bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐I‐75: Evaluation of An Orthopedic Metal Artifact Reduction (O‐MAR) Algorithm On Patients with Spinal Prostheses Near Spinal Tumors
Authors: Shen Z , Klahr P , Xia P , Djemil T 
Published: July 2014

Purpose:To evaluate the impact of a commercial orthopedic metal artifact reduction (O‐MAR) algorithm on CT image quality and dose calculation for patients with spinal prostheses near spinal tumors.Methods:A CT electron density phantom was scanned twice: with tissue‐simulating inserts only, and with a titanium insert replacing solid water. A patient plan was mapped to the phantom images in two ways: with the titanium inside or outside of the spinal tumor. Pinnacle and Eclipse were used to evaluate the dosimetric effects of O‐MAR on 12‐bit and 16‐bit CT data, respectively. CT images from five patients with spinal prostheses were reconstructed with and without O‐MAR. Two observers assessed the image quality improvement from O‐MAR. Both pencil beam and Monte Carlo dose calculation in iPlan were used for the patient study. The percentage differences between non‐OMAR and O‐MAR datasets were calculated for PTV_min, PTV_max, PTV_mean, PTV_V100, PTV_D90, OAR_V10Gy, OAR_max, and OAR_D0.1cc.Results:O‐MAR improved image quality but did not significantly affect the dose distributions and DVHs for both 12‐bit and 16‐ bit CT phantom data. All five patient cases demonstrated some degree of image quality improvement from O‐MAR, ranging from small to large metal artifact reduction. For pencil beam, the largest discrepancy was observed for OARV_10Gy at 5.4%, while the other seven parameters were ≤0.6%. For Monte Carlo, the differences between non‐O‐MAR and O‐MAR datasets were ≤3.0%.Conclusion:Both phantom and patient studies indicated that O‐MAR can substantially reduce metal artifacts on CT images, allowing better visualization of the anatomical structures and metal objects. The dosimetric impact of O‐MAR was insignificant regardless of the metal location, image bit‐depth, and dose calculation algorithm. O‐MAR corrected images are recommended for radiation treatment planning on patients with spinal prostheses because of the improved image quality and no need to modify current dose constraints.This work was supported by a research grant from Philips Healthcare. Paul Klahr is an employee of Philips Healthcare.
SU‐E‐I‐76: Matching Primary and Scattered X‐Ray Spectra for Use in Calculating the Diagnostic Radiation Index of Protection
Authors: Pasciak A , Jones A , Wagner L 
Published: July 2014

Purpose:Lightweight lead‐free or lead‐composite protective garments exploit k‐edge interactions to attenuate scattered X‐rays. Manufacturers specify the protective value of garments in terms of lead equivalence at a single kVp. This is inadequate, as the protection provided by such garments varies with radiation quality in different use conditions. We present a method for matching scattered X‐ray spectra to primary X‐ray spectra. The resulting primary spectra can be used to measure penetration through protective garments, and such measurements can be weighted and summed to determine a Diagnostic Radiation Index for Protection (DRIP).Methods:Scattered X‐ray spectra from fluoroscopic procedures were modeled using Monte Carlo techniques in MCNP‐X 2.7. Data on imaging geometry, operator position, patient size, and primary beam spectra were gathered from clinical fluoroscopy procedures. These data were used to generate scattered X‐ray spectra resulting from procedural conditions. Technical factors, including kV and added filtration, that yielded primary X‐ray spectra that optimally matched the generated scattered X‐ray spectra were identified through numerical optimization using a sequential quadratic programming (SQP) algorithm.Results:The primary spectra generated with shape functions matched the relative flux in each bin of the scattered spectra within 5%, and half and quarter‐value layers matched within 0.1%. The DRIP for protective garments can be determined by measuring the penetration through protective garments using the matched primary spectra, then calculating a weighted average according to the expected clinical use of the garment. The matched primary spectra are specified in terms of first and second half‐value layers in aluminum and acrylic.Conclusion:Lead equivalence is inadequate for completely specifying the protective value of garments. Measuring penetration through a garment using full scatter conditions is very difficult. The primary spectra determined in this work allow for practical primary penetration measurements to be made with equipment readily available to clinical medical physicists.
SU‐E‐I‐79: Effect of Number of Pinholes in Onboard Robotic Multi‐Pinhole SPECT System
Authors: Touch M , Bowsher J , Yan S , Yin F 
Published: July 2014

