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Biomedical subjects

H C Yoon

Publications and source records attributed to H C Yoon.

25 records · Page 2Linked to original sources
PubMed1996

MR angiography for mapping potential central venous access sites in patients with advanced venous occlusive disease.

OBJECTIVE: Patients who depend on long-term central venous catheter support frequently develop thrombi in central veins. An accurate, noninvasive technique is needed to find patent central veins for future access. We evaluated the suitability of MR angiography for this use. SUBJECTS AND METHODS: Using five healthy volunteers and 19 patients who had malfunctioning central venous catheters and a history of central venous occlusive disease, we tested the ability of MR angiography to assess central vein status. Three radiologists experienced in MR angiography blindly interpreted both source images and three-dimensional reconstructed images. RESULTS: In the volunteers, MR angiography provided diagnostic-quality images of the internal and external jugular, innominate, subclavian, axillary, femoral, and iliac veins, and of the superior and inferior venae cavae. Interobserver interpretations did not vary. In the patients, MR angiography of venous patency was confirmed by venography in 27 segments, by sonography n 32 segments, and by attempted line placement in 21 placements. Images were diagnostically adequate in 206 of 216 segments (95%). For detection of occlusion, sensitivity was 97% and specificity was 94%. MR angiography predicted 100% of successful line placements and 80% of failures. Interobserver interpretations varied by 44%. MR angiography directly influenced therapy in 19 of 21 studies. CONCLUSION: We conclude that MR angiography provides risk-free, thorough, relatively accurate, and clinically useful assessment of most available central venous access sites, although interpretation may prove difficult in patients with extensive occlusions because of complex collateral drainage patterns.

Adolescent↗
PubMedDate not supplied

Limited abdominal MRI in the evaluation of acute right upper quadrant pain.

BACKGROUND: We investigated whether limited abdominal magnetic resonance imaging (MRI) is as effective as transabdominal ultrasound (US) in evaluating patients presenting with acute right upper quadrant pain. METHODS: Twenty-four patients underwent evaluation with a limited abdominal MRI using single-shot fast spin-echo sequences and a right upper quadrant US within 24 h. Two MRI and two US readers independently evaluated the images for gallstones, gallbladder wall thickness, pericholecystic fluid, acute cholecystitis, visualization of the common bile duct, and requests for further imaging. US and MRI findings were compared. Surgical pathology was the gold standard. RESULTS: MRI and US demonstrated no statistically significant difference in the diagnosis of gallbladder wall thickening, the presence of gallstones or pericholecystic fluid, or the diagnosis of acute cholecystitis (p > 0.05). The sensitivity of both for acute cholecystitis was 50%, with specificities of 89% and 86% for US and MRI, respectively. US readers more frequently requested additional tests and displayed more variability in whether they could adequately see the common bile duct. CONCLUSION: Limited MRI is equivalent to US in diagnosing gallstones, gallbladder wall thickening, pericholecystic fluid, and acute cholecystitis in patients presenting with symptoms of acute right upper quadrant pain. Especially in sonographically challenging patients, limited MRI may provide a faster, easier method of diagnosis.

Abdomen, Acute↗
PubMedDate not supplied

Prevention of significant hemobilia during placement of transhepatic biliary drainage catheters: technique modification and initial results.

PURPOSE: The authors evaluated a technique for the prevention of significant hemobilia during placement of transhepatic biliary drainage catheters (TBDCs). PATIENTS AND METHODS: Twenty patients with strictures were randomized to two groups. In the control group, the biliary tree was accessed with an Accustick system and a TBDC was placed routinely. In the experimental group, following initial access, a rotating hemostatic valve was attached and the outer sheath was pulled back over the wire while contrast material was injected. If a major vascular structure was encountered, the tract was not used for TBDC placement. However, the outer sheath was re-advanced and used to opacify the ducts. This facilitated separate access. Once access was achieved without traversing a major vascular structure, a TBDC was placed, and the Accustick system was removed. If a portal vein or hepatic vein branch was traversed, no additional maneuvers were performed. However, if a branch of the hepatic artery had been traversed, the tract and biliary-arterial fistula were embolized with gelatin sponge pledgets. Both groups were evaluated for hemobilia for 6 weeks. RESULTS: In the control group, there were three cases of significant hemobilia; two were mild, one was severe. In the experimental group, the tract communicated with a major vascular structure in three patients. In these patients, a second access was used for TBDC placement. None of the patients in the experimental group experienced significant hemobilia. CONCLUSION: Visualization prevents the usage of tracts that communicate with large vascular structures. Initial results indicate that this reduces the frequency of significant hemobilia when TBDCs are placed.

