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Biomedical subjects

E K Yucel

Publications and source records attributed to E K Yucel.

At least 73 records · Page 4Linked to original sources
PubMed1992

Magnetic resonance angiography of the lower extremity and renal arteries.

Magnetic resonance angiography (MRA) has been used to image the arteries to the lower extremities and to the kidneys, with promising initial results. In the case of the lower extremity arterial system, MRA provides a first opportunity to obtain anatomic images in a completely noninvasive fashion, including evaluation of the iliac and tibial vessels, to supplement the hemodynamic measurements that are a routine part of the preoperative evaluation. In the case of renal artery stenosis, MRA may soon become the initial screening modality of choice, especially in patients with renal insufficiency, in whom contrast scintigraphy may have limited accuracy and in whom contrast angiography is relatively contraindicated.

Arterial Occlusive Diseases↗
PubMed1991

Isolated calf venous thrombosis: diagnosis with compression US.

Compression ultrasound (US) is an excellent means of evaluating the femoral and popliteal veins but is generally regarded as inadequate for the diagnosis of calf vein thrombosis. This prospective study evaluated compression sonography of the calf veins in 45 symptomatic patients with normal femoral and popliteal veins. All patients underwent correlative venography. Compression US enabled identification of 15 of 17 patients with calf vein thrombosis (sensitivity, 88%). The two false-negative results were in patients with small isolated thrombi. Compression US results were true-negative in 26 of 27 patients with normal venograms (specificity, 96%). If these results can be duplicated by other investigators in larger series of patients, compression US will be an adequate screening modality for calf vein thrombosis.

Acute Disease↗
PubMed1991

Transfemoral venous catheterization through inferior vena caval filters: results in seven cases.

Use of the transfemoral route for venous catheterization has been considered contraindicated in patients with inferior vena caval (IVC) filters. The transjugular route has been used instead in such patients when subsequent diagnostic or therapeutic procedures are required. Many radiologists, however, are more accustomed to the transfemoral approach, and may not find the transjugular route a desirable alternative. We describe seven patients with previously placed IVC filters in whom the transfemoral route was used to perform pulmonary arteriography (five patients) or to place additional IVC filters (two patients). After venographic confirmation of caval patency, filters were catheterized under fluoroscopic control and the procedures were performed. All procedures were technically successful; no complications occurred. We believe the transfemoral route to be a safe and feasible approach for performing venous procedures in selected patients with IVC filters, obviating the less familiar and potentially more hazardous transjugular approach.

Angiography↗
PubMed1991

Sonographic measurement of abdominal aortic diameter: interobserver variability.

Twenty-eight patients undergoing sonographic evaluation of the abdominal aorta were examined by two separate observers. Three measurements were obtained from each patient: the anteroposterior diameter from an axial image (APA), the right-left diameter from an axial image (RLA), and the anteroposterior diameter from a longitudinal image (APL). Calculation of the interobserver variability gave the following results (in mm): APL, 2.22; APA, 2.53; and RLA, 2.84. The calculated 95% confidence intervals for a single measurement (in mm) were APL, 4.35; APA, 4.94; and RLA, 5.58.

Aged↗
PubMed1990

Peripheral vascular and abdominal applications of MR flow imaging techniques.

Many MR flow imaging techniques that have been successfully applied in the carotid arteries and intracranial circulation have been tested in the peripheral and abdominal vasculature. The results have been variable. The lack of success can be attributed to different imaging requirements as well as different patterns of blood flow. These requirements include a large field of view, sensitivity to a wide range of blood flow velocities and complex flow directions, and suppression of overlapping vascular structures and stationary tissue. We have designed strategies using phase contrast MR angiography (MRA) for imaging the arteries and veins of the lower extremity and the abdominal vasculature in normal subjects. This strategy takes advantage of the pulsatile flow pattern present in normal arteries. Overlapping blood flow and stationary tissue were suppressed by a combination of spatial presaturation, optimization of the amplitude and duration of the velocity sensitive gradients, and postprocessing techniques.

Blood Flow Velocity↗
PubMed1990

Penetrating aortic ulcers: diagnosis with MR imaging.

The authors studied seven patients with penetrating aortic ulcers with use of magnetic resonance (MR) imaging. All patients were evaluated for acute chest symptoms, and the presence of aortic ulcers was confirmed by means of angiography in all seven patients. Five patients also underwent computed tomography (CT). Three patients underwent surgical repair of the thoracic aorta. MR findings included intramural hematoma and focal aortic wall ulceration in four patients, focal ulceration in one, focal intramural hematoma in one, and focal intramural hematoma with rupture in one. The diagnosis of intramural hematoma was made by the detection of increased signal intensity on T1- and T2-weighted MR images. MR imaging was superior to angiography in depicting the extent of intramural thrombus, although one ulceration diagnosed at angiography was missed at MR imaging. MR imaging was superior to CT in differentiating acute intramural hematoma from atherosclerotic plaque and chronic intraluminal thrombus, although it did not depict displaced intimal calcification in one patient with extensive intramural hematoma.

Aged↗
PubMedDate not supplied

MR angiography of lower-extremity arterial disease: preliminary experience.

