 6, 9, and 12 targets each planned with 3, 5, and 7 arcs using Eclipse TPS. The beam geometries were 1 full coplanar and half non‐coplanar arcs. A prescription dose of 20Gy was used for all targets. The following optimization criteria was used (OPT vs. CAP): (No upper limit vs.108% upper limit for target volume), (priority 140–150 vs. 75–85 for normal‐brain‐tissue), and (selection of automatic sparing Normal‐Tissue‐Objective (NTO) vs. Manual NTO). Both had priority 50 to critical structures such as brainstem and optic‐chiasm, and both had an NTO priority 150. Normal‐brain‐tissue doses along with Paddick Conformity Index (PCI) were evaluated.Results:In all cases PCI was higher for OPT plans. The average PCI (OPT,CAP) for all targets was (0.81,0.64), (0.81,0.63), (0.79,0.57), and (0.72,0.55) for 3, 6, 9, and 12 target plans respectively. The percent decrease in normal brain tissue volume (OPT/CAP*100) achieved by OPT plans was (reported as follows: V4, V8, V12, V16, V20) (184, 343, 350, 294, 371%), (192, 417, 380, 299, 360%), and (235, 390, 299, 281, 502%) for the 3, 5, 7 arc 12 target plans, respectively. The maximum brainstem dose decreased for the OPT plan by 4.93, 4.89, and 5.30 Gy for 3, 5, 7 arc 12 target plans, respectively.Conclusion:Substantial increases in PCI, critical structure sparing, and decreases in normal brain tissue dose were achieved by eliminating upper limits from optimization, using automatic sparing of normal tissue function with high priority, and a high priority to normal brain tissue.
SU‐E‐T‐589: Optimization of Patient Head Angle Position to Spare Hippocampus During the Brain Radiation Therapy
Authors: Cheon G , Kang S , Kim T , Kim D , Kang Y , Suh T 
Published: June 2015

Purpose:Hippocampus is one of the important organs which controls emotions, behaviors, movements the memorizing and learning ability. In the conventional head & neck therapy position, it is difficult to perform the hippocampal‐sparing brain radiation therapy. The purpose of this study is to investigate optimal head angle which can save the hippocampal‐sparing and organ at risk (OAR) in conformal radiation therapy (CRT), Intensity modulation radiation therapy (IMRT) and helical tomotherapy (HT).Methods:Three types of radiation treatment plans, CRT, IMRT and Tomotherapy plans, were performed for 10 brain tumor patients. The image fusion between CT and MRI data were used in the contour due to the limited delineation of the target and OAR in the CT scan. The optimal condition plan was determined by comparing the dosimetric performance of the each plan with the use of various parameters which include three different techniques (CRT, IMRT, HT) and 4 angle (0, 15, 30, 40 degree). The each treatment plans of three different techniques were compared with the following parameters: conformity index (CI), homogeneity index (HI), target coverage, dose in the OARs, monitor units (MU), beam on time and the normal tissue complication probability (NTCP).Results:HI, CI and target coverage was most excellent in head angle 30 degree among all angle. When compared by modality, target coverage and CI showed good results in IMRT and TOMO than compared to the CRT. HI at the head angle 0 degrees is 1.137±0.17 (CRT), 1.085±0.09 (IMRT) and 1.077±0.06 (HT). HI at the head angle 30 degrees is 1.056±0.08 (CRT), 1.020±0.05 (IMRT) and 1.022±0.07 (HT).Conclusion:The results of our study show that when head angle tilted at 30 degree, target coverage, HI, CI were improved, and the dose delivered to OAR was reduced compared with conventional supine position in brain radiation therapy.This work was supported by the Radiation Technology R&D program (No. 2013M2A2A7043498) and the Mid‐career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐E‐T‐594: Out‐Of‐Field Neutron and Gamma Dose Estimated Using TLD‐600/700 Pairs in the Wobbling Proton Therapy System
Authors: Chen Y , Lin Y , Chen H , Tsai H 
Published: June 2015

