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Biomedical subjects

D C Levin

Publications and source records attributed to D C Levin.

At least 109 records · Page 6Linked to original sources
PubMed1984

Digital subtraction angiography: principles and pitfalls of image improvement techniques.

The technology of imaging methods in digital subtraction angiography (DSA) is discussed in detail. Areas covered include function of the video camera in both interlaced and sequential scan modes, digitization by the analog-to-digital converter, logarithmic signal processing, dose rates, and acquisition of images using frame integration and pulsed-sequential techniques. Also discussed are various methods of improving image content and quality by both hardware and software modifications. These include the development of larger image intensifiers, larger matrices, video camera improvements, reregistration, hybrid subtraction, matched filtering, recursive filtering, DSA tomography, and edge enhancement.

Angiography↗
PubMed1983

Causes of cine image quality deterioration in cardiac catheterization laboratories.

Deterioration of cineangiographic image quality can result from malfunctions or technical errors at a number of points along the cine imaging chain: generator and automatic brightness control, x-ray tube, x-ray beam geometry, image intensifier, optics, cine camera, cine film, film processing, and cine projector. Such malfunctions or errors can result in loss of image contrast, loss of spatial resolution, improper control of film optical density (brightness), or some combination thereof. While the electronic and photographic technology involved is complex, physicians who perform cardiac catheterization should be conversant with the problems and what can be done to solve them. Catheterization laboratory personnel have control over a number of factors that directly affect image quality, including radiation dose rate per cine frame, kilovoltage or pulse width (depending on type of automatic brightness control), cine run time, selection of small or large focal spot, proper object-intensifier distance and beam collimation, aperture of the cine camera lens, selection of cine film, processing temperature, processing immersion time, and selection of developer.

Cineangiography↗
PubMed1983

Transcatheter embolotherapy for congenital renal arteriovenous malformations. Long-term follow-up.

Transcatheter embolization was performed five times in 3 patients with congenital renal arteriovenous malformations (AVM). The patients were followed for one to seven and a half years. Two patients whose AVM were completely occluded with Gelfoam have been asymptomatic with no evidence of hematuria. A third patient, embolized with Gelfoam and Ivalon without complete occlusion of the AVM, bled ten months after the first procedure, was re-embolized, and later had the AVM removed surgically. Superselective transcatheter embolization should be the initial treatment modality for congenital AVM with the aim to control bleeding and occlude those malformations supplied by the terminal portion of interlobar arteries. Large malformations supplied by multiple feeders may require operative ligation and removal of the AVM when vessels cannot be occluded satisfactorily because of massive shunting.

Adult↗
PubMed1983

Compound angulation for the angiographic evaluation of renal artery stenosis.

The increasing role of percutaneous transluminal angioplasty in the therapy of renal artery stenosis has, in turn, emphasized the need to optimize imaging of the entire length of the main renal artery and its major branches. The usual angiographic positioning techniques for anteroposterior and oblique views may not be adequate to define the precise location and extent of a stenosis. The authors combine oblique projections with sagittal angulation of the x-ray tube to augment the standard imaging methods for selective renal arteriography.

Angiography↗
PubMed1983

The reliability of angiography in predicting quality and caliber of the distal coronary artery lumen in preparation for bypass surgery.

To determine whether coronary arteriograms accurately predict the presence of distal coronary lumena that are inadequate for bypass because of diffuse disease and/or small caliber, angiographic grading of distal lumen (DL) caliber was carried out on 867 diseased coronary arteries on which bypass was subsequently attempted. Where the DL was graded as normal, bypasses could be successfully constructed in 96% of cases. Where the general DL caliber was normal but one or more localized distal stenoses were present, bypasses could be successfully constructed in 95.6% of cases. Where the DL caliber was reduced to a mild-moderate degree angiographically, bypasses were successfully constructed in 83.6%. Where the DL had a severely reduced caliber or could not be visualized at all, bypasses were successfully constructed in 73.0%. Thus, even when a severely narrowed or totally occluded DL appears present, bypass can still be performed in almost 75% of cases. The angiographic diagnosis of a nongraftable distal segment is therefore unreliable and patients should not be denied bypass on this basis alone.

