bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐G‐206‐06: Analytic Dose Function for CT Scans in Infinite Cylinders as a Function of Scan Length and Cylinder Radius
Authors: Bakalyar D , Feng W , McKenney S 
Published: July 2016

Purpose:The radiation dose absorbed at a particular radius ρ within the central plane of a long cylinder following a CT scan is a function of the length of the scan L and the cylinder radius R along with kVp and cylinder composition. An analytic function was created that that not only expresses these dependencies but is integrable in closed form over the area of the central plane. This feature facilitates explicit calculation of the planar average dose. The “approach to equilibrium” h(L) discussed in the TG111 report is seamlessly included in this function.Methods:For a cylindrically symmetric radiation field, Monte Carlo calculations were performed to compute the dose distribution to long polyethylene cylinders for scans of varying L for cylinders ranging in radius from 5 to 20 cm. The function was developed from the resultant Monte Carlo data. In addition, the function was successfully fit to data taken from measurements on the 30 cm diameter ICRU/TG200 phantom using a real‐time dosimeter.Results:Symmetry and continuity dictate a local extremum at the center which is a minimum for the larger sizes. There are competing effects as the beam penetrates the cylinder from the outside: attenuation, resulting in a decrease; scatter, abruptly increasing at the circumference. This competition may result in an absolute maximum between the center and outer edge leading to a “gull wing” shape for the radial dependence. For the smallest cylinders, scatter may dominate to the extent that there is an absolute maximum at the center.Conclusion:An integrable, analytic function has been developed that provides the radial dependency of dose for the central plane of a scan of length L for cylinders of varying diameter. Equivalently, we have developed h(L,R,ρ).
SU‐G‐206‐07: Dual‐Energy CT Inter‐ and Intra‐Scanner Variability Within One Make and Model
Authors: Jacobsen M , Wood C , Cody D 
Published: July 2016

Purpose:It can be logistically quite difficult to scan patients on the same exact device for their repeat visits in multi‐scanner facilities. The reliability between dual‐energy CT scanners’ quantitative results is not known, nor is their individual repeatability. Therefore, we evaluated inter‐ and intra‐scanner variability with respect to several key clinical quantitative metrics specific to dual‐energy CT.Methods:Eleven identical GE HD‐750 CT scanners in a busy clinical environment were used to perform dual‐energy (DE) CT scans of a large elliptical quality control (QC) phantom (Gammex, Inc.; Middleton, WI) which contains many standard insert materials. The DE‐QC phantom was scanned bi‐weekly during 2016; 3 to 4 scans were obtained from each scanner (a total of 35 data sets were used for analysis). Iodine accuracy for the 2mg/ml, 5mg/ml and 15mg/ml rods (from the Iodine(Water) image set) and soft tissue HU (40 HU based on NIST constants) from the 50keV data set were used to assess inter‐ and intra‐scanner variability (standard deviation).Results:Intra‐scanner variability average for 2mg/ml Iodine was 0.10 mg/ml (range 0.05–0.15 mg/ml), for 5mg/ml Iodine was 0.12 mg/ml (range 0.07–0.16 mg/ml), for 15 mg/ml Iodine was 0.25 mg/ml (range 0.16–0.37 mg/ml), and for the soft tissue inserts was 2.1 HU (range 1.8–2.6 HU). Inter‐scanner variability average for 2mg/ml Iodine was 0.16 mg/ml (range 0.11–0.19 mg/ml), for 5mg/ml Iodine was 0.18 mg/ml (range 0.11–0.22 mg/ml), for 15 mg/ml Iodine was 0.35 mg/ml (range 0.23–0.44 mg/ml), and for the soft tissue inserts was 3.8 HU (range 3.1–4.5 HU).Conclusion:Intra‐scanner variability for the iodine and soft tissue inserts averaged 3.1% and 5.2% respectively, and inter‐scanner variability for these regions analyzed averaged 5.0% and 9.5%, respectively. Future work will include determination of smallest measurable change and acceptable limits for DE‐CT scanner variability over longer time intervals.This research has been supported by funds from Dr. William Murphy, Jr., the John S. Dunn, Sr. Distinguished Chair in Diagnostic Imaging at MD Anderson Cancer Center.
SU‐G‐206‐13: Validating Dose Split: A Method to Image the Same Patient at Multiple Doses with a Single CT Acquisition
Authors: Solomon J , Zhang Y , Marin D , Samei E 
Published: July 2016

