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Biomedical subjects

C Yuan

Publications and source records attributed to C Yuan.

At least 91 records · Page 5Linked to original sources
PubMed1996

Magnetic resonance imaging to study lesions of atherosclerosis in the hyperlipidemic rabbit aorta.

We have developed a high resolution magnetic resonance (MR) imaging technique to serially assess lesions of atherosclerosis in a rabbit model. A volume phased array coil was designed and used to image the abdominal aortas of six atherosclerotic rabbits and two age-, sex-, and weight-matched controls. Lesions of atherosclerosis were induced by a combination of repeat balloon injury and a hyperlipidemic diet. All animals were imaged on at least two occasions 9-16 months after initiation of atherosclerosis. In addition, animals were imaged immediately after sacrifice. Anatomic dissection and histology were performed to verify the MR findings. The volume phased array coil improves the image signal-to-noise ratio over existing extremity coils and resulted in higher resolution images of the abdominal aorta. Proton density-weighted images acquired with 2D/3D fast spin-echo are the most useful sequence to outline the vessel wall and to differentiate wall from lumen and background. Progressive wall thickening and lumen stenosis were observed in the serial images of the diseased rabbits. Wall thickness and lumen area derived noninvasively from the in vivo MR images correlate with postmortem MR images and sections of aorta examined by dissection microscopy and histology. Spin-echo and fast spin-echo imaging with a phased array body coil can be used to accurately assess plaque dimensions, and potentially can be used to image intraplaque features and to monitor lesion progression or regression. It should also be possible to adapt these techniques to assess human disease, especially for peripheral vascular problems.

Animals↗
PubMed1996

MR angiography of the peripheral vasculature.

MR angiography (MRA) for the evaluation of peripheral arterial occlusive disease is a rapidly evolving technique. Recent prospective clinical trials have indicated that MRA may play an important role in the evaluation of patients with peripheral arterial disease. This article discusses the pertinent technical aspects and limitations of peripheral MRA as well as some of the clinical data available.

Angiography↗
PubMed1996

[Surgical treatment of juxta-renal abdominal aortic occlusion: report of 27 cases].

Juxta-renal abdominal aortic occlusion is a relatively rare disease. We have treated 27 patients (25 males and 2 females) since 1984. Operations were performed on 25 patients, of whom 4 died and 84% improved. The main etiology was aorto-iliac stenosis or occlusion due to atherosclerosis and Takayasu's arteritis. Diagnostic basis included ischemia of lower limbs, pulselessness of abdominal aorta and both femoral arteries, sexual dysfunction, and positive result of angiography. Effective control of aorta below the left renal vein, aortotomy and retrograde endarterectomy were the main operative procedures. Axillo-bifemoral arterial bypass is recommended for patients associated with multiple diseases. The operative result is determined by associated diseases and the condition of run-off vessel. Associated diseases directly affect the mortality rate.

Adult↗
PubMed1995

Two prototype blood-pool agents for contrast-enhanced magnetic resonance angiography of the portal vein in pigs.

RATIONALE AND OBJECTIVES: Macromolecular "blood-pool" agents such as polylysine-gadopentetate dimeglumine or albumin-gadopentetate dimeglumine, which provide prolonged intravascular enhancement, were tested as magnetic resonance (MR) angiography contrast agents for the portal vein in pigs. METHODS: Phase-contrast MR angiography of the portal veins was performed on six pigs before and after intravenous administration of polylysine-gadopentetate dimeglumine (n = 3) or albumin-gadopentetate dimeglumine (n = 3). RESULTS: The contrast-to-noise ratio of the portal veins was improved by 74% and 52%, respectively, using polylysine-gadopentetate dimeglumine or albumin-gadopentetate dimeglumine. More branches of the intrahepatic portal veins were visualized on postcontrast images. CONCLUSION: Blood-pool paramagnetic contrast agents improved the visualization of hepatic vasculature using phase-contrast MR angiography in our experimental model.

