bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐52: Dosimetric Benefit of Adaptive Re‐Planning in Lung Cancer Stereotactic Body Radiotherapy (SBRT)
Authors: Jia J , Tian Z , Gu X , Yan H , Jia X , Jiang S 
Published: July 2014

Purpose:To investigate the dosimetric benefit of adaptive re‐planning for lung stereotactic body radiotherapy(SBRT).Methods:Five lung cancer patients with SBRT treatment were retrospectively investigated. Our in‐house supercomputing online re‐planning environment (SCORE) was used to realize the re‐planning process. First a deformable image registration was carried out to transfer contours from treatment planning CT to each treatment CBCT. Then an automatic re‐planning using original plan DVH guided fluence‐map optimization is performed to get a new plan for the up‐to‐date patient geometry. We compared the re‐optimized plan to the original plan projected on the up‐to‐date patient geometry in critical dosimetric parameters, such as PTV coverage, spinal cord maximum and volumetric constraint dose, esophagus maximum and volumetric constraint dose.Results:The average volume of PTV covered by prescription dose for all patients was improved by 7.56% after the adaptive re‐planning. The volume of the spinal cord receiving 14.5Gy and 23Gy (V14.5, V23) decreased by 1.48% and 0.68%, respectively. For the esophagus, the volume receiving 19.5Gy (V19.5) reduced by 1.37%. Meanwhile, the maximum dose dropped off by 2.87% for spinal cord and 4.80% for esophagus.Conclusion:Our experimental results demonstrate that adaptive re‐planning for lung SBRT has the potential to minimize the dosimetric effect of inter‐fraction deformation and thus improve target coverage while reducing the risk of toxicity to nearby normal tissues.
SU‐E‐J‐53: Dosimetric Evaluation at Volumetric Modulated Arc Therapy for Treatment of Prostate Cancer Using Single Or Double Arcs
Authors: Silva D , Salmon H , Pavan G , Nardi S , Anderson E , Fairbanks L , Junior J , Cursino F , Colodette K 
Published: July 2014

Purpose:Evaluate and compare retrospective prostate treatment plan using Volumetric Modulated Arc Therapy (RapidArc™ – Varian) technique with single or double arcs at COI Group.Methods:Ten patients with present prostate and seminal vesicle neoplasia were replanned as a target treatment volume and a prescribed dose of 78 Gy. A baseline planning, using single arc, was developed for each case reaching for the best result on PTV, in order to minimize the dose on organs at risk (OAR). Maintaining the same optimization objectives used on baseline plan, two copies for optimizing single and double arcs, have been developed. The plans were performed with 10 MV photon beam energy on Eclipse software, version 11.0, making use of Trilogy linear accelerator with Millenium HD120 multileaf collimator. Comparisons on PTV have been performed, such as: maximum, minimum and mean dose, gradient dose, as well as the quantity of monitor units, treatment time and homogeneity and conformity index. OARs constrains dose have been evaluated, comparing both optimizations.Results:Regarding PTV coverage, the difference of the minimum, maximum and mean dose were 1.28%, 0.7% and 0.2% respectively higher for single arc. When analyzed the index of homogeneity found a difference of 0.99% higher when compared with double arcs. However homogeneity index was 0.97% lower on average by using single arc. The doses on the OARs, in both cases, were in compliance to the recommended limits RTOG 0415. With the use of single arc, the quantity of monitor units was 10,1% lower, as well as the Beam‐On time, 41,78%, when comparing double arcs, respectively.Conclusion:Concerning the optimization of patients with present prostate and seminal vesicle neoplasia, the use of single arc reaches similar objectives, when compared to double arcs, in order to decrease the treatment time and the quantity of monitor units.
SU‐E‐J‐54: Dosimetric Evaluation of Amplitude‐Based Gating in Volumetric Modulated Arc Therapy (VMAT)
Authors: Lee Chang Yeol , Huh Hyun Do , Kim Woo Chul , Kim Hun Jeong , Min Chul Kee , Ji Young Hoon , Kim Kum Bae 
Published: July 2014

