bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐J‐96: Comparison of Frame‐Based and Mutual Information Registration Techniques for CT and MR Image Sets
Authors: Popple R , Bredel M , Brezovich I , Dobelbower M , Fisher W , Fiveash J , Guthrie B , Riley K , Wu X 
Published: July 2016

Purpose:To compare the accuracy of CT‐MR registration using a mutual information method with registration using a frame‐based localizer box.Methods:Ten patients having the Leksell head frame and scanned with a modality specific localizer box were imported into the treatment planning system. The fiducial rods of the localizer box were contoured on both the MR and CT scans. The skull was contoured on the CT images. The MR and CT images were registered by two methods. The frame‐based method used the transformation that minimized the mean square distance of the centroids of the contours of the fiducial rods from a mathematical model of the localizer. The mutual information method used automated image registration tools in the TPS and was restricted to a volume‐of‐interest defined by the skull contours with a 5 mm margin. For each case, the two registrations were adjusted by two evaluation teams, each comprised of an experienced radiation oncologist and neurosurgeon, to optimize alignment in the region of the brainstem. The teams were blinded to the registration method.Results:The mean adjustment was 0.4 mm (range 0 to 2 mm) and 0.2 mm (range 0 to 1 mm) for the frame and mutual information methods, respectively. The median difference between the frame and mutual information registrations was 0.3 mm, but was not statistically significant using the Wilcoxon signed rank test (p=0.37).Conclusion:The difference between frame and mutual information registration techniques was neither statistically significant nor, for most applications, clinically important. These results suggest that mutual information is equivalent to frame‐based image registration for radiosurgery. Work is ongoing to add additional evaluators and to assess the differences between evaluators.
SU‐F‐J‐117: Impact of Motion Artifacts On Image Quality and Accuracy of Tumor Motion Reconstruction in 4D CT‐On‐Rails and MV‐CBCT Scans: A Phantom Study
Authors: Lin T , Ma C 
Published: July 2016

Purpose:To compare and quantify respiratory motion artifacts in images from free breathing 4D‐CT‐on‐Rails(CTOR) and those from MV‐Cone‐beam‐CT(MVCB) and facilitate respiratory motion guided radiation therapy.Methods:4D‐CTOR: Siemens Somatom CT‐on‐Rails system with Anzai belt loaded with pressure sensor load cells. 4D scans were performed in helical mode, pitch 0.1, gantry rotation time 0.5s, 1.5mm slice thickness, 120kVp, 400 mAs. Normal and fast breathing (>12rpm) scanning protocols were investigated. Helical scan, AIP(average intensity projection) and MIP(maximum intensity projection) were generated from 4D‐CTOR scans with amplitude sorting into 10 phases.MVCB: Siemens Artiste diamond view(1MV)MVCB was performed with 5MU thorax protocol with 60 second of full rotation.Phantom: Anzai AZ‐733V respiratory phantom. The settings were set to normal and resp. modes with repetition rates at 15 rpm and 10 rpm. Surgical clips, acrylic, wooden, rubber and lung density, total six mock‐ups were scanned and compared in this study.Signal‐to‐noise ratio(SNR), contrast‐to‐noise ratio(CNR) and reconstructed motion volume were compared to different respiratory setups for the mock‐ups.Results:Reconstructed motion volume was compared to the real object volume for the six test mock‐ups. It shows that free breathing helical in all instances underestimates the object excursions largest to −67.4% and least −6.3%. Under normal breathing settings, MIP can predict very precise motion volume with minimum 0.4% and largest −13.9%. MVCB shows underestimate of the motion volume with −1.11% minimum and −18.0% maximum. With fast breathing, AIP provides bad representation of the object motion; however, the MIP can predict the motion volume with −2.0% to −11.4% underestimate.Conclusion:Respiratory motion guided radiation therapy requires good motion recording. This study shows that regular CTOR helical scans provides bad guidance, 4D CTOR AIP cannot represent the fast breathing pattern, MIP can represent the best motion volume, MVCBCT can only be used for normal breathing with acceptable uncertainties.
SU‐F‐J‐130: Margin Determination for Hypofractionated Partial Breast Irradiation
Authors: Geady C , Keller B , Ruschin M , Hahn E , Makhani N , Bosnic S , Vesprini D , Soliman H , Lee J , McCann C 
Published: July 2016