Nineteen patients underwent magnetic resonance (MR) angiography for evaluation of lower-extremity arterial disease. The underlying conditions included atherosclerotic occlusive disease in 12 patients, femoral or popliteal aneurysms in four, and bypass graft stenoses or occlusion in four. In the patients with occlusive disease, the iliac and femoropopliteal vessels were classified as patent, moderately stenotic, severely stenotic, or occluded. Fifteen of 16 occlusions (accuracy = 94%) were correctly classified. In the one missed case, there was a long delay between MR angiography and x-ray angiography and it is likely that the occlusion occurred during the interval. Three of five severe stenoses were correctly classified with MR angiography. In two cases of iliac artery stenosis, there was a signal void at the point of maximal stenosis, which on the basis of anatomic features could be recognized as severe stenosis rather than an occlusion. Three of four moderate stenoses were correctly classified. Correlation with x-ray angiography or surgery demonstrated the ability of MR angiography to accurately depict the status of runoff vessels.

Adolescent↗
PubMedDate not supplied

Dynamic gadolinium-enhanced three-dimensional abdominal MR arteriography.

The abdominal aorta and renal, visceral, and iliac arteries were evaluated in 16 patients with three-dimensional Fourier transform imaging enhanced with gadopentetate dimeglumine. By imaging dynamically during the arterial phase of a 5-minute injection (0.2 mmol/kg), highly significant (P < .0001) preferential arterial enhancement (signal-to-noise ratio +/- standard deviation, 10 +/- 0.9), with minimal enhancement of the inferior vena cava (5.1 +/- 1.4) or background tissues (fat, 4.3 +/- 0.7; muscle, 2.4 +/- 0.5), was achieved in every patient. In six patients with angiographic and/or surgical correlation, 10 of 10 stenoses and two of two occlusions were correctly identified. No in-plane saturation or pulsatility artifact was identified in any of the 16 patients. In conclusion, dynamic imaging during the injection of gadopentetate dimeglumine is a promising technique for evaluation of the abdominal aorta and branch vessels.

Abdomen↗
PubMedDate not supplied

Multislice T1-weighted hybrid RARE in CNS imaging: assessment of magnetization transfer effects and artifacts.

Using a T1-weighted hybrid rapid acquisition with relaxation enhancement (RARE) MR sequence that implements an echo-to-view mapping scheme termed "low-high profile order," we evaluated signal intensity changes in different brain tissues as a function of number of slices, interslice gap, and echo train length (ETL). We also measured phase-encode and frequency-encode noise as well as blurring artifacts along the phase-encode direction as a function of ETL. Off-resonance magnetization transfer effects were demonstrated to be responsible for signal intensities changes in white matter and gray matter when using multislice techniques. These effects are amplified by increasing the number of slices and ETL. Due to the nature of the implemented echo-to-view mapping scheme, no on-resonance magnetization transfer effects were observed from the intraslice echo train. Selective background (white matter and gray matter) suppression in multislice T1-weighted hybrid RARE, secondary to off-resonance magnetization transfer effects, may provide better contrast resolution of enhancing central nervous system (CNS) lesions at much shorter scan time as compared to conventional spin-echo T1-weighted sequences. This improvement in contrast resolution as a function of ETL may be limited by worsening phase-encode noise and blurring artifacts.

Artifacts↗
PubMedDate not supplied

Black-blood MR angiography with GRASE: measurement of flow-induced signal attenuation.

We investigated the feasibility of performing black-blood MR angiography (MRA) with the gradient and spin-echo (GRASE) pulse sequence. Phantom experiments and human testing were conducted, and the results were compared with those of turbo spin-echo (TSE). We demonstrated that both techniques are able to produce signal suppression of flowing fluid to background level. With fewer radiofrequency (RF)-refocusing pulses, GRASE pulse sequences could serve as an alternative black-blood technique of reduced RF power exposure and shorter scan time. These relative advantages of GRASE may become useful when high-resolution images are taken.

Blood Flow Velocity↗
PubMedDate not supplied

In vivo determination of human arterial compliance: preliminary investigation of a new technique.

PURPOSE: To obtain more detailed information about the dynamic mechanical properties of human arteries in vivo, using a new technique based on intravascular ultrasound. (IVUS). METHODS: Arterial compliance was measured in the common and/or external iliac arteries of 6 patients using an IVUS device, concurrently obtained intraarterial pressure measurements, and a video motion analysis system. RESULTS: Compliance decreased with increasing vessel diameter and mean arterial pressure. Pre- and postangioplasty measurements were obtained in 2 patients but did not demonstrate a consistent change in compliance following angioplasty. CONCLUSION: We conclude that IVUS provides an accurate means for in vivo determination of human arterial compliance, the practical value of which needs to be established.

Adult↗
PubMedDate not supplied

STIR imaging of synthetic vascular graft infection.

Nine patients with suspected prosthetic vascular graft infection were studied with axial spin echo (SE) and short TI inversion recovery (STIR) magnetic resonance imaging. Images were assessed for presence and extent of abnormality. All patients had either surgical (8/9) or bacteriologic (6/9) confirmation of infection. STIR images better defined the extent of infection and had greater fat-fluid contrast than SE images in 6/9 studies. In 3 cases with peri-graft fluid alone, T2-weighted images had slightly greater contrast, although the STIR images were still diagnostic. STIR imaging can offer improved accuracy in evaluation of suspected prosthetic graft infection when used in conjunction with SE techniques.

Adipose Tissue↗