Purpose:The purpose of this work is to evaluate the dosimetric influence in the gated volumetric modulated arc therapy.Methods:This study is performed in three liver cancer patients. Execution of 4D CT simulation and plan deliveries on one‐dimensional respiratory motion phantom were based on patient's respiratory trace data sets. We chose the regular and irregular respiratory amplitude patterns among the patient respiratory‐gated treatment log file. Dose distributions were evaluated using EBT3 film by comparing the gated delivery with static delivery.Results:The presented results of static measured and calculated dose distributions showed good agreement with gamma‐index passing rates above 97% for 3%/3 m dose accuracy/distance‐to‐agreement criteria. In regular respiratory amplitude pattern, the results of two in three patients evaluated gamma‐index passing rates above 92% except for another patient who was evaluated of 87.16%. Patients whose plans had the largest percentage failing the gamma statistics exhibited irregular respiratory amplitude pattern that evaluated less than 70%. Minimum passing rate was 37.40%. This results showed that the correlation of between sorted 4D CT phase and irregular patient respiratory amplitude pattern may results in considerable dosimetric difference.Conclusion:The effort to maintain regular patient respiratory amplitude pattern between 4D CT simulation and treatment is the most important in gated volumetric modulated arc therapy.
SU‐E‐J‐55: Dosimetric Evaluation of Centrally Located Lung Tumors: A Monte Carlo (MC) Study of Lung SBRT Planning
Authors: Pokhrel D , Badkul R , Jiang H , Saleh H , Estes C , Park J , Kumar P , Wang F 
Published: July 2014

Purpose:To compare dose distributions calculated using the iPlan XVMC algorithm and heterogeneities corrected/uncorrected Pencil Beam (PB‐hete/PB‐homo) algorithms for SBRT treatments of lung tumors.Methods:Ten patients with centrally located solitary lung tumors were treated using MC‐based SBRT to 60Gy in 5 fractions for PTVV100%=95%. ITV was delineated on MIP‐images based on 4D‐CT scans. PTVs(ITV+5mm margins) ranged from 10.1–106.5cc(mean=48.6cc). MC‐SBRT plans were generated with a combination of non‐coplanar conformal arcs/beams using iPlan‐XVMC‐algorithm (BrainLABiPlan ver.4.1.2) for Novalis‐TX consisting of HD‐MLCs and 6MV‐SRS(1000MU/min) mode, following RTOG 0813 dosimetric criteria. For comparison, PB‐hete/PB‐homo algorithms were used to re‐calculate dose distributions using same beam configurations, MLCs/monitor units. Plans were evaluated with isocenter/maximal/mean doses to PTV. Normal lung doses were evaluated with V5/V10/V20 and mean‐lung‐dose(MLD), excluding PTV. Other OAR doses such as maximal spinal cord/2cc‐esophagus/max bronchial tree (BT/maximal heart doses were tabulated.Results:Maximal/mean/isocenter doses to PTV calculated by PB‐hete were uniformly larger than MC plans by a factors of 1.09/1.13/1.07, on average, whereas they were consistently lower by PB‐homo by a factors of 0.9/0.84/0.9, respectively. The volume covered by 5Gy/10Gy/20Gy isodose‐lines of the lung were comparable (average within±3%) when calculated by PB‐hete compared to XVMC, but, consistently lower by PB‐homo by a factors of 0.90/0.88/0.85, respectively. MLD was higher with PB‐hete by 1.05, but, lower by PB‐homo by 0.9, on average, compared to XVMC. XVMC max‐cord/max‐BT/max‐heart and 2cc of esophagus doses were comparable to PB‐hete; however, PB‐homo underestimates by a factors of 0.82/0.89/0.88/0.86, on average, respectively.Conclusion:PB‐hete significantly overestimates dose to PTV relative to XVMC ‐hence underdosing the target. MC is more complex and accurate with tissue‐heterogeneities. The magnitude of variation significantly varies with ‘small‐island‐tumor’ surrounded by low‐density lung tissues ‐PB algorithms lacks later electron scattering. Dose calculation with XVMC for lung SBRT is routinely performed in our clinic, its performance for head' neck/sinus cases will also be investigated.
SU‐E‐J‐56: Dosimetric Impact of Patient Roll Variability in Peripheral‐Lung SBRT
Authors: Casto B , Ying J , Ku L 
Published: July 2014

