bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐AB‐BRA‐03: Non‐Invasive Controlled Release from Implantable Hydrogel Scaffolds Using Ultrasound
Authors: Moncion A , Kripfgans O.D , Putnam A.J , Frances chi R.T , Fabiilli M.L 
Published: July 2016

Purpose:To control release of a model payload in acoustically responsive scaffolds (ARSs) using focused ultrasound (FUS).Methods:Fluorescently‐labeled dextran (10 kDa) was encapsulated in sonosensitive perfluorocarbon (C6F14 or C5F12) double emulsions (mean diameter: 2.9±0.1 µm). For in vitro release studies, 0.5 mL ARSs (10 mg/mL fibrin, 1% (v/v) emulsion) were polymerized in 24 well plates and covered with 0.5 mL medium. Starting one day after polymerization, ARSs were exposed to FUS (2.5 MHz, Pr = 8 MPa, 13 cycles, 100 Hz PRF) for 2 min daily. The amount of dextran released into the media was quantified. For in vivo studies, 0.25 mL ARSs were prepared as described previously and injected subcutaneously in the lower back of BALB/c mice. After polymerization, a subset of the implanted ARSs were exposed to FUS (as previously described). Animals were imaged longitudinally using a fluorescence imaging system to quantify the amount of dextran released from the ARSs.Results:In vitro: Over 6 days, +FUS displayed an 8.2‐fold increase in dextran release compared to −FUS (−FUS: 2.7±0.6%; +FUS: 22.2±3.0%) for C6F14 ARSs, and a 6.7‐fold increase (−FUS: 5.0±0.8%; +FUS: 38.5±1.6%) for C5F12:C6F14 ARSs. In vivo: +FUS displayed statistically greater dextran release compared to −FUS one day after implantation for C5F12:C6F14 ARSs (−FUS: 55.1±1.5%; +FUS: 74.1±2.2%) and three days after implantation for C6F14 ARSs (−FUS: 1.4±6.5%; +FUS: 30.4±5.4%).Conclusion:FUS enables non‐invasive control of payload release from an ARS, which could benefit growth factor delivery for tissue regeneration. ARS are versatile due to their tunability (i.e. stiffness, emulsion composition, FUS pressure, FUS frequency, etc.) and can be modified to for optimal payload release. Future work will optimize ARS formulations for in vivo use to minimize payload release in the absence of FUS.This work was supported by NIH Grant R21 AR065010 (M.L. Fabiilli) and the Basic Radiologic Sciences Innovative Research Award (M.L. Fabiilli). A. Moncion is supported by the National Science Foundation Graduate Student Research Fellowship (Grant DGE 1256260).
WE‐AB‐BRA‐10: Assessment of Fiber Bragg Grating (FBG)‐Based Sensing for Real‐Time Needle Tracking During MR‐Guided Brachytherapy
Authors: Borot de Battisti M , Denis de Senneville B , Maenhout M , Hautvast G , Binnekamp D , Lagendijk J J W , Van Vulpen M , Moerland M A 
Published: July 2016

Purpose:This study assesses the potential of Fiber Bragg Grating (FBG)‐based sensing for real‐time needle (including catheter or tube) tracking during MR‐guided HDR brachytherapy.Methods:The proposed FBG‐based sensing tracking approach involves a MR‐compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. When the stylet is inserted inside the lumen of the needle, the FBG sensing system can measure the needle's deflection. For localization of the needle in physical space, the position and orientation of the stylet base are mandatory. For this purpose, we propose to fix the stylet base and determine its position and orientation using a MR‐based calibration as follows. First, the deflection of a needle inserted in a phantom in two different configurations is measured during simultaneous MR‐imaging. Then, after segmentation of the needle shapes on the MR‐images, the position and orientation of the stylet base is determined using a rigid registration of the needle shapes on both MR and FBG‐based measurements. The calibration method was assessed by measuring the deflection of a needle in a prostate phantom in five different configurations using FBG‐based sensing during simultaneous MR‐imaging. Any two needle shapes were employed for the calibration step and the proposed FGB‐tracking approach was subsequently evaluated on the other three needles configurations. The tracking accuracy was evaluated by computing the Euclidian distance between the 3D FBG vs. MR‐based measurements.Results:Over all needle shapes tested, the average(standard deviation) Euclidian distance between the FBG and MR‐based measurements was 0.79mm(0.37mm). The update rate and latency of the FBG‐based measurements were 100ms and 300ms respectively.Conclusion:The proposed FBG‐based protocol can measure the needle position with an accuracy, precision, update rate and latency eligible for accurate needle steering during MR‐guided HDR brachytherapy.M. Borot de Battisti is funded by Philips Medical Systems Nederland B.V.; M. Moerland is principal investigator on a contract funded by Philips Medical Systems Nederland B.V.; G. Hautvast and D. Binnekamp are fulltime employees of Philips Medical Systems Nederland B.V.
WE‐AB‐202‐02: Incorporating Regional Ventilation Function in Predicting Radiation Fibrosis After Concurrent Chemoradiotherapy for Lung Cancer
Authors: Lan F , Jeudy J , Senan S , van Sornsen de Koste J , Tseng H , Zhou J , D'Souza W , Zhang H 
Published: July 2016