Purpose:To determine the Planning Target Volume (PTV) margin for Hypofractionated Partial Breast Irradiation (HPBI) using the van Herk formalism (M=2.5∑+0.7σ). HPBI is a novel technique intended to provide local control in breast cancer patients not eligible for surgical resection, using 40 Gy in 5 fractions prescribed to the gross disease.Methods:Setup uncertainties were quantified through retrospective analysis of cone‐beam computed tomography (CBCT) data sets, collected prior to (prefraction) and after (postfraction) treatment delivery. During simulation and treatment, patients were immobilized using a wing board and an evacuated bag. Prefraction CBCT was rigidly registered to planning 4‐dimensional computed tomography (4DCT) using the chest wall and tumor, and translational couch shifts were applied as needed. This clinical workflow was faithfully reproduced in Pinnacle (Philips Medical Systems) to yield residual setup and intrafractional error through translational shifts and rigid registrations (ribs and sternum) of prefraction CBCT to 4DCT and postfraction CBCT to prefraction CBCT, respectively. All ten patients included in this investigation were medically inoperable; the median age was 84 (range, 52–100) years.Results:Systematic (and random) setup uncertainties (in mm) detected for the left‐right, craniocaudal and anteroposterior directions were 0.4 (1.5), 0.8 (1.8) and 0.4 (1.0); net uncertainty was determined to be 0.7 (1.5). Rotations >2° in any axis occurred on 8/72 (11.1%) registrations.Conclusion:Preliminary results suggest a non‐uniform setup margin (in mm) of 2.2, 3.3 and 1.7 for the left‐right, craniocaudal and anteroposterior directions is required for HPBI, given its immobilization techniques and online setup verification protocol. This investigation is ongoing, though published results from similar studies are consistent with the above findings. Determination of margins in breast radiotherapy is a paradigm shift, but a necessary step in moving towards hypofractionated regiments, which may ultimately redefine the standard of care for this select patient population.
SU‐F‐J‐131: Reproducibility of Positioning Error Due to Temporarily Indwelled Urethral Catheter for Urethra‐Sparing Prostate IMRT
Authors: Hirose K , Sato M , Hatayama Y , Kawaguchi H , Aoki M , Akimoto H , Komai F , Souma M , Obara H , Suzuki M , Takai Y 
Published: July 2016

Purpose:The purpose of this study was to prospectively assess the reproducibility of positioning errors due to temporarily indwelled catheter in urethra‐sparing image‐guided (IG) IMRT.Methods:Ten patients received urethra‐sparing prostate IG‐IMRT with implanted fiducials. After the first CT scan was performed in supine position, 6‐Fr catheter was indwelled into urethra, and the second CT images were taken for planning. While the PTV received 80 Gy, 5% dose reduction was applied for the urethral PRV along the catheter. Additional CT scans were also performed at 5th and 30th fraction. Positions of interests (POIs) were set on posterior edge of prostate at beam isocenter level (POI1) and cranial and caudal edge of prostatic urethra on the post‐indwelled CT images. POIs were copied into the pre‐indwelled, 5th and 30th fraction's CT images after fiducial matching on these CT images. The deviation of each POI between pre‐ and post‐indwelled CT and the reproducibility of prostate displacement due to catheter were evaluated.Results:The deviation of POI1 caused by the indwelled catheter to the directions of RL/AP/SI (mm) was 0.20±0.27/−0.64±2.43/1.02±2.31, respectively, and the absolute distances (mm) were 3.15±1.41. The deviation tends to be larger if closer to the caudal edge of prostate. Compared with the pre‐indwelled CT scan, a median displacement of all POIs (mm) were 0.3±0.2/2.2±1.1/2.0±2.6 in the post‐indwelled, 0.4±0.4/3.4±2.1/2.3±2.6 in 5th, and 0.5±0.5/1.7±2.2/1.9±3.1 in 30th fraction's CT scan with a similar data distribution. There were 6 patients with 5‐mm‐over displacement in AP and/or CC directions.Conclusion:Reproducibility of positioning errors due to temporarily indwelling catheter was observed. Especially in case of patients with unusually large shifts by indwelling catheter at the planning process, treatment planning should be performed by using the pre‐indwelled CT images with transferred contour of the urethra identified by post‐indwelled CT images.
SU‐F‐J‐138: An Extension of PCA‐Based Respiratory Deformation Modeling Via Multi‐Linear Decomposition
Authors: Iliopoulos AS , Pitsianis N , Sun X , Yin FF , Ren L 
Published: July 2016

