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Biomedical subjects

S K Mun

Publications and source records attributed to S K Mun.

47 records · Page 3Linked to original sources
PubMed1989

Image management and communication systems: a new challenge in radiology.

The spectacular advances in diagnostic imaging technologies, such as CT, MRI, and NM, have improved the quality of radiological diagnosis. On the other hand, the vast amount of image data produced by these digital modalities have created unique problems in managing the information. The increased use of digital imaging systems has set the stage for the development of comprehensive medical image and information management systems for large medical facilities. These image management and communication systems (IMACS) vary, depending on imaging, display and output devices connected, network configurations used, and storage devices available. This paper will discuss the important technical aspects in developing an IMACS network, imaging devices ideally suited for connection to an IMACS, integration with computerized hospital and radiology information systems, performance issues, clinical acceptance and specific implementation experience.

Computer Communication Networks↗
PubMed1979

Origin of observed changes in 14N hyperfine interaction accompanying R leads to T transition in nitrosylhemoglobin.

Theoretical investigations of electronic distributions in eight different structural forms of nitrosylhemoglobin were carried out to study the changes in (14)N hyperfine interaction observed with the transition from R to T structures under the influence of inositol hexaphosphate or changing pH. Four of the eight forms studied consisted of protonated and deprotonated N(pros) in the proximal imidazole ligand with linear and bent Fe-N-O structures. Two other forms had a straight Fe-N-O structure and Fe-Im bond stretched by 0.5 and 1.0 A. The other two systems we have studied are five-liganded NO-heme with bent and straight Fe-N-O structures. Our investigations show that arrangements of energy levels did not differ significantly among all the structures, the unpaired electron always occupying an antibonding orbital with d(z)2 symmetry. The protonated and deprotonated systems with either linear or bent Fe-N-O structure showed substantial hyperfine interaction of the (14)N nuclei of the NO group and the N(epsilon) atom of the proximal imidazole, indicating that a 9-line electron spin resonance hyperfine pattern (R structure) would be expected in all four cases. On the other hand, the extensions of the Fe-Im bond produce a sizeable decrease in the (14)N(epsilon) hyperfine interaction, indicating that an extension beyond 1.0 A would provide a 3-line hyperfine pattern close to that found for the five-liganded NO-heme system. Our results thus provide quantitative support for the model of severe extension or cleavage of the Fe-N(epsilon) bond proposed in the literature for explaining the R-to-T transition of the alpha-chain of nitrosylhemoglobin.

Electron Spin Resonance Spectroscopy↗
PubMed1977

Critical appraisal of electronic structure of metmyoglobin. 14N and 57Fe hyperfine interactions.

The electronic structure of metmyoglobin is subjected to a critical examination by comparison of results of recent ENDOR measurements of nitrogen hyperfine interaction constants on the porphyrin ring and on the proximal histidine linking the heme to the protein with theoretical values for these properties from calculated electronic wavefunctions for this molecule. The observed interesting trends of the 14N hyperfine data as well as available 57Fe data are both successfully explained showing that theory has provided a satisfactory description of the electronic distribution in this important molecule.

Ferric Compounds↗
PubMedDate not supplied

PACS clinical experience at Georgetown University.

Georgetown University Hospital has been operating an image management and communications system (IMACS or PACS) for three-and-a-half years. This work was initially funded under the Army Medical Research and Development Command Digital Imaging Network Systems (DINS) project. The system was taken from a research system supporting only radiology tasks to one extended to clinical use, and has been used in clinical work for two-and-a-half years. This paper will summarize our PACS clinical experience and will describe the operational features implemented and those still necessary.

Computer Systems↗
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↗
PubMedDate not supplied

Deployable teleradiology and telemedicine for the US military.

The US military has been an effective proponent of digital imaging and teleradiology for the past 15 years. A digital imaging network that can eliminate the use of X-ray film can make the requirements simpler for military medicine. X-ray film requires the storage of new, unexposed films that have a fixed shelf life, and the storage and use of chemicals and water for processing. In some deployed situations, the chemical discharge has to be collected and shipped out of the deployed area. The technology of electronic imaging is therefore intrinsically important to military medicine. In December of 1995, the US government started to deploy 20000 US troops to Bosnia-Herzegovina as part of NATO's peace keeping operation (IFOR). A full complement of medical support facilities was to be established in the Bosnia region and Hungary where the deployment was staged. Primetime III was a project to deploy telemedicine and teleradiology capabilities linking these medical treatment facilities (MTF). The deployment of telemedicine was not the responsibility of our engineering team. This paper deals with the deployable teleradiology (DEPRAD) system that was installed by the ISIS Center at a number of facilities for filmless radiology and teleradiology services.

Evaluation Studies as Topic↗
PubMedDate not supplied

In vivo NMR imaging of sodium-23 in the human head.

We report the first clinical nuclear magnetic resonance (NMR) images of cerebral sodium distribution in normal volunteers and in patients with a variety of pathological lesions. We have used a 1.5 T NMR magnet system. When compared with proton distribution, sodium shows a greater variation in its concentration from tissue to tissue and from normal to pathological conditions. Image contrast calculated on the basis of sodium concentration is 7 to 18 times greater than that of proton spin density. Normal images emphasize the extracellular compartments. In the clinical studies, areas of recent or old cerebral infarction and tumors show a pronounced increase of sodium content (300-400%). Actual measurements of image density values indicate that there is probably a further accentuation of the contrast by the increased "NMR visibility" of sodium in infarcted tissue. Sodium imaging may prove to be a more sensitive means for early detection of some brain disorders than other imaging methods.

Brain Neoplasms↗
PubMedDate not supplied

A method for splitting digital value in radiological image compression.

A new decomposition method using image splitting and gray-level remapping has been proposed for image compression, particularly for images with high contrast resolution. The effects of this method are especially evident in this radiological image compression study. In these experiments, the impact of this decomposition method was tested on image compression by employing it with two coding techniques on a set of clinically used CT images and several laser film digitized chest radiographs. One of the compression techniques used as zonal full-frame bit-allocation in the discrete cosine transform (DCT) domain, which is an enhanced full-frame DCT technique that has been proven to be an effective technique for radiological image compression. The other compression technique used was vector quantization with pruned tree-structured encoding, which through recent research has also been found to produce a low mean-square error and a high compression ratio. The parameters used in this study were mean-square error and the bit rate required for the compressed file. In addition to these parameters, the differences between the original and reconstructed images were presented so that the specific artifacts generated by both techniques could be discerned through visual perception.

Brain↗
PubMedDate not supplied

Hemodialysis patient management by telemedicine: design and implementation.

The authors describe the design and implementation of a personal computer based telemedicine system for managing patients by telemedicine. With three identical systems connected by high speed T1 lines, the physician (or allied healthcare giver) can interact, by videoconferencing, and by using multimedia files, with patients at two remote hemodialysis sites. The physician is able to visualize specifically the patient's fistula/graft, and auscultate fistula, heart and lung sounds, and incorporate still pictures or audio sounds in the patient's multimedia database folder, which also contains an electronic and paperless medical record. In addition there is the capability of downloading into this database all the machine parameters during dialysis.

Databases, Factual↗