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Biomedical subjects

R G Levitt

Publications and source records attributed to R G Levitt.

At least 19 recordsLinked to original sources
PubMed1992

Subclavian artery angioplasty for treatment of coronary artery steal syndrome.

Three patients underwent percutaneous transluminal angioplasty for treatment of subclavian artery stenosis producing the coronary artery steal syndrome. Technical success and immediate relief of angina were achieved in all three patients. Clinical follow-up ranged from 4 to 16 months. One patient developed clinical evidence of restenosis. Subclavian artery angioplasty may be a safe and efficacious technique for the treatment of the coronary artery steal syndrome.

Aged↗
PubMed1992

Splenopneumopexy: evaluation with splenoportography.

Splenopneumopexy is a procedure designed to create a portopulmonary shunt in patients with esophageal variceal bleeding who are not candidates for conventional portosystemic shunts. Splenoportography was performed in three patients who underwent this surgical procedure. Portopulmonary shunts were identified in two of three patients. No complications resulted from splenoportography. Splenoportography is the procedure of choice to identify portopulmonary shunts in splenopneumopexy patients who have undergone splenic artery embolization.

Adult↗
PubMed1987

Differentiation of proximal bronchogenic carcinoma from postobstructive lobar collapse by magnetic resonance imaging. Comparison with computed tomography.

MRI and CT studies in 18 patients with proximal bronchogenic carcinoma and postobstructive lobar collapse were analyzed retrospectively. The relative abilities of these imaging techniques to identify central tumor by a contour abnormality and to distinguish tumor mass from collapsed lung by CT attenuation values and MRI signal intensities were compared. MRI and CT were equivalent in their ability to identify a contour abnormality, both succeeding in 13 of 18 (72%) patients. CT was more successful than MRI in differentiating tumor mass from collapsed lung. Dynamic computed tomography scanning differentiated tumor from collapsed lung in eight of ten (80%) patients. MRI demonstrated different signal intensities of tumor and collapsed lung in 8 of 18 (44%) patients. T2-weighted images more often separated tumor from collapsed lung than other imaging sequences.

Aged↗
PubMed1986

Oblique magnetic resonance imaging of the cardiovascular system.

This exhibit demonstrates that cardiac anatomy can be imaged by MRI in oblique planes that are equivalent to views obtained radiographically or at angiocardiography. These MR images may be obtained either by simple patient positioning or by electronic rotation of the imaging axis. The advantages of this technique include its simplicity and its ability to show detailed anatomy noninvasively. Major cardiac structures including chambers, walls, vessels and bronchi are optimally demonstrated in long axis or cross section. This permits estimation of chamber volume, wall thickness, vessel position and variations from normal. Smaller structures are also well visualized. These include the pericardium, papillary muscles, azygos vein and some cross sectional anatomy of the coronary arteries and veins. The valvular structures can be shown during diastole or systole. The ability of MRI to show these cardiac structures due to the intrinsic contrast differences in signal intensity between muscle, fat, flowing blood and lung suggest an important future for MR cardiac imaging in a broad group of congenital and acquired diseases of the heart, pericardium and great vessels.

Heart↗
PubMed1986

Neck neoplasms: MR imaging. Part I. Initial evaluation.

Untreated neoplasms of the neck (tumors of the oropharynx, supraglottic area, carotid body, and thyroid, in addition to malignant lymphadenopathy) were evaluated in 23 patients with magnetic resonance (MR) imaging. The results were compared with computed tomographic (CT) scans in 20 patients. Contrast between tumor and fat was best on relatively T1-weighted images (500/30-35 [TR msec/TE msec]), whereas separation of tumor and muscle was best with relatively T2-weighted pulse sequences (1,500/90). Balanced images (1,500/30-35) provided best overall image quality and best demonstrated vascular anatomy. MR imaging was usually superior to CT in showing the relationship of tumor mass to muscle. MR imaging and contrast material-enhanced CT were equivalent in most patients in defining vascular anatomy, but MR imaging was superior when intravenous contrast material was not administered. However, CT was more helpful in showing bone and cartilage anatomy, and in some patients CT also was better in showing airway abnormalities. Despite these limitations, MR imaging is a promising imaging technique for studying neoplasms of the neck.

Adult↗
PubMed1986

Neck neoplasms: MR imaging. Part II. Posttreatment evaluation.

