PubMed Health⌕ Search

Biomedical subjects

S K Mun

Publications and source records attributed to S K Mun.

18 recordsLinked to original sources
PubMed1992

A comparison of case retrieval times: film versus picture archiving and communications systems.

One of the advantages that a picture archiving and communications system (PACS) is supposed to provide over a film-based operation is improved performance in retrieving images. Although it seems self-evident that this should be so, this experiment was intended to verify this and to provide some time comparisons for the two methods. The experiment consisted of randomly selecting ultrasound and computed tomography cases and determining how long it took to retrieve files at a PACS workstation or in person from the file room. To simulate actual retrieval volumes, a total of 40 cases from current to 6 months old, 20 cases from the past year, and 10 cases more than 1 year old was selected. Results indicate that PACS retrieval can indeed be faster than file room retrieval. However, the difference is less for recent cases than for older cases. For cases 6 or fewer months old, the workstation retrieval was approximately 2.5 minutes faster per case than the film file room. This time difference increased markedly when extended to the 1-year and older-than-1-year groups. This report details the results of this study and provides information about the reliability of the two archives.

Filing↗
PubMed1992

PACS clinical experience at Georgetown University.

Georgetown University Hospital has been operating an image management and communications system (IMACS or PACS) for 3.5 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 3 years. This paper will summarize our PACS clinical experience and will describe the operational features implemented and those still necessary.

Computer Systems↗
PubMed1992

An image management and communications (IMAC) system for radiology.

Managing x-ray films is a difficult problem in a hospital. Advances in digital imaging, high speed networks and high fidelity displays make it possible to develop an image management and communication system for a hospital. As many of the technical problems are solved, many operational problems remain. Experience with a prototype installation became the basis for a much more comprehensive implementation of a fully digital filmless imaging support system in a number of hospitals. The use of IMAC technology will bring about profound changes in the radiology community; physicians, administrators, manufactures of imaging systems and the users of radiology service, the patients.

Academic Medical Centers↗
PubMed1991

Picture archiving and communication in radiology: an American perspective.

A comprehensive image management and communication (IMAC) network has been installed at Georgetown University Hospital (GUH) for an extensive clinical evaluation. The network is based on the AT&T CommView system and includes interfaces to 12 imaging devices, 15 workstations (inside and outside the radiology department), a teleradiology link to an imaging center, an optical jukebox, and a number of advanced image display and processing systems. Two years of clinical experience with the network enable us to develop a plan for future activities from an American perspective. The IMAC project is not just a technical challenge, but also a professional, organizational, and administrative one. Several obstacles remain, but they are gradually being overcome as more cost-effective and streamlined technologies become available and as users and developers gain more operational experience in managing diagnostic images in an electronic environment.

Computer Communication Networks↗
PubMed1990

Contrast information of digital imaging in laser film digitizer and display monitor.

A 10-bit or 12-bit gray scale is provided in commercial laser film digitizers. The true contrast resolution on the digitized image within a laser spot area of 200 microns in diameter is limited by both the quantum mottle and instrumentation noise. In this report, we investigated the mean value, standard deviation, and adjacent pixel correlation coefficient on a calibrated step wedge film with two laser digitizers. The results were disappointing, because we found that the evaluated contrast information is inferior to the manufacturers' specifications. On the output side, the brightnesses of different gray levels from a clinical monitor were measured with a narrow angle luminance probe and evaluated by a brief human perception study. In addition, the implications for teleradiology applications are discussed.

Data Display↗
PubMed1989

Image management and communication in patient care: perspectives on implementation and impact.

Image management and communication (IMAC) systems are automated and integrated systems that capture digital medical images and related patient information and transmit them electronically, display them for interpretation, and store them for future retrieval. The IMAC system concept includes images and relevant information from all clinical sources. The First International Conference on Image Management and Communication in Patient Care (IMAC 89) provides a forum for expert presentations, poster sessions, and discussion and debate among all attendees interested in the implementation and impact of IMAC systems. Plenary sessions provide an international perspective and explore the role of image-based information in patient care, approaches to improved IMAC systems, current technical barriers, quality of care issues, evaluation approaches, and scenarios for the future. Invited participants are from North America, Europe, Japan, Australia, and the WHO. Conference organizers are working with numerous professional organizations and representatives of meetings which focus on IMAC-related technology to complement, and not duplicate, the contribution of other groups.

Delivery of Health Care↗
PubMed1989

Environmental designs for reading from imaging work stations: ergonomic and architectural features.

Despite the rapid progress made in the electronic design of imaging work stations for medicine, much less effort has gone into the design of environments in which such systems will be used. Based on studies of radiologist film reading sessions, considerable time will be spent working at such viewing systems. If the rooms in which the work stations are placed are not conducive to comfortable work, it will certainly not favor electronic viewing over film reading. In examining existing reading environments, it is also apparent that they are not optimal, even for film. Since some of the problems for film and electronic viewing overlap, such as heat generation (by the alternators, viewboxes, or work station electronics) and glare from light sources, it should be possible to develop solutions that are applicable to both environments, or to rooms that will feature both viewing systems. This paper will discuss some of the approaches to designing environments in which viewing of images is supported by the room architecture and engineering, rather than being degraded by it. To illustrate these points a design, based on the constraint of a real room size and available architectural materials, will be developed.

Architecture↗
PubMed1989

Renal calculi after shock wave lithotripsy: US evaluation with an in vitro phantom.

Fragments of renal calculi from patients who had undergone extracorporeal shock wave lithotripsy (ESWL) were embedded in an in vitro tissue-equivalent ultrasound (US) phantom to assess (a) the accuracy with which such fragments could be measured; (b) the influence of stone composition, stone depth, and transducer frequency; and (c) the effect of fragment "clumping" on size determinations and acoustic shadowing. Fragments as small as 0.8 mm in diameter could be detected at 7.5 MHz, although a practical limitation of 1-2 mm for lower transducer frequencies (3.5 and 5.0 MHz) was observed. Fragment diameter tended to be overestimated with US by a mean of 1 mm. Transducers of 5 and 7.5 MHz were more accurate in determination of size than 3.5-MHz transducers. Struvite fragments were less echogenic and were therefore measured more accurately, but smaller struvite fragments were less detectable than other fragment types. Fragment "clumping" led to significant overestimation of residual stone size even when small fragments were separated by as much as the distance equal to the diameter of one fragment. This study demonstrates that even under the best circumstances the disadvantages of US in assessing residual stone disease are significant.

Humans↗
PubMed1989

Cerebral blood flow in humans following resuscitation from cardiac arrest.

Cerebral blood flow was measured by xenon-133 washout in 13 patients 6-46 hours after being resuscitated from cardiac arrest. Patients regaining consciousness had relatively normal cerebral blood flow before regaining consciousness, but all patients who died without regaining consciousness had increased cerebral blood flow that appeared within 24 hours after resuscitation (except in one patient in whom the first measurement was delayed until 28 hours after resuscitation, by which time cerebral blood flow was increased). The cause of the delayed-onset increase in cerebral blood flow is not known, but the increase may have adverse effects on brain function and may indicate the onset of irreversible brain damage.

Adult↗
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

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↗