Purpose:To study the effect of number of pinholes for a novel Single Photon Emission Computed Tomography (SPECT) system for onboard molecular and functional imaging.Methods:Comparison studies were performed using simulation for the 49‐pinhole SPECT system and a series of reductions in number of pinholes. Trajectories about the breast of a supine patient were considered. Minimum distances, radii of rotation (RORs), were determined by requirements to fully view the region of interest (ROI) and to avoid collision between the detector and the patient. Reductions in RORs translate into improvements in sensitivity. Starting from the 49‐pinhole system, pinholes were removed pod by pod. The furthest two end pods in the Sup‐Inf direction were removed first for their higher likelihood of alleviating the collision avoidance criteria. After iterating through different combinations of pinhole pods, and selecting three combinations, the corresponding RORs were used to analytically calculate sensitivities.Results:Based on the Methods procedure, 3 combination of pods removal were identified: 1) Superior peripheral pod 2) Inferior peripheral pod 3) both pods. RORs were reduced at only one multi‐pinhole stop. Analytic calculation showed that sensitivities were reduced from 0.032 for the 49‐pinhole system to 0.028 for 42‐pinhole and to 0.023 for 39‐pinhole system respectively. The sensitivity per pinhole detector was approximately the same for all three cases.Conclusion:For the trajectories considered, only minimal improvements in RORs were identified by removing pinhole pods. Consequently, sensitivities decreased in proportion to the number of pinholes. Studies of other anatomical sites are needed to determine if in some cases sensitivity per pinhole can be improved by removing some pinholes.PHS/NIH/NCI grant R21‐CA156390‐01A1
SU‐E‐I‐81: Assessment of CT Radiation Dose and Image Quality for An Automated Tube Potential Selection Algorithm Using Adult Anthropomorphic and ACR Phantoms
Authors: Mahmood U , Erdi Y , Wang W 
Published: July 2014

Purpose:To assess the impact of General Electrics (GE) automated tube potential algorithm, kV assist (kVa) on radiation dose and image quality, with an emphasis on optimizing protocols based on noise texture.Methods:Radiation dose was assessed by inserting optically stimulated luminescence dosimeters (OSLs) throughout the body of an adult anthropomorphic phantom (CIRS). The baseline protocol was: 120 kVp, Auto mA (180 to 380 mA), noise index (NI) = 14, adaptive iterative statistical reconstruction (ASiR) of 20%, 0.8s rotation time. Image quality was evaluated by calculating the contrast to noise ratio (CNR) and noise power spectrum (NPS) from the ACR CT accreditation phantom. CNRs were calculated according to the steps described in ACR CT phantom testing document. NPS was determined by taking the 3D FFT of the uniformity section of the ACR phantom. NPS and CNR were evaluated with and without kVa and for all available adaptive iterative statistical reconstruction (ASiR) settings, ranging from 0 to 100%. Each NPS was also evaluated for its peak frequency difference (PFD) with respect to the baseline protocol.Results:The CNR for the adult male was found to decrease from CNR = 0.912 ± 0.045 for the baseline protocol without kVa to a CNR = 0.756 ± 0.049 with kVa activated. When compared against the baseline protocol, the PFD at ASiR of 40% yielded a decrease in noise magnitude as realized by the increase in CNR = 0.903 ± 0.023. The difference in the central liver dose with and without kVa was found to be 0.07%.Conclusion:Dose reduction was insignificant in the adult phantom. As determined by NPS analysis, ASiR of 40% produced images with similar noise texture to the baseline protocol. However, the CNR at ASiR of 40% with kVa fails to meet the current ACR CNR passing requirement of 1.0.
SU‐E‐I‐83: Parallel Programming Upgrades for the Control Acquisition, Processing and Image Display System (CAPIDS) of the Micro Angiographic Fluoroscope (MAF)
Authors: S Setlur Nagesh , Loughran B , Rana R , Ionita C , Bednarek D , Rudin S 
Published: July 2014