Purpose:Dose optimization studies in CT have a need for images acquired at multiple dose levels. This presents ethical and logistical challenges for performing such research with human subjects. As a result, most studies rely on phantom data. The purpose of this study was to perform a physics‐based validation of a method to obtain images of the same patient at multiple dose levels using a single CT acquisition on a dual‐source CT system.Methods:The Dose Split (DS) method relies on acquiring raw projection data simultaneously from two separate sources/detectors (denoted Tube A and Tube B) on a dual‐source system. By distributing the dose unevenly between Tube A and Tube B (at the same kVp), it is possible to reconstruct images corresponding to any dose in the range of min(A,B) to A+B. CT data of the ACR phantom were acquired on a dual‐source system (SOMATOM Flash, Siemens Healthcare) with a traditional single‐source (SS) technique at 6 dose levels (25, 50, 75, 100, 150, and 200 mAs). Corresponding data using the DS technique were acquired and compared with the SS data in terms of noise magnitude (pixel STD), contrast, contrast‐to‐noise ratio, noise power spectrum (average spatial frequency), modulation transfer function (50% frequency) and detectability index (for a non‐prewhitening matched filter observer).Results:Between the DS and SS techniques, the differences (SS–DS) in noise magnitude, contrast, and CNR were on average (across doses) 1.2 HU (4.1%), 0.7 HU (11%), and 0.02 (6.9%), respectively. The differences in NPS average frequency, MTF 50% frequency, and detectability index were 0.01 cycles/mm (2.5%), 0.03 cycles/mm (7.5%), and −.03 (−6.8%), respectively.Conclusion:The dose split method can be used to acquire images of the same patient equivalent to many dose levels in a single acquisition. Differences in noise, CNR, NPS, MTF, and detectability were all negligible.
SU‐G‐IeP1‐07: Inaccuracy of Lesion Blood Flow Quantification Related to the Proton Density Reference Image in Arterial Spin Labeling MRI of Brain Tumors
Authors: Jen M , Johnson J , Hou P , Liu H 
Published: July 2016

Purpose:Cerebral blood flow quantification in arterial spin labeling (ASL) MRI requires an estimate of the equilibrium magnetization of blood, which is often obtained by a set of proton density (PD) reference image. Normally, a constant blood‐brain partition coefficient is assumed across the brain. However, this assumption may not be valid for brain lesions. This study aimed to evaluate the impact of lesion‐related PD variations on ASL quantification in patients with brain tumors.Methods:MR images for posttreatment evaluation of 42 patients with brain tumors were retrospectively analyzed. These images were acquired on a 3T MRI scanner, including T2‐weighted FLAIR, 3D pseudo‐continuous ASL and post‐contrast T1‐weighted images. Anatomical images were coregistered with ASL images using the SPM software. Regions of interest (ROIs) of the enhancing and FLAIR lesions were manually drawn on the coregistered images. ROIs of the contralateral normal appearing tissues were also determined, with the consideration of approximating coil sensitivity patterns in lesion ROIs. Relative lesion blood flow (lesion/contralateral tissue) was calculated from both the CBF map (dependent on the PD) and the ΔM map for comparison.Results:The signal intensities in both enhancing and FLAIR lesions were significantly different than contralateral tissues on the PD reference image (p<0.001). The percent signal difference ranged from −15.9 to 19.2%, with a mean of 5.4% for the enhancing lesion, and from −2.8 to 22.9% with a mean of 10.1% for the FLAIR lesion. The high/low lesion‐related PD signal resulted in inversely proportional under‐/over‐estimation of blood flow in both enhancing and FLAIR lesions.Conclusion:Significant signal differences were found between lesions and contralateral tissues in the PD reference image, which introduced errors in blood flow quantification in ASL. The error can be up to 20% in individual patients with an average of 5‐ 10% for the group of patients with brain tumors.
SU‐G‐IeP1‐11: Resting‐State Fluctuation of BOLD Signal Amplitude for Mapping Cerebrovascular Reactivity in Presurgical Functional MRI
Authors: Wang P , Hou P , Kesler S , Colen R , Kumar A , Prabhu S , Liu H 
Published: July 2016

