bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐420: Dosimetry Comparison of Advanced External Beam Radiation Treatment Modalities to Brachytherapy Treatments in Patients with Cervical Cancer
Authors: Mwidu U , Devic S , Shehadeh M , AlKafi M , Mahmood R , Moftah B 
Published: July 2016

Purpose:A retrospective comparison of dose distributions achievable by High dose rate brachytherapy (HDRBT), Helical TomoTherapy (TOMO), CyberKnife (CK) and RapidArc (RA) in locally advanced inoperable cervical cancer patients is presented.Methods:Five patients with advanced stage cervical carcinoma were selected for this study after a full course of external beam radiotherapy (EBRT), chemotherapy and HDR Brachytherapy. To highlight any significant similarities/differences in dose distributions, high‐risk clinical target volume (HRCTV) coverage, organs at risk (OAR) sparing, and machine specific delivery limitations, we used D90 (dose received by 90% of the volume) as the parameter for HRCTV coverage as recommended by the GEC‐ESTRO Working Group. We also compared both integral and differential dose volume histograms (DVH) between different dose distributions treatment modalities for HRCTV and OAR.Results:TOMO and RA provided the most conformal dose distributions to HRCTV. Median doses (in Gy) to organs at risk were; for rectal wall: 1.7±0.6, 2.5±0.6,1.2±0.3, and 1.5±0.6, and for bladder wall: 1.6±0.1, 2.4±0.4, 0.8±0.6, and 1.5±0.5, for HDRBT, TOMO, CK, and RA, respectively.Conclusion:Contemporary EBRT modalities might be able to replace brachytherapy treatments for cervix cancer. While brachytherapy dose distributions feature high dose gradients, EBRT modalities provide highly conformal dose distributions to the target. However, it is still not clear whether a highly conformal dose or high gradient dose is more clinically relevant for the HRCTV in cervix cancer patients.
SU‐F‐T‐422: Detection of Optimal Tangential Partial Arc Span for VMAT Planning in IntactLeft‐Breast Treatment
Authors: Giri U , Sarkar B , Munshi A , Kaur H , Jassal K , Rathinamuthu S , Kumar S , Ganesh T , Mohanti B 
Published: July 2016

Purpose:This study was designed to investigate an appropriate arc span for intact partial Left breast irradiation by VMAT planning.Methods:Four cases of carcinoma left intact breast was chosen randomly for this study. Both medial tangential and left‐lateral tangential arc (G20°, G25°, G30°, G35°, G40°) were used having the same length and bilaterally symmetric. For each patient base plan was generated for 30° arc and rest of other arc plans were generated by keeping all plan parameters same, only arc span were changed. All patient plans were generated on treatment planning system Monaco (V 5.00.02) for 50 Gy dose in 25 fractions. PTV contours were clipped 3 mm from skin (patient). All plans were normalized in such a way that 95 % of prescription dose would cover 96 % of PTV volume.Results:Mean MU for 20°, 25°, 30°, 35° and 40° were 509 ± 18.8, 529.1 ± 20.2, 544.4 ± 20.8, 579.1 ±51.8, 607.2 ± 40.2 similarly mean hot spot (volume covered by 105% of prescription dose) were 2.9 ± 1.2, 3.7 ± 3.0, 1.5 ± 1.7, 1.3±0.6, 0.4 ± 0.4, mean contralateral breast dose (cGy) were 180.4 ± 242.3, 71.5 ± 52.7, 76.2 ± 58.8, 85.9 ± 70.5, 90.7 ± 70.1, mean heart dose (cGy) were 285.8 ± 87.2, 221.2 ± 62.8, 274.5 ± 95.5, 234.8 ± 73.8, 263.2 ± 81.6, V20 for ipsilateral lung were 15.4 ± 5.3, 14.3 ± 3.6, 15.3 ± 2.9, 14.2 ± 3.9, 14.7 ± 3.2 and V5 for ipsilateral lung were 33.9 ± 8.2, 31.0 ± 3.5, 42.6 ±15.6, 36.4 ± 12.9, 37.0 ± 7.5.Conclusion:The study concluded that appropriate arc span used for tangential intact breast treatment was optimally 30° because larger arc span were giving lower isodose spill in ipsilateral lung and smaller arc were giving heterogeneous dose distribution in PTV.
SU‐F‐T‐423: Automating Treatment Planning for Cervical Cancer in Low‐ and Middle‐ Income Countries
Authors: Kisling K , Zhang L , Yang J , Jhingran A , Balter P , McCarroll R , Beadle B , Howell R , Schmeler K , Court L 
Published: July 2016