Purpose:To investigate the incorporation of pre‐therapy regional ventilation function in predicting radiation fibrosis (RF) in stage III non‐small‐cell lung cancer (NSCLC) patients treated with concurrent thoracic chemoradiotherapy.Methods:37 stage III NSCLC patients were retrospectively studied. Patients received one cycle of cisplatin‐gemcitabine, followed by two to three cycles of cisplatin‐etoposide concurrently with involved‐field thoracic radiotherapy between 46 and 66 Gy (2 Gy per fraction). Pre‐therapy regional ventilation images of the lung were derived from 4DCT via a density‐change‐based image registration algorithm with mass correction. RF was evaluated at 6‐months post‐treatment using radiographic scoring based on airway dilation and volume loss. Three types of ipsilateral lung metrics were studied: (1) conventional dose‐volume metrics (V20, V30, V40, and mean‐lung‐dose (MLD)), (2) dose‐function metrics (fV20, fV30, fV40, and functional mean‐lung‐dose (fMLD) generated by combining regional ventilation and dose), and (3) dose‐subvolume metrics (sV20, sV30, sV40, and subvolume mean‐lung‐dose (sMLD) defined as the dose‐volume metrics computed on the sub‐volume of the lung with at least 60% of the quantified maximum ventilation status). Receiver operating characteristic (ROC) curve analysis and logistic regression analysis were used to evaluate the predictability of these metrics for RF.Results:In predicting airway dilation, the area under the ROC curve (AUC) values for (V20, MLD), (fV20, fMLD), and (sV20, and sMLD) were (0.76, 0.70), (0.80, 0.74) and (0.82, 0.80), respectively. The logistic regression p‐values were (0.09, 0.18), (0.02, 0.05) and (0.004, 0.006), respectively. With regard to volume loss, the corresponding AUC values for these metrics were (0.66, 0.57), (0.67, 0.61) and (0.71, 0.69), and p‐values were (0.95, 0.90), (0.43, 0.64) and (0.08, 0.12), respectively.Conclusion:The inclusion of regional ventilation function improved predictability of radiation fibrosis. Dose‐subvolume metrics provided a promising method for incorporating functional information into the conventional dose‐volume parameters for outcome assessment.
WE‐AB‐202‐04: Statistical Evaluation of Lung Function Using 4DCT Ventilation Imaging: Proton Therapy VS IMRT
Authors: Huang Q , Zhang M , Chen T , Yue N , Zou J 
Published: July 2016