Purpose:CAPIDS is a unique software platform designed to control and acquire images from the high‐resolution MAF detector, process them and display them in a clinical environment. The images are then stored for optional playback at a later stage. CAPIDS also acquires and records the exposure parameters from the x‐ray unit. We present new parallel programming modifications using the host computer system's Graphics Processing Unit (GPU) and Central Processing unit (CPU) to improve the system performance for the various MAF imaging tasks.Methods:Multicore CPU's allow for concurrent tasks to be executed at the same time in parallel. During runtime, CAPIDS has three concurrent tasks: image acquisition and processing, image saving, and exposure parameter acquisition. Parallel programming constructs from LabVIEW allow each tasks to be executed on a separate core.GPU's allow for the same task to be performed on independent data sets in parallel. During runtime, all the image processing including flat‐field correction, digital image subtraction, image averaging, and temporal recursive filtering are performed on the GPU.Results:The new version of CAPIDS with all the parallel programming updates was successfully used for the first time to control the MAF, acquire the images, process the images and display the images during an actual clinical intervention. The images were acquired under fluoroscopy, digital subtraction angiography, and roadmap modes.Conclusion:Distributing concurrent tasks to different cores of a multicore CPU results in an efficient utilization of resources, efficient power management and increases operation speed. Use of GPU's for image processing further enhances the speed of operation.Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation
SU‐E‐I‐84: MRI Relaxation Properties of a Pre‐Clinical Hypoxia‐Sensitive MRI Contrast Agent
Authors: Yee S , Wilson G , Chavez F 
Published: July 2014

Purpose:A possible hypoxia‐sensitive MRI agent, hexamethyldisiloxane (HMDSO), has been tried to image oxygen level in proton‐based MRI (Kodibagkar et al, NMR Biomed, 2008). The induced changes of T1 (or R1) value by the HMDSO as the oxygenation level changes are the principle that the hypoxia agent is based on: the R1 increases as the oxygen level increases. However, as reported previously, the range of R1 values (0.1–0.3 s‐1, corresponding to 3–10 s of T1) is not in the range where a regular MRI technique can easily detect the change. In order for this agent to be widely applied in an MRI environment, more relaxation properties of this agent, including T1 in the rotating frame (T1rho) and T2, need to be explored. Here, the relaxation properties of this agent are explored.Methods:A phantom was made with HMDSO, water and mineral oil, each of which was prepared with oxygen and nitrogen, and was imaged in a 3T MRI system. The T1 properties were explored by the inversion recovery (TR=3000ms, TE=65ms) while varying the inversion time (TI), and also by the fast‐field‐echo (TR=2 ms, TE=2.8ms) while varying the flip angle (FA). T1rho was explored with a 5‐pulse spin‐locking technique (TR=5000ms, TE=10ms, spin‐lock field=500Hz) while varying the spin‐lock duration. T2 was explored with multi‐shot TSE (TR=2500ms) while varying TE.Results:With the variable FA and TI, the signals of HMDSO with oxygen and nitrogen change in a similar way and do not respond well by the change of oxygen level, which confirms the large T1 value of HMDSO. The T1rho and T2, however, have a better sensitivity.Conclusion:For the possible pre‐clinical hypoxia MRI agent (HMDSO), the detection of T1 (or R1) changes may be more challenging than the detection of other relaxation properties, particularly T2, as the oxygen level changes.
SU‐E‐I‐86: Evaluation of the New RaySafe Unfors X2 Dosimetry System
Authors: Heintz P , Chambers G , Sandoval D 
Published: July 2014

Purpose:To evaluate the new RaySafe Unfors X2 (X2) dosimetry system and compare it to the operation of the RaySafe Unfors Xi (Xi) and Radcal Accugold (RCAG) dosimetry systems. The comparison was done for the radiographic/fluoroscopic detectors, mammography detectors and the CT ionization chambers.Methods:This study used several R/F rooms, GE AMX4 portable x‐ray unit, Siemens Biograph 16 slice CT scanner and a Hologic Dimensions mammography unit to evaluate the dosimetry systems. The three X2 detectors were compared to similar detectors of the older Xi and RCAG detectors under clinical conditions used for diagnostic medical physics testing. Measurements of kVp, HVL and exposure were made under identical conditions.Results:For radiography and fluoroscopy the three systems agreed to within +2 kVp in the 60 to 140 kVp range, HVL measurements agreed to within +2 mm Al and the exposures agreed to within +5%. The RCAG 6 cc ionization chamber measured at least 3% higher than the diode systems. The X2 R/F detector appeared to be transparent to the fluoroscopy AEC system. For exposures made using both the CT ACR dose phantoms, the X2 agreed to within +3% of the other two systems. For mammography measurements, the three systems agreed to within +0.4kVp (25‐49 kVp range), HVL measurements agreed to within +0.05 mm Al and the exposures agreed to within +1% of the ionization chamber.Conclusion:The X2 system is a new version of the older Xi system. The system is faster, more robust, very easy to use, has a larger dynamic range, produced less errors and stores 1000 exposures. The measurements showed that the system performs well in the clinical environment and the X2 is within + 5% agreement of the other two calibrated systems.
SU‐E‐I‐87: Automated Liver Segmentation Method for CBCT Dataset by Combining Sparse Shape Composition and Probabilistic Atlas Construction
Authors: Li Dengwang , Liu Li , Chen Jinhu , Li Hongsheng 
Published: July 2014