Purpose:Positional variation about the patient longitudinal axis may introduce deleterious effects to clinical treatment plans, the effects of which are exacerbated by hypo‐fractionated treatment regimens. Our goal is to evaluate the dosimetric impact of rotational setup error in stereotactic body radiation therapy (SBRT) for peripherally‐located lung lesions.Methods:Six patients who had been treated for peripheral lung lesions using varying SBRT techniques were analyzed. Each patient's planning CT was processed using custom in‐house software to simulate 1, 3, and 5 degree roll in both directions about their longitudinal axis. The original plan was fused and re‐calculated. Agreement between planned and error‐simulated dose distributions was quantified using 3%, 3mm criteria for the 3‐dimensional gamma metric, and changes in target coverage and adjacent normal anatomy were also quantified.Results:Increased rotational setup error resulted in reduced target coverage, with changes in equivalent uniform dose ranging from −1.24% to −6.11% for simulated roll greater than or equal to 3 degrees, increasing with magnitude of error and skewed for roll directed toward the involved side. Changes to normal tissue metrics are linearly related to simulated roll, with rib D(1cc) changes ranging from −4.23% to 3.27% relative to the original treatment plan. Error‐simulated dose distributions demonstrate agreement by the gamma metric in the planned target of 72.56%, 81.02%, and 99.52% for 5, 3, and 1 degree simulated roll scenarios, respectively. Corresponding agreement for the regional dose in excess of 50% of the maximum were 65.71%,70.77%, and 97.88%.Conclusion:This study suggests that the ability to detect and compensate for rotational positioning variations beyond a threshold level may improve care for patients with peripherally‐located lesions beyond that which may be accomplished using only translational axes. Positional error of one degree of roll had little influence, though three or more degrees of error introduced significant discrepancy.
SU‐E‐J‐58: Dosimetric Verification of Metal Artifact Effects: Comparison of Dose Distributions Affected by Patient Teeth and Implants
Authors: Lee M , Lee J , Park J , Park H , Lee B , Kang S , Lee S , Suh T 
Published: July 2014

Purpose:Implant‐supported dentures seem particularly appropriate for the predicament of becoming edentulous and cancer patients are no exceptions. As the number of people having dental implants increased in different ages, critical dosimetric verification of metal artifact effects are required for the more accurate head and neck radiation therapy. The purpose of this study is to verify the theoretical analysis of the metal(streak and dark) artifact, and to evaluate dosimetric effect which cause by dental implants in CT images of patients with the patient teeth and implants inserted humanoid phantom.Methods:The phantom comprises cylinder which is shaped to simulate the anatomical structures of a human head and neck. Through applying various clinical cases, made phantom which is closely allied to human. Developed phantom can verify two classes: (i)closed mouth (ii)opened mouth. RapidArc plans of 4 cases were created in the Eclipse planning system. Total dose of 2000 cGy in 10 fractions is prescribed to the whole planning target volume (PTV) using 6MV photon beams. Acuros XB (AXB) advanced dose calculation algorithm, Analytical Anisotropic Algorithm (AAA) and progressive resolution optimizer were used in dose optimization and calculation.Results:In closed and opened mouth phantom, because dark artifacts formed extensively around the metal implants, dose variation was relatively higher than that of streak artifacts. As the PTV was delineated on the dark regions or large streak artifact regions, maximum 7.8% dose error and average 3.2% difference was observed. The averaged minimum dose to the PTV predicted by AAA was about 5.6% higher and OARs doses are also 5.2% higher compared to AXB.Conclusion:The results of this study showed that AXB dose calculation involving high‐density materials is more accurate than AAA calculation, and AXB was superior to AAA in dose predictions beyond dark artifact/air cavity portion when compared against the measurements.
SU‐E‐J‐59: Effective Adaptive DMLC Gated Radiotherapy with OAR Sparing
Authors: Chen Y , Wu H , Zhou Z , Sandison MinGeorge 
Published: July 2014

Purpose:Patient respiratory motion degrades the effectiveness of cancer radiation treatment. Advanced respiratory gating delivers radiation dose accurately yet with elongated treatment time. The goal of this research is to propose a novel adaptive dMLC dynamic gating with high delivery efficiency and precision.Methods:The dose delivery of dMLC is aided by simultaneous tracking of tumor and organ at risk (OAR). The leaf opening/closing will follow the motion trajectory of the tumor while sparing the OAR. The treatment beam turns on only when there is no overlapping between OAR and tumor in BEV. A variety of evaluation metrics were considered and calculated, including duty cycle, beam toggling rate, and direct irradiation avoidance to OAR, under various combinations of different tumor margins and the distance between the centers of the tumor and OAR in BEV (expressed as dx).Results:Retrospective simulation was performed to investigate the feasibility and superiority of this technique using four groups of synchronized tumor and OAR motion data. The simulation results indicate that the tumor and OAR motion patterns and their relative positions are the dominant influential factors. The duty cycle can be greater than 96.71% yet can be as low as 6.69% depending different motion groups. This proposed technique provides good OAR protection, especially for such cases with low duty cycle for which as high as 77.71% maximal direct irradiation to OAR can be spared. Increasing dx improves the duty cycle (treatment efficiency) and provides better OAR volume sparing, whereas, that of the tumor margins has the opposite influence.Conclusion:This real‐time adaptive dMLC gated radiation treatment with synchronous tumor and OAR tracking has inherent accurate dose delivery to tumor with reduced treatment time. In addition, the OAR protection capability make it an outstanding potential treatment strategy for mobile tumors.
SU‐E‐J‐60: Efficient Monte Carlo Dose Calculation On CPU‐GPU Heterogeneous Systems
Authors: Xiao K , Zhou B , Chen D. Z , Hu X. S 
Published: July 2014

