bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐J‐37: Feasibility of Utilizing Carbon Fiducials to Increase Localization Accuracy of Lumpectomy Cavity for Partial Breast Irradiation
Authors: Zhang Y , Hieken T , Mutter R , Park S , Yan E , Brinkmann D , Pafundi D 
Published: June 2015

PurposeTo investigate the feasibility of utilizing carbon fiducials to increase localization accuracy of lumpectomy cavity for partial breast irradiation (PBI).MethodsCarbon fiducials were placed intraoperatively in the lumpectomy cavity following resection of breast cancer in 11 patients. The patients were scheduled to receive whole breast irradiation (WBI) with a boost or 3D‐conformal PBI. WBI patients were initially setup to skin tattoos using lasers, followed by orthogonal kV on‐board‐imaging (OBI) matching to bone per clinical practice. Cone beam CT (CBCT) was acquired weekly for offline review. For the boost component of WBI and PBI, patients were setup with lasers, followed by OBI matching to fiducials, with final alignment by CBCT matching to fiducials. Using carbon fiducials as a surrogate for the lumpectomy cavity and CBCT matching to fiducials as the gold standard, setup uncertainties to lasers, OBI bone, OBI fiducials, and CBCT breast were compared.ResultsMinimal imaging artifacts were introduced by fiducials on the planning CT and CBCT. The fiducials were sufficiently visible on OBI for online localization. The mean magnitude and standard deviation of setup errors were 8.4mm ± 5.3 mm (n=84), 7.3mm ± 3.7mm (n=87), 2.2mm ± 1.6mm (n=40) and 4.8mm ± 2.6mm (n=87), for lasers, OBI bone, OBI fiducials and CBCT breast tissue, respectively. Significant migration occurred in one of 39 implanted fiducials in a patient with a large postoperative seroma.ConclusionOBI carbon fiducial‐based setup can improve localization accuracy with minimal imaging artifacts. With increased localization accuracy, setup uncertainties can be reduced from 8mm using OBI bone matching to 3mm using OBI fiducial matching for PBI treatment. This work demonstrates the feasibility of utilizing carbon fiducials to increase localization accuracy to the lumpectomy cavity for PBI. This may be particularly attractive for localization in the setting of proton therapy and other scenarios in which metal clips are contraindicated.
SU‐E‐J‐39: Dosimetric Benefit of Implanted Marker‐Based CBCT Setup for Definitive Prostatic Radiotherapy
Authors: Zhen H , Wu Z , Bluemenfeld P , Chu J , Wang D 
Published: June 2015

PurposeDaily setup for definitive prostatic radiotherapy is challenged by suboptimal visibility of the prostate boundary and daily variation of rectum shape and position. For patients with improved bowel preparation, we conducted a dosimetric comparison between prostate implanted marker (IM)‐based daily setup and anterior rectal wall (ARW)‐based setup, with the hypothesis that the former leads to adequate target coverage with better rectal sparing.MethodsFive IMRT/VMAT prostate cases with implanted markers were selected for analysis. Daily CBCT showed improvement of the rectal volume compared to planning CT. For each patient, the prostate and rectum were contoured on three CBCT images (fraction 5/15/25) with subsequent physician review. The CBCTs were then registered to a planning CT using IM‐based registration. The deviation of ARW positions from planning CT to CBCT were analyzed at various sup‐inf levels (−1.8 cm to 1.8 cm from level of prostate center). To estimate the potential dosimetric impact from ARW‐based setup, the treatment plans were recalculated using A‐P shifts ranging from −1mm to +6mm. Clinically important rectum DVH values including Dmax, D3cc and Dmean were computed.ResultsFor the studied patients, we observed on average 32% rectum volume reduction from planning CT to CBCT. As a Results, the ARW on average shifts posteriorly by −1mm to +5mm, depending on the sup‐inf level of observation, with larger shifts observed at more superior levels. Recalculation shows that when ARW shifts 1mm posteriorly, ARW‐based CBCT setup leads to a 1.0%, 4.2%, and 3.2% increase in rectum Dmax, D3cc, and Dmean, respectively, compared to IM‐based setup. The dosimetric deviations increase to 4.7%, 25.8% and 24.7% when ARW shifts 6mm posteriorly. No significant prostate‐only dose difference was observed.ConclusionFor patients with improved bowel preparation, IM‐based CBCT setup leads to accurate prostate coverage along with significantly lower rectal dose, compared to ARW‐based setup.
SU‐E‐J‐42: Evaluation of Fiducial Markers for Ultrasound and X‐Ray Images Used for Motion Tracking in Pancreas SBRT
Authors: Ng SK , Armour E , Su L , Zhang Y , Iordachita I , Wong J , Sen H Tutkun , Kazanzides P , Bell M Lediju , Ding K 
Published: June 2015