Purpose:The aiming of this study was to extract liver structures for daily Cone beam CT (CBCT) images automatically.Methods:Datasets were collected from 50 intravenous contrast planning CT images, which were regarded as training dataset for probabilistic atlas and shape prior model construction. Firstly, probabilistic atlas and shape prior model based on sparse shape composition (SSC) were constructed by iterative deformable registration. Secondly, the artifacts and noise were removed from the daily CBCT image by an edge‐preserving filtering using total variation with L1 norm (TV‐L1). Furthermore, the initial liver region was obtained by registering the incoming CBCT image with the atlas utilizing edge‐preserving deformable registration with multi‐scale strategy, and then the initial liver region was converted to surface meshing which was registered with the shape model where the major variation of specific patient was modeled by sparse vectors. At the last stage, the shape and intensity information were incorporated into joint probabilistic model, and finally the liver structure was extracted by maximum a posteriori segmentation.Regarding the construction process, firstly the manually segmented contours were converted into meshes, and then arbitrary patient data was chosen as reference image to register with the rest of training datasets by deformable registration algorithm for constructing probabilistic atlas and prior shape model. To improve the efficiency of proposed method, the initial probabilistic atlas was used as reference image to register with other patient data for iterative construction for removing bias caused by arbitrary selection.Results:The experiment validated the accuracy of the segmentation results quantitatively by comparing with the manually ones. The volumetric overlap percentage between the automatically generated liver contours and the ground truth were on an average 88%–95% for CBCT images.Conclusion:The experiment demonstrated that liver structures of CBCT with artifacts can be extracted accurately for following adaptive radiation therapy.This work is supported by National Natural Science Foundation of China (No. 61201441), Research Fund for Excellent Young and Middle‐aged Scientists of Shandong Province (No. BS2012DX038), Project of Shandong Province Higher Educational Science and Technology Program (No. J12LN23), Jinan youth science and technology star (No.20120109)
SU‐E‐I‐92: Is Photon Starvation Preventing Metal Artifact Reduction Algorithm From Working in KVCT?
Authors: Paudel M , MacKenzie M , Fallone B , Rathee S 
Published: July 2014

Purpose:High density/high atomic number metallic objects create shading and streaking metal artifacts in the CT image that can cause inaccurate delineation of anatomical structures or inaccurate radiation dose calculation. A modified iterative maximum‐likelihood polychromatic algorithm for CT (mIMPACT) that models the energy response of detectors, photon interaction processes and beam polychromaticity has successfully reduced metal artifacts in MVCT. Our extension of mIMPACT in kVCT did not significantly reduce metal artifacts for high density metal like steel. We hypothesize that photon starvation may result in the measured data in a commercial kVCT imaging beam.Methods:We measured attenuation of a range of steel plate thicknesses, sandwiched between two 12cm thick solid water blocks, using a Phillips Big Bore CTTM scanner in scout acquisition mode with 120kVp and 200mAs. The transmitted signal (y) was normalized to the air scan signal (y0) to get attenuation [i.e., ln(y/y0)] data for a detector.Results:Below steel plate thickness of 13.4mm, the variations in measured attenuation as a function of view number are characterized by a quantum noise and show increased attenuation with metal thickness. On or above this thickness the attenuation shows discrete levels in addition to the quantum noise. Some views have saturated attenuation value. The histograms of the measured attenuation for up to 36.7mm of steel show this trend. The detector signal is so small that the quantization levels in the analog to digital (A‐to‐D) converter are visible, a clear indication of photon starvation.Conclusion:Photons reaching the kVCT detector after passing through a thick metal plate are either so low in number that the signal measured has large quantum noise, or are completely absorbed inside the plate creating photon starvation. This is un‐interpretable by the mIMPACT algorithm and cannot reduce metal artifacts in kVCT for certain realistic thicknesses of steel hip implants.Moti Raj Paudel is supported by the Vanier Canada Graduate Scholarship, the Endowed Graduate Scholarship in Oncology and the Dissertation Fellowship at the University of Alberta. The authors acknowledge the CIHR operating grant number MOP 53254.
SU‐E‐I‐94: Automated Image Quality Assessment of Radiographic Systems Using An Anthropomorphic Phantom
Authors: Wells J , Wilson J , Zhang Y , Samei E , Ravin Carl E. 
Published: July 2014