Purpose:To develop and test two independent algorithms that automatically create the photon treatment fields for a four‐field box beam arrangement, a common treatment technique for cervical cancer in low‐ and middle‐income countries.Methods:Two algorithms were developed and integrated into Eclipse using its Advanced Programming Interface:3DMethod:We automatically segment bony anatomy on CT using an in‐house multi‐atlas contouring tool and project the structures into the beam's‐eye‐view. We identify anatomical landmarks on the projections to define the field apertures. 2DMethod:We generate DRRs for all four beams. An atlas of DRRs for six standard patients with corresponding field apertures are deformably registered to the test patient DRRs. The set of deformed atlas apertures are fitted to an expected shape to define the final apertures. Both algorithms were tested on 39 patient CTs, and the resulting treatment fields were scored by a radiation oncologist. We also investigated the feasibility of using one algorithm as an independent check of the other algorithm.Results:96% of the 3D‐Method‐generated fields and 79% of the 2D‐method‐generated fields were scored acceptable for treatment (“Per Protocol” or “Acceptable Variation”). The 3D Method generated more fields scored “Per Protocol” than the 2D Method (62% versus 17%). The 4% of the 3D‐Method‐generated fields that were scored “Unacceptable Deviation” were all due to an improper L5 vertebra contour resulting in an unacceptable superior jaw position. When these same patients were planned with the 2D method, the superior jaw was acceptable, suggesting that the 2D method can be used to independently check the 3D method.Conclusion:Our results show that our 3D Method is feasible for automatically generating cervical treatment fields. Furthermore, the 2D Method can serve as an automatic, independent check of the automatically‐generated treatment fields. These algorithms will be implemented for fully automated cervical treatment planning.
SU‐F‐T‐425: Head‐Scatter Off‐Axis for FFF Megavoltage Photon Beams
Authors: Zhu T , Penjweini R , Dimofte A 
Published: July 2016

Purpose:Head‐scatter photons inside a clinical accelerator cause the output to change with collimator setting. On the central‐axis, this contribution is well‐described by output factor in air (or head‐scatter factor). However, a few studies have examined this component at off‐axis points.Methods:We define the head‐scatter off‐axis ratio, HOA, as the ratio of the water kerma in air due to head‐scatter photons at the off‐axis position x to the water kerma from direct primary photons on the central axis: HOA(cx,cy,xy) = (Q(cx,cy,x) – QP(cx,cy,x))/QP(cx,cy,0), where Q(cx, cy,x), QP(cx,cy,x) are charges measured by an ionization chamber in a miniphantom for collimator setting cx × cy and cx × 3 cm, respectively, at off‐axis point x. “Direct primary” is those photons that come from the source without interactions in the intervening structures.Results:We measured HOA for two energies (6XFFF and 6X) along X and Y jaw directions for various collimator settings. The shape of HOA has well defined penumbra for collimator setting larger than 10 × 10 cm2.Conclusion:The narrow gaussian component is interpreted as the source of photons scattered in the flattening filter and the primary collimator. The broad component is attributed to photons scattered in the secondary (variable) collimators. By a direct comparison between 6X and 6XFFF beams, we can confirm that the second component is indeed coming from collimator jaws and identify the parts coming from the primary collimator and the flattening filter, respectively.
SU‐F‐T‐428: An Optimization‐Based Commissioning Tool for Finite Size Pencil Beam Dose Calculations
Authors: Li Y , Tian Z , Song T , Jia X , Gu X , Jiang S 
Published: July 2016

Purpose:Finite size pencil beam (FSPB) algorithms are commonly used to pre‐calculate the beamlet dose distribution for IMRT treatment planning. FSPB commissioning, which usually requires fine tuning of the FSPB kernel parameters, is crucial to the dose calculation accuracy and hence the plan quality. Yet due to the large number of beamlets, FSPB commissioning could be very tedious. This abstract reports an optimization‐based FSPB commissioning tool we have developed in MatLab to facilitate the commissioning.Methods:A FSPB dose kernel generally contains two types of parameters: the profile parameters determining the dose kernel shape, and a 2D scaling factors accounting for the longitudinal and off‐axis corrections. The former were fitted using the penumbra of a reference broad beam's dose profile with Levenberg‐Marquardt algorithm. Since the dose distribution of a broad beam is simply a linear superposition of the dose kernel of each beamlet calculated with the fitted profile parameters and scaled using the scaling factors, these factors could be determined by solving an optimization problem which minimizes the discrepancies between the calculated dose of broad beams and the reference dose.Results:We have commissioned a FSPB algorithm for three linac photon beams (6MV, 15MV and 6MVFFF). Dose of four field sizes (6*6cm2, 10*10cm2, 15*15cm2 and 20*20cm2) were calculated and compared with the reference dose exported from Eclipse TPS system. For depth dose curves, the differences are less than 1% of maximum dose after maximum dose depth for most cases. For lateral dose profiles, the differences are less than 2% of central dose at inner‐beam regions. The differences of the output factors are within 1% for all the three beams.Conclusion:We have developed an optimization‐based commissioning tool for FSPB algorithms to facilitate the commissioning, providing sufficient accuracy of beamlet dose calculation for IMRT optimization.
SU‐F‐T‐437: 3 Field VMAT Technique for Irradiation of Large Pelvic Tumors
Authors: Stakhursky V 
Published: July 2016