Purpose:Secondary fast neutrons and gamma rays are mainly produced due to the interaction of the primary proton beam with the beam delivery nozzle. These secondary radiation dose to patients and radiation workers are unwanted. The purpose of this study is to estimate the neutron and gamma dose equivalent out of the treatment volume during the wobbling proton therapy system.Methods:Two types of thermoluminescent (TL) dosimeters, TLD‐600 (6LiF: Mg, Ti) and TLD‐700 (7LiF: Mg, Ti) were used in this study. They were calibrated in the standard neutron and gamma sources at National Standards Laboratory. Annealing procedure is 400°C for 1 hour, 100°C for 2 hours and spontaneously cooling down to the room temperature in a programmable oven. Two‐peak method (a kind of glow curve analysis technique) was used to evaluate the TL response corresponding to the neutron and gamma dose. The TLD pairs were placed outside the treatment field at the neutron‐gamma mixed field with 190‐MeV proton beam produced by the wobbling system through the polyethylene plate phantom. The results of TLD measurement were compared to the Monte Carlo simulation.Results:The initial experiment results of calculated dose equivalents are 0.63, 0.38, 0.21 and 0.13 mSv per Gy outside the field at the distance of 50, 100, 150 and 200 cm.Conclusion:The TLD‐600 and TLD‐700 pairs are convenient to estimate neutron and gamma dosimetry during proton therapy. However, an accurate and suitable glow curve analysis technique is necessary. During the wobbling system proton therapy, our results showed that the neutron and gamma doses outside the treatment field are noticeable.This study was supported by the grants from the Chang Gung Memorial Hospital (CMRPD1C0682).
SU‐E‐T‐595: Output Factor Calculation for a Uniform Scanning Proton Therapy System
Authors: Hecksel D , Stauffer N , DeFillippo G , Edwards J , Pankuch M 
Published: June 2015

Purpose:To develop an analytical model that predicts dose output factors for patient treatment fields in a uniform scanning proton therapy system.Methods:A model to predict output factors for patient specific treatment fields was produced based on the methods developed by Kooy et al. (2003). The Kooy model predicts the output factor based on the ratio of the entrance dose under calibration conditions to that for a given range and modulation corrected for the inverse square effect. Field specific output factors were plotted as a function of a single parameter r, where r = (Range‐Modulation)/Modulation. The model targeted user range 1 sub‐span 3 through user range 2 sup‐span 2 of the IBA uniform scanning proton therapy system. The data set included points measured using the 10 cm and 18 cm snout sizes to eliminate stem effects on the monitor unit chambers. The data was fit using equation 15 from Kooy et al. (2003), and the resulting model was tested against measurements that were not included in the original data set.Results:For the range and sub span investigated, 120 data points were tested against the model prediction. The model predicted the output factor within 2% for 96% of the points tested and within 2.5% for 99% of the points tested. All points were within 3% of the predicted values.Conclusion:Monitor units for patient treatment fields with proton ranges that fall within the tested interval can be predicted using a model based on the methods developed at MGH. With further evaluation, it will be possible to model all user ranges and sub‐spans of the IBA system. Further testing is also needed to predict output factors using a 25 cm snout which introduces variable scanning pattern sizes and stem effects on the monitor unit chambers.
SU‐E‐T‐596: P3DVHStats ‐ a Novel, Automatic, Institution Customizable Program to Compute and Report DVH Quantities On Philips Pinnacle TPS
Authors: Wu C 
Published: June 2015

