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Biomedical subjects

J M Cohen

Publications and source records attributed to J M Cohen.

At least 91 records · Page 5Linked to original sources
PubMed1986

Venous thrombosis: clinical and experimental MR imaging.

Five venous thrombi were induced in the external jugular veins of three laboratory dogs, and were repeatedly imaged over 3 weeks using a 0.35-T magnetic resonance (MR) imager. MR magnitude and phase images, T1 and T2 relaxation times, venography, and histologic sections of these thrombi were evaluated to determine the changes in appearance on MR images with time. Venous thrombi appeared hyperintense compared with muscle on both relatively T1- and T2-weighted spin-echo sequences regardless of the age of the clot. Organization of the thrombus beyond 1 week was manifested as increased prominence of flow signal void in and around the clot. Distinction between intraluminal thrombus and flow-related artifacts was aided by phase image reconstruction. Nineteen venous thrombi locations in 13 patients revealed an MR appearance similar to that of the experimental animal model. Three patients (six thrombi locations) had serial examinations over 4 weeks. No significant change in thrombus signal characteristics was noted with time. It is concluded that MR imaging at 0.35 T cannot be used to predict the age of thrombus (up to 3 weeks) but may be helpful in following its resolution.

Animals↗
PubMed1986

Postoperative assessment of splenorenal shunts with MRI: preliminary investigation.

Magnetic resonance imaging (MRI) was performed on nine patients with hepatic cirrhosis and portal hypertension after selective distal splenorenal shunt for decompression of bleeding esophageal varices. MRI demonstrated the splenorenal anastomosis and patency of the shunt, splenic vein, and left renal vein in each case. Imaging in the transverse plane provided optimal visualization of the shunts. The authors conclude that MRI is a safe, noninvasive technique for the postoperative evaluation of selective distal splenorenal shunts.

Adolescent↗
PubMed1986

MRI evaluation of mediastinal and thoracic inlet venous obstruction.

Fourteen patients with clinical and/or radiographic evidence of mediastinal or thoracic inlet venous obstruction were studied with magnetic resonance imaging (MRI) on a 0.35-T superconducting system using multislice spin-echo technique. The MRI examinations were retrospectively evaluated for their ability to provide information about the presence, level, and cause of venous obstruction, local extent of disease causing obstruction, and presence of collateral venous pathways. The results were compared to the information available from correlative studies including CT (11) and venography (four). In each instance, MRI provided detailed information about the precise site and extent of venous obstruction. The specific cause of the obstruction was suggested by MRI findings in one case of teratoma and in one case of postradiation fibrosis. Otherwise, all masses had relatively prolonged T1 T1 and T2 relaxation times and could not be differentiated on the basis of their and T2 relaxation times and could not be differentiated on the basis of their MRI appearances. Transaxial images most clearly and unequivocally depicted patent and obstructed superior vena cava (SVC). Enlarged venous collateral pathways were apparent in four cases. CT scans with intravenous contrast material in general provided information similar to that available with MRI, except in two cases where there was a discrepancy between CT and MRI concerning complete versus partial occlusion of the SVC. This initial study indicates that MRI can provide information about the presence, cause, and precise level of mediastinal and thoracic inlet venous obstruction.

Adult↗
PubMed1986

Imaging the pediatric liver: MRI and CT.

The livers of 27 children, 2 weeks to 16 years old, were examined with MRI and CT. Fourteen children had normal livers, 9 had focal liver disease, and 4 had diffuse liver disease. Normal intrahepatic venous anatomy was visualized more frequently with MRI than with CT, regardless of presence of disease, type of disease, or age. Focal hepatic lesions were either iso- or hypointense on relatively T1-weighted images and were hyperintense on T2-weighted images regardless of the pathology. In three cases, lesions seen with MRI were not detected with CT. In two other cases, CT was interpreted as equivocal or abnormal, but the liver was normal on MRI. MRI was superior to CT for evaluation of patency of the intrahepatic portion of the inferior vena cava. Other than in cases of fatty infiltration, CT provided no information additional to MRI. MRI has the potential to replace CT as a technique for imaging the pediatric liver in many cases, especially for infants and young children.