Purpose:To address and lift the limited degree of freedom (DoF) of globally bilinear motion components such as those based on principal components analysis (PCA), for encoding and modeling volumetric deformation motion.Methods:We provide a systematic approach to obtaining a multi‐linear decomposition (MLD) and associated motion model from deformation vector field (DVF) data. We had previously introduced MLD for capturing multi‐way relationships between DVF variables, without being restricted by the bilinear component format of PCA‐based models. PCA‐based modeling is commonly used for encoding patient‐specific deformation as per planning 4D‐CT images, and aiding on‐board motion estimation during radiotherapy. However, the bilinear space‐time decomposition inherently limits the DoF of such models by the small number of respiratory phases. While this limit is not reached in model studies using analytical or digital phantoms with low‐rank motion, it compromises modeling power in the presence of relative motion, asymmetries and hysteresis, etc, which are often observed in patient data. Specifically, a low‐DoF model will spuriously couple incoherent motion components, compromising its adaptability to on‐board deformation changes. By the multi‐linear format of extracted motion components, MLD‐based models can encode higher‐DoF deformation structure.Results:We conduct mathematical and experimental comparisons between PCA‐ and MLD‐based models. A set of temporally‐sampled analytical trajectories provides a synthetic, high‐rank DVF; trajectories correspond to respiratory and cardiac motion factors, including different relative frequencies and spatial variations. Additionally, a digital XCAT phantom is used to simulate a lung lesion deforming incoherently with respect to the body, which adheres to a simple respiratory trend. In both cases, coupling of incoherent motion components due to a low model DoF is clearly demonstrated.Conclusion:Multi‐linear decomposition can enable decoupling of distinct motion factors in high‐rank DVF measurements. This may improve motion model expressiveness and adaptability to on‐board deformation, aiding model‐based image reconstruction for target verification.NIH Grant No. R01‐184173
SU‐F‐J‐145: MRI‐Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy
Authors: Kleijnen J J E , Couwenberg A M , van Asselen B , Lagendijk J J W , Intven M , Raaymakers B W 
Published: July 2016

Purpose:The recent development of an MRI‐linac allows adaptation of treatments to the anatomy of the moment. This anatomy, in turn, could be altered into a more favorable situation for radiotherapy purposes. The purpose of this study is to investigate the potential dosimetric benefits of manipulating rectal anatomy in MRI‐guided interventional external‐beam radiotherapy for rectal cancer.Methods:For this retrospective analysis, four patients (1M/3F) diagnosed with rectal cancer were included. These underwent MR‐imaging using sonography transmission gel as endorectal contrast at time of diagnosis and standard, non‐contrast, MR‐imaging prior to radiotherapy planning. In the contrast scan, the rectum is inflated by the inserted contrast gel, thereby potentially increasing the distance between tumor and the organs‐at‐risk (OAR). Both anatomies were delineated and 7‐ beam IMRT‐plans were calculated for both situations (RT‐standard and RT‐inflated), using in‐house developed treatment planning software. Each plan was aimed to deliver 15Gy to the planning target volume (PTV; tumor+3mm margin) with a D99>95% and Dmax<120% of the planned dose. The D2cc dose to the OAR were then compared for both situations.Results:At equal (or better) target coverage, we found a mean reduction in D2cc of 4.1Gy/237% [range 2.6Gy–6.3Gy/70%–621%] for the bladder and of 2.0Gy/145% [range −0.7Gy–7.9Gy/−73%–442%] for the small‐bowel, for the RT‐inflated compared to the RT‐standard plans. For the three female patients, a reduction in D2cc of 5.2Gy/191% [range 3.2Gy–9.2Gy/44%–475%] for the gynecological organs was found. We found all D2cc doses to be better for the RT‐inflated plans, except for one patient for whom the bladder D2cc dose was slightly increased.Conclusion:Reduction of OAR dose by manipulation of anatomy is feasible. Inflation of the rectum results in more distance between OAR and PTV. This leads to a substantial reduction in dose to OAR at equal or better target coverage.
SU‐F‐J‐151: Evaluation of a Magnetic Resonance Image Gated Radiotherapy System Using a Motion Phantom and Radiochromic Film
Authors: Lamb J , Ginn J , O'Connell D , Thomas D , Agazaryan N , Cao M , Yang Y , Low D 
Published: July 2016