Purpose:VMAT treatment planning for large pelvic volume irradiation could be suboptimal due to inability of Varian linac to split MLC carriage during VMAT delivery for fields larger than 14.5cm in X direction (direction of leaf motion). We compare the dosimetry between 3 VMAT planning techniques, two 2‐arc field techniques and a 3‐arc field technique: a) two small in X direction (less than 14.5cm) arc fields, complementing each other to cover the whole lateral extent of target during gantry rotation, b) two large arc fields, each covering the targets completely during the rotation, c) a 3 field technique with 2 small in X direction arcs and 1 large field covering whole target.Methods:5 GYN cancer patients were selected to evaluate the 3 VMAT planning techniques. Treatment plans were generated using Varian Eclipse (ver. 11) TPS. Dose painting technique was used to deliver 5300 cGy to primary target and 4500 cGy to pelvic/abdominal node target. All the plans were normalized so that the prescription dose of 5300 cGy covered 95% of primary target volume. PTV and critical structures DVH curves were compared to evaluate all 3 planning techniques.Results:The dosimetric differences between the two 2‐arc techniques were minor. The small field 2‐arc technique showed a colder hot spot (0.4% averaged), while variations in maximum doses to critical structures were statistically nonsignificant (under 1.3%). In comparison, the 3‐field technique demonstrated a colder hot spot (1.1% less, 105.8% averaged), and better sparing of critical structures. The maximum doses to larger bowel, small bowel and gluteal fold were 3% less, cord/cauda sparing was 4.2% better, and bladder maximum dose was 4.6% less. The differences in maximum doses to stomach and rectum were statistically nonsignificant.Conclusion:3‐arc VMAT technique for large field irradiation of pelvis demonstrates dosimetric advantages compared to 2‐arc VMAT techniques.
SU‐F‐T‐439: Proposal of An Index That Identifies Left‐Sided Breast/chest‐Wall Patients Who Benefit From VMAT Planning
Authors: Xu H 
Published: July 2016

Purpose:To propose an index called field‐heart‐overlap‐index (FHOI) that can be used to determine if a left‐sided breast (or chest‐wall) patient will benefit from VMAT planning; Calculation of FHOI does not need creation of either VMAT or field‐in‐field (FinF) plans.Methods:Four indices were defined: 1) total heart volume; 2) total PTV volume; 3) breast/chest‐wall separation; and 4) field‐heart‐overlap‐index (FHOI). FHOI is defined as the ratio of the heart volume inside the FOV to the total heart volume. VMAT plans were deemed superior to FinF plans when V10Gy for heart is substantially lower while PTV coverage was not compromised. A point biserial correlation coefficient (r_pb) is used to quantitatively describe the correlation between a dichotomous variable (Y_p) and a continuous variable (an index under investigation); with 0 being completely uncorrelated and 1 being completely correlated. If VMAT planning is superior to FinF planning for a patient, Y_p=1, otherwise Y_p=0. r_pb will be calculated for four potential correlations: FHOI and Y_p, PTV volume and Y_p, heart volume and Y_p, separation and Y_p. For each of the four indices, the correlation relation was retrospectively analyzed for twelve breast patients and twelve chest‐wall patients.Results:Calculation of the four indices for 12 breast patients and 12 chest‐wall patients indicates that FHOI was strongly correlated with the choice of VMAT or FinF techniques, while the other three indices were poorly correlated the choice of the techniques. r_pb for FHOI and Y_p is 0.93 for breast patients and 0.99 for chest‐wall patients, respectively. r_pb for PTV volume and Y_p, heart volume and Y_p, separation and Y_p are 0.17, 0.55, 0.06, respectively.Conclusion:This study shows that FHOI is an appropriate to determine left‐sided breast/chestwall patients who will benefit from VMAT. Patients with high FHOI tend to benefit from VMAT as heart dose is significantly decreased.
SU‐F‐T‐440: The Feasibility Research of Checking Cervical Cancer IMRT Pre‐ Treatment Dose Verification by Automated Treatment Planning Verification System
Authors: Liu X , Yin Y , Lin X 
Published: July 2016