Purpose:Variation in function of different lung regions has been ignored so far for conventional lung cancer treatment planning, which may lead to higher risk of radiation induced lung disease. 4DCT based lung ventilation imaging provides a novel yet convenient approach for lung functional imaging as 4DCT is taken as routine for lung cancer treatment. Our work aims to evaluate the impact of accounting for spatial heterogeneity in lung function using 4DCT based lung ventilation imaging for proton and IMRT plans.Methods:Six patients with advanced stage lung cancer of various tumor locations were retrospectively evaluated for the study. Proton and IMRT plans were designed following identical planning objective and constrains for each patient. Ventilation images were calculated from patients’ 4DCT using deformable image registration implemented by Velocity AI software based on Jacobian‐metrics. Lung was delineated into two function level regions based on ventilation (low and high functional area). High functional region was defined as lung ventilation greater than 30%. Dose distribution and statistics in different lung function area was calculated for patients.Results:Variation in dosimetric statistics of different function lung region was observed between proton and IMRT plans. In all proton plans, high function lung regions receive lower maximum dose (100.2%–108.9%), compared with IMRT plans (106.4%–119.7%). Interestingly, three out of six proton plans gave higher mean dose by up to 2.2% than IMRT to high function lung region. Lower mean dose (lower by up to 14.1%) and maximum dose (lower by up to 9%) were observed in low function lung for proton plans.Conclusion:A systematic approach was developed to generate function lung ventilation imaging and use it to evaluate plans. This method hold great promise in function analysis of lung during planning. We are currently studying more subjects to evaluate this tool.
WE‐AB‐202‐12: Voxel‐Wise Analysis of Apparent Diffusion Coefficient and Perfusion Maps in Multi‐Parametric MRI of Prostate Cancer
Authors: Engstroem K , Casares‐Magaz O , Roervik J , Andersen E , Muren L 
Published: July 2016

Purpose:Multi‐parametric MRI (mp‐MRI) is being introduced in radiotherapy (RT) of prostate cancer, including for tumour delineation in focal boosting strategies. We recently developed an image‐based tumour control probability model, based on cell density distributions derived from apparent diffusion coefficient (ADC) maps. Beyond tumour volume and cell densities, tumour hypoxia is also an important determinant of RT response. Since tissue perfusion from mp‐MRI has been related to hypoxia we have explored the patterns of ADC and perfusion maps, and the relations between them, inside and outside prostate index lesions.Methods:ADC and perfusion maps from 20 prostate cancer patients were used, with the prostate and index lesion delineated by a dedicated uro‐radiologist. To reduce noise, the maps were averaged over a 3×3×3 voxel cube. Associations between different ADC and perfusion histogram parameters within the prostate, inside and outside the index lesion, were evaluated with the Pearson's correlation coefficient. In the voxel‐wise analysis, scatter plots of ADC vs perfusion were analysed for voxels in the prostate, inside and outside of the index lesion, again with the associations quantified with the Pearson's correlation coefficient.Results:Overall ADC was lower inside the index lesion than in the normal prostate as opposed to ktrans that was higher inside the index lesion than outside. In the histogram analysis, the minimum ktrans was significantly correlated with the maximum ADC (Pearson=0.47; p=0.03). At the voxel level, 15 of the 20 cases had a statistically significant inverse correlation between ADC and perfusion inside the index lesion; ten of the cases had a Pearson < −0.4.Conclusion:The minimum value of ktrans across the tumour was correlated to the maximum ADC. However, on the voxel level, the ‘local’ ktrans in the index lesion is inversely (i.e. negatively) correlated to the ‘local’ ADC in most patients.Research agreement with Varian Medical Systems, not related to the work presented in this abstract.
WE‐AB‐207A‐09: Optimization of the Design of a Moving Blocker for Cone‐Beam CT Scatter Correction: Experimental Evaluation
Authors: Chen X , Ouyang L , Yan H , Jia X , Zhang Y , Wang J 
Published: July 2016

Purpose:A moving blocker based strategy has shown promising results for scatter correction in cone‐beam computed tomography (CBCT). Different geometry designs and moving speeds of the blocker affect its performance in image reconstruction accuracy. The goal of this work is to optimize the geometric design and moving speed of the moving blocker system through experimental evaluations.Methods:An Elekta Synergy XVI system and an anthropomorphic pelvis phantom CIRS 801‐P were used for our experiment. A blocker consisting of lead strips was inserted between the x‐ray source and the phantom moving back and forth along rotation axis to measure the scatter signal. Accoriding to our Monte Carlo simulation results, three blockers were used, which have the same lead strip width 3.2mm and different gap between neighboring lead strips, 3.2, 6.4 and 9.6mm. For each blocker, three moving speeds were evaluated, 10, 20 and 30 pixels per projection (on the detector plane). Scatter signal in the unblocked region was estimated by cubic B‐spline based interpolation from the blocked region. CBCT image was reconstructed by a total variation (TV) based algebraic iterative reconstruction (ART) algorithm from the partially blocked projection data. Reconstruction accuracy in each condition is quantified as CT number error of region of interest (ROI) by comparing to a CBCT reconstructed image from analytically simulated unblocked and scatter free projection data.Results:Highest reconstruction accuracy is achieved when the blocker width is 3.2 mm, the gap between neighboring lead strips is 9.6 mm and the moving speed is 20 pixels per projection. RMSE of the CT number of ROIs can be reduced from 436 to 27.Conclusions:Image reconstruction accuracy is greatly affected by the geometry design of the blocker. The moving speed does not have a very strong effect on reconstruction result if it is over 20 pixels per projection.
WE‐AB‐209‐03: Adaptive SBRT Planning for Interfraction Motion
Authors: Wu V , Epelman M , Brock K , Feng M , Ten Haken R , Matuszak M 
Published: July 2016

