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Biomedical subjects

J Weinreb

Publications and source records attributed to J Weinreb.

At least 19 recordsLinked to original sources
PubMed2000

Efficacy and safety of mangafodipir trisodium (MnDPDP) injection for hepatic MRI in adults: results of the U.S. Multicenter phase III clinical trials. Efficacy of early imaging.

The efficacy of contrast-enhanced magnetic resonance imaging (MRI) for detecting and characterizing, or excluding, hepatic masses was assessed in 404 patients, following the intravenous administration of mangafodipir trisodium (MnDPDP) injection, a hepatic MRI contrast agent. An initial contrast-enhanced computed tomography (CT) examination was followed by unenhanced MRI, injection of MnDPDP (5 micromol/kg IV), and enhanced MRI at 15 minutes post injection. Agreement of the radiologic diagnoses with the patients' final diagnoses was higher for enhanced MRI and for the combined unenhanced and enhanced MRI evaluations than for unenhanced MRI alone or enhanced CT using the clinical diagnosis as the gold standard. Mangafodipir-enhanced MRI uniquely provided additional diagnostic information in 48% of the patients, and patient management was consequently altered in 6% of the patients. MnDPDP-enhanced MRI was comparable or superior to unenhanced MRI and enhanced CT for the detection, classification, and diagnosis of focal liver lesions in patients with known or suspected focal liver disease.

Adult↗
PubMed1997

Fatty and fibroglandular tissue volumes in the breasts of women 20-83 years old: comparison of X-ray mammography and computer-assisted MR imaging.

OBJECTIVE: A method for segmenting MR images of the breast was applied to determine fatty and fibroglandular tissue volumes in breasts of women in different age groups. The results were compared with subjective assessments of breast density from X-ray mammograms in the same patients. MATERIALS AND METHODS: Two experienced mammographers assessed the percentage of fat in the breasts of 40 women who were 20-83 years old. MR images were obtained on a 1.0-T scanner equipped with a bilateral receive-only breast coil. Images were acquired using a three-dimensional T1-weighted gradient-echo sequence with a 1.25 x 1.4 x 2.5 mm resolution. On average, breast parenchyma appeared in 30 images in each breast. Image segmentation was based on a semiautomated, two-compartmental (fatty and fibroglandular tissue) model that accounts for partial volume effects. To validate the accuracy of the MR imaging segmentation technique, we performed a phantom study using an identical imaging sequence. RESULTS: The accuracy of the MR imaging segmentation of the phantom was of the order of 2%. In our subjects, fat content was 42.5% +/- 30.3% (mean +/- SD) on mammography versus 66.5% +/- 18% on MR images. Although we found a significant correlation (r = .63) between the two techniques, mammography poorly differentiated breasts containing less than 45% fat. When our analysis included only dense breasts (i.e., those containing less than 75% fat on MR images), the correlation coefficient decreased to .34. The largest discrepancies between mammography and MR imaging occurred in breasts that had 60-80% fat as measured on MR imaging. CONCLUSION: Fatty and fibroglandular tissue can be differentiated on MR images of the breast with high precision and accuracy, therefore allowing assessment of breast density. The conclusions of researchers who used mammographic density patterns should be reassessed.

Adipose Tissue↗
PubMed1996

Gadolinium-enhanced three-dimensional MR angiography of the thoracoabdominal aorta.

MR angiography (MRA) of the thoracoabdominal aorta is a noninvasive technique that can rapidly acquire a volume of data with the capability of multiplaner reformations (MPR) and "bright blood" maximum intensity projection (MIP) angiographic images. These MIP images can display long tortuous vessels in a single three-dimensional (3D) volume, with excellent delineation of branch vessel diseases and without the flow artifacts or long examination times of conventional spin-echo (SE) imaging. Two-dimensional (2D) time-of-flight (TOF) imaging is used most widely because of familiarity and ease of implementation, but this method has limitations in evaluating thoracoabdominal aortic disease. Sequential 2D axial imaging (which maximizes flow-related enhancement) is time consuming, subject to slice-to-slice misregistration, and can be degraded by pulsatile and turbulent flow. Coronal or parasagittal imaging is more time efficient, but image degradation secondary to in plane saturation and stagnant or turbulent flow from aneurysmal disease may lead to nondiagnostic studies. Three-dimensional TOF techniques offer the advantages of higher signal-to-noise ratio, better spatial resolution with near isotropic voxels, and shorter echo times (TEs), which lessen signal loss because of intravoxel phase dispersion. Although these techniques provide excellent image quality in the carotid arteries, they are of limited use in the aorta because of saturation effects. However, the addition of gadolinium chelates shortens the T1 relaxation rate of blood, which obviates the need for flow-related enhancement, allowing for inplane imaging without saturation effects, even in regions of virtually stagnant flow. The enormous signal enhancement of gadolinium chelates enables imaging with high-resolution matrices, providing diagnostic angiograms in as little as 2 minutes. With improved hardware, faster and stronger gradients, and phased-array coils that increase the signal-to-noise ratio, breath-hold gadolinium-enhanced 3D schemes with ultrashort TEs will become the optimal method for imaging the aorta and its branch vessels. Using this technique, the aorta can be imaged in less than 1 minute.