Purpose:To assess the preliminary feasibility of automated treatment planning verification system in cervical cancer IMRT pre‐treatment dose verification.Methods:The study selected randomly clinical IMRT treatment planning data for twenty patients with cervical cancer, all IMRT plans were divided into 7 fields to meet the dosimetric goals using a commercial treatment planning system(PianncleVersion 9.2and the EclipseVersion 13.5). The plans were exported to the Mobius 3D (M3D)server percentage differences of volume of a region of interest (ROI) and dose calculation of target region and organ at risk were evaluated, in order to validate the accuracy automated treatment planning verification system.Results:The difference of volume for Pinnacle to M3D was less than results for Eclipse to M3D in ROI, the biggest difference was 0.22± 0.69%, 3.5±1.89% for Pinnacle and Eclipse respectively. M3D showed slightly better agreement in dose of target and organ at risk compared with TPS. But after recalculating plans by M3D, dose difference for Pinnacle was less than Eclipse on average, results were within 3%.Conclusion:The method of utilizing the automated treatment planning system to validate the accuracy of plans is convenientbut the scope of differences still need more clinical patient cases to determine. At present, it should be used as a secondary check tool to improve safety in the clinical treatment planning.
SU‐F‐T‐442: Dose Distribution Comparison for Post‐Laryngectomy Stoma Area Between Conventional AP and VMAT Plans with Or Without Bolus
Authors: Lee B , Zhang J , Leu M , Cho‐Lim J , Inouye W , Lorentz W , Lee S 
Published: July 2016

Purpose:To compare dose distributions of conventional AP vs. VMAT treatment plans with or without bolus around post‐laryngectomy stoma.Methods:Radiation dose coverage for post‐laryngectomy stoma was analyzed using a set of real‐case CT‐simulation images. After meticulous contouring of the catheter cuff, stoma lumen, peri‐stoma skin and subclinical tumor bed at the larynx, the resulting dosimetry plans were analyzed with or without a 5 mm bolus placement. Wet gauze was used to minimize the effect of any air gap. Four plans were generated: AP superclavicular (SCV) plan with or without bolus, and VMAT plan with or without bolus. A dose of 60Gy in 30 fractions was prescribed at 3 cm depth for AP SCV plan, and to 95% of the PTV volume for VMAT plan.Results:For the conventional AP SCV plan, the peri‐stoma skin dose is sensitive to bolus placement as well as air gap compensation by wetted gauze (V95% of 20.7%, 33.0% and 94.8% for no bolus, bolus without and with air gap compensation, respectively). For stoma lumen, the dose drops off rapidly in depth. The catheter cuff may have certain dose‐buildup effect, but air gap around it and under the bolus placed can pose a more serious problem. The dose distributions of the two VMAT plans are moderately different for peri‐stoma skin (V95% of 95.0% with bolus and air gap compensation, and 82.3% without bolus), but nearly identical for stoma lumen (V95% of 91.5% and 92.0%, respectively). VMAT allows beamlets with different angles of incidence that helped achieve such dose distribution around the stoma even without bolus placement.Conclusion:Overall, the dose coverage around the stoma in the VMAT plan is better than the conventional AP SCV plan. To achieve optimal dose distribution, it is still recommended to place physical bolus and reduce the air gaps.
SU‐F‐T‐443: Quantification of Dosimetric Effects of Dental Metallic Implant On VMAT Plans
Authors: Lin C , Feng Y , Huang Z , Jiang W 
Published: July 2016