PurposeUltrasound tracking of target motion relies on visibility of vascular and/or anatomical landmark. However this is challenging when the target is located far from vascular structures or in organs that lack ultrasound landmark structure, such as in the case of pancreas cancer. The purpose of this study is to evaluate visibility, artifacts and distortions of fusion coils and solid gold markers in ultrasound, CT, CBCT and kV images to identify markers suitable for real‐time ultrasound tracking of tumor motion in SBRT pancreas treatment.MethodsTwo fusion coils (1mm × 5mm and 1mm × 10 mm) and a solid gold marker (0.8mm × 10mm) were embedded in a tissue–like ultrasound phantom. The phantom (5cm × 12cm × 20cm) was prepared using water, gelatin and psyllium‐hydrophilic‐mucilloid fiber. Psylliumhydrophilic mucilloid acts as scattering medium to produce echo texture that simulates sonographic appearance of human tissue in ultrasound images while maintaining electron density close to that of water in CT images. Ultrasound images were acquired using 3D‐ultrasound system with markers embedded at 5, 10 and 15mm depth from phantom surface. CT images were acquired using Philips Big Bore CT while CBCT and kV images were acquired with XVI‐system (Elexta). Visual analysis was performed to compare visibility of the markers and visibility score (1 to 3) were assigned.ResultsAll markers embedded at various depths are clearly visible (score of 3) in ultrasound images. Good visibility of all markers is observed in CT, CBCT and kV images. The degree of artifact produced by the markers in CT and CBCT images are indistinguishable. No distortion is observed in images from any modalities.ConclusionAll markers are visible in images across all modalities in this homogenous tissue‐like phantom. Human subject data is necessary to confirm the marker type suitable for real‐time ultrasound tracking of tumor motion in SBRT pancreas treatment.
SU‐E‐J‐46: Evaluation of the Accuracy of a Six Degree of Freedom Robotic Couch Using ConeBeam CT Images of the Isocal Phantom
Authors: Zhang Q , Driewer J , Wang S , Li S , Zheng D , Zhu X , Zhen W , Wahl A , Lin C , Thompson R , Zhou S , Enke C 
Published: June 2015

PurposeThe accuracy of Varian PerfectPitch six degree of freedom (DOF) robotic couch was examined using Varian Isocal phantom and cone‐beam CT (CBCT) system.MethodsCBCT images of the Isocal phantom were taken at different pitch and roll angles. The pitch and roll angles were varied from 357 to 3 degrees in one degree increments by input from service console, generating a total of 49 combinations with couch angle (yaw) zero. The center positions of the 16 tungsten carbide BBs contained in the Isocal were determined with in‐house image processing software. Expected BBs positions at different rotation angles were determined mathematically by applying a combined translation/rotation operator to BB positions at zero pitch and roll values. A least square method was used to minimize the difference between the expected BB positions and their measured positions. In this way rotation angles were obtained and compared with input values from the console.ResultsA total of 49 CBCT images with voxel sizes 0.51 mm × 0.51 mm × 1 mm were used in analysis. Among the 49 calculations, the maximum rotation angle differences were 0.1 degree, 0.15 degree, and 0.09 degree, for pitch, roll, and couch rotation, respectively. The mean ± standard‐deviation angle differences were 0.028±0.001 degree, −0.043±0.003 degree, and −0.009±0.001 degree, for pitch, roll, and couch rotation, respectively. The maximum isocenter shifts were 0.3 mm, 0.5 mm, 0.4 mm in x, y, z direction respectively following IEC6127 convention. The mean isocenter shifts were 0.07±0.02 mm, −0.05±0.06 mm, and −0.12±0.02 mm in x, y and z directions.ConclusionThe accuracy of the Varian PerfectPitch six DOF couch was studied with CBCTs of the Isocal phantom. The rotational errors were less than 0.15 degree and isocenter shifts were less than 0.5 mm in any direction. This accuracy is sufficient for stereotactic radiotherapy clinical applications.
SU‐E‐J‐49: Design and Fabrication of Custom 3D Printed Phantoms for Radiation Therapy Research and Quality Assurance
Authors: Jenkins C , Xing L 
Published: June 2015