Aorta, Abdominal↗
PubMed1995

Gadoteridol-enhanced MR imaging of malignant hepatic tumors: effects of triple versus standard doses on lesion-liver contrast.

OBJECTIVE: The purpose of this study was to compare liver signal-to-noise ratio (SNR), lesion SNR, and lesion-liver contrast-to-noise-ratio (CNR) in patients with malignant liver lesions after the administration of a standard dose (0.1 mmol/kg of body weight) or a triple dose (0.3 mmol/kg) of a gadolinium chelate (gadoteridol). We hypothesized that the higher dose would produce a higher lesion-liver CNR and therefore increase the conspicuity of hepatic lesions. MATERIALS AND METHODS: A total of 85 patients with malignant hepatic masses (61 metastases, 22 hepatocellular carcinomas, and two lymphomas) proved by histologic or follow-up studies underwent MR imaging at 1.5 T. T1-weighted spin-echo imaging and gradient-echo imaging were done before and within 1 min after (gradient echo) as well as 5 (spin echo) and 15 (spin echo) min after the injection of 0.1 or 0.3 mmol of gadoteridol per kg, randomized before the start of the study (39 patients received the standard dose, and 46 received the triple dose). The signal intensities of the liver and lesions and the SD of background noise were measured by use of regions of interest to calculate the SNR of the liver and malignant lesions and the lesion-liver CNR. RESULTS: The lesion-liver CNR was increased significantly at 5 and 15 min after the administration of gadoteridol. No significant differences in the liver SNR, lesion SNR, and lesion-liver CNR (after 1 min: standard dose, -5 +/- 8, and triple dose, -4 +/- 14; after 5 min: standard dose, -1 +/- 5, and triple dose, 2 +/- 8; and after 15 min: standard dose, 1 +/- 5, and triple dose, 6 +/- 20) were found between the doses at all time points. CONCLUSION: Triple-dose gadoteridol does not improve the lesion-liver contrast of malignant hepatic lesions over that provided by the standard dose and is not warranted for liver MR imaging.

Adult↗
PubMed1994

Hepatic metastases and cavernous hemangiomas: distinction with standard- and triple-dose gadoteridol-enhanced MR imaging.

PURPOSE: To determine if hepatic metastases can be distinguished from cavernous hemangiomas by pattern analysis of magnetic resonance (MR) images obtained prior to and following administration of gadoteridol at standard (0.1 mmol/kg) and triple (0.3 mmol/kg) doses. MATERIALS AND METHODS: Ninety-five patients with proved hepatic metastases (n = 71) or cavernous hemangiomas (n = 24) underwent MR imaging at 16 different institutions. T2-weighted spin-echo and T1-weighted images were obtained before and after gadoteridol administration. Two independent blinded reviewers rated individual features of benignancy versus malignancy on a five-point confidence scale. RESULTS: The most useful diagnostic features, with 100% specificity, were nodular enhancement for hemangiomas and rim enhancement for metastases. Confident (definitely benign or definitely malignant) diagnoses were rendered in 80 of 95 cases (84%), with an accuracy of a confident diagnosis of 96%. CONCLUSION: The pattern of enhancement on T1-weighted images is highly accurate for distinction between hemangiomas and metastases in images obtained with both doses.

Contrast Media↗
PubMed1994

Insulin sensitivity in cystic fibrosis.

Cystic fibrosis (CF) patients demonstrate a spectrum of pancreatic beta-cell abnormalities. Those with no exocrine insufficiency (NEXO) have normal insulin secretion. Exocrine-insufficient CF patients with overt diabetes (EXO-IT) have impaired insulin secretion and fasting hyperglycemia. Exocrine-insufficient patients without diabetes (EXO) have impaired insulin secretion but maintain normoglycemia. We postulated that EXO individuals compensate for insulin deficiency by increasing insulin sensitivity and investigated glucose utilization in CF. To examine hepatic and peripheral insulin sensitivity, euglycemic-hyperinsulinemic clamp studies were performed by using the hot GINF isotope dilution technique. Insulin was sequentially infused at 0.25, 1.0, and 10.0 mU.kg-1.min-1. Glucose-mediated glucose uptake (GMGU) was assessed on another day with hyperglycemic clamp studies, during which insulin and somatostatin were infused to hold insulin-mediated glucose uptake constant between the two clamp studies. Skeletal muscle GLUT4 levels were assessed in EXO and control patients with Western blotting. Three patterns of peripheral and hepatic insulin sensitivity were seen that were related to the degree of pancreatic beta-cell dysfunction. NEXO individuals had normal peripheral and hepatic insulin sensitivity. EXO individuals had enhanced peripheral insulin sensitivity that was not associated with a change in skeletal muscle glucose transporter abundance compared with control patients; paradoxically, EXO subjects demonstrated hepatic insulin resistance. EXO-IT had peripheral and hepatic insulin resistance. GMGU was diminished in both EXO and EXO-IT subjects. The unique combination of increased hepatic glucose production and increased peripheral glucose utilization seen in EXO may be a metabolic adaptation to increased peripheral energy needs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Magnetic resonance imaging of glenohumeral instability.