Purpose:To evaluate the dosimetric impact of metallic implant that correlates with the size of targets and metallic implants and distance in between on volumetric‐modulated arc therapy (VMAT) plans for head and neck (H&N) cancer patients with dental metallic implant.Methods:CT images of H&N cancer patients with dental metallic implant were used. Target volumes with different sizes and locations were contoured. Metal artifact regions excluding surrounding critical organs were outlined and assigned with CT numbers close to water (0HU). VMAT plans with half‐arc, one‐full‐arc and two‐full‐arcs were constructed and same plans were applied to structure sets with and without CT number assignment of metal artifact regions and compared. D95% was utilized to investigate PTV dose coverage and SNC Patient− Software was used for the analysis of dose distribution difference slice by slice.Results:For different targets sizes, variation of PTV dose coverage (Delta_D95%) with and without CT number replacement reduced with larger target volume for all half‐arc, one‐arc and two‐arc VMAT plans even though there were no clinically significant differences. Additionally, there were no significant variations of the maximum percent difference (max.%diff) of dose distribution. With regard to the target location, Delta_D95% and max. %diff dropped with increasing distance between target and metallic implant. Furthermore, half‐arc plans showed greater impact than one‐arc plans, and two‐arc plans had smallest influence for PTV dose coverage and dose distribution.Conclusion:The target size has less correlation of doseimetric impact than the target location relative to metallic implants. Plans with more arcs alleviate the dosimetric effect of metal artifact because of less contribution to the target dose from beams going through the regions with metallic artifacts. Incorrect CT number causes inaccurate dose distribution, therefore appropriately overwriting metallic artifact regions with reasonable CT numbers is recommended. More patient data are collected and under further analysis.
SU‐F‐T‐447: The Impact of Treatment Planning Methods On RapidPlan Modeling for Rectum Cancer
Authors: Lu S , Peng J , Li K , Wang J , Hu W 
Published: July 2016

Purpose:To investigate the dose volume histogram (DVH) prediction varieties based on intensity modulate radiotherapy (IMRT) plan or volume arc modulate radiotherapy (VMAT) plan models on the RapidPlan.Methods:Two DVH prediction models were generated in this study, including an IMRT model trained from 83 IMRT rectum plans and a VMAT model trained from 60 VMAT rectum plans. In the internal validation, 20 plans from each training database were selected to verify the clinical feasibility of the model. Then, 10 IMRT plans (PIMRT_by_IMRT_model) generated from IMRT model and 10 IMRT plans generated from VMAT model (PIMRT_by_VMAT_model) were compared on the dose to organs at risk (OAR), which included bladder, left and right femoral heads. The similar comparison was also performed on the VMAT plans generated from IMRT model (PVMAT_by_IMRT_model) and VMAT plans generated from VMAT (PVMAT_by_VMAT_model) model.Results:For the internal validation, all plans from IMRT or VMAT model shows significantly improvement on OAR sparing compared with the corresponded clinical ones. Compared to the PIMRT_by_VMAT_model, the PIMRT_by_IMRT_model has a reduction of 6.90±3.87%(p<0.001) on V40 6.63±3.62%(p<0.001) on V45 and 4.74±2.26%(p<0.001) on V50 in bladder; and a mean dose reduction of 2.12±1.75Gy(p=0.004) and 2.84±1.53Gy(p<0.001) in right and left femoral head, respectively. There was no significant difference on OAR sparing between PVMAT_by_IMRT_model and PVMAT_by_VMAT_model.Conclusion:The IMRT model for the rectal cancer in the RapidPlan can be applied to for VMAT planning. However, the VMAT model is not suggested to use in the IMRT planning. Cautions should be taken that the planning model based on some technique may not feasible to other planning techniques.
SU‐F‐T‐450: The Investigation of Radiotherapy Quality Assurance and Automatic Treatment Planning Based On the Kernel Density Estimation Method
Authors: Fan J , Fan J , Hu W , Wang J 
Published: July 2016

Purpose:To develop a fast automatic algorithm based on the two dimensional kernel density estimation (2D KDE) to predict the dose‐volume histogram (DVH) which can be employed for the investigation of radiotherapy quality assurance and automatic treatment planning.Methods:We propose a machine learning method that uses previous treatment plans to predict the DVH. The key to the approach is the framing of DVH in a probabilistic setting. The training consists of estimating, from the patients in the training set, the joint probability distribution of the dose and the predictive features. The joint distribution provides an estimation of the conditional probability of the dose given the values of the predictive features. For the new patient, the prediction consists of estimating the distribution of the predictive features and marginalizing the conditional probability from the training over this. Integrating the resulting probability distribution for the dose yields an estimation of the DVH. The 2D KDE is implemented to predict the joint probability distribution of the training set and the distribution of the predictive features for the new patient. Two variables, including the signed minimal distance from each OAR (organs at risk) voxel to the target boundary and its opening angle with respect to the origin of voxel coordinate, are considered as the predictive features to represent the OAR‐target spatial relationship. The feasibility of our method has been demonstrated with the rectum, breast and head‐and‐neck cancer cases by comparing the predicted DVHs with the planned ones.Results:The consistent result has been found between these two DVHs for each cancer and the average of relative point‐wise differences is about 5% within the clinical acceptable extent.Conclusion:According to the result of this study, our method can be used to predict the clinical acceptable DVH and has ability to evaluate the quality and consistency of the treatment planning.