Purpose:It is well‐known that the performance of GPU‐based Monte Carlo dose calculation implementations is bounded by memory bandwidth. One major cause of this bottleneck is the random memory writing patterns in dose deposition, which leads to several memory efficiency issues on GPU such as un‐coalesced writing and atomic operations. We propose a new method to alleviate such issues on CPU‐GPU heterogeneous systems, which achieves overall performance improvement for Monte Carlo dose calculation.Methods:Dose deposition is to accumulate dose into the voxels of a dose volume along the trajectories of radiation rays. Our idea is to partition this procedure into the following three steps, which are fine‐tuned for CPU or GPU: (1) each GPU thread writes dose results with location information to a buffer on GPU memory, which achieves fully‐coalesced and atomic‐free memory transactions; (2) the dose results in the buffer are transferred to CPU memory; (3) the dose volume is constructed from the dose buffer on CPU. We organize the processing of all radiation rays into streams. Since the steps within a stream use different hardware resources (i.e., GPU, DMA, CPU), we can overlap the execution of these steps for different streams by pipelining.Results:We evaluated our method using a Monte Carlo Convolution Superposition (MCCS) program and tested our implementation for various clinical cases on a heterogeneous system containing an Intel i7 quad‐core CPU and an NVIDIA TITAN GPU. Comparing with a straightforward MCCS implementation on the same system (using both CPU and GPU for radiation ray tracing), our method gained 2‐5X speedup without losing dose calculation accuracy.Conclusion:The results show that our new method improves the effective memory bandwidth and overall performance for MCCS on the CPU‐GPU systems. Our proposed method can also be applied to accelerate other Monte Carlo dose calculation approaches.This research was supported in part by NSF under Grants CCF‐1217906, and also in part by a research contract from the Sandia National Laboratories.
SU‐E‐J‐68: Evaluation of Liver Deformation During Breathing Using Deformable Image Registration: A Comparison Between 4D CT and 4D MRI
Authors: Liang X , Czito B , Palta M , Bashir M , Yin F , Cai J 
Published: July 2014

Purpose:It is of clinical interest to study liver deformation during breathing by applying deformable image registration (DIR) on respiratory correlated 4D images. This study aims to evaluate and compare the accuracy of DIR‐derived liver deformation based on 4D CT and 4D MRI.Methods:4D CT, 4D MR and cine MR images of liver region were acquired from 5 patients with liver cancer under an IRB‐approved protocol. Tumor trajectories were tracked from cine MR images. DVFs from 4D CT and 4D MR were generated via DIR implemented in Velocity AI. To enable comparison between DVFs and tumor trajectories from cine images, deformation vectors from each frame were linked together, forming DVF‐based trajectories. All DVF‐based trajectories within each tumor region were averaged. Absolute difference, relative difference and correlation coefficient between each pair of averaged DVF‐based trajectory and trajectory from cine MR images were calculated.Results:All metrics did not give consistent indications of which modality can provide more accurate DVFs. In superior‐inferior (SI) direction, averaging over all the five patients, 4D CT trajectories exhibited smaller absolute (2.05±0.52mm) and relative difference (0.43±0.14) and larger correlation coefficient (0.92±0.06) than 4D MR trajectories (2.54±1.45mm, 0.47±0.18, 0.88±0.10) whereas 4D MR (1.02±1.20mm, 0.90±0.69, 0.59±0.30) surpassed 4D CT (1.35±1.42mm, 1.35±1.25, 0.12±0.64) in every metric in right‐left direction. In anterior‐posterior direction, 4D MR trajectories has smaller absolute (1.17±0.74mm) and relative difference (0.50±0.18) with slightly smaller correlation coefficient (0.72±0.23) than 4D CT trajectories (1.51±0.64mm, 0.69±0.09, 0.75±0.26).Conclusion:We have implemented a novel approach for evaluating accuracy of DVFs based on 4D imaging for studying liver deformation. Initial results indicate that DVFs from 4D CT and 4D MRI are comparable. Further study on more patients is warranted and is undergoing to determine whether there is significant difference between 4D CT and 4D MRI.
SU‐E‐J‐75: Importance of 4DCT for Target Volume Definition in Stereotactic Lung Radiotherapy
Authors: Goksel E , Cone D , Tezcanli E , Kucucuk H , Senkesen O , Yilmaz M , Garipagaoglu M , Aslay I , Sengoz M 
Published: July 2014