Purpose:In a large, academic medical center, consistent radiographic imaging performance is difficult to routinely monitor and maintain, especially for a fleet consisting of multiple vendors, models, software versions, and numerous imaging protocols. Thus, an automated image quality control methodology has been implemented using routine image quality assessment with a physical, stylized anthropomorphic chest phantom.Methods:The “Duke” Phantom (Digital Phantom 07‐646, Supertech, Elkhart, IN) was imaged twice on each of 13 radiographic units from a variety of vendors at 13 primary care clinics. The first acquisition used the clinical PA chest protocol to acquire the post‐processed “FOR PRESENTATION” image. The second image was acquired without an antiscatter grid followed by collection of the “FOR PROCESSING” image. Manual CNR measurements were made from the largest and thickest contrast‐detail inserts in the lung, heart, and abdominal regions of the phantom in each image. An automated image registration algorithm was used to estimate the CNR of the same insert using similar ROIs. Automated measurements were then compared to the manual measurements.Results:Automatic and manual CNR measurements obtained from “FOR PRESENTATION” images had average percent differences of 0.42%±5.18%, −3.44%±4.85%, and 1.04%±3.15% in the lung, heart, and abdominal regions, respectively; measurements obtained from “FOR PROCESSING” images had average percent differences of ‐0.63%±6.66%, −0.97%±3.92%, and −0.53%±4.18%, respectively. The maximum absolute difference in CNR was 15.78%, 10.89%, and 8.73% in the respective regions. In addition to CNR assessment of the largest and thickest contrast‐detail inserts, the automated method also provided CNR estimates for all 75 contrast‐detail inserts in each phantom image.Conclusion:Automated analysis of a radiographic phantom has been shown to be a fast, robust, and objective means for assessing radiographic image quality. The method reduces the burden of manual measurements and provides a means by which to monitor and compare radiographic system performance.
SU‐E‐I‐96: A Study About the Influence of ROI Variation On Tumor Segmentation in PET
Authors: Li L , Lu W , D' Souza W , Tan S 
Published: July 2014

Purpose:To study the influence of different regions of interest (ROI) on tumor segmentation in PET.Methods:The experiments were conducted on a cylindrical phantom. Six spheres with different volumes (0.5ml, 1ml, 6ml, 12ml, 16ml and 20 ml) were placed inside a cylindrical container to mimic tumors of different sizes. The spheres were filled with 11C solution as sources and the cylindrical container was filled with 18F‐FDG solution as the background. The phantom was continuously scanned in a Biograph‐40 True Point/True View PET/CT scanner, and 42 images were reconstructed with source‐to‐background ratio (SBR) ranging from 16:1 to 1.8:1. We took a large and a small ROI for each sphere, both of which contain the whole sphere and does not contain any other spheres. Six other ROIs of different sizes were then taken between the large and the small ROI. For each ROI, all images were segmented by eitht thresholding methods and eight advanced methods, respectively. The segmentation results were evaluated by dice similarity index (DSI), classification error (CE) and volume error (VE). The robustness of different methods to ROI variation was quantified using the interrun variation and a generalized Cohen's kappa.Results:With the change of ROI, the segmentation results of all tested methods changed more or less. Compared with all advanced methods, thresholding methods were less affected by the ROI change. In addition, most of the thresholding methods got more accurate segmentation results for all sphere sizes.Conclusion:The results showed that the segmentation performance of all tested methods was affected by the change of ROI. Thresholding methods were more robust to this change and they can segment the PET image more accurately.This work was supported in part by National Natural Science Foundation of China (NNSFC), under Grant Nos. 60971112 and 61375018, and Fundamental Research Funds for the Central Universities, under Grant No. 2012QN086. Wei Lu was supported in part by the National Institutes of Health (NIH) Grant No. R01 CA172638.