Adolescent↗
PubMed1985

Doxorubicin plus cisplatin in the treatment of apudomas.

Twelve patients with advanced apudomas--six with carcinoid tumors, two with chemodectomas, two with pancreatic islet cell tumor, and one each of medullary carcinoma of the thyroid and paraganglioma of unknown primary--were treated with a combination of doxorubicin 50 mg/m2 and cisplatin 50 mg/m2 every 3 to 4 weeks. Biochemical markers were present in 8 of the 12 patients. Five of the 12 patients (3 with carcinoid and 2 with chemodectomas) responded with more than 50% regression of tumor size measured as hypothetical area. Three others (two with islet cell tumors and one with carcinoid) had clinical and/or biochemical improvements. A median duration of response was 6 months. Nausea, vomiting, and alopecia were universal. Mild or moderate leukopenia was the most frequent toxicity. No sustained nephrotoxicity was seen. The combination of doxorubicin and cisplatin provides a new palliative therapy for patients with APUD tumors.

Adolescent↗
PubMed1985

Prevalence of mitral valve prolapse in normal children.

Although echocardiography has become the standard noninvasive method of diagnosing mitral valve prolapse, the diagnostic criteria have been established without clearly defining the range of normal patterns for mitral valve closure. The current study reports the analysis of mitral valve closure patterns in 193 children (aged 5 days to 18 years) making scheduled visits for well child care who were screened by history and physical examination to exclude structural heart disease. Mitral valve systolic leaflet position was analyzed for the appearance of any portion of either leaflet superior to the plane of the anulus. Superior systolic motion was noted in 13% of the overall study group; this pattern was uncommon in infants but more frequent in older children, with a prevalence of 35% in the 10 to 18 year age group. There was no statistically significant difference between male and female children at any age. The prevalence of superior systolic motion decreased markedly if consideration was given to its presence in more than one echocardiographic view (1%) or to displacement of the coaptation point of the mitral valve leaflets (0.5%). Superior systolic motion occurs with such frequency in normal children as to call into question the reliability of this pattern of mitral valve closure as a standard for the diagnosis of mitral valve prolapse. More restrictive diagnostic criteria which consider the degree of leaflet displacement or its presence in multiple echocardiographic views may be necessary to identify those subjects whose mitral valve closure patterns truly fall outside the range of normal.

Adolescent↗
PubMed1985

Fluid collections in the intraperitoneal and extraperitoneal spaces: comparison of MR and CT.

Fourteen patients with abnormal subdiaphragmatic fluid collections (eight intraperitoneal, two extraperitoneal, and four intra- and extraperitoneal) were examined with computed tomography (CT) and magnetic resonance (MR) imaging. MR and CT provided equivalent information concerning the presence and extent of fluid collections in 13 of the 14 cases. Image acquisitions with two different repetition times (TRs) and two echo times (TEs) were necessary, in most cases, to detect and discriminate between different types of pathologic fluids. Transudative ascites demonstrated long T1 and T2 relaxation times, whereas abscesses, phlegmon, pancreatic pseudocyst, exudative pancreatitis, and chronic hematoma demonstrated an intermediate or short T1 and a long T2.

Abdomen↗
PubMed1985

Iliopsoas muscles: MR study of normal anatomy and disease.

Magnetic resonance (MR) imaging was performed on 15 healthy subjects to define the appearance of the iliopsoas muscle and on 15 patients with iliopsoas disease. Seven patients had tumorous involvement of the muscles, five had inflammatory disease, one had retroperitoneal hemorrhage, one had iliopsoas bursitis, and one had bilateral hypertrophy. MR imaging permitted delineation of the muscles and depiction of the disease condition. Transverse MR images alone almost always provided the necessary data to determine the origin and extent of disease. Sagittal images were occasionally useful in defining the extension of disease into the spine. T1-weighted images provided optimal contrast between the muscles and adjacent tissues, while T2-weighted images were more useful for depicting disease within the muscles themselves.

