Seung-Oh Jin

Determination of accurate stent graft configuration in abdominal aortic aneurysm using computed tomography: a preliminary study.

An aortic stent graft is frequently used to cure an abdominal aortic aneurysm (AAA). It is critical to accurately fit the size and shape of the stent graft to the target region on the aorta. Proper sizing and shaping require the measurement of the orthogonal diameter of the target region from medical images. The present study aimed to acquire an accurate three-dimensional (3D) reconstruction of the aorta to determine the shape of the cross-sectional area where the stent graft would be implanted. A conventional geometric-active contour model was enhanced to prevent blurring and to improve edge detection with high noise resistivity. After the segmentation of two-dimensional (2D) images using the model, a 3D-reconstructed configuration of the aorta was achieved using a surface-rendering technique. The model could segment several selected synthetic images more accurately than conventional methods. Also, a 3D-reconstructed configuration of the abdominal aorta could be achieved using boundary coordinates extracted from 2D image segmentation. This preliminary study indicates the utility of the approach in optimizing stent graft configuration for AAA patients, thus enhancing stent graft healing.

Fast image reconstruction from fan beam projections using parallel digital signal processors and special purpose processors

Conventional CT (Computed Tomography) has recently been replaced rapidly by Spiral CT. In X-ray CT spiral scanning has achieved various advantages resulting in better image quality, reduced scan time (in a single breath-hold), a lower X-ray dose by continuous and simultaneous source rotation, object translation and data acquisition. This paper describes the rapid image reconstruction techniques with filtered back projection based on the general purpose DSP (Digital Signal Processors) and BPSP (Back Projection Specific Processors) in parallel. After verification of the reconstruction algorithm through the simulation, an optimized BPSP is proposed for real-time imaging.

Effect of a Guard-Ring on the Leakage Current in a Si-PIN X-Ray Detector for a Single Photon Counting Sensor

PIN diodes for digital X-ray detection as a single photon counting sensor were fabricated on a floating-zone (FZ) n-type (111), high resistivity (5-10 kΩcm) silicon substrates (500μm thickness). Its electrical properties such as the leakage current and the breakdown voltage were characterized. The size of pixels was 100μm×100μm. The p+ guard-ring was formed around the active area to reduce the leakage current. After the p+ active area and guard-ring were fabricated by the ion-implantation, the extrinsic-gettering on the wafer backside was performed to reduce the leakage current by n+ ion-implantation. PECVD oxide was deposited as an IMD layer on front side and then, metal lines were formed on both sides of wafers. The leakage current of detectors was significantly reduced with a guard-ring when compared with that without a guard ring. The leakage current showed the strong dependency on the gap distance between the active area and the guard ring. It was possible to achieve the leakage current lower than 0.2nA/cm2.