Adolescent↗
PubMedDate not supplied

A porcine model of chronic peripheral arterial occlusion.

PURPOSE: To create a simple and reproducible model of chromic thrombosis for the evaluation of thrombolytic agents and devices. MATERIALS AND METHODS: A stenosis was created in the superficial femoral artery of domestic swine, and autologous blood clot was deposited above the stenosis. Follow-up last for up to 3 months. Degree of clot organization was determined at histologic examination. Two thrombolytic agents, urokinase and collagenase, were used to test this model. RESULTS: There was a 27% delayed recanalization rate with this model. At histologic examination, early thrombus organization was seen at the vessel periphery after 10 days. One-month-old thrombus was substantial but variable in amount. Three-month-old thrombus was completely organized. Neither urokinase nor collagenase proved effective against chronic clot in the doses and time course of this study. CONCLUSION: This simple method yields a chronic porcine clot in a reliable number of domestic swine in 1 month.

Animals↗
PubMedDate not supplied

Prevention of hemobilia during percutaneous biliary drainage: long-term follow-up.

PURPOSE: The authors evaluated a technique for the prevention of hemobilia when placing transhepatic biliary drainage catheters (THBDCs). MATERIALS AND METHODS: Initially, 20 patients were randomized into two groups. In the control group, a THBDC was placed after blind needle passage without contrast material opacification of the needle tract. In the experimental group, the tract was studied and then abandoned if a major vascular structure was encountered. Once a tract was found that did not traverse a major vascular structure, a THBDC was placed. An additional 35 patients undergoing 40 procedures were studied with use of the technique as outlined for the original experimental group. The original experimental group patients and the additional 35 patients were followed for up to 3 years. RESULTS: There were three cases of hemobilia in the initial control group. None of the patients in the initial experimental group experienced hemobilia. In the additional 35 patients, there were three cases of bloody drainage from the THBDC; however, the etiology of hemobilia was not secondary to transgression of a vascular structure. CONCLUSION: Visualization of the tract prevents the usage of tracts that communicate with large vascular structures. This technique reduces the incidence of hemobilia when placing THBDCs.

Adolescent↗
PubMedDate not supplied

Intraluminal irradiation for TIPS stenosis: preliminary results in a swine model.

PURPOSE: To evaluate the ability of 32phosphorus intraluminal irradiation to reduce pseudointimal hyperplasia in a transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: TIPS were successfully placed in 11 swine with normal portal pressures. Six animals received 15.2 Gy intraluminal irradiation to the hepatic parenchyma and venous outflow tract at the time of TIPS placement with use of a NA32P-filled balloon angioplasty catheter. Five control animals underwent TIPS and balloon angioplasty with saline. All animals were followed up for 28 days, at which time percutaneous portography was performed, the animals were killed, and the tissue around the TIPS stent was processed for histologic analysis. Maximum pseudointimal hyperplasia as a percentage of estimated TIPS diameter was calculated for each animal. RESULTS: At the time of euthanasia, all five control TIPS and all but one irradiated TIPS were occluded. Histologic analysis demonstrated considerable variability in the degree of pseudointimal hyperplasia within each TIPS and between animals. No statistically significant difference was found in the maximum pseudointimal hyperplasia, measured as a percentage of stent radius, between control (80.2%+/-17.4%) and irradiated animals (69.2%+/-25.2%). CONCLUSIONS: Irradiation of TIPS with 15.2 Gy 32P delivered at the time of TIPS placement did not significantly improve TIPS patency or reduce the degree of pseudointimal hyperplasia in swine with normal portal pressures.

Angioplasty, Balloon↗