Biomedical subjects

Chien-Min Kao

Publications and source records attributed to Chien-Min Kao.

3 recordsLinked to original sources

PubMed2005

Spatial-resolution enhancement in computed tomography.

We propose an approach that combines an asymmetric fan-beam configuration and a new reconstruction algorithm to enhancing spatial resolution in computed tomography (CT). The asymmetric configuration can be achieved by changing the center of rotation (COR) from the conventional symmetric configuration. It does not, however, require new detectors and X-ray source nor alter the relative geometry between the detector and the X-ray source. By effectively reducing the distance of the COR to the X-ray source, the asymmetric configuration can increase the effective sampling density in projection data without reducing the size of the field of view (FOV). The proposed algorithm, on the other hand, can reconstruct images directly from data acquired with this asymmetric configuration. We performed numerical studies to demonstrate and validate the proposed acquisition/reconstruction approach. Results in these studies confirm that the proposed approach can lead to enhanced spatial resolution in reconstructed images. The proposed acquisition/reconstruction approach may find applications in micro-CT and industrial CT in which the CORs may be changed.

Algorithms↗

PubMed2004

An exact Fourier rebinning algorithm for 3D PET imaging using panel detectors.

Abstract We present an exact Fourier-based algorithm for rebinning 3D data generated by a stationary dual-panel PET system to obtain direct slices for subsequent slice-by-slice reconstruction. The algorithm is computationally efficient and can greatly reduce the problem dimensionality and computation complexity of the reconstruction task. By conducting computer simulation studies in which the effects of scatter, randoms, detector response functions and attenuation correction are not considered, we demonstrate that direct slices generated by the proposed algorithm are quantitatively accurate and exhibit substantially better noise characteristics than the original direct slices. However, image artefacts, occurring at axial intensity discontinuities and in regions close to the axial axis, can be observed. With preliminary supporting evidence, we stipulate that these artefacts are due to errors in discrete implementations of partial derivatives of the 3D data. Although general weightings can be used in the proposed rebinning algorithm, in this work we only study the use of uniform weightings and the resulting direct slices exhibit non-uniform noise distributions, with the central slices being less noisy. In future studies, by using general weightings to reduce contributions of the data that are acquired at large oblique angles, we expect that more uniform noise distributions can be achieved, and axial blurring due to parallax errors can be reduced, at the cost of overall image variance.

Algorithms↗

PubMed2002

Short-scan SPECT imaging with non-uniform attenuation and 3D distance-dependent spatial resolution.

Image quality and quantitative accuracy in single-photon emission computed tomography (SPECT) can be degraded by, e.g., the effects of photon attenuation and finite spatial resolution. It is generally considered that adequate compensation for such effects on SPECT images requires data acquired over 2 pi. Recently, using the existing consistency condition on the data function, Noo and Wagner (2001 Inverse Problems 17 1357-72) have shown analytically that data acquired over only pi can be used to correct completely for the effect of uniform attenuation in SPECT. It remains unknown, however, whether data acquired only over pi in SPECT with non-uniform attenuation and/or 3D distance-dependent spatial resolution (DDSR) contain complete information for accurate image reconstruction. In this work, we develop a heuristic perspective, which is referred to as the potato peeler perspective to show conceptually that data in SPECT with non-uniform attenuation and/or 3D DDSR acquired over 2 pi contain redundant information and that such information can be used to reduce the scanning angle in SPECT. Specifically, we show heuristically that, in SPECT with only non-uniform attenuation, the scanning angle can be reduced from 2 pi to pi and that, in SPECT with both non-uniform attenuation and DDSR with a physically realistic form, the scanning angle can be reduced from 2 pi to pi in a practical sense. We conduct computer simulation studies, and the results from these studies corroborate the observations obtained based upon the heuristic potato peeler perspective.

Algorithms↗