Feasibility of Using Virtual Unenhanced Images to Replace Pre-contrast Images in Multiphase Renal CT Examinations

Multiphase renal CT exams are a commonly used imaging technique for the diagnosis of renal masses. The pre-contrast, or true unenhanced (TUE), image provides a baseline for enhancement measurements which is an important criteria used to characterize renal lesions, consequently it is crucial that CT numbers measured in TUE images be accurate. The purpose of this work is to assess the feasibility of replacing TUE with virtual unenhanced (VUE) images derived from DECT data in renal CT exams. Eliminating TUE image acquisition would reduce patient dose and increase patient throughput, improving clinical efficiency. A retrospective study was conducted for 60 consecutively selected patient exams. VUE and TUE images were compared qualitatively and the differences were tested using a Bayesian Hierarchical model. VUE images were found to be inferior to TUE images for visualization of major vessels and depiction of liver parenchyma. CT numbers were measured in the liver, spleen, spine, aorta, cystic lesions, subcutaneous fat, renal cortex and medulla, and the differences were tested with a Student’s paired t-test. There were significant differences between TUE and VUE measurements ( p-value \u3e 0.05) in the spleen, spine, aorta, renal cortex, subcutaneous fat, and inferior vena cava. However, evaluation of the clinical relevance based on grayscale perceptibly indicated that the difference for the spleen and subcutaneous fat are not clinically meaningful. The rapid kVp-switching GE CT750HD scanner was used to assess enhancement accuracy when using VUE compare to TUE images as the baseline for enhancement calculations across a wide range of clinical scenarios simulated in a phantom study, and the results were analyzed using Bayesian Hierarchical models. For simulation of angiomyolipoma and benign cystic lesions, enhancement values were not significantly different. However, for simulation of Bosniak category II-IV lesions, differences in measured enhancement were found to be significant. Additionally, the effect of ASIR level used in image reconstruction was assessed, and found not to affect measured CT number using a mixed effects model. Differences in measured enhancement values for simulated borderline enhancing renal lesions demonstrate that replacement of TUE with VUE images is not feasible with the current iteration of the algorithm

Ultrasound Imaging

In this book, we present a dozen state of the art developments for ultrasound imaging, for example, hardware implementation, transducer, beamforming, signal processing, measurement of elasticity and diagnosis. The editors would like to thank all the chapter authors, who focused on the publication of this book

Applications of micro-CT in the Criminal Justice System of England and Wales: an impact assessment

The Criminal Justice System of England and Wales is currently facing major challenges. One is the financial pressure of government funding cuts, the other the increasing need for professionalisation and rigour within the system. This thesis presents the use of micro Computed Tomography, Additive Manufacturing, and 3D visualisation to address both challenges. By drawing on data from live murder investigations the project examines how these digital technologies can be used to improve the investigation of strangulation deaths, sharp force injuries, and fractures. Each of these categories was treated as a separate case in the overall multiple-case study research design. The increased detail enabled by micro-CT assisted pathologists in the diagnosis of strangulation as previously undetected injuries of the larynx could be identified. A validation study comparing injured to uninjured samples was conducted to increase the strength of the interpretations. For sharp force injuries analysis, micro-CT proved useful for providing the necessary injury characteristics and highly accurate measurements to allow weapon identification. The high resolution of micro-CT scanning also enabled the visualisation of trauma on the smallest of skeletal elements, often encountered in non-accidental injuries in children. The cross-case synthesis revealed the main themes of clarity, objectivity, and visualisation which were improved by using micro-CT irrespective of type of homicide. The significance of these themes further crystallised in semi-structured interviews conducted with various stakeholders of the Criminal Justice System. Management concepts proved suitable to assess the project’s success as the themes used in operations management such as quality, delivery, and cost apply to the delivery of justice as well. A good working relationship with West Midlands Police’s homicide investigators and researchers at WMG was crucial to providing the technology and expertise to address real-life problems whilst ultimately saving taxpayers’ money

Statistical Image Reconstruction and Motion Estimation for Image-Guided Radiotherapy.

Image reconstruction and motion estimation are very important for image-guided radiotherapy (IGRT). Three-dimensional reconstruction of patient anatomy using X-ray computed tomography (CT) allows identification of the location of a tumor prior to treatment. The locations of tumorsmay change during actual treatment due to movement such as respiratory motion. Motion estimation helps optimize the accuracy and precision of radiotherapy so that more of the normal surrounding tissue can be spared. This dissertation addresses several important issues related to these two core components of IGRT. Firstly, we developed two new separable footprint (SF) projector methods for X-ray conebeam CT. The SF projectors approximate the voxel footprint functions as 2D separable functions. The SF-TR projector uses trapezoid functions in the transaxial direction and rectangular functions in the axial direction, whereas the SF-TT projector uses trapezoid functions in both directions. Both SF projector methods are more accurate than the distance-driven (DD) projector, which is a current state-of-the-art method in the field. The SF-TT projector is more accurate than the SF-TR projector for rays associated with large cone angles. In addition, the SF-TR projector has similar computation speed with the DD projector and the SF-TT projector is about two times slower. Secondly, we proposed a statistical penalized weighted least-squares (PWLS) method with edge-preserving regularization to reconstruct two basis materials from a single-energy CT scan acquired with differential filtration, such as a split filter or a bow-tie filter. It requires only the use of suitable filters between the X-ray tube and the patient. For both filtration methods, the proposed PWLS method reconstructed soft tissue and bone images with lower RMS errors, reduced the beam-hardening artifacts much more effectively and produced lower noise, as compared with the traditional non-iterative Joseph and Spital method. Thirdly, we conducted an objective characterization of the influence of rotational arc length on accuracy of motion estimation for projection-to-volume targeting during rotational therapy. Simulations illustrate the potential accuracy of limited-angle projection-to-volume alignment. Registration accuracy can be sensitive to angular center, tends to be lower along direction of the projection set, and tends to decrease away from the rotation center.Ph.D.Electrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86254/1/yonglong_1.pd