Purpose:Cerebrovascular reactivity (CVR) MRI with hypercapnia challenges, such as a breath‐hold (BH) task, has been proposed to indicate areas with neurovascular uncoupling potentials for presurgical functional MRI (fMRI). This study aimed to explore the use of resting‐state (RS) fMRI, in particular, the RS fluctuation of amplitude (RSFA) for detecting the impaired CVR and compare with BH MRI in patients with gliomas.Methods:The BH and RS fMRI from six patients as part of their presurgical fMRI studies were analyzed. Functional images were coregistered to the 3D T1‐weighted images and spatially smoothed using a 4‐mm Gaussian kernel. A band‐pass filter (0.01–0.08 Hz) was then applied to the RS time series. Temporal standard deviations of the BH and the filtered RS signal changes were computed for each voxel to indicate CVR and subsequently transformed to Z‐scores. For quantitative comparison, a region of interest (ROI) with significant CVR in the sensorimotor cortex on the contralateral side of the tumor was determined for each patient as Z‐scores greater than 50% of the local maxima. In addition, a tumor ROI was determined by referencing the T2 FLAIR and post‐contrast T1‐weighted images of each patient.Results:Significant cross‐subject correlations between the BH CVR and RSFA were found in both the sensorimotor and tumor ROIs (r=0.59, p<0.05 and r=0.83, p<0.05, respectively). Within individuals, voxel‐based analyses showed significant correlations between two methods in both ROIs in all patients. The spatial patterns of BH CVR and RSFA maps appeared similar across the brain with sparse local discrepancies.Conclusion:The RSFA derived from RS‐fMRI is a promising method for probing impaired CVR in presurgical fMRI mapping. Unlike BH, RS‐fMRI is less dependent on patient performance. In addition, with its proven relation to neural activity, RSFA of certain frequency bands has potentials to better indicate the neurovascular uncoupling.
SU‐G‐IeP1‐15: Towards Accurate Cerebral Blood Flow Quantification with Distortion‐ Corrected Pseudo‐Continuous Arterial Spin Labeling
Authors: Hoff M , Rane‐Levandovsky S , Andre J 
Published: July 2016

Purpose:Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL's ability to accurately quantify cerebral blood flow (CBF) and assess disease‐specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans.Methods:Four subjects were imaged on a 3T Philips Ingenia scanner using a 16‐channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field‐of‐view. An ASL sequence with a pseudo‐continuous ASL (pCASL) labeling scheme was employed to acquire thirty dynamics of single‐shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post‐labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI‐reference images and T1‐weighted spin‐echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps.Results:pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1‐weighted reference image, and deviations in corrected CBF maps were evident.Conclusion:Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal pulse sequence modifications and no additional scan time, improving ASL's clinical applicability.
SU‐G‐JeP1‐01: A Combination of Real Time Electromagnetic Localization and Tracking with Cone Beam Computed Tomography in Stereotactic Radiosurgery for Brain Tumors
Authors: Muralidhar K Raja , Pangam Suresh , Ponaganti Srinivas , Krishna Jayarama , Sujana Kolla V , Komanduri Priya K 
Published: July 2016

Purpose:1. online verification of patient position during treatment using calypso electromagnetic localization and tracking system. 2. Verification and comparison of positional accuracy between cone beam computed tomography and calypso system. 3. Presenting the advantage of continuation localization in Stereotactic radiosurgery treatments.Methods:Ten brain tumor cases were taken for this study. Patients with head mask were under gone Computed Tomography (CT). Before scanning, mask was cut on the fore head area to keep surface beacons on the skin. Slice thickness of 0.65 mm were taken for this study. x, y, z coordinates of these beacons in TPS were entered into tracking station. Varian True Beam accelerator, equipped with On Board Imager was used to take Cone beam Computed Tomography (CBCT) to localize the patient. Simultaneously Surface beacons were used to localize and track the patient throughout the treatment. The localization values were compared in both systems. For localization CBCT considered as reference. Tracking was done throughout the treatment using Calypso tracking system using electromagnetic array. This array was in tracking position during imaging and treatment. Flattening Filter free beams of 6MV photons along with Volumetric Modulated Arc Therapy was used for the treatment. The patient movement was observed throughout the treatment ranging from 2 min to 4 min.Results:The average variation observed between calypso system and CBCT localization was less than 0.5 mm. These variations were due to manual errors while keeping beacon on the patient. Less than 0.05 cm intra‐fraction motion was observed throughout the treatment with the help of continuous tracking.Conclusion:Calypso target localization system is one of the finest tools to perform radiosurgery in combination with CBCT. This non radiographic method of tracking is a real beneficial method to treat patients confidently while observing real‐time motion information of the patient.
SU‐G‐JeP1‐06: Correlation of Lung Tumor Motion with Tumor Location Using Electromagnetic Tracking
Authors: Muccigrosso D , Maughan N , Schultejans H , Bera R , Parikh P 
Published: July 2016

