bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐D‐12A‐03: Improve Scatter Correction in CBCT Reconstruction to Improve the Image Quality for Large Patients
Authors: Tan Jun , Li Hua , Li Hui , Anastasio Mark , Yang Deshan 
Published: July 2014

Purpose:CBCT images by pelvis scan of larger patients often have lower soft tissue perceptibility, larger amount of artifacts, and lower image intensity uniformity than images of smaller patients. We hypothesize that the poor image quality is related to inaccurate or non‐optimal scattering correction during image reconstruction. To test the hypothesis, we implemented a new scattering correction algorithm and optimized its coefficients in order to understand if pelvis CBCT image qualities can be improved with better scattering correction methods and more optimal coefficients.Methods:A scatter correction algorithm using a fast scatter kernel superimposition with multiple kernel groups was implemented. The kernel parameters are the same as Varian TrueBeam machine, including 3 thickness groups, detector point‐scatter function parameters. Detector scatter correction and bowtie filter correction were also implemented. A 48 cm wide phantom and another 43 cm wide phantom were simulated by enclosing a 38 cm pelvis phantom with 5 cm thick plastic flaps. A comparison was made between the phantom CBCT images reconstructed by the TrueBeam machine and the ones reconstructed by our in‐house reconstruction program with the new scattering correction method.Results:CBCT images reconstructed using our in‐house program with the new scattering correction method showed much less streaking artifacts, better intensity uniformity and comparative soft tissue contrast. The standard deviation of a soft tissue region is 17.1 HU for the 48 cm phantom and 16.8 for the 43 cm phantom using our program, compared to 36.9 HU for the 48 cm phantom and 25.9 for the 43 cm phantom using the TrueBeam machine.Conclusion:Our results suggested that a better scattering algorithm could improve the pelvis CBCT scan image quality considerably for larger patients.
SU‐D‐12A‐05: Iterative Reconstruction Techniques to Enable Intrinsic Respiratory Gated CT in Mice
Authors: Sun T , Liu Y , Sun N , Mistry N , Tan S 
Published: July 2014

Purpose:Longitudinal studies of lung function in mice need the ability to image different phases of ventilation in free‐breathing mice using retrospective gating. However, retrospective gating often produces under‐sampled and uneven angular samples, resulting in severe reconstruction artifacts when using traditional FDK based reconstruction algorithms. We wanted to demonstrate the utility of iterative reconstruction method to enable intrinsic respiratory gating in small‐animal CT.Methods:Free‐breathing mice were imaged using a Siemens Inveon PET/micro‐CT system. Evenly distributed projection images were acquired at 360 angles. Retrospective respiratory gating was performed using an intrinsic marker based on the average intensity in a region covering the diaphragm. Projections were classified into 4 and 6 phases (finer temporal resolution) resulting in 138 and 67 projections respectively. Reconstruction was carried out using 3 Methods: conventional FDK, iterative penalized least‐square (PWLS) with total variation (TV), and PWLS with edge‐preserving penalty. The performance of the methods was compared using contrast‐to‐noise (CNR) in a region of interest (ROI). Line profile through a specific region was plotted to evaluate the preserving of edges.Results:In both the cases with 4 and 6 phases, inadequate and non‐uniform angular sampling results in artifacts using conventional FDK. However, such artifacts are minimized using both the iterative methods. Using both 4 and 6 phases, the iterative techniques outperformed FDK in terms of CNR and maintaining sharp edges. This is further evidenced especially with increased artifacts using FDK for 6 phases.Conclusion:This work indicates fewer artifacts and better image details can be achieved with iterative reconstruction methods in non‐uniform under‐sampled reconstruction. Using iterative methods can enable free‐breathing intrinsic respiratory gating in small‐animal CT. Further studies are needed to compare the computational complexity for large datasets.
SU‐E‐P‐01: An Informative Review On the Role of Diagnostic Medical Physicist in the Academic and Private Medical Centers
Authors: Weir V , Zhang J 
Published: July 2014