Purpose:Interfraction changes in abdominal SBRT patient anatomy are challenging to address with image guidance alone because avoidance of an overlapping high‐priority gastrointestinal normal structure may come at the expense of tumor coverage. This work investigates the benefit of anticipating interfraction motion and exploiting favorable geometries at the time of treatment through dose adaptive planning.Methods:Beyond no change, six scenarios of duodenum shifts per fraction are generated (±1 cm XYZ) and sample five‐fraction paths (combinations of no and/or the indicated changes) are simulated. Under the baseline (nominal) plan, generated assuming no uncertainty, three scenarios result in overdosing the duodenum while the others result in safe or reduced dose. The nominal plan under‐doses the PTV (36.1 Gy‐EQD2) due to duodenum proximity. Three adaptive strategies are considered: i) Standard IGRT: for duodenum overdose, patient's isocenter is shifted to satisfy the duodenum dose tolerance; nominal plan is delivered otherwise; ii) Scaling: nominal plan scaled up/down in favorable/unfavorable patient geometries; iii) Mixed: shifting as in i) but boosting otherwise. If max duodenum dose (limit 6 Gy/Fx) is exceeded, dose distributions are shifted or scaled down, depending on the strategy considered. In all adaptive fractions, critical structure dose limits are satisfied, even if the PTVs are under‐dosed.Results:Generally, scaling dose allows better PTV dose (gEUD in Gy‐EQD2); however, in some scenarios, shifting is better than scaling down dose. In a path with 2 fractions of the duodenum not moving and 3 fractions of an unfavorable duodenum position, scaling dose results in the best coverage, with 36.8 Gy‐EQD2. In another path with 2 favorable and 3 unfavorable duodenum positions, the mixed strategy achieves the highest coverage with 41.0 Gy‐EQD2.Conclusions:Anticipating interfraction motion and exploiting favorable geometries through dose adaptive scaling can improve overall tumor coverage by compensating for conservative IGRT in unfavorable fractions.NIH‐P01‐CA059827
WE‐AB‐209‐05: Development of an Ultra‐Fast High Quality Whole Breast Radiotherapy Treatment Planning System
Authors: Sheng Y , Li T , Yoo S , Yin F , Blitzblau R , Horton J , Palta M , Hahn C , Ge Y , Wu Q 
Published: July 2016

Purpose:To enable near‐real‐time (<20sec) and interactive planning without compromising quality for whole breast RT treatment planning using tangential fields.Methods:Whole breast RT plans from 20 patients treated with single energy (SE, 6MV, 10 patients) or mixed energy (ME, 6/15MV, 10 patients) were randomly selected for model training. Additional 20 cases were used as validation cohort. The planning process for a new case consists of three fully automated steps:1. Energy Selection. A classification model automatically selects energy level. To build the energy selection model, principle component analysis (PCA) was applied to the digital reconstructed radiographs (DRRs) of training cases to extract anatomy‐energy relationship.2. Fluence Estimation. Once energy is selected, a random forest (RF) model generates the initial fluence. This model summarizes the relationship between patient anatomy's shape based features and the output fluence. 3. Fluence Fine‐tuning. This step balances the overall dose contribution throughout the whole breast tissue by automatically selecting reference points and applying centrality correction. Fine‐tuning works at beamlet‐level until the dose distribution meets clinical objectives. Prior to finalization, physicians can also make patient‐specific trade‐offs between target coverage and high‐dose volumes.The proposed method was validated by comparing auto‐plans with manually generated clinical‐plans using Wilcoxon Signed‐Rank test.Results:In 19/20 cases the model suggested the same energy combination as clinical‐plans. The target volume coverage V100% was 78.1±4.7% for auto‐plans, and 79.3±4.8% for clinical‐plans (p=0.12). Volumes receiving 105% Rx were 69.2±78.0cc for auto‐plans compared to 83.9±87.2cc for clinical‐plans (p=0.13). The mean V10Gy, V20Gy of the ipsilateral lung was 24.4±6.7%, 18.6±6.0% for auto plans and 24.6±6.7%, 18.9±6.1% for clinical‐plans (p=0.04, <0.001). Total computational time for auto‐plans was < 20s.Conclusion:We developed an automated method that generates breast radiotherapy plans with accurate energy selection, similar target volume coverage, reduced hotspot volumes, and significant reduction in planning time, allowing for near‐real‐time planning.
WE‐AB‐209‐07: Explicit and Convex Optimization of Plan Quality Metrics in Intensity‐Modulated Radiation Therapy Treatment Planning
Authors: Engberg L , Eriksson K , Forsgren A , Hardemark B 
Published: July 2016