Coronary Angiography↗
PubMed1983

Bronchoscopic diagnosis of pulmonary infections. Comparison of protected-specimen brush and cytology brush with lung aspirates.

In a recent study the use of a new plugged double-lumen protected-specimen brush with the flexible fiberoptic bronchoscope was advocated to isolate pathogens in lower respiratory tract infections while avoiding upper respiratory tract contamination. To compare the efficacy of this brush and a standard single-lumen cytology brush in identifying the etiologic agent in lower respiratory tract infections, we studied 18 patients with lung infections. Transthoracic lung aspiration was done in all but two patients in an attempt to identify the specific etiologic agent. In these two cases, cultures of specimens of blood or postmortem lung tissue yielded the causative organism. In 12 patients anaerobic or aerobic bacteria (or both) were identified, whereas one patient had a mixed bacterial and fungal infection. Using the cytology brush and the protected-specimen brush we identified at least one pathogen in 10 of 12 and 10 of 13 cases, whereas both brushes missed one or more causative organisms in 8 of 12 and 8 of 13 cases, respectively. Nonetiologic organisms were found in 8 of 12 cases by the cytology brush and 8 of 13 cases by the protected-specimen brush. Quantitative culture techniques improved the specificity of the brush results in infections where aerobes predominated. Our data show that bronchoscopic cultures of lower respiratory tract infections do not consistently recover the causative agent and are frequently subject to contamination by nonetiologic organisms. There was no difference between the brushes in avoiding contamination.

Adolescent↗
PubMed1982

Evaluation of coronary bypass grafts.

Coronary artery bypass graft (CABG) surgery is in widespread use. Bypass graft angiography continues to be an integral part of the evaluation of the post-CABG patient. Future methods may include computed tomography and digital subtraction angiography to assist in this evaluation.

Coronary Angiography↗
PubMed1982

Angiography of nonneoplastic retroperitoneal masses.

Although noninvasive imaging modalities can be used to initially detect retroperitoneal masses, angiography is still desirable for several reasons in those cases in which surgery is contemplated. The latter can forewarn the surgeon as to possible hemorrhagic complications in highly vascular lesions. In some cases it can predict the malignant potential of the lesion. Finally, since these masses may derive blood supply from multiple sources, a vascular "road map" is provided to the surgeon. The angiographic findings of malignant retroperitoneal tumors are well known, but very little has been published dealing with benign nonneoplastic retroperitoneal masses. We have performed angiography in 11 surgically proven nonneoplastic retroperitoneal masses (9 inflammatory lesions, 2 hematomas). Major arterial or renal displacement occurred in 10. The 2 hematomas and 3 inflammatory lesions were totally avascular; 6 of the 9 inflammatory lesions revealed fine neovascularity and 5 of these 6 had an associated capillary blush. Sources of vascular supply included the lumbar, renal capsular, superior mesenteric, and gastroduodenal arteries. Although angiography is helpful in preoperative evaluation of retroperitoneal masses for the aforementioned reasons, it may be difficult or impossible to differentiate benign from malignant lesions based on the angiographic findings alone.

Abscess↗
PubMed1982

Incomplete myocardial reperfusion despite a patent coronary bypass: a generally unrecognized shortcoming of the surgical approach to coronary artery disease.