Purpose:The role of physicist in the academic and private hospital environment continues to evolve and expand. This becomes more obvious with the newly revised requirements of the Joint Commission (JC) on imaging modalities and the continued updated requirements of ACR accreditation for medical physics (i.e., starting in June 2014, a physicists test will be needed before US accreditation). We provide an informative review on the role of diagnostic medical physicist and hope that our experience will expedite junior physicists in understanding their role in medical centers, and be ready to more opportunities.Methods:Based on our experience, diagnostic medical physicists in both academic and private medical centers perform several clinical functions. These include providing clinical service and physics support, ensuring that all ionizing radiation devices are tested and operated in compliance with the State and Federal laws, regulations and guidelines. We also discuss the training and education required to ensure that the radiation exposure to patients and staff is as low as reasonably achievable. We review the overlapping roles of medical and health physicist in some institutions.Results:A detailed scheme on the new requirements (effective 7/1/2014) of the JC is provided. In 2015, new standards for fluoroscopy, cone beam CT and the qualifications of staff will be phased in. A summary of new ACR requirements for different modalities is presented. Medical physicist have other duties such as sitting on CT and fluoroscopy committees for protocols design, training of non‐radiologists to meet the new fluoroscopy rules, as well as helping with special therapies such as Yittrium 90 cases.Conclusion:Medical physicists in both academic and private hospitals are positioned to be more involved and prominent. Diagnostic physicists need to be more proactive to involve themselves in the day to day activities of the radiology department.
SU‐E‐P‐04: Transport Theory Learning Module in the Maple Environment
Authors: Both J 
Published: July 2014

Purpose:The medical physics graduate program at the University of Miami is developing a computerized instructional module which provides an interactive mechanism for students to learn transport theory. While not essential in the medical physics curriculum, transport theory should be taught because the conceptual level of transport theory is fundamental, a substantial literature exists and ought to be accessible, and students should understand commercial software which solves the Boltzmann equation.But conventional teaching and learning of transport theory is challenging. Students may be under prepared to appreciate its methods, results, and relevance, and it is not substantially addressed in textbooks for the medical physicists. Other resources an instructor might reasonably use, while excellent, may be too briskly paced for beginning students. The purpose of this work is to render teaching of transport theory more tractable by making learning highly interactive.Methods:The module is being developed in the Maple mathematics environment by instructors and graduate students. It will refresh the students' knowledge of vector calculus and differential equations, and will develop users' intuition for phase space concepts. Scattering concepts will be developed with animated simulations using tunable parameters characterizing interactions, so that students may develop a “feel” for cross section. Transport equations for one and multiple types of radiation will be illustrated with phase space animations. Numerical methods of solution will be illustrated.Results:Attempts to teach rudiments of transport theory in radiation physics and dosimetry courses using conventional classroom techniques at the University of Miami have had small success, because classroom time is limited and the material has been hard for our students to appreciate intuitively.Conclusion:A joint effort of instructor and students to teach and learn transport theory by building an interactive description of it will lead to deeper appreciation of the transport theoretical underpinnings of dosimetry.
SU‐E‐P‐10: Imaging in the Cardiac Catheterization Lab – Technologies and Clinical Applications
Authors: Fetterly K 
Published: July 2014