Albumins↗
PubMed1995

Serial magnetic resonance imaging of experimental atherosclerosis detects lesion fine structure, progression and complications in vivo.

A major problem in the study of lesions of atherosclerosis is the difficulty of imaging noninvasively the lesions and following their progression in vivo. To address this problem, we have developed advanced magnetic resonance techniques to noninvasively and serially image advanced lesions of atherosclerosis in the rabbit abdominal aorta. Both lumen and wall were imaged with high resolution. Progression of disease, resulting in increase in lesion mass, decrease in arterial lumen, or stenosis, and intralesion complications, can be detected. Images acquired in vivo correlate with the fine structure of the lesions of atherosclerosis, including the fibrous cap, necrotic core, and lesion fissures, as verified by gross examination, dissection microscopy, and histology. The ability to noninvasively identify the features of atherosclerotic plaques, has significant implications for determining risks and benefits associated with different therapeutic approaches.

Animals↗
PubMed1995

Workplace assaults on minority health and mental health care workers in Los Angeles.

Workplace violence is becoming increasingly recognized as a serious problem in health care settings. All 628 workers' compensation assaults claimed by minority Los Angeles County health care workers from 1986 through 1990 were abstracted. Population-at-risk data from county personnel computer tapes provided denominators by age, sex, race, job classification, and type of facility. Rates varied by type of facility (rate ratio = 38 for psychiatric hospitals vs public health facilities) and varied by job, with inpatient nursing attendants having the highest rate for caregivers. Most assaults were committed by patients (86%), followed by coworkers (8%). The average cost of an assault ($4879) was relatively low but related to the costlier problem of work-related emotional illness.

Absenteeism↗
PubMed1995

Evaluation of the portal venous system before liver transplantation: value of phase-contrast MR angiography.

OBJECTIVE: The purpose of this study was to assess the accuracy of phase-contrast MR angiography with gadolinium in evaluating the patency and blood flow direction of the portal venous system; the presence, extent, and type of varices; and the patency of surgical decompressive shunts in patients before liver transplantation. This information is essential in management and care of patients with chronic liver disease and portal hypertension and those who are candidates for liver transplantation. SUBJECTS AND METHODS: Twenty-four patients with portal venous hypertension were evaluated with phase-contrast MR angiography. Two patients had surgical splenorenal shunts and one had a mesocaval shunt. Phase-contrast angiograms were acquired as a series of two-dimensional sequential coronal sections during breath-holding and after IV administration of gadopentetate dimeglumine. Correlative findings from color flow Doppler sonography, contrast-enhanced CT scanning, and conventional angiography were available in 23, 20, and 10 patients, respectively, and were used as standards. The images from each technique were analyzed independently for patency of and flow direction in the portal vein, splenic vein, superior mesenteric vein, and surgically created shunts, and for detection, distribution, and extent of five variceal groups. RESULTS: Findings from phase-contrast MR angiography completely agreed with those of sonography, CT scanning, and conventional angiography. The main portal vein was patent in 18 patients, stenosed in one, partially thrombosed in one, and occluded in four. Phase-contrast MR angiography correctly showed hepatofugal flow in three patients and hepatopetal flow in 17 patients. Both the splenic and superior mesenteric veins were patent in 20, partially thrombosed in one, and occluded in three cases. Phase-contrast MR angiograms showed 85% of the variceal groups, and MR rating of variceal size was not significantly different from that of CT rating. Phase-contrast MR angiography correctly showed the patency of all three surgical decompressive shunts. CONCLUSION: Phase-contrast MR angiography is accurate for evaluating the patency and flow direction of the portal venous system, detecting and determining the distribution and extent of varices, and assessing the patency of surgically created shunts. Therefore, it is a reliable and noninvasive technique that can provide crucial information in the preoperative workup of liver transplant recipients.

Adult↗