Purpose:We aimed to investigate the importance of 4DCT for lung tumors treated with SBRT and whether maximum intensity projection (MIP) and free breathing (FB) images can compansate for tumor movement.Methods:Six patients with primary lung cancer and 2 patients with lung metastasis with a median age of 69.5 (42–86) were included. Patients were positioned supine on a vacuum bag. In addition to FB planning CT images, 4DCT images were obtained at 3 mm intervals using Varian RPM system with (Siemens Somatom Sensetion 64). MIP series were reconstructed using 4DCT images. PTV‐FB and PTV‐MIP (GTV+5mm) volumes were contoured using FB and MIP series, respectively. GTVs were defined on each of eight different breathing phase images and were merged to create the ITV. PTV‐4D was generated with a 5 mm margin to ITV. PTV‐MIP and PTV‐4D contours were copied to FB CT series and treatment plans for PTV‐MIP and PTV‐FB were generated using RapidArc (2 partial arc) technique in Eclipse (version 11, AAA algorithm). The prescription dose was 5600cGy in 7 fractions. ITV volumes receiving prescription dose (%) and V95 for ITV were calculated for each treatment plan.Results:The mean PTV‐4B, PTV‐MIP and PTV‐FB volumes were 23.2 cc, 15.4cc ve 11cc respectively. Median volume of ITV receiving the prescription dose was 34.6% (16.4–70 %) and median V95 dose for ITV was 1699cGy (232cGy‐5117cGy) in the plan optimized for PTV‐FB as the reference. When the plan was optimized for PTV‐MIP, median ITV volume receiving the prescription dose was 67.15% (26–86%) and median V95 dose for ITV was 4231cGy (1735cGy‐5290cGy).Conclusion:Images used in lung SBRT are critical for treatment quality; FB and MIP images did not compensate target movement, therefore 4DCT images should be obtained for all patients undergoing lung SBRT or the safety margins should be adjusted.
SU‐E‐J‐82: Intra‐Fraction Proton Beam‐Range Verification with PET Imaging: Feasibility Studies with Monte Carlo Simulations and Statistical Modeling
Authors: Lou K , Mirkovic D , Sun X , Zhu X , Poenisch F , Grosshans D , Clark J , Shao Y 
Published: July 2014

Purpose:To study the feasibility of intra‐fraction proton beam‐range verification with PET imaging.Methods:Two phantoms homogeneous cylindrical PMMA phantoms (290 mm axial length, 38 mm and 200 mm diameter respectively) were studied using PET imaging: a small phantom using a mouse‐sized PET (61 mm diameter field of view (FOV)) and a larger phantom using a human brain‐sized PET (300 mm FOV). Monte Carlo (MC) simulations (MCNPX and GATE) were used to simulate 179.2 MeV proton pencil beams irradiating the two phantoms and be imaged by the two PET systems. A total of 50 simulations were conducted to generate 50 positron activity distributions and correspondingly 50 measured activity‐ranges. The accuracy and precision of these activity‐ranges were calculated under different conditions (including count statistics and other factors, such as crystal cross‐section). Separate from the MC simulations, an activity distribution measured from a simulated PET image was modeled as a noiseless positron activity distribution corrupted by Poisson counting noise. The results from these two approaches were compared to assess the impact of count statistics on the accuracy and precision of activity‐range calculations.Results:MC Simulations show that the accuracy and precision of an activity‐range are dominated by the number (N) of coincidence events of the reconstructed image. They are improved in a manner that is inversely proportional to 1/sqrt(N), which can be understood from the statistical modeling. MC simulations also indicate that the coincidence events acquired within the first 60 seconds with 10^9 protons (small phantom) and 10^10 protons (large phantom) are sufficient to achieve both sub‐millimeter accuracy and precision.Conclusion:Under the current MC simulation conditions, the initial study indicates that the accuracy and precision of beam‐range verification are dominated by count statistics, and intra‐fraction PET image‐based beam‐range verification is feasible.This work was supported by a research award RP120326 from Cancer Prevention and Research Institute of Texas.