Purpose:Diagnosis and treatment of cardiovascular disease in the cardiac catheterization laboratory is often aided by a multitude of imaging technologies. The purpose of this work is to highlight the contributions to patient care offered by the various imaging systems used during cardiovascular interventional procedures.Methods:Imaging technologies used in the cardiac catheterization lab were characterized by their fundamental technology and by the clinical applications for which they are used. Whether the modality is external to the patient, intravascular, or intracavity was specified. Specific clinical procedures for which multiple modalities are routinely used will be highlighted.Results:X‐ray imaging modalities include fluoroscopy/angiography and angiography CT. Ultrasound imaging is performed with external, trans‐esophageal echocardiography (TEE), and intravascular (IVUS) transducers. Intravascular infrared optical coherence tomography (IVOCT) is used to assess vessel endothelium. Relatively large (>0.5 mm) anatomical structures are imaged with x‐ray and ultrasound. IVUS and IVOCT provide high resolution images of vessel walls. Cardiac CT and MRI images are used to plan complex cardiovascular interventions. Advanced applications are used to spatially and temporally merge images from different technologies. Diagnosis and treatment of coronary artery disease frequently utilizes angiography and intra‐vascular imaging, and treatment of complex structural heart conditions routinely includes use of multiple imaging modalities.Conclusion:There are several imaging modalities which are routinely used in the cardiac catheterization laboratory to diagnose and treat both coronary artery and structural heart disease. Multiple modalities are frequently used to enhance the quality and safety of procedures. The cardiac catheterization laboratory includes many opportunities for medical physicists to contribute substantially toward advancing patient care.
SU‐E‐I‐01: A Fast, Analytical Pencil Beam Based Method for First Order X‐Ray Scatter Estimation of Kilovoltage Cone Beam X‐Rays
Authors: Liu J , Bourland J 
Published: July 2014

Purpose:To analytically estimate first‐order x‐ray scatter for kV cone beam x‐ray imaging with high computational efficiency.Methods:In calculating first‐order scatter using the Klein‐Nishina formula, we found that by integrating the point‐to‐point scatter along an interaction line, a “pencil‐beam” scatter kernel (BSK) can be approximated to a quartic expression when the imaging field is small. This BSK model for monoenergetic, 100keV x‐rays has been verified on homogeneous cube and cylinder water phantoms by comparing with the exact implementation of KN formula. For heterogeneous medium, the water‐equivalent length of a BSK was acquired with an improved Siddon's ray‐tracing algorithm, which was also used in calculating pre‐ and post‐ scattering attenuation. To include the electron binding effect for scattering of low‐kV photons, the mean corresponding scattering angle is determined from the effective point of scattered photons of a BSK. The behavior of polyenergetic x‐rays was also investigated for 120kV x‐rays incident to a sandwiched infinite heterogeneous slab phantom, with the electron binding effect incorporated. Exact computation and Monte Carlo simulations were performed for comparisons, using the EGSnrc code package.Results:By reducing the 3D volumetric target (o(n3)) to 2D pencil‐beams (o(n2)), the computation expense can be generally lowered by n times, which our experience verifies. The scatter distribution on a flat detector shows high agreement between the analytic BSK model and exact calculations. The pixel‐to‐pixel differences are within (‐2%, 2%) for the homogeneous cube and cylinder phantoms and within (0, 6%) for the heterogeneous slab phantom. However, the Monte Carlo simulation shows increased deviation of the BSK model toward detector periphery.Conclusion:The proposed BSK model, accommodating polyenergetic x‐rays and electron binding effect at low kV, shows great potential in efficiently estimating the first‐order scatter from small imaging fields. We are investigating more thoroughly to improve performance and explore applications.
SU‐E‐I‐10: Automatic Monitoring of Accumulated Dose Indices From DICOM RDSR to Improve Radiation Safety in X‐Ray Angiography
Authors: Omar A , Bujila R , Nowik P , Karambatsakidou A 
Published: July 2014

Purpose:To investigate the potential benefits of automatic monitoring of accumulated patient and staff dose indicators, i.e., CAK and KAP, from DICOM Radiation Dose Structured Reports (RDSR) in x‐ray angiography (XA).Methods:Recently RDSR has enabled the convenient aggregation of dose indices and technique parameters for XA procedures. The information contained in RDSR objects for three XA systems, dedicated to different types of clinical procedures, has been collected and aggregated in a database for over one year using a system developed with open‐source software at the Karolinska University Hospital. Patient weight was complemented to the RDSR data via an interface with the Hospital Information System (HIS).Results:The linearly approximated trend in KAP over a time period of a year for cerebrovascular, pelvic/peripheral vascular, and cardiovascular procedures showed a decrease of 12%, 20%, and 14%, respectively. The decrease was mainly due to hardware/software upgrades and new low‐dose imaging protocols, and partially due to ongoing systematic radiation safety education of the clinical staff. The CAK was in excess of 3 Gy for 15 procedures, and exceeded 5 Gy for 3 procedures. The dose indices have also shown a significant dependence on patient weight for cardiovascular and pelvic/peripheral vascular procedures; a 10 kg shift in mean patient weight can result in a dose index increase of 25%.Conclusion:Automatic monitoring of accumulated dose indices can be utilized to notify the clinical staff and medical physicists when the dose index has exceeded a predetermined action level. This allows for convenient and systematic follow‐up of patients in risk of developing deterministic skin injuries. Furthermore, trend analyses of dose indices over time is a valuable resource for the identification of potential positive or negative effects (dose increase/decrease) from changes in hardware, software, and clinical work habits.
SU‐E‐I‐11: Cascaded Linear System Model for Columnar CsI Flat Panel Imagers with Depth Dependent Gain and Blur
Authors: Peng B , Lubinsky A , Teymurazyan A , Zheng H , Zhao W 
Published: July 2014