PurposeThe rapid proliferation of affordable 3D printing techniques has enabled the custom fabrication of items ranging from paper weights to medical implants. This study investigates the feasibility of utilizing the technology for developing novel phantoms for use in radiation therapy quality assurance (QA) procedures.MethodsA phantom for measuring the geometric parameters of linear accelerator (LINAC) on‐board imaging (OBI) systems was designed using SolidWorks. The design was transferred to a 3D printer and fabricated using a fused deposition modeling (FDM) technique. Fiducials were embedded in the phantom by placing 1.6 mm diameter steel balls in predefined holes and securing them with silicone. Several MV and kV images of the phantom were collected and the visibility and geometric accuracy were evaluated. A second phantom, for use in the experimental evaluation of a high dose rate (HDR) brachytherapy dosimeter, was designed to secure several applicator needles in water. The applicator was fabricated in the same 3D printer and used for experiments.ResultsThe general accuracy of printed parts was determined to be 0.1 mm. The cost of materials for the imaging and QA phantoms were $22 and $5 respectively. Both the plastic structure and fiducial markers of the imaging phantom were visible in MV and kV images. Fiducial marker locations were determined to be within 1mm of desired locations, with the discrepancy being attributed to the fiducial attachment process. The HDR phantom secured the applicators within 0.5 mm of the desired locations.Conclusion3D printing offers an inexpensive method for fabricating custom phantoms for use in radiation therapy quality assurance. While the geometric accuracy of such parts is limited compared to more expensive methods, the phantoms are still highly functional and provide a unique opportunity for rapid fabrication of custom phantoms for use in radiation therapy QA and research.
SU‐E‐J‐50: An Evaluation of the Stability of Image Quality Parameters of the Elekta XVI and IView Imaging Systems
Authors: Stanley D , Papanikolaou N , Gutierrez A 
Published: June 2015

IntroductionQuality assurance of the image quality for image guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, the long term stability of selected image parameters was assessed and evaluated for CBCT mode, planar radiographic kV mode and MV mode. Methods and Materials: The CATPHAN, QckV‐1 and QC‐3 phantoms were used to evaluate the image quality parameters. The planar radiographic images were analyzed in PIPSpro™ with spatial resolution (f30, f40, f50) being recorded. For XVI CBCT, Head and Neck Small20 (S20) and Pelvis Medium20 (M20) standard acquisition modes were evaluated for Uniformity, Noise, Spatial Resolution and HU constancy. Dose and kVp for the XVI were recorded using the Unfors RaySafe Xi system with the R/F Low Detector for the kV planar radiographic mode.ResultsA total of 20 and 10 measurements were acquired for the planar radiographic and CBCT systems respectively over a two month period. Values were normalized to the mean and the standard deviations (STD) were recorded. For the planar radiographic spatial resolution, the STD for f30, f40, f50 were 0.004, 0.002, 0.002 and 0.005, 0.007, 0.008 for the kV and MV, respectively. The average recorded dose for kV was 38.7±2.7 μGy. The STD of the evaluated metrics for the S20 acquisition were: 0.444(f30), 0.067(f40), 0.062(f50), 0.018(Water/poly‐HU constancy), 0.028(uniformity) and 0.106(noise). The standard deviations for the M20 acquisition were: 0.108(f30), 0.073(f40), 0.091(f50), 0.008(Water/poly‐HU constancy), 0.005(uniformity) and 0.005(noise). Using these, tolerances can be reported as a warning and action threshold of 1σ and 2σ.ConclusionA study was performed to assess the stability of the basic image quality parameters recommended by TG‐142 for the Elekta XVI and iView imaging systems. Consistent imaging and dosimetric properties over the evaluated time frame were noted.This work was funded in part by the Cancer Prevention Research Institute of Texas Pre doctoral fellowship training grant (RP140105) to Dennis N. Stanley M.Sc.
SU‐E‐J‐114: A Practical Hybrid Method for Improving the Quality of CT‐CBCT Deformable Image Registration for Head and Neck Radiotherapy
Authors: Liu C , Kumarasiri A , Chetvertkov M , Gordon J , Chetty I , Siddiqui F , Kim J 
Published: June 2015