Thirty-three patients who had undergone prior surgery and/or radiation therapy for malignant neoplasms of the neck were studied with magnetic resonance (MR) imaging. Twenty-seven of these patients were also evaluated with computed tomography (CT). Ten patients were healthy posttreatment volunteers, and 23 had documented tumor recurrence. MR images better demonstrated normal muscular landmarks, especially in patients with obliterated fat planes. Areas of posttreatment fibrosis or scarring were low in signal intensity with all MR pulse sequences. However, in three patients, high signal intensity from postradiation edema of the supraglottic area mimicked neoplasm. In patients with recurrent tumor, MR imaging was superior to CT in defining the relationship of tumor and muscle and in demonstrating vascular anatomy when no intravenous contrast material was given during the CT examination. In two patients tumor and fibrosis were separated on MR images because of signal intensity differences. CT scans, however, showed adjacent bone and cartilage anatomy better. Our data indicate that an MR examination may be helpful in patients in whom CT is indeterminate either because of anatomical distortion or suboptimal demonstration of vascular anatomy.

Head and Neck Neoplasms↗
PubMed1986

Mediastinal vessels: postoperative evaluation with MR imaging.

The mediastinal vessels in 27 patients who had previously undergone vascular surgery were evaluated with use of magnetic resonance (MR) imaging for patency and the presence of stenosis. Thirty-six postoperative vessels or shunts were studied, including 11 aortas after coarctation or stenosis repair, 18 systemic-pulmonary shunts, four pulmonary artery or vein repairs, and three spiral vein grafts. Angiographic (n = 21), direct surgical (n = 1), contrast material-enhanced computed tomography (n = 1), or clinical (n = 13) findings were correlated with the MR findings. Overall, the accuracy of MR imaging for determination of patency was 100%. In patients with angiographic correlation and technically adequate MR examinations, MR imaging results were used to identify or exclude stenoses correctly in 66.7% of patent vessels. The four missed or underestimated stenoses occurred in vessels 10 mm or less in diameter.

Adolescent↗
PubMed1986

Magnetic resonance imaging of spiral vein graft bypass of superior vena cava in fibrosing mediastinitis.

Magnetic resonance imaging (MRI) was used for postoperative evaluation of spiral vein grafts in three patients with fibrosing mediastinitis who had undergone bypass of the superior vena cava (SVC) for SVC syndrome. The MRI images, obtained without ECG triggering, were compared retrospectively with postoperative bilateral arm venograms. Patent grafts were identified by MRI in all patients. Significant stenoses at innominate vein-spiral vein graft anastomoses in two patients were better demonstrated by venography than by MRI. MRI shows promise as a non-invasive technique for postoperative evaluation of spiral vein bypass grafts.

Adult↗
PubMed1985

Multispectral analysis of magnetic resonance images.

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.

Basal Ganglia Diseases↗
PubMed1985

Oblique views of the heart by magnetic resonance imaging.

We describe a simple method that uses patient positioning to obtain oblique views of the human heart by magnetic resonance (MR) imaging. These views provide MR images that directly correlate with conventional anterior or posterior oblique radiography.

Heart↗
PubMed1985

Radiation fibrosis: differentiation from recurrent tumor by MR imaging.

Magnetic resonance (MR) images of 21 patients who had undergone radiation therapy were analyzed and compared with those of 15 patients who had untreated tumors. T2-weighted images (TR = 1,500 msec, TE = 90 msec) were most helpful in distinguishing recurrent tumor from radiation fibrosis. Radiation fibrosis, like muscle, usually remained low in signal intensity on T2-weighted images, while tumor demonstrated higher signal intensity. In no patient was the signal intensity of tumor the same or less than muscle on the T2-weighted images. However, relatively high signal intensity on T2-weighted images is not specific for tumor recurrence and may be seen in acute radiation pneumonitis, infection, hemorrhage, and even pulmonary radiation fibrosis.

Adult↗
PubMed1985

The thoracic aorta studied by MR imaging.

Thirty-three patients with a variety of disorders of the thoracic aorta (aneurysm, dissection, Marfan syndrome, coarctation/pseudocoarctation, L-transposition, and Takayasu disease) were evaluated with magnetic resonance (MR) imaging. MR imaging delineated the presence and extent of thoracic aortic aneurysms and showed the relationship of the aneurysm to arch vessels; it also demonstrated intimal flaps and individual lumina in types A and B aortic dissection. Dilation of the ascending aorta in Marfan syndrome and focal narrowing of the aorta in coarctation were well visualized. The anteroposterior and side-to-side relationships of the aorta and pulmonary artery in L-transposition were demonstrated, as were aortic wall thickening and branch vessel narrowing in Takayasu arteritis. Initial experience suggests that MR imaging may provide a noninvasive method for evaluating thoracic aortic disease. Limitations include inferior spatial resolution, occasional difficulty in imaging the entire region of interest in one section, lack of signal from calcifications, and inability to monitor critically ill patients.

Adolescent↗