When assessing a coronary artery bypass graft, the patency rate is virtually the sole criterion of success. However, this fails to identify grafts which are patent by incompletely reperfuse the diseased vessel. Angiograms of 82 patients with 172 bypassed coronary arteries confirmed patency in 126 (73%); however, in 30 reperfusion was incomplete though the graft was patent, making the rate of complete reperfusion only 56% (96/172). Causes included localized narrowings in the region of the anastomosis [9], significant narrowing along the graft [6], pre-existing additional stenoses in the native vessel, remote from the anastomosis and the lesion [7], stenoses not present preoperatively but seen postoperatively in the native vessel, remote from the anastomosis and original lesion [6], and separate obstructions of unbypassed branches [2]. While incomplete reperfusion is often unavoidable and is certainly preferable to total occlusion, evaluation based purely on patency rates is misleading, since it overlooks the fact that a significant proportion of patent grafts will not totally reperfuse the diseased vessel.

Adult↗
PubMed1982

Comparison and significance of bypass patency rates in noncritical versus critical coronary obstruction.

Preoperative and postoperative angiograms were compared in 81 patients who had undergone coronary artery bypass surgery. In these patients, 135 bypassed vessels had had critical stenoses or total occlusion; 99 of these bypasses (73.3%) were patent. Of 36 bypassed vessels that had had noncritical stenoses, 26 (72.2%) were patent. This difference was not significant. Thus, competitive inflow does not lead to excessive graft failure in noncritically diseased vessels, and they can be bypassed with the same expectation of success as critically obstructed vessels. The risk and the advantages of bypassing mild lesions at the same time that severe obstructions are surgically treated are discussed.

Adult↗
PubMed1982

Significance of the angiographic morphology of localized coronary stenoses: histopathologic correlations.

Postmortem coronary angiographic morphology was correlated with histologic sections of 73 localized subtotal coronary artery stenoses (50-99% reduction of luminal diameter) to determine whether complicated or uncomplicated atherosclerotic lesions could be detected angiographically. Lesions were divided into two types, according to angiographic morphology: Type I stenoses had smooth borders, an hourglass configurations, and no intraluminal lucencies; type II stenoses had irregular borders or intraluminal lucencies. Histologic sections were also divided into two types: "uncomplicated" stenoses had fatty or fibrous plaques with intact intimal surfaces and no superimposed thrombus; "complicated" stenoses manifested plaque rupture, plaque hemorrhage, superimposed partially occluding thrombus, or recanalized thrombus. Among 35 lesions with type I angiographic morphology, four (11.4%) were complicated lesions histologically. Among the 38 stenoses showing type II angiographic morphology, 30 (78.9%) were complicated lesions. Postmortem angiography thus had a sensitivity of 88% and specificity of 79% for detecting complicated stenoses on the basis of irregular borders or intraluminal lucencies. Pathologic studies have shown that acute occlusive thrombosis of a coronary artery is usually associated with complicated atherosclerotic stenoses. Thus, complicated lesions represent a greater risk factor for acute myocardial infarction or sudden death than do uncomplicated lesions. This study suggests that coronary stenoses characterized angiographically by irregular borders or intraluminal lucencies are probably the clinically more dangerous "complicated" type.

Angiography↗
PubMed1982

Comparison of the beta 1 and beta 2 adrenoceptor blocking properties of acebutolol and propranolol.

The purposes of this study were to evaluate the beta 1 and beta 2 adrenoceptor blocking properties of acebutolol and propranolol and measure the plasma levels of acebutolol, its acetylated metabolite and propranolol. Ten patients with reversible obstructive airways disease and hypertension received two separate dose levels of acebutolol and propranolol for five days each. Cardioselective properties were assessed by determining the beta 1 and beta 2 adrenergic-stimulating effects of terbutaline 5 mg before and at the end of each five-day treatment period. Both acebutolol and propranolol were clinically well tolerated. Following study drug there was a 100 percent inhibition of the beta 1 terbutaline effect, and an approximate 83 percent inhibition of the beta 2 terbutaline effect. There were no clinically significant differences between acebutolol and propranolol. The acetylated acebutolol metabolite accumulated levels two to three times higher than the parent compound, and its effects may have destroyed the cardioselectivity of acebutolol. Thus, acebutolol did not demonstrate clinically relevant cardioselectivity.

Acebutolol↗