Purpose:Magnetic resonance image (MRI) guided radiotherapy enables gating directly on target position for soft‐tissue targets in the lung and abdomen. We present a dosimetric evaluation of a commercially‐available FDA‐approved MRI‐guided radiotherapy system's gating performance using a MRI‐compatible respiratory motion phantom and radiochromic film.Methods:The MRI‐compatible phantom was capable of one‐dimensional motion. The phantom consisted of a target rod containing high‐contrast target inserts which moved inside a body structure containing background contrast material. The target rod was equipped with a radiochromic film insert. Treatment plans were generated for a 3 cm diameter spherical target, and delivered to the phantom at rest and in motion with and without gating. Both sinusoidal and actual tumor trajectories (two free‐breathing trajectories and one repeated‐breath hold) were used. Gamma comparison at 5%/3mm was used to measure fidelity to the static target dose distribution.Results:Without gating, gamma pass rates were 24–47% depending on motion trajectory. Using our clinical standard of repeated breath holds and a gating window of 3 mm with 10% of the target allowed outside the gating boundary, the gamma pass rate was 99.6%. Relaxing the gating window to 5 mm resulted in gamma pass rate of 98.6% with repeated breath holds. For all motion trajectories gated with 3 mm margin and 10% allowed out, gamma pass rates were between 64–100% (mean:87.5%). For a 5 mm margin and 10% allowed out, gamma pass rates were between 57–98% (mean: 82.49%), significantly lower than for 3 mm by paired t‐test (p=0.01).Conclusion:We validated the performance of respiratory gating based on real‐time cine MRI images with the only FDA‐approved MRI‐guided radiotherapy system. Our results suggest that repeated breath hold gating should be used when possible for best accuracy. A 3 mm gating margin is statistically significantly more accurate than a 5 mm gating margin.
SU‐F‐J‐154: Harmonic Analysis for Arbitrary 3D MR Image Distortion Fields
Authors: Stanescu T , Jaffray D 
Published: July 2016

Purpose:To study the practical feasibility of harmonic analysis for the full quantification of 3D MR image distortion fields associated with arbitrarily‐shaped regions of interest.Methods:The 3D scanner‐related distortion field (F) is innate to the MR image data. Since it is implicitly related to the magnetic fields required to perform MR imaging, F is in a steady‐state and can be described by a boundary value problem in which the Laplace's equation is solved with Dirichlet boundary conditions. Specifically, to fully derive a unique solution for F inside an arbitrarily‐shaped domain (D) the minimum input data required is given by the boundary of D. In practice, the data that needs to be measured by means of image acquisition and post‐processing is on the 3D surface of D (e.g. ellipsoid, cylinder, cuboid). Data from a large FOV phantom with a dense grid structure was used as a reference to explore multiple scenarios. The harmonic analysis solver was based on a finite element method and the domains were defined as binary STL structures for robust meshing. Simple and complex (non‐)quadratic shapes were analyzed to test the applicability of the harmonic approach. The harmonic solution and reference data were compared inside D using histograms and typical metrics such as max/mean/stdev using a residual error threshold set by the accuracy of the reference data (i.e. 1 mm).Results:The harmonic analysis showed good performance for all cases investigated. The percentage of control points inside D exhibiting residual values above 1 mm was lower than 1%.Conclusion:Harmonic analysis can be used to characterize geometric distortions inside arbitrary volumes given availability of the surface data with a certain accuracy.
SU‐F‐J‐156: The Feasibility of MR‐Only IMRT Planning for Prostate Anatomy
Authors: Vaitheeswaran R , Sivaramakrishnan KR , Kumar Prashant , Gattamaneni Raja , Kumar Girish 
Published: July 2016

Purpose:For prostate anatomy, previous investigations have shown that simulated CT (sCT) generated from MR images can be used for accurate dose computation. In this study, we demonstrate the feasibility of MR‐only IMRT planning for prostate case.Methods:Regular CT (rCT) and MR images of the same patient were acquired for prostate anatomy. Regions‐of‐interest (ROIs) i.e. target and risk structures are delineated on the rCT. A simulated CT (sCT) is generated from the MR image using the method described by Schadewaldt N et al. Their work establishes the clinical acceptability of dose calculation results on the sCT when compared to rCT. rCT and sCT are rigidly registered to ensure proper alignment between the two images. rCT and sCT are overlaid on each other and slice‐wise visual inspection confirms excellent agreement between the two images. ROIs on the rCT are copied over to sCT. Philips AutoPlanning solution is used for generating treatment plans. The same treatment technique protocol (plan parameters and clinical goals) is used to generate AutoPlan‐rCT and AutoPlan‐sCT respectively for rCT and and sCT. DVH comparison on ROIs and slice‐wise evaluation of dose is performed between AutoPlan‐rCT and AutoPlan‐sCT. Delivery parameters i.e. beam and corresponding segments from the AutoPlan‐sCT are copied over to rCT and dose is computed to get AutoPlan‐sCT‐on‐rCT.Results:Plan evaluation is done based on Dose Volume Histogram (DVH) of ROIs and manual slice‐wise inspection of dose distribution. Both AutoPlan‐rCT and AutoPlan‐sCT provide a clinically acceptable plan. Also, AutoPlan‐sCT‐on‐rCT shows excellent agreement with AutoPlan‐sCT.Conclusion:The study demonstrates that it is feasible to do IMRT planning on the simulated CT image obtained from MR image for prostate anatomy.The research is supported by Philips India Ltd
SU‐F‐J‐160: Clinical Evaluation of Targeting Accuracy in Radiosurgery Using Tractography
Authors: Juh R , Suh T , Han J , Kim C , Oh C 
Published: July 2016

