Biomedical subjects

Jiang Hsieh

Publications and source records attributed to Jiang Hsieh.

3 recordsLinked to original sources

PubMed2003

Investigation of an image artefact induced by projection noise inhomogeneity in multi-slice helical computed tomography.

The introduction of multi-slice helical computed tomography has fundamentally changed the way radiologists view CT images. Increasing numbers of clinical cases are examined with advanced visualization tools, such as maximum intensity projection, multi-planar reformation and volume rendering. It has been discovered that new image artefacts, which do not appear in the traditional two-dimensional reconstructed images, become visible in images generated by these new tools. In this paper, we investigate the causes of one such artefact, the Venetian blind artefact, which appears as bright-and-dark bands superimposed on three-dimensional images. We demonstrate that such an artefact is caused by the periodical noise variation in the reconstructed images. The image noise variation is, in turn, caused by the interaction of the noise inhomogeneity in the projections with the helical weights. An analytical formula is developed that accurately predicts the presence of such artefacts. Based on our analysis, several approaches are proposed for the artefact reduction or elimination.

Artifacts↗

PubMed2003

Analytical models for multi-slice helical CT performance parameters.

One of the most recent technological advancements in computed tomography (CT) is the introduction of multi-slice CT (MSCT). When combined with the helical scan mode, MSCT offers significant improvements in volume coverage, isotropic spatial resolution, and contrast utilization. Although experimental studies have been conducted on MSCT performance, there is a lack of theoretical analysis on the slice sensitivity profile (SSP) and noise performance. In this paper, we derive several closed-form expressions, for linear interpolation based helical reconstruction algorithms, to characterize these performance parameters under different detector configurations and acquisition modes. Following the common practice, the expressions are explicitly described for regions near the iso-center, although the same approach can be used to describe system performances away from the iso-center. These models are validated against phantom experiments.

Algorithms↗

PubMed2002

Computer-simulated radiation dose reduction for abdominal multidetector CT of pediatric patients.

OBJECTIVE: Limiting CT radiation dose is especially critical when imaging children. The purpose of our study was to modify and test an accurate and safe tool for evaluating systematic dose reduction for abdominal multidetector CT (MDCT) in pediatric patients. MATERIALS AND METHODS: After validating the computer-simulation technique with a water phantom, we subjected the original digital scanning data for 26 contrast-enhanced abdominal MDCT scans (120 mA) obtained in infants and children (age range, 1 month-9 years; mean age, 3.1 years) to simulated tube current reduction (100, 80, 60, and 40 mA) by adding noise. this procedure created four additional examinations per child that were identical to the originals except for image noise. The 130 examinations were scored randomly, independently, and without prior knowledge of the children's diagnoses by three radiologists for depiction of high-visibility structures, such as adrenal glands and fat in the intrahepatic falciform ligament, and low-visibility structures, such as the extrahepatic hepatic artery, small intrahepatic vessels, and common bile duct. Aligned rank and Wilcoxon's signed rank tests were used for statistical analyses. RESULTS: Simulated tube current reduction significantly affected the detection of low-visibility structures (p < 0.001). Reduced detection in low-visibility structures was evident at a level less than or equal to 80 mA. No loss of detection in high-visibility structures was found at any tube current level (p > 0.5). CONCLUSION: The results of this computer simulation suggest that accurate abdominal MDCT can be performed in pediatric patients using substantially reduced radiation, depending on the indication for imaging. (In our case, the reduction was between 33% and 67%, depending on whether a high-visibility or low-visibility structure was being assessed.) This simulation technology can be applied to MDCT of other organ systems for systematic evaluation of radiation dose reduction.

Child↗