The authors present an unusual case of a highly mobile gallbladder which simulated a pancreatic mass on computed tomograms. Radiographic features of this interesting variant are illustrated.

Abscesses developing within the retroperitoneal spaces are complicated and serious infections. These abscesses present insidiously, leading to considerable mortality and morbidity. A high clinical suspicion can help diagnose and treat this potentially fatal illness. Computed axial tomography is the best diagnostic modality for retroperitoneal abscess. Computed tomographic scan is useful, not only for diagnosing the retroperitoneal abscess, but can be used for therapeutic drainage of abscesses in high-surgical-risk patients. We present an illustrative case of retroperitoneal abscess and discuss the pathogenesis of retroperitoneal abscess, diagnosis, and treatment.

ECG-gated multidetector computed tomography (MDCT) is an imaging modality widely utilized for the evaluation of cardiac pathology by physicians. However, there has been little research of cardiac MDCT imaging in veterinary patients. Presently, ECG-gating is an upgrade for MDCT, which few veterinary institutions currently possess. The purpose of this study was to compare image quality between a 16 non ECG-gated and 64 ECG-gated MDCT for clinically important cardiac anatomy in dogs. In a crossover trial, six dogs were scanned using 16 non ECG-gated and 64 ECG-gated MDCT. A standardized anesthetic protocol, designed to induce bradycardia (mean HR 45 bpm ± 12.6) was used. Five post-contrast sequential scans through the heart were performed for each patient when utilizing the 16 non ECG-gated MDCT, in attempt to obtain a motion free series of images of the heart. For each scan, assessment of cardiac morphology was performed by evaluating a group of 21 cardiac structures, using a 3-point scale. Each of the images were scored as 0 (motion present, scan non-diagnostic), 1 (motion present, scan diagnostic), and 2 (no motion, therefore diagnostic scan of high quality). Quality scores (QS) from all scans within a dog (30 scans total) were assigned for each cardiac structure. QS from the six ECG-gated MDCT scans were of high diagnostic quality, generating diagnostic images for all of the 21 cardiac structures evaluated for each of the 6 scans. Individual non ECG-gated scans were of variable quality, primarily generating QS of 1 or 2. A complete set of diagnostic images for all 21 structures was not achieved from an individual scan. Minimum number of non ECG-gated scans to identify a single structure was calculated, and ranged from 1-2 scans for all structures. Cumulative number of sequential non ECG-gated scans needed to achieve images of all cardiac structures was calculated and determined to be 5. A 16 non ECG-gated MDCT scanner can produce cardiac images that are similar in quality, to those of 64 ECG-gated MDCT. Cardiac motion negatively impacts image quality in studies acquired without ECG-gating. However, this can be overcome by performing multiple sequential scans through the heart. / Master of Science

X-ray Computed Tomography (CT) is a process that produces three-dimensional x-ray images, allowing for better diagnosis and analysis of complex internal medical conditions. New advances in the optical techniques used in this process promise to produce better results while reducing patient risk. One of these developments calls for precise optical gratings that can be expensive and difficult to manufacture. This paper presents a simple process developed specifically for the production of these gratings using cost effective techniques. The process uses well understood semiconductor fabrication steps including oxidation, deep reactive ion etching and electroplating. While not entirely successful, the process presented within provides a proof of concept for development of the gratings and discusses improvements that could be made to allow for success. / Master of Science