Purpose:To implement a novel, automatic, institutional customizable DVH quantities evaluation and PDF report tool on Philips Pinnacle treatment planning system (TPS)Methods:An add‐on program (P3DVHStats) is developed by us to enable automatic DVH quantities evaluation (including both volume and dose based quantities, such as V98, V100, D2), and automatic PDF format report generation, for EMR convenience. The implementation is based on a combination of Philips Pinnacle scripting tool and Java language pre‐installed on each Pinnacle Sun Solaris workstation. A single Pinnacle script provide user a convenient access to the program when needed. The activated script will first export DVH data for user selected ROIs from current Pinnacle plan trial; a Java program then provides a simple GUI interface, utilizes the data to compute any user requested DVH quantities, compare with preset institutional DVH planning goals; if accepted by users, the program will also generate a PDF report of the results and export it from Pinnacle to EMR import folder via FTP.Results:The program was tested thoroughly and has been released for clinical use at our institution (Pinnacle Enterprise server with both thin clients and P3PC access), for all dosimetry and physics staff, with excellent feedback. It used to take a few minutes to use MS‐Excel worksheet to calculate these DVH quantities for IMRT/VMAT plans, and manually save them as PDF report; with the new program, it literally takes a few mouse clicks in less than 30 seconds to complete the same tasks.Conclusion:A Pinnacle scripting and Java language based program is successfully implemented, customized to our institutional needs. It is shown to dramatically reduce time and effort needed for DVH quantities computing and EMR reporting.
SU‐E‐T‐598: Parametric Equation for Quick and Reliable Estimate of Stray Neutron Doses in Proton Therapy and Application for Intracranial Tumor Treatments
Authors: Bonfrate A , Farah J , De Marzi L , Delacroix S , Herault J , Sayah R , Lee C , Bolch W , Clairand I 
Published: June 2015

Purpose:Development of a parametric equation suitable for a daily use in routine clinic to provide estimates of stray neutron doses in proton therapy.Methods:Monte Carlo (MC) calculations using the UF‐NCI 1‐year‐old phantom were exercised to determine the variation of stray neutron doses as a function of irradiation parameters while performing intracranial treatments. This was done by individually changing the proton beam energy, modulation width, collimator aperture and thickness, compensator thickness and the air gap size while their impact on neutron doses were put into a single equation. The variation of neutron doses with distance from the target volume was also included in it. Then, a first step consisted in establishing the fitting coefficients by using 221 learning data which were neutron absorbed doses obtained with MC simulations while a second step consisted in validating the final equation.Results:The variation of stray neutron doses with irradiation parameters were fitted with linear, polynomial, etc. model while a power‐law model was used to fit the variation of stray neutron doses with the distance from the target volume. The parametric equation fitted well MC simulations while establishing fitting coefficients as the discrepancies on the estimate of neutron absorbed doses were within 10%. The discrepancy can reach ∼25% for the bladder, the farthest organ from the target volume. Finally, the validation showed results in compliance with MC calculations since the discrepancies were also within 10% for head‐and‐neck and thoracic organs while they can reach ∼25%, again for pelvic organs.Conclusion:The parametric equation presents promising results and will be validated for other target sites as well as other facilities to go towards a universal method.
SU‐E‐T‐599: Patient Safety Enhancements Through a Study of R&V System Override Data
Authors: Hendrickson K , Vimolchalao S 
Published: June 2015

Purpose:Record and verify (R&V) software systems include safety checks that compare actual machine parameters with prescribed values for a patient's treatment, such as treatment couch position, linac, energy, and MUs. The therapist is warned of a mismatch with a pop‐up and prompted to approve an override in order to continue without changes. Override approval is often legitimate, but the pop‐up can also genuinely indicate a problem that would Result in the wrong treatment. When there are numerous pop‐up warnings, human nature leads us to approve any override without careful reading, undermining the effectiveness of the safety mechanism.Methods:Override data was collected from our R&V system for all patients treated between October 8 and 29, 2012, on four linacs and entered into a spreadsheet. Additional data collected included treatment technique, disease site, immobilization, time, linac, and whether localization images were obtained. Data were analyzed using spreadsheet tools to reveal trends, patterns and associations that might suggest appropriate process changes that could decrease the total number of overrides.Results:76 out of 113 patients had overrides. Out of the 944 treatments, 599 override items were generated. The majority were due to couch positions. 74 of the 84 overrides on a linac equipped with a 6D couch were due to the use of the rotational corrections and the fact that the 6D couch control does not communicate with the R&V system; translations required to rotate the couch appear to the R&V system as translations outside the tolerance range.Conclusion:Many findings were interesting but did not suggest a process change. Proposed process changes include creating site‐specific instead of just technique‐specific tolerance tables for couch shifts. Proposed improvements to the vendor are to facilitate direct communication between the 6D couch and the R&V system to eliminate those override warnings related to lack of communication.