PubMed Health⌕ Search

Biomedical subjects

H W Park

Publications and source records attributed to H W Park.

15 recordsLinked to original sources
PubMed1992

Hardware and software requirements for a picture archiving and communication system's diagnostic workstations.

Electronic systems (picture archiving and communications systems [PACS]) for image and multimedia data distribution, archiving, and transmission, represent the future of radiology. The workstation is the point of contact between a PACS and the radiologist or referring physician. Therefore, the acceptance of PACS is highly dependent on workstation functionality and performance. This paper, based on our experience in evaluating commercial workstations and on a review of recent literature, describes hardware and software requirements for diagnostic workstations that could be used for making primary diagnoses in a radiology department. Requirements for PACS workstations for use in referring clinics are also briefly described. These workstations must be able to handle the large volume of images to be viewed efficiently, add new functionality to improve the productivity of physicians, technologists, and other health care providers, and provide enough flexibility to allow the electronic systems to grow as medical imaging technology evolves.

Computer Systems↗
PubMed1992

Morphogenic development of the pancreas in the staged human embryo.

The Carnegie stage is widely applied in the field of human embryology, and it is more logical to analyze the embryos by this stage than CR length or menstrual age. In this study, the early development of the pancreas is studied by tissue observation and reconstruction using serial sections of 33 human embryo ranging from Carnegie stages 11 to 23. The dorsal pancreas develops from the dorsal wall of the duodenum in stage 12, and the ventral pancreas from the proximal part of the cystic primordium in stage 13 or 14 as a single epithelial thickening, but in one case, as a bilateral thickening which contains some isolated spaces. The rotation of the ventral pancreas starts in stage 15, and completes in stage 17. Surrounding connective tissue differentiates in stage 18.

Female↗
PubMed1992

Development of elastin layers in the aortic wall of human fetuses.

The presence of elastin layers in the aortic walls of twelve human fetuses was confirmed with scanning electron microscope pictures after hot alkali treatment and histochemical examination. In addition, the number of elastin layers in aortic walls of 5 different segments were compared in fetuses of varying ages. Aldehyde fuchsin stained slides of elastin ascending aortas showed a range between 27 and 55 layers of elastin in fetuses of 8 weeks to 32 weeks. However, in the lower abdominal aortas, elastin layers decreased from 28 to only 3 layers for fetuses of the same age. Furthermore, as elastin layers decreased from ascending aorta to abdominal aorta with the progression of fetal life, similar changes in the elastin lamellae were observed. These results suggest that while aortas grow rapidly in length, the medial elastin thickens slowly, perhaps due to slow development of hydrodynamic forces and pressures. Also the adventitial elastin appears to lose out gradually along the length from ascending aorta to abdominal aorta.

Aorta↗
PubMed1991

Piriformis syndrome--a case report.

Piriformis syndrome, a term applied to an abnormal condition of the piriformis muscle, is characterized by symptoms and signs due to sciatic nerve entrapment at the greater sciatic notch. Recently we reviewed a case of unusual low back pain, radiating to the left lower extremity with tenderness particular in the left buttock. The patient was successfully treated by sectioning the piriformis tendon. We described the clinical features of a case of piriformis syndrome and reviewed the foreign literature.

Humans↗
PubMed1991

Assessment of bone mineral density in postmenopausal and senile osteoporosis using quantitative CT.

The authors analyzed bone mineral density in 213 patients from January 1988 to September 1989. Bone mineral density of the vertebral body in the osteoporosis group of patients was compared with that in the normal group to investigate the correlation between bone mineral density and age distribution, and to estimate fracture threshold in the osteoporosis group. It was found that men, by linear regression, lose an average of 0.91% of bone per year, and women, by cubic regression, lose an average of 1.14% per year, accelerating at menopause. In the osteoporotic group, bone mineral density of men decreased an average of 29.7% compared with the non-osteoporotic group; that of women decreased an average of 29.9%. There was no difference between sexes. The fracture threshold of the osteoporotic patient was estimated to be about 90 mg/cm3.

Adult↗
PubMed1990

Detection of keratinolytic proteinase in skin tissues from guinea pigs infected with Microsporum canis by an immunoperoxidase technique.

An immunoperoxidase technique was performed to detect keratinolytic proteinase (KPase) in sections of the skin taken from guinea pigs infected with Microsporum canis and in cultured M. canis using polyclonal antisera to purified KPase. Of tissue samples from guinea pigs infected with M. canis, all sections of erythematous lesions showed positive staining mainly in the horny layer and the hair follicles. Positive depositions were seen only at the level of the outer and inner root sheaths of the hair follicles in sections of skin lesions showing scales and crusts. However, sections from areas of alopecia following desquamation of the crust showed no depositions of bright red reaction products. The patterns of deposition of KPase according to the clinical course of experimental dermatophytosis were consistent with the existence of organisms observed by PAS and methenamine silver stains. These results suggest that KPase may be produced during infection with M. canis after the development of erythema and before desquamation of the crust.

Animals↗
PubMed1988

Fast gradient-echo chemical-shift imaging.