Purpose:To implement a depth dependent gain and blur cascaded linear system model (CLSM) for optimizing columnar structured CsI indirect conversion flat panel imager (FPI) for advanced imaging applications.Methods:For experimental validation, depth dependent escape efficiency, e(z), was extracted from PHS measurement of different CsI scintillators (thickness, substrate and light output). The inherent MTF and DQE of CsI was measured using high resolution CMOS sensor. For CLSM, e(z) and the depth dependent MTF(f,z), were estimated using Monte Carlo simulation (Geant4) of optical photon transport through columnar CsI. Previous work showed that Monte Carlo simulation for CsI was hindered by the non‐ideality of its columnar structure. In the present work we allowed variation in columnar width with depth, and assumed diffusive reflective backing and columns. Monte Carlo simulation was performed using an optical point source placed at different depth of the CsI layer, from which MTF(z,f) and e(z) were computed. The resulting e(z) with excellent matching with experimental measurements were then applied to the CLSM, Monte Carlo simulation was repeated until the modeled MTF, DQE(f) also match experimental measurement.Results:For a 150 micron FOS HL type CsI, e(z) varies between 0.56 to 0.45, and the MTF at 14 cycles/mm varies between 62.1% to 3.9%, from the front to the back of the scintillator. The overall MTF and DQE(f) at all frequencies are in excellent agreement with experimental measurements at all frequencies.Conclusion:We have developed a CLSM for columnar CsI scintillators with depth dependent gain and MTF, which were estimated from Monte Carlo simulation with novel optical simulation settings. Preliminary results showed excellent agreement between simulation results and experimental measurements. Future work is aimed at extending this approach to optimize CsI screen optic design and sensor structure for achieving higher DQE(f) in cone‐beam CT, which uses high kVp.
SU‐E‐I‐14: Comparison of Iodine‐Labeled and Indium‐Labeled Antibody Biodistributions
Authors: Williams L 
Published: July 2014

Purpose:It is often assumed that animal biodistributions of novel proteins are not dependent upon the radiolabel used in their determination. In units of percent injected dose per gram of tissue (%ID/g), organ uptake results (u) may be obtained using either iodine or metal as radioactive labels. Iodination is preferred as it is a one‐step process whereas metal labeling requires two chemical procedures and therefore more protein material. It is important to test whether the radioactive tag leads to variation in the uptake value.Methods:Uptakes of 3antibodies to Carcinoembryonic Antigen (CEA) were evaluated in a nude mouse model bearing 150 to 300 mg LS174T human colon cancer xenografts. Antibodies included diabody (56 kDa), minibody (80kDa) and intact M5A (150 kDa) anti‐CEA cognates. Both radioiodine and indium‐111 labels were used with uptakes evaluated at 7 time(t) points out to 96 h. Ratios (R) of u(iodine‐label)/u(indium‐label) were determined for liver, spleen, kidneys, lung and tumor.Results:Hepatic loss was rapid for diabody and minibody; by 24 h their R values were only 2%; i.e., uptake of iodine was 2% of that of indium for these 2 antibodies. By contrast, R for the intact cognate was 50% at that time point. Splenic results were similar. Tumor uptake ratios did not depend upon the antibody type and were 50% at 24 h.Conclusions:Relatively rapid loss of iodine relative to indium in liver and spleen was observed in lower mass antibodies. Tumor ratios were larger and independent of antibody type. Aside from tumor, the R ratio of uptakes depended on the antibody type. R values decreased monotonically with time in all tissues and for all cognates. Using this ratio, one can possibly correct iodine‐based u (t) results so that they resemble radiometal‐derived biodistributions.
SU‐E‐I‐17: Comparison of Two Novel Algorithms for the Modulation Transfer Function of CT Using a Simple Cylindrical Phantom
Authors: Kam S , Jeon H , Youn H , Kim H , Park D 
Published: July 2014