Purpose:Accurate deformable image registration (DIR) between CT and CBCT in H&N is challenging. In this study, we propose a practical hybrid method that uses not only the pixel intensities but also organ physical properties, structure volume of interest (VOI), and interactive local registrations.Methods:Five oropharyngeal cancer patients were selected retrospectively. For each patient, the planning CT was registered to the last fraction CBCT, where the anatomy difference was largest. A three step registration strategy was tested; Step1) DIR using pixel intensity only, Step2) DIR with additional use of structure VOI and rigidity penalty, and Step3) interactive local correction. For Step1, a public‐domain open‐source DIR algorithm was used (cubic B‐spline, mutual information, steepest gradient optimization, and 4‐level multi‐resolution). For Step2, rigidity penalty was applied on bony anatomies and brain, and a structure VOI was used to handle the body truncation such as the shoulder cut‐off on CBCT. Finally, in Step3, the registrations were reviewed on our in‐house developed software and the erroneous areas were corrected via a local registration using level‐set motion algorithm.Results:After Step1, there were considerable amount of registration errors in soft tissues and unrealistic stretching in the posterior to the neck and near the shoulder due to body truncation. The brain was also found deformed to a measurable extent near the superior border of CBCT. Such errors could be effectively removed by using a structure VOI and rigidity penalty. The rest of the local soft tissue error could be corrected using the interactive software tool. The estimated interactive correction time was approximately 5 minutes.Conclusion:The DIR using only the image pixel intensity was vulnerable to noise and body truncation. A corrective action was inevitable to achieve good quality of registrations. We found the proposed three‐step hybrid method efficient and practical for CT/CBCT registrations in H&N.My department receives grant support from Industrial partners: (a) Varian Medical Systems, Palo Alto, CA, and (b) Philips HealthCare, Best, Netherlands
SU‐E‐J‐118: A Systematic Analysis of Rigid Image Registration Using Patient CTs and Simulated Setup Images with a Unique Gold Standard Registration
Authors: Kieselmann J , Rosselet A , Scheib S , Thieme‐Marti S 
Published: June 2015

Purpose:To quantify the reliability of fully automated image registration (IR) of planning CTs with 2D MV/kV projections or kV‐CBCTs in terms of its failure rate, and to investigate the influence of algorithmic and external parameters on registration quality.Methods:A gold standard registration is necessary to evaluate the failure rate. We develop a novel framework to obtain unique gold standards for MV imaging: we simulate setup images from 50 patient CTs (5 anatomic sites), using HU mapping, simple raytracing, a semi‐empirical scatter model and noise addition. Comparing simulated and acquired images yields excellent agreement. We introduce translations (≤2cm) and rotations (≤2°) with respect to the planned isocenter between planning CTs and setup images according to reported setup‐errors in the literature, followed by using the clinically available IR software from Varian Medical Systems (Palo Alto). Application of this simulation framework to 2D/3D kV imaging is work in progress.Results:We investigate the dependence of the registration failure rate on the field size of MV projection images (square, centered at planned isocenter, detected shift >2mm from known shift). The results suggest a minimum field size of 10×10 cm2 to achieve reasonably small failure rates (<10%). We define an optimized parameter set for 2D/3D MV IR, which outperforms the default one of the IR software with respect to the failure rate (<3%), while not significantly (<50%) increasing computation time.Conclusion:The developed framework demonstrates the possibility of systematic tests of automated IR for arbitrarily large patient datasets. To our current knowledge this is a novel strategy. We are able to define optimized default parameter sets for registration algorithms and to estimate the influence of parameters, such as imaging dose, on the quality of IR. The improvements made for MV IR in this work look promising. Similar studies for kV based IR are work in progress.
SU‐E‐J‐120: Comparing 4D CT Computed Ventilation to Lung Function Measured with Hyperpolarized Xenon‐129 MRI
Authors: Neal B , Chen Q 
Published: June 2015