Abscess↗
PubMed1985

Human fetal anatomy: MR imaging.

Twenty-four pregnant women carrying 26 fetuses (two sets of twins) were imaged with magnetic resonance (MR) imaging at 0.35 T following sonographic evaluation. Each study was retrospectively evaluated to determine which of 33 normal fetal structures were visible on the images and which imaging parameters were most useful for depicting fetal anatomy. Fetal motion degraded fetal images in all but two cases, both with oligohydramnios and in the third trimester of gestation. Nevertheless, many fetal structures were identifiable, particularly in the third trimester. Visualization of fetal anatomy improved with intravenous maternal sedation in five cases. Relatively T1-weighted images occasionally offered the advantage of less image degradation owing to fetal motion and improved contrast between different fetal structures. More T2 weighting was believed to be advantageous in one case for outlining the fetal head and in one case for delineation of the brain. In many cases, structures were similarly identifiable (though with different signal intensities) regardless of the parameters selected. The authors conclude that MR imaging of many fetal structures is currently unsatisfactory and is probably of limited value, particularly in the first and second trimesters. However, the relative frequency and detail with which the fetal head and liver can be depicted indicate that these may be areas for further investigation, and the potential utility of imaging fetal fat warrants further investigation.

Amniotic Fluid↗
PubMed1985

Chemical shift artifact in clinical magnetic resonance images at 0.35 T.

A thin, low-intensity line, which partially surrounds many structures on magnetic resonance imaging (MRI), is an artifact due to the phenomenon of chemical shift and should not be mistaken for a normal or abnormal morphologic structure. This artifact can be recognized by its characteristic appearance perpendicular to the direction of the frequency-encoding gradient at the interface of tissues with different chemical shift properties. Confinement within or extension beyond this thin, low-intensity line cannot be used as a criterion for staging neoplasms. Once recognized, the chemical shift artifact should not impede the use of MRI for clinical imaging at 0.35 T.

Diagnostic Errors↗
PubMed1983

Pseudorheumatoid nodules in an adult.

The finding of soft tissue lesions that present as rheumatoid nodules in a patient with no history or symptoms of rheumatoid arthritis or rheumatic fever sets the stage for a variety of differential diagnoses. One of the diagnoses that must be considered is the pseudorheumatoid nodule, which is rarely found in the adult. This article deals with one such case. A review of the literature is discussed along with a description of the remaining diagnoses from which it is distinguished. In this particular case, the patient presented lesions typifying those of rheumatoid nodules with the absence of any constitutional symptoms. Follow-up to date shows no signs of rheumatoid arthritis, although the literature does suggest the possibility that these lesions may be the precursor of the disease.

Adult↗
PubMed1982

Role of carotid artery resistance to collapse during high-intrathoracic-pressure CPR.

The driving force for carotid artery flow during high-intrathoracic-pressure cardiopulmonary resuscitation is a peripheral arteriovenous pressure gradient resulting from differential transmission of the high intrathoracic pressure to the carotid artery but not to the jugular vein. To study the role of carotid artery resistance to collapse in establishing this differential pressure transmission, we manipulated the upstream, downstream, and surrounding pressures and measured the resultant carotid artery flow in both intact dogs and in excised arteries. Stepwise reductions in downstream pressure produced a narrowing near the outlet from the high-pressure chamber (the thorax in vivo), but increments in flow continued despite the presence of a positive (outside--inside) transmural pressure gradient. Flow limitation occurred only when downstream pressure was further decreased. Resistance to collapse was indexed by the transmural pressure at the onset of flow limitation (Pcrit), which was 7.2 +/- 1.6 mmHg in eight intact dogs. After administration of norepinephrine Pcrit increased by 2.6 +/- 0.7 mmHg, P less than 0.001). Seven excised carotid arteries also demonstrated resistance to collapse which was enhanced somewhat with norepinephrine. Thus resistance of the carotid artery to collapse is a critical factor in maintaining forward flow during high intrathoracic pressure. This resistance to collapse is also seen in vitro and can be enhanced by vasoconstricting agents.

Animals↗