Dissertation

An adaptive pre-clinical x-ray computed tomography system, named "FaCT" was designed, built, and tested at the University of Arizona's Center for Gamma-Ray Imaging (CGRI). The FaCT system possesses the unique ability to change its magnification and dynamically mask the x-ray beam profile. Using these two abilities, the FaCT system can adapt its configuration to the object being imaged, and the task being performed, while achieving a reduction in the radiation dose applied for imaging.Development of the system included the design of all mechanical components, motion systems, and safety systems. It also included system integration of all electronics, motors, and communication channels. Control software was developed for the system and several high-performance reconstruction algorithms were implemented on graphics processing units for reconstructing tomographic data sets acquired by the system. A new geometrical calibration method was developed for calibrating the system that makes use of the full image data gathered by the system and does not rely on markers.An adaptive imaging procedure consisting of a preliminary scout scan, human guidance, and a diagnostic quality scan was developed for imaging small volumes of interest in the interior of an object at substantially reduced dose. The adaptive imaging procedure makes use of FaCT's adjustable magnification, beam-masking capability, and high-performance reconstruction software to achieve high-quality reconstruction of a volume of interest with less dose than would be required by a traditional x-ray computed tomography system without adaptive capabilities.To address ongoing research into mathematical rules for adapting an imaging system, such as FaCT, to better perform a given estimation task, a method of quantifying a system's ability to estimate a parameter of interest in the presence of nuisance parameters based on the Fisher Information was proposed. The method requires a statistical model of object variability. Possible strategies for increasing the performance of an estimation task, given an adaptive system, were suggested.

Spine needle injections are widely applied to alleviate pain and to remove nerve sensation through anesthesia. Current treatment is performed either blindly having no image guidance or using fluoroscopy or computed tomography (CT). Both CT and fluoroscopy guidance expose patients to ionizing radiation. Alternatively, ultrasound (US) guidance for spine needle procedures is becoming more prevalent since US is a non-ionizing and more accessible image modality. An inherent challenge to US imaging of the spine is the acoustic shadows created by the bony structures of the vertebra limiting visibility. It is challenging to use US as the sole imaging modality for intraoperative guidance of spine needle injections. However, it is possible to enhance the anatomical information through a preoperative diagnostic CT. To achieve this, image registration between the CT and the US images is proposed in this thesis. Image registration integrates the anatomical information from the CT with the US images. The aligned CT augments anatomical visualization for the clinician during spinal interventions. To align the preoperative CT and intraoperative US, a novel registration pipeline is presented that involves automatic global and multi-vertebrae registration. The registration pipeline is composed of two distinct phases: preoperative and intraoperative. Preoperatively, artificial spring points are selected between adjacent vertebrae. Intraoperatively, the lumbar spine is first aligned between the CT and US followed by a multi-vertebrae registration. The artificial springs are used to constrain the movement of the individually transformed vertebrae to ensure the optimal alignment is a pose of the lumbar spine that is physically possible. Validation of the algorithm is performed on five clinical patient datasets. A protocol for US data collection was created to eliminate variability in the quality of acquired US images. The registration pipeline was able to register the datasets from initial misalignments of up to 25 mm with a mean TRE of 1.17 mm. From these results, it is evident that the proposed registration pipeline offers a robust registration between clinical CT and US data. / Thesis (Master, Computing) -- Queen's University, 2013-08-19 12:50:54.521

In the first part of this work, we present two methods for improving the shape-threat detection performance of x-ray computed tomography. Our work uses a fixed-gantry system employing 25 x-ray sources. We first utilize Kullback-Leibler divergence and Mahalanobis distance to determine the optimal single-source single-exposure measurement. The second method employs gradient search on Bhattacharyya bound on error rate (P-e) to determine an optimal multiplexed measurement that simultaneously utilizes all available sources in a single exposure. With limited total resources of 10(6) photons, the multiplexed measurement provides a 41.8x reduction in P-e relative to the single-source measurement. In the second part, we consider multiple exposures and develop an adaptive measurement strategy for x-ray threat detection. Using the adaptive strategy, we design the next measurement based on information retrieved from previous measurements. We determine both optimal "next measurement" and stopping criterion to insure a target P-e using sequential hypothesis testing framework. With adaptive single-source measurements, we can reduce P-e by a factor of 40x relative to the measurements employing all sources in sequence. We also observe that there is a trade-off between measurement SNR and number of detectors when we study the performance of systems with reduced detector numbers. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