A fast chemical-shift imaging using the gradient-echo technique is proposed for the separation of the water and fat in human in vivo imaging. This technique also incorporates magnetic field inhomogeneity correction in the fast chemical-shift imaging. Experimental results of the proposed imaging technique demonstrate that the method would be useful for quick in vivo water-fat separation imaging with a substantially shorter time than the conventional spin-echo imaging sequence.

Adipose Tissue↗
PubMed1988

Measurement of the magnetic susceptibility effect in high-field NMR imaging.

The magnetic susceptibility effect often obtained in clinical NMR imaging is analysed and a measurement method of the magnetic susceptibility effect is proposed. The method of extraction of the susceptibility effect alone in high-field NMR imaging where usually the chemical shift and main magnetic field inhomogeneity effects are intermingled with the susceptibility effect is discussed. The proposed susceptibility measurement uses the susceptibility weighted echo-time encoding technique (SWEET) to modulate the NMR signal as a function of echo time with which the image intensity can be weighted. Both phantom-oriented physical experiments and human volunteer experiments were performed to demonstrate the usefulness of the technique for human imaging.

Humans↗
PubMed1987

Gradient reversal technique and its applications to chemical-shift-related NMR imaging.

The chemical-shift effect often degrades slice selectivity thereby degrading the contrast and spatial resolutions in a high-field NMR imaging. We propose a new pulse sequence which can compensate for this chemical-shift effect during slice selection. This technique provides correct slice definition as well as clear separation between water and lipid protons in high-field proton NMR imaging. Particular applications of this technique are 2D imaging with a thin-slice selection and chunk 3D imaging, where correction of the chemical-shift effect in slice selection is important. Another interesting application of the technique is chemical-shift-selective (CHESS) imaging. This technique does not require spectral-selective rf pulses and it takes advantage of the chemical-shift effect during slice selection. The latter is found to be useful for human in vivo chemical-shift imaging in high-field NMR. In this paper, the theoretical derivation of the proposed gradient reversal technique, its applications, and related experimental results are presented.

Humans↗
PubMed1987

Methods and algorithms for Fourier-transform nuclear magnetic resonance tomography.

In nuclear magnetic resonance (NMR) imaging there are two main image formation approaches, the direct Fourier imaging method proposed by Kumar et al. [J. Mag. Res. 88, 69 (1975)] and the projection reconstruction technique commonly used in conventional computed tomography. In this paper these two approaches are reviewed with particular reference to Fourier-transform NMR imaging or tomography. Although Fourier imaging is the most conventional imaging method, useful applications for projection reconstruction techniques have often been found in NMR imaging. Therefore, in this paper, the emphasis is placed more on the projection reconstruction techniques that may not be readily available in NMR imaging.

Algorithms↗
PubMed1986

Real-value representation in inversion-recovery NMR imaging by use of a phase-correction method.

A new technique of real-value representation in inversion-recovery (IR) imaging by use of a phase-correction method is proposed. In this scheme, negative magnetizations at the beginning of the inversion point (T1 approximately equal to 0) are correctly represented as negative values rather than positive. By use of this new scheme, a consistent IR image set as a function of several inversion times (T1) can be obtained. The latter, i.e., consistent image set which represents the real value of T1 weighted images at several inversion times is important in the search for tumors and abnormalities since the inversion time (T1) in the pulse sequence strongly affects T1 contrast.

Brain↗
PubMed1986

Quadrature-multiplexed rf excitation for information doubling in NMR imaging.

A quadrature multiplexed pulse sequence to double the data information in a given acquisition time is proposed for NMR tomography. This technique takes advantage of the Hermitian property of the Fourier transform operation in NMR imaging. The proposed technique uses two rf pulses with 90 degrees phase difference simultaneously applied for the excitation of the spins in two different slices. The method results in truly simultaneous data acquisition coming from two different anatomical slices which can be separated into the real and imaginary parts of the image domain. This technique, therefore, also allows us either to reduce the experiment time by half or double the number of slices in the same examination time, depending on the applied imaging scheme. As a preliminary study, simultaneous dual-slice imaging of a human head using a conventional single-slice imaging scheme was performed.

Fourier Analysis↗
PubMed1985

Chemical-shift artifact correction scheme using echo-time encoding technique.

An investigation has been undertaken to study the effects of chemical shift on NMR image obtained by the projection reconstruction technique. Mathematical simulation studies indicate that chemical shift causes blurring in NMR images regardless of the image reconstruction technique. A systematic study of such artifacts is presented and possible correction schemes are proposed. Exemplary results with and without correction of the chemical-shift artifact and pulse schemes employed for projection reconstruction are presented. The present chemical-shift correction scheme is basically the same as a spectroscopic imaging technique such as the existing 4-D NMR imaging method except that the encoding steps required can be reduced substantially in the case of modest spectroscopic resolution.

Magnetic Resonance Spectroscopy↗
PubMed1985

Time-multiplexed multislice inversion-recovery techniques for NMR imaging.

Multislice imaging techniques effectively applicable to inversion-recovery (IR) imaging are developed and applied to human imaging. These new multislice IR imaging sequences employ the time-multiplexing (TM) technique conventionally used in the slice-by-slice saturation-recovery (SR) imaging. Two new time-multiplexed multislice (TMM) IR imaging sequences are proposed and some of the experimental results obtained with the methods are presented.

Humans↗