Purpose:To compare and analyze two novel algorithms for the assessment of modulation transfer functions (MTFs) of computed tomography (CT) systems using a simple acrylic cylindrical phantomMethod and Materials:Images of the acrylic cylindrical phantom were acquired by a GE LightSpeed 16 RT (GE Healthcare, Milwaukee, WI) using 120 kVp, 330 mA, 2.5 mm slice thickness, 10 cm field‐of view (FOV), four reconstruction kernels (e.g. standard, soft, detail, bone, and lung). Two different algorithms were used to analyze images for MTF assessment. First, Richard et al. suggested a task‐based MTF assessment method through an edge spread function (ESF) which described pixel intensities as a function of distance from the center. The MTF was obtained as the absolute value of Fourier transform of the differentiated ESF. Second, Ohkubo et al. devised an effective method to determine the point spread function (PSF) of CT system accompanied with verification. The line spread function (LSF), which was the one‐dimensional integration of the PSF, was used to obtain the MTF. We validated the reliability of two above‐mentioned methods through the comparison with a conventional method using a thin tungsten wire phantom.Results:The measured MTFs by two methods were mostly similar each other for standard, soft, and detail kernels. In 0.6 lp/mm, the MTF difference between two methods were 0.012(standard), 0.004(soft), and 0.037(detail). They also coincided with the MTF by the conventional method well. However, there were considerable distinctions for bone and lung kernels containing edge enhancement that might cause undershoots near the peak of the LSF.Conclusions:We compared two novel methods to assess task‐based MTFs for clinical CT systems especially using a simple acrylic cylindrical phantom with high‐convenience and low‐cost, and validated them against a conventional method. This work can provide a practical solution to users for the quality assurance of CT.
SU‐E‐I‐19: CTDI Values for All Protocols: Using the Ratio of the DLP Measured in CTDI Phantoms to the Measured Air Exposure
Authors: Raterman G , Gauntt D 
Published: July 2014

Purpose:To propose a method other than CTDI phantom measurements for routine CT dosimetry QA. This consists of taking a series of air exposure measurements and calculating a factor for converting from this exposure measurement to the protocol's associated head or body CTDI value using DLP. The data presented are the ratios of phantom DLP to air exposure ratios for different scanners, as well as error in the displayed CTDI.Methods:For each scanner, the CTDI is measured at all available tube voltages using both the head and body phantoms. Then, the exposure is measured using a pencil chamber in air at isocenter. A ratio of phantom DLP to exposure in air for a given protocol may be calculated and used for converting a simple air dose measurement to a head or body CTDI value. For our routine QA, the exposure in air for different collimations, mAs, and kVp is measured, and displayed CTDI is recorded. Therefore, the ratio calculated may convert these exposures to CTDI values that may then be compared to the displayed CTDI for a large range of acquisition parameter combinations.Results:It was found that all scanners tend to have a ratio factor that slightly increases with kVp. Also, Philips scanners appear to have less of a dependence on kVp; whereas, GE scanners have a lower ratio at lower kVp. The use of air exposure times the DLP conversion yielded CTDI values that were less than 10% different from the displayed CTDI on several scanners.Conclusion:This method may be used as a primary method for CT dosimetry QA. As a result of the ease of measurement, a dosimetry metric specific to that scanner may be calculated for a wide variety of CT protocols, which could also be used to monitor display CTDI value accuracy.