by Ho, Chi-Kin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 62-64). / Chapter 1 --- Introduction / Chapter 2 --- Previous Work --- p.2-1 / Chapter 2.1 --- Thresholding --- p.2-1 / Chapter 2.2 --- Edge Detection --- p.2-2 / Chapter 2.3 --- Region Growing --- p.2-2 / Chapter 2.4 --- Radial Contour Model --- p.2-3 / Chapter 2.5 --- Regularized Region Contrast --- p.2-3 / Chapter 2.6 --- Deformable Model --- p.2-4 / Chapter 3 --- The ODD-Balloons Model --- p.3-1 / Chapter 3.1 --- Design Rationale --- p.3-1 / Chapter 3.2 --- Overview --- p.3-5 / Chapter 3.3 --- 2-D Deformations --- p.3-8 / Chapter 3.4 --- Orthogonal Cut and Volume Transfer --- p.3-11 / Chapter 3.5 --- Smoothing Operation --- p.3-17 / Chapter 3.6 --- Properties --- p.3-20 / Chapter 3.6.1 --- Conformation to 3-D Shape --- p.3-20 / Chapter 3.6.2 --- Noise Sensitivity --- p.3-20 / Chapter 3.6.3 --- Convergence and Efficiency --- p.3-22 / Chapter 3.6.4 --- Easy-to-Use --- p.3-23 / Chapter 3.7 --- Summary --- p.3-24 / Chapter 4 --- Experiment Results --- p.4-1 / Chapter 4.1 --- Synthetic Data Experiments --- p.4-1 / Chapter 4.2 --- Real Data Experiment --- p.4-3 / Chapter 4.3 --- Discussions --- p.4-6 / Chapter 5 --- Conclusion and Future Work --- p.5-1 / Chapter 5.1 --- Conclusion --- p.5-1 / Chapter 5.2 --- Recommended Future Work --- p.5-2 / Appendix A Discrete Implementation of 2-D Deformation --- p.A-1 / Appendix B Choosing Elasticity and Rigidity Coefficients of 2-D Deformation --- p.B-1 / Bibliography --- p.BIB-1

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Medicine in Diagnostic Radiology Johannesburg, 2014 / INTRODUCTION South Africa presents a complex scenario with regard to patients consenting for medical procedures, because of the differing profiles of the population and the health care workers who perform the consenting procedures. AIM To evaluate consenting practice for CT scanning, within the South African tertiary referral setting and to determine if there are any associations between patient demographic profile and the level of understanding with the adequacy of consent. METHOD A prospective survey regarding consenting practices for CT scanning was performed in a form of an interview questionnaire in patients presenting to Chris Hani Baragwanath Academic and Charlotte Maxeke Johannesburg Academic hospitals. Determination of any associations between patient age, racial group, language and education was made with the level of understanding and adequacy of consent. RESULTS The survey was conducted on 117 patients; 86 from Charlotte Maxeke Johannesburg Academic Hospital and 31 from Chris Hani Baragwanath Academic Hospital. We found no significant association between gender and age category (p=0.11), racial group (p=0.17), education (p=0.26), home language (p=0.21) or residential area type (p=0.70). vi There was a significant, weak, association between age category and education (p=0.043; Cramer’s V=0.29). There was a significant, moderate association between the understanding of the language of consent and the home language of the patients (p=0.0013; phi coefficient=0.43). There was also some association between education and age. Just over 50% of patients felt that they had been given enough information and had had an opportunity to ask questions and only 33% had been offered an alternative to the CT scan. There was a significant difference in the mean adequacy of consent score with regards to racial group (p<0.0001), home language (p=0.0073), residential area type (p<0.0001) and level of education (p<0.0001). CONCLUSION Language differences between patients and personnel performing the consent procedure proved to be a major barrier in offering adequate consenting for CT Scans.