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Biomedical subjects

Y S Yoon

Publications and source records attributed to Y S Yoon.

66 records · Page 4Linked to original sources
PubMed1984

MR imaging of the skull base.

Fifty-four patients with abnormalities primarily involving the base of the skull were evaluated by magnetic resonance (MR) imaging. The results were compared with information obtained by other radiologic studies, primarily X-ray CT. On MR imaging, better anatomic definition of soft tissues in the deep compartments of the nasopharynx was achieved through the high level of tissue contrast discrimination and lack of bone artifacts. The parapharyngeal fat plane, separating pterygoid from pharyngeal musculatures, was consistently demonstrated. However, the inability of MR to image compact bone proved to be a major drawback where bony detail was required. In general, MR imaging demonstrated 100% sensitivity to abnormalities involving the posterior compartment (clivus and craniovertebral junction) and was least valuable in the evaluation of the anterior compartment (orbits, cribiform plate, and sinuses.

Adolescent↗
PubMed1984

Magnetic resonance imaging in the spinal column and craniovertebral junction.

The sensitivity of magnetic resonance imaging (MRI) to tissue alterations is particularly useful in spinal cord imaging. In addition to excellent anatomic display of this compact and complex area, syrinx cavities, tumors, and degenerating disks can be identified before they cause the anatomic distortion often necessary for detection by conventional means.

Astrocytoma↗
PubMed1984

Nuclear magnetic resonance imaging in Legg-Calvé-Perthes disease.

We employed nuclear magnetic resonance imaging in the evaluation of fourteen children with Legg-Calvé-Perthes disease, and found that it accurately identified infarction of the femoral head and, with appropriate techniques, could produce an arthrogram-like image of the hip without the use of ionizing radiation or injection of a contrast agent. Partial saturation-recovery and inversion-recovery pulse sequences with two-dimensional Fourier transformation produced the best results. Nuclear magnetic resonance scanning provides a noninvasive method for the study of the contours of the hip joint, and may give clearer insight into the pathophysiology of infarction and revascularization.

Cartilage, Articular↗
PubMed1983

Total therapeutic embolization of the kidney for hypertension in a child with a mycotic aneurysm.

A 7-year-old boy with bacterial endocarditis developed renal artery mycotic aneurysm and diffuse distal occlusions of the renal branches. Blood pressure in the patient returned to normal after obliteration of flow to the left kidney with Gelfoam, Ivalon, and a Gianturco coil. An end loop of the coil used for embolization remained in the lumen of the aorta against its lateral side. Improper coil placement did not result in complications; the boy later died due to neurologic and pulmonary complications. We discuss the therapeutic potential of renal embolization, as well as the risks of particulate and ethanol embolization, in the treatment of renal vascular hypertension from mycotic aneurysms.

Aneurysm, Infected↗
PubMed1982

The passive elastic moment at the hip.

The passive elastic moment at the hip was measured in normal male subjects in situ. The influence of two joint muscles crossing the hip was evaluated by performing hip moment measurements over a continuous range of hip angles and at prescribed knee angles. The experimentally acquired data was fitted by exponential functions which separately modeled the moment contribution of tissues deformed by hip flexion and extension. The results of the investigation are discussed with regard to the possible role of the passive joint moments as an energy storage and release mechanism during human walking.

Adult↗
PubMedDate not supplied

MR imaging of pediatric cerebral abnormalities.

One hundred sixteen magnetic resonance (MR) imaging studies from 105 pediatric patients with a variety of cerebral abnormalities were reviewed to determine the diagnostic efficacy of MR in the pediatric population. All subjects tolerated the MR procedure well, although sedation was necessary for younger children. Compared with CT, MR proved to be advantageous in detection and characterization of the pathology in 23 of 105 patients, especially when the abnormality was located along the base of the brain and midline, or when it involved primarily the white matter. Intracranial calcification was the one abnormality not detected with MR although dense calcifications could be seen as areas of low signal intensity. Some characteristics of various pathological entities were compared in an attempt to differentiate among abnormalities in the same anatomical location: craniopharyngioma from optic chiasm and hypothalamic glioma, cystic glioma from arachnoid cyst, and chronic subdural hematoma from subdural hygroma. The lack of ionizing radiation in MR is of particular interest in pediatric neuroradiology since radiation is of special concern in the young age group.