Purpose:It is well known that lung tumors move with respiration. However, most measurements of lung tumor motion have studied long treatment times with intermittent imaging; those populations may not necessarily represent conventional LINAC patients. We summarized the correlation between tumor motion and location in a multi‐institutional trial with electromagnetic tracking, and identified the patient cohort that would most benefit from respiratory gating.Methods:Continuous electromagnetic transponder data (Varian Medical, Seattle, WA) of lung tumor motion was collected from 14 patients (214 total fractions) across 3 institutions during external beam radiation therapy in a prospective clinical trial (NCT01396551). External intervention from the clinician, such as couch shifts, instructed breath‐holds, and acquisition pauses, were manually removed from the 10 Hz tracking data according to recorded notes. The average three‐dimensional displacement from the breathing cycle's end‐expiratory to end‐inhalation phases (peak‐to‐peak distance) of the transponders’ isocenter was calculated for each patient's treatment. A weighted average of each isocenter was used to assess the effects of location on motion. A total of 14 patients were included in this analysis, grouped by their transponders’ location in the lung: upper, medial, and lower.Results:8 patients had transponders in the upper lung, and 3 patients each in the medial lobe and lower lung. The weighted average ± standard deviation of all peak‐to‐peak distances for each group was: 1.04 ± 0.39 cm in the lower lung, 0.56 ± 0.14 cm in the medial lung, and 0.30 ± 0.06 cm in the upper lung.Conclusion:Tumors in the lower lung are most susceptible to excessive motion and daily variation, and would benefit most from continuous motion tracking and gating. Those in the medial lobe might be at moderate risk. The upper lobes have limited motion. These results can guide different motion management strategies between lung tumor locations.This is part of an NIH‐funded prospective clinical trial (NCT01396551), using an electromagnetic transponder tracking system and additional funding from Varian Medical (Seattle, WA).
SU‐G‐TeP2‐09: Evaluation of the MaxFOV Extended Field of View (EFOV) Reconstruction Algorithm On a GE RT590 CT Scanner
Authors: Grzetic S , Weldon M , Noa K , Gupta N 
Published: July 2016

Purpose:This study compares the newly released MaxFOV Revision 1 EFOV reconstruction algorithm for GE RT590 to the older WideView EFOV algorithm. Two radiotherapy overlays from Q‐fix and Diacor, are included in our analysis. Hounsfield Units (HU) generated with the WideView algorithm varied in the extended field (beyond 50cm) and the scanned object's border varied from slice to slice. A validation of HU consistency between the two reconstruction algorithms is performed.Methods:A CatPhan 504 and CIRS062 Electron Density Phantom were scanned on a GE RT590 CT‐Simulator. The phantoms were positioned in multiple locations within the scan field of view so some of the density plugs were outside the 50cm reconstruction circle. Images were reconstructed using both the WideView and MaxFOV algorithms. The HU for each scan were characterized both in average over a volume and in profile.Results:HU values are consistent between the two algorithms. Low‐density material will have a slight increase in HU value and high‐density material will have a slight decrease in HU value as the distance from the sweet spot increases. Border inconsistencies and shading artifacts are still present with the MaxFOV reconstruction on the Q‐fix overlay but not the Diacor overlay (It should be noted that the Q‐fix overlay is not currently GE‐certified). HU values for water outside the 50cm FOV are within 40HU of reconstructions at the sweet spot of the scanner. CatPhan HU profiles show improvement with the MaxFOV algorithm as it approaches the scanner edge.Conclusion:The new MaxFOV algorithm improves the contour border for objects outside of the standard FOV when using a GE‐approved tabletop. Air cavities outside of the standard FOV create inconsistent object borders. HU consistency is within GE specifications and the accuracy of the phantom edge improves. Further adjustments to the algorithm are being investigated by GE.
SU‐G‐JeP3‐02: Comparison of Magnitude and Frequency of Patient Positioning Errors in Breast Irradiation Using AlignRT 3D Optical Surface Imaging and Skin Mark Techniques
Authors: Yao R , Chisela W , Dorbu G 
Published: July 2016