Purpose:To correlate ventilation parameters computed from 4D CT to ventilation, profusion, and gas exchange measured with hyperpolarized Xenon‐129 MRI for a set of lung cancer patients.Methods:Hyperpolarized Xe‐129 MRI lung scans were acquired for lung cancer patients, before and after radiation therapy, measuring ventilation, perfusion, and gas exchange. In the standard clinical workflow, these patients also received 4D CT scans before treatment. Ventilation was computed from 4D CT using deformable image registration (DIR). All phases of the 4D CT scan were registered using a B‐spline deformable registration. Ventilation at the voxel level was then computed for each phase based on a Jacobian volume expansion metric, yielding phase sorted ventilation images. Ventilation based upon 4D CT and Xe‐129 MRI were co‐registered, allowing qualitative visual comparison and qualitative comparison via the Pearson correlation coefficient.Results:Analysis shows a weak correlation between hyperpolarized Xe‐129 MRI and 4D CT DIR ventilation, with a Pearson correlation coefficient of 0.17 to 0.22. Further work will refine the DIR parameters to optimize the correlation. The weak correlation could be due to the limitations of 4D CT, registration algorithms, or the Xe‐129 MRI imaging. Continued development will refine parameters to optimize correlation.Conclusion:Current analysis yields a minimal correlation between 4D CT DIR and Xe‐129 MRI ventilation.Funding provided by the 2014 George Amorino Pilot Grant in Radiation Oncology at the University of Virginia.
SU‐E‐J‐122: The CBCT Dose Calculation Using a Patient Specific CBCT Number to Mass Density Conversion Curve Based On a Novel Image Registration and Organ Mapping Method in Head‐And‐Neck Radiation Therapy
Authors: Zhou J , Lasio G , Yi B , Huang J , Chen S , Zhang B , Langen K , Prado K , D'souza W 
Published: June 2015

Purpose:To develop a CBCT HU correction method using a patient specific HU to mass density conversion curve based on a novel image registration and organ mapping method for head‐and‐neck radiation therapy.Methods:There are three steps to generate a patient specific CBCT HU to mass density conversion curve. First, we developed a novel robust image registration method based on sparseness analysis to register the planning CT (PCT) and the CBCT. Second, a novel organ mapping method was developed to transfer the organs at risk (OAR) contours from the PCT to the CBCT and corresponding mean HU values of each OAR were measured in both the PCT and CBCT volumes. Third, a set of PCT and CBCT HU to mass density conversion curves were created based on the mean HU values of OARs and the corresponding mass density of the OAR in the PCT. Then, we compared our proposed conversion curve with the traditional Catphan phantom based CBCT HU to mass density calibration curve. Both curves were input into the treatment planning system (TPS) for dose calculation. Last, the PTV and OAR doses, DVH and dose distributions of CBCT plans are compared to the original treatment plan.Results:One head‐and‐neck cases which contained a pair of PCT and CBCT was used. The dose differences between the PCT and CBCT plans using the proposed method are −1.33% for the mean PTV, 0.06% for PTV D95%, and −0.56% for the left neck. The dose differences between plans of PCT and CBCT corrected using the CATPhan based method are −4.39% for mean PTV, 4.07% for PTV D95%, and −2.01% for the left neck.Conclusion:The proposed CBCT HU correction method achieves better agreement with the original treatment plan compared to the traditional CATPhan based calibration method.
SU‐E‐J‐123: Assessing Segmentation Accuracy of Internal Volumes and Sub‐Volumes in 4D PET/CT of Lung Tumors Using a Novel 3D Printed Phantom
Authors: Soultan D , Murphy J , James C , Hoh C , Gill B , Moiseenko V , Cervino L 
Published: June 2015

Purpose:To assess the accuracy of internal target volume (ITV) segmentation of lung tumors for treatment planning of simultaneous integrated boost (SIB) radiotherapy as seen in 4D PET/CT images, using a novel 3D‐printed phantom.Methods:The insert mimics high PET tracer uptake in the core and 50% uptake in the periphery, by using a porous design at the periphery. A lung phantom with the insert was placed on a programmable moving platform. Seven breathing waveforms of ideal and patient‐specific respiratory motion patterns were fed to the platform, and 4D PET/CT scans were acquired of each of them. CT images were binned into 10 phases, and PET images were binned into 5 phases following the clinical protocol. Two scenarios were investigated for segmentation: a gate 30–70 window, and no gating. The radiation oncologist contoured the outer ITV of the porous insert with on CT images, while the internal void volume with 100% uptake was contoured on PET images for being indistinguishable from the outer volume in CT images. Segmented ITVs were compared to the expected volumes based on known target size and motion.Results:3 ideal breathing patterns, 2 regular‐breathing patient waveforms, and 2 irregular‐breathing patient waveforms were used for this study. 18F‐FDG was used as the PET tracer. The segmented ITVs from CT closely matched the expected motion for both no gating and gate 30–70 window, with disagreement of contoured ITV with respect to the expected volume not exceeding 13%. PET contours were seen to overestimate volumes in all the cases, up to more than 40%.Conclusion:4DPET images of a novel 3D printed phantom designed to mimic different uptake values were obtained. 4DPET contours overestimated ITV volumes in all cases, while 4DCT contours matched expected ITV volume values. Investigation of the cause and effects of the discrepancies is undergoing.