Adolescent↗
PubMedDate not supplied

Development of digoxin dry elixir as a novel dosage form using a spray-drying technique.

A rapidly absorbed new novel oral dosage form for digoxin termed 'digoxin dry elixir' was developed by the spray-drying technique. Digoxin, dextrin and sodium lauryl sulphate were dissolved in a ethanol-water mixture (20:25 w/w) and therefore spray-dried to form the digoxin dry elixir. According to scanning electron micrographs, digoxin dry elixir is spherical in shape with a smooth surface. The geometric mean diameter of dry elixir determined by laser particle size analysis was about 13 microns. The appearance and flow properties were almost unchanged and about 10% of ethanol contents in the dry elixir decreased during 180 days in a sealed bottle at room temperature. Comparative studies on the in vitro dissolution and in vivo absorption of digoxin in the form of digoxin dry elixir, digoxin elixir and digoxin powder were carried out. Digoxin in the dry elixirs was completely dissolved within 2 min. On the other hand, only about 87% of digoxin powder dissolved in 60 min. The initial dissolution rates of digoxin in the dry elixirs markedly increased in distilled water at 37 degrees C, which were over 100 fold higher than that of digoxin powder alone. The maximal plasma concentration of digoxin (Cmax) and area under the digoxin concentration-time curve from zero to 6 h (AUC0-6h) after the oral administration of digoxin dry elixir were almost 3.8 and 5.5 fold increased compared to digoxin powder alone. No significant difference of AUC0-6 h between dry elixir and elixir was observed, but the Cmax of digoxin in the form of dry elixir was significantly reduced compared to the digoxin elixir (0.57 versus 0.83). Digoxin dry elixir might be a useful solid dosage form to improve the dissolution rate and bioavailability of poorly water-soluble digoxin compared to digoxin powder alone. It also indicates that dry elixir might reduce the side effects in oral digitalis glycoside therapy compared to the digoxin elixir due to the reduction of Cmax.

Animals↗
PubMedDate not supplied

The role of functional MR imaging in patients with ischemia in the visual cortex.

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging is based on changes in regional blood flow. The purpose of this study was to evaluate the role of fMR imaging for detection of a vascular compromised status in the occipital lobe in patients with ischemia in the visual cortex. METHODS: We performed fMR imaging in seven control subjects and seven patients with symptoms and signs of visual cortical transient ischemia and/or infarct. fMR imaging was performed using a gradient-echo sequence with the 2D fast low-angle shot technique. An axial slice including both visual cortices was selected, and stimulation of the visual cortex was performed using a red photostimulator. The number of activated pixels in each primary visual cortex area were counted and an asymmetry ratio [AR (%) = 100 x (R-L)/(R+L)/2] was calculated. Patients and control subjects underwent visual field examination, conventional MR imaging, and vascular imaging (MR angiography in all patients and control subjects, conventional catheter angiography in two patients). fMR imaging results were compared with the results of a visual field examination, conventional MR imaging, and vascular imaging. RESULTS: fMR imaging of the patients showed significant activation asymmetry (P <.05) compared with that of control subjects. Vascular abnormalities in the posterior circulation were found in all seven patients. By conventional MR imaging, five patients were found to have infarction in the occipital lobe and the remaining two patients showed no abnormality. In visual field examination, six of the seven patients showed homonymous hemi- or quadrantanopsia suggesting postchiasmic abnormalities, and the remaining patient had normal findings. fMR imaging showed decreased activity in the visual cortices corresponding to vascular abnormalities (seven of seven patients), permanent infarction (five of seven patients), or visual field defect (six of seven patients). Two patients with normal conventional MR imaging had vascular lesions in the posterior circulation, and fMR imaging showed decreased activity in the corresponding visual cortices. One patient with normal visual field examination had multifocal stenosis in the posterior cerebral artery without infarction, and fMR imaging showed decreased activity in the corresponding visual cortex. CONCLUSION: fMR imaging of the visual cortex may be a sensitive method for the detection of vascular-compromised status in the occipital lobe.

Adult↗