Purpose:Focal radiosurgery is a common treatment modality for trigeminal neuralgia (TN), a neuropathic facial pain condition. Assessment of treatment effectiveness is primarily clinical, given the paucity of investigational tools to assess trigeminal nerve changes. The efficiency of radiosurgery is related to its highly precise targeting. We assessed clinically the targeting accuracy of radiosurgery with Gamma knife. We hypothesized that trigeminal tractography provides more information than 2D‐MR imaging, allowing detection of unique, focal changes in the target area after radiosurgery.Methods:Sixteen TN patients (2 females, 4 males, average age 65.3 years) treated with Gamma Knife radiosurgery, 40 Gy/50% isodose line underwent 1.5Tesla MR trigeminal nerve. Target accuracy was assessed from deviation of the coordinates of the target compared with the center of enhancement on post MRI. Radiation dose delivered at the borders of contrast enhancement was evaluated.Results:The median deviation of the coordinates between the intended target and the center of contrast enhancement was within 1mm. The radiation doses fitting within the borders of the contrast enhancement the target ranged from 37.5 to 40 Gy. Trigeminal tractography accurately detected the radiosurgical target. Radiosurgery resulted in 47% drop in FA values at the target with no significant change in FA outside the target, suggesting that radiosurgery primarily affects myelin. Tractography was more sensitive, since FA changes were detected regardless of trigeminal nerve enhancement.Conclusion:The median deviation found in clinical assessment of gamma knife treatment for TN Is low and compatible with its high rate of efficiency. DTI parameters accurately detect the effects of focal radiosurgery on the trigeminal nerve, serving as an in vivo imaging tool to study TN. This study is a proof of principle for further assessment of DTI parameters to understand the pathophysiology of TN and treatment effects.
SU‐F‐J‐166: Volumetric Spatial Distortions Comparison for 1.5 Tesla Versus 3 Tesla MRI for Gamma Knife Radiosurgery Scans Using Frame Marker Fusion and Co‐Registration Modes
Authors: Neyman G 
Published: July 2016

Purpose:To compare typical volumetric spatial distortions for 1.5 Tesla versus 3 Tesla MRI Gamma Knife radiosurgery scans in the frame marker fusion and co‐registration frame‐less modes.Methods:Quasar phantom by Modus Medical Devices Inc. with GRID image distortion software was used for measurements of volumetric distortions. 3D volumetric T1 weighted scans of the phantom were produced on 1.5 T Avanto and 3 T Skyra MRI Siemens scanners. The analysis was done two ways: for scans with localizer markers from the Leksell frame and relatively to the phantom only (simulated co‐registration technique). The phantom grid contained a total of 2002 vertices or control points that were used in the assessment of volumetric geometric distortion for all scans.Results:Volumetric mean absolute spatial deviations relatively to the frame localizer markers for 1.5 and 3 Tesla machine were: 1.39 ± 0.15 and 1.63 ± 0.28 mm with max errors of 1.86 and 2.65 mm correspondingly. Mean 2D errors from the Gamma Plan were 0.3 and 1.0 mm. For simulated co‐registration technique the volumetric mean absolute spatial deviations relatively to the phantom for 1.5 and 3 Tesla machine were: 0.36 ± 0.08 and 0.62 ± 0.13 mm with max errors of 0.57 and 1.22 mm correspondingly.Conclusion:Volumetric spatial distortions are lower for 1.5 Tesla versus 3 Tesla MRI machines localized with markers on frames and significantly lower for co‐registration techniques with no frame localization. The results show the advantage of using co‐registration technique for minimizing MRI volumetric spatial distortions which can be especially important for steep dose gradient fields typically used in Gamma Knife radiosurgery.Consultant for Elekta AB