Purpose:To evaluate clinical usefulness of AlignRT (Vision RT Ltd., London, UK) in reducing patient positioning errors in breast irradiation.Methods:60 patients undergoing whole breast irradiation were selected for this study. Patients were treated to the left or right breast lying on Qfix Access breast board (Qfix, Avondale, PA) in supine position for 28 fractions using tangential fields. 30 patients were aligned using AlignRT by aligning a breast surface region of interest (ROI) to the same area from a reference surface image extracted from planning CT. When the patient's surface image deviated from the reference by more than 3mm on one or more translational and rotational directions, a new reference was acquired using AlignRT in‐room cameras. The other 30 patients were aligned to the skin marks with room lasers. On‐Board MV portal images of medial field were taken daily and matched to the DRRs. The magnitude and frequency of positioning errors were determined from measured translational shifts. Kolmogorov‐Smirnov test was used to evaluate statistical differences of positional accuracy and precision between AlignRT and non‐AlignRT patients.Results:The percentage of port images with no shift required was 46.5% and 27.0% in vertical, 49.8% and 25.8% in longitudinal, 47.6% and 28.5% in lateral for AlignRT and non‐AlignRT patients, respectively. The percentage of port images requiring more than 3mm shifts was 18.1% and 35.1% in vertical, 28.6% and 50.8% in longitudinal, 11.3% and 24.2% in lateral for AlignRT and non‐AlignRT patients, respectively. Kolmogorov‐Smirnov test showed that there were significant differences between the frequency distributions of AlignRT and non‐AlignRT in vertical, longitudinal, and lateral shifts.Conclusion:As confirmed by port images, AlignRT‐assisted patient positioning can significantly reduce the frequency and magnitude of patient setup errors in breast irradiation compared to the use of lasers and skin marks.
SU‐G‐JeP3‐15: Is the Reproducibility with Respect to Bone of Tumor Position at Simulation for Breath Hold CT Scans Correlated to the Reproducibility for Multiple Breath Hold CBCTs at Treatment in SBRT Thoracic Patients?
Authors: Pollard J , Prajapati S , Gao S , Nitsch P , Sadagopan R , Wang X , Balter P 
Published: July 2016

Purpose:To evaluate correlation between the reproducibility of tumor position under feedback guided voluntary deep inspiration breath hold gating at simulation and at treatment.Methods:All patients treated with breath hold (BH) have 3‐6 BH CTs taken at simulation (sim). In addition, if the relationship between the tumor and nearby bony anatomy on treatment BH CT(or CBCT) is found to be greater than 5 mm different at treatment than it was at sim, a repeat BH CT is taken before treatment. We retrospectively analyzed the sim CTs for 19 patients who received BH SBRT lung treatments and had repeat BH CT on treatment. We evaluated the reproducibility of the tumor position during the simulation CTs and compared this to the reproducibility of the tumor position on the repeat treatment CT with our in‐house CT alignment software (CT‐Assisted Targeting for Radiotherapy).Results:Comparing the tumor position for multiple simulation BH CTs, we calculated: maximum difference (max) = 0.69cm; average difference (x) = 0.28cm; standard deviation (σ) = 0.18cm. Comparing the repeat BH CBCTs on treatment days we calculated: max = 0.44cm; x = 0.16cm; σ = 0.22cm. We also found that for 95% of our BH cases, the absolute variation in tumor position within the same imaging day was within 5mm of the range at the time of simulation and treatment. We found that 75% of the BH cases had less residual tumor motion on treatment days than at simulation.Conclusion:This suggests that a GTV contour based upon the residual tumor motion in multiple BH datasets plus 2 mm margin should be sufficient to cover the full range of residual tumor motion on treatment days.