Purpose:To formulate objective functions of a multicriteria fluence map optimization model that correlate well with plan quality metrics, and to solve this multicriteria model by convex approximation.Methods:In this study, objectives of a multicriteria model are formulated to explicitly either minimize or maximize a dose‐at‐volume measure. Given the widespread agreement that dose‐at‐volume levels play important roles in plan quality assessment, these objectives correlate well with plan quality metrics. This is in contrast to the conventional objectives, which are to maximize clinical goal achievement by relating to deviations from given dose‐at‐volume thresholds: while balancing the new objectives means explicitly balancing dose‐at‐volume levels, balancing the conventional objectives effectively means balancing deviations. Constituted by the inherently non‐convex dose‐at‐volume measure, the new objectives are approximated by the convex mean‐tail‐dose measure (CVaR measure), yielding a convex approximation of the multicriteria model.Results:Advantages of using the convex approximation are investigated through juxtaposition with the conventional objectives in a computational study of two patient cases. Clinical goals of each case respectively point out three ROI dose‐at‐volume measures to be considered for plan quality assessment. This is translated in the convex approximation into minimizing three mean‐tail‐dose measures. Evaluations of the three ROI dose‐at‐volume measures on Pareto optimal plans are used to represent plan quality of the Pareto sets. Besides providing increased accuracy in terms of feasibility of solutions, the convex approximation generates Pareto sets with overall improved plan quality. In one case, the Pareto set generated by the convex approximation entirely dominates that generated with the conventional objectives.Conclusion:The initial computational study indicates that the convex approximation outperforms the conventional objectives in aspects of accuracy and plan quality.
WE‐AB‐209‐10: Optimizing the Delivery of Sequential Fluence Maps for Efficient VMAT Delivery
Authors: Craft D , Balvert M 
Published: July 2016

Purpose:To develop an optimization model and solution approach for computing MLC leaf trajectories and dose rates for high quality matching of a set of optimized fluence maps to be delivered sequentially around a patient in a VMAT treatment.Methods:We formulate the fluence map matching problem as a nonlinear optimization problem where time is discretized but dose rates and leaf positions are continuous variables. For a given allotted time, which is allocated across the fluence maps based on the complexity of each fluence map, the optimization problem searches for the best leaf trajectories and dose rates such that the original fluence maps are closely recreated. Constraints include maximum leaf speed, maximum dose rate, and leaf collision avoidance, as well as the constraint that the ending leaf positions for one map are the starting leaf positions for the next map. The resulting model is non‐convex but smooth, and therefore we solve it by local searches from a variety of starting positions. We improve solution time by a custom decomposition approach which allows us to decouple the rows of the fluence maps and solve each leaf pair individually. This decomposition also makes the problem easily parallelized.Results:We demonstrate method on a prostate case and a head‐and‐neck case and show that one can recreate fluence maps to high degree of fidelity in modest total delivery time (minutes).Conclusion:We present a VMAT sequencing method that reproduces optimal fluence maps by searching over a vast number of possible leaf trajectories. By varying the total allotted time given, this approach is the first of its kind to allow users to produce VMAT solutions that span the range of wide‐field coarse VMAT deliveries to narrow‐field high‐MU sliding window‐like approaches.