Familiarity with normal anatomy and pathologic features of the capsulolabral complex as well as high resolution imaging are important factors in achieving a consistently high accuracy rate in diagnosis of glenohumeral instabilities by conventional MR imaging. The various types of glenoid labrum lesions and features that are most often associated with glenohumeral instability are defined.

Humans↗
PubMed1990

Rotator cuff lesions: signal patterns at MR imaging.

The signal intensity patterns of rotator cuff lesions at magnetic resonance (MR) imaging were evaluated in 80 patients who had surgical correlation and in 13 asymptomatic individuals (14 shoulders). Six cadaver shoulders were examined with MR, and histologic correlation was obtained in four. All studies were performed at 1.5 T with a flexible circular surface coil. The accuracy of MR imaging in detection of full-thickness cuff tears (31 patients) was 0.95 and of partial thickness tears (16 patients), 0.84. The most common and accurate pattern for full-thickness cuff tears (22 of 31 tears) was a region of intense signal seen on T2-weighted images. Less often the torn region consisted of an extremely degenerated and attenuated tendon with moderate signal intensity or was obscured by low-signal-intensity scar. The intense signal pattern on T2-weighted images was also accurate, although a less common finding (seven of 16 cases), in the diagnosis of partial tears. Tendinitis was recognized as focal or diffuse regions of increased signal intensity or a nonhomogeneous pattern of increased signal often associated with tendinous enlargement. In some patients, manifestations of subacromial-subdeltoid bursitis was present. Tendon degeneration was also manifested as regions of increased signal intensity. Some similarity and overlap of signal patterns of partial interstitial tears, tendinitis, and tendon degeneration are observed.

Adult↗
PubMed1989

Tears of the triangular fibrocartilage of the wrist: MR imaging.

Magnetic resonance (MR) imaging of the wrist was performed in 35 patients with specific complaints of pain and soft-tissue swelling in the medial side of the wrist. Twenty of the 35 subsequently underwent surgery. In 14 of the patients who underwent surgery, a diagnosis of triangular fibrocartilage (TFC) tear was made at MR imaging; in 13 of the 14 the tear was confirmed by surgical findings. In the six patients with an MR diagnosis of an intact TFC, surgical findings confirmed the diagnosis. These patients were operated on for an abnormality in the vicinity of the TFC (avascular necrosis, ganglion cyst, xanthoma). On the basis of findings from the 20 patients with surgical correlation, the accuracy of MR imaging in the detection of TFC tears was 95%. MR imaging is a valuable noninvasive method in the study of pathologic conditions of the TFC.

Adolescent↗
PubMed1985

Magnetic resonance imaging in human pregnancy.

Magnetic resonance imaging is a new noninvasive diagnostic technique that involves no ionizing radiation, has no known significant adverse biologic effects, and produces high resolution cross-sectional body images. When compared with sonography and x-ray computed axial tomography, magnetic resonance imaging may have several advantages. To investigate its clinical role in obstetrics, magnetic resonance imaging was used to examine 11 women with abnormal pregnancies. Prior ultrasound examination showed abnormal appearing fetuses in five, abnormalities of the amnionic fluid volume in five, and one each with a large adnexal mass and a molar pregnancy. Examples of images obtained from these women are presented and described. Maternal anatomy was well visualized in all women studied. Based on the preliminary experience, the authors believe that magnetic resonance imaging will be a useful adjunct for diagnostic visualization of normal and abnormal maternal anatomy. Detailed fetal imaging was also possible, and it is anticipated that magnetic resonance imaging will prove useful for fetal evaluation, especially fetal intracranial anatomy and fetal anatomy in pregnancies complicated by oligohydramnios. Because fetal subcutaneous fat is prominently depicted with magnetic resonance imaging, this technology may be useful for assessment of fetal nutritional status.

Female↗
PubMed1983

CT of gastric masses: image patterns and a note on potential pitfalls.

Computed tomography (CT) was performed in 9 consecutive cases of primary gastric neoplasm. Lesions were surgically or endoscopically proved; cross-sectional images are correlated to specific histopathology in each case. The CT images of leiomyoma and leiomyoblastoma are characterized as models of pure bulging intramural growth resulting in a lunate contrast distribution when imaged in the cross-sectional plane. In 5 cases of lymphoma, distortion of the contrast-filled hollow viscus is relatively consistent. Nodular growth is reflected on the CT image as a series of digitations encroaching on the opacified portion of the gastric lumen. Image pattern recognition, relative to histopathology, is of more than academic interest since endoscopy is frequently unreliable in cases of submucosal and exophytic pathology. Further, biopsy of such lesions is commonly nondiagnostic as a result of random choice of biopsy site or inadequate depth of tissue sample. Additionally, this report includes images of lesions that simulate the primary gastric pathology and may be a source of erroneous interpretation. These include: pseudocyst of the pancreas (2 cases) and enlargement of the left lobe of the liver with encroachment on the gastric lumen (1 case). Image specificity on CT examination is increasingly essential to diagnosis and surgical planning.

Humans↗