PubMed Health⌕ Search

Biomedical subjects

S L Lou

Publications and source records attributed to S L Lou.

6 recordsLinked to original sources
PubMed1992

Assessment of a neuroradiology picture archiving and communication system in clinical practice.

The goal of this study was to determine if our neuroradiology picture archiving and communication system (PACS) is capable of improving the efficiency and function of the management and review of neuroradiologic images. A neuroradiology PACS module developed in our department was evaluated in the clinical environment from February 1990 through July 1991. The overall evaluation focused on three aspects: (1) image delivery performance, (2) system availability, and (3) user acceptance. Image delivery performance was evaluated by analyzing the time spent on each modularized task with both the film-based system and the PACS system. The system availability was examined by observing the downtime occurrence and uptime probability of individual hardware components in the PACS module. User acceptance was evaluated through a survey done with the display workstation. Under regular operating conditions, the PACS outperforms the current film-based operation. The overall PACS module availability is more than 92%, with the display workstation available more than 99% of the time. The overall user acceptance of the system is 3.4 on a four-point ranking scale. This study has demonstrated the full functionality and clinical usefulness of our neuroradiology PACS. On the basis of the results of this study, a large-scale PACS has been designed and implemented in our department.

Computers↗
PubMed1991

An ultrafast network for communication of radiologic images.

The three most difficult problems in making picture archiving and communication systems (PACS) a clinical reality in radiology are image archiving, very high-resolution display stations, and high-speed networking. This article considers high-speed image transmission through a high-capacity network. Our laboratory has tested several commercially available high-speed networks over the past year. Only one of these networks (UltraNet) has adequate throughput and capacity potential necessary for our PACS. The focus of this experiment is to determine the throughput and capacity characteristics of this star topology networking scheme as they relate to the operation of a PACS in the clinical environment. A large-scale test was done to gauge network performance for three networking configurations modeling those in a PACS: duplex, parallel, and relay. Ten computers used in our PACS (Sun 3 and 4 computers) were connected with UltraNet. For point-to-point throughput (half-duplex model), the network delivers up to 3.1 megabytes/sec for Sun 3 computers and 6.8 megabytes/sec for the Sun Sparcserver 490. As regards capacity considerations (parallel model), five parallel image transfer processes generated a maximum of 13.9 megabytes/sec through the network. Only a slight degradation in individual process throughput was observed (1.4%). With regard to shared access to high-contention resources on the PACS network (e.g., archive servers), this network demonstrated equal sharing of server networking capacity between the various client computers. With the encouraging results of this experiment, we believe that the UltraNet network will be sufficient for the image communication requirements of our PACS. We are proceeding with the implementation of UltraNet as the high-speed backbone of our extended PACS network.

Computers↗
PubMed1989

Full-frame transform compression of CT and MR images.

Compression algorithms based on full-frame discrete cosine transforms have achieved compression ratios as high as 10:1 to 20:1 with almost imperceptible image degradation, when applied to projection radiographs digitized with 2,048 X 2,048 X 8-bit matrices. Compared with such radiographs, images obtained with computed tomography (CT) and magnetic resonance (MR) are smaller in size, have lower signal-to-noise ratios, and, in the case of CT, have a larger dynamic range. These differences result in qualitatively different spectral properties. The authors studied the efficiency of the full-frame technique when applied to CT and MR images. They achieved excellent results, with compression ratios in the neighborhood of 5:1. The study was performed with the use of a hardware implementation of the authors' algorithm, which can compress a 512 X 512 X 12-bit image in less than 1.5 seconds.

Algorithms↗
PubMedDate not supplied

Radiological image compression using full-frame cosine transform with adaptive bit-allocation.

We report a new bit-allocation scheme based on the full-frame cosine transform for radiological image compression. The new technique differs from a previously reported method in its use of a two-dimensional bit-allocation table to encode the compression data. This allows for an improved treatment of high frequency components in the transform domain. Consequently, it has the capability of faithfully reproducing limited numbers of high-contrast sharp edges in the image. Previously reported artifacts, induced in the reconstructed image by sharp edges in the original, have been eliminated. Experiments with 10 radiological chest images show almost no perceivable degradation in the reconstructed image at compression ratios below 10:1. Image quality at a fixed compression ratio is, in every case, comparable or superior to results using the old method. Furthermore, the new algorithm lends itself to hardware implementations that are both simple and fast.

Algorithms↗
PubMedDate not supplied

Projection domain compensation of missing angles for fan-beam CT reconstruction.

An improved method is proposed for fan-beam computed tomographic (CT) reconstruction from data with limited views. Compensation for the missing projections for fan-beam CT can be partially accomplished by using the coincident ray or by an interpolation technique using circular sample theory. In this article, the authors propose a more accurate compensation method for the missing projections whether the coincident ray pairs exist or not. The fan-beam reprojection algorithm, which is the inverse operator of the convolution filter, was extended from the projection space iteration reconstruction-reprojection (PSIRR) in parallel beam geometry. In addition, this algorithm was validated by applying the Shepp-Logan phantom for a computer simulation in the equi-angular fan-beam CT geometry.

Algorithms↗