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Biomedical subjects

S A Mirowitz

Publications and source records attributed to S A Mirowitz.

At least 55 records · Page 3Linked to original sources
PubMed1991

Normal abdominal enhancement patterns with dynamic gadolinium-enhanced MR imaging.

The objective of this study was to quantitatively and qualitatively determine contrast enhancement patterns of normal abdominal organs with dynamic gadolinium-enhanced magnetic resonance (MR) imaging. Dynamic gadolinium-enhanced, T1-weighted, spin-echo imaging was performed during a 23-second breath hold in 38 patients, with images acquired before, during, and at 1,2, and 5 minutes after bolus injection of gadopentetate dimeglumine. Enhancement patterns of normal liver, spleen, pancreas, adrenal gland, kidney, aorta, inferior vena cava, and fat were determined by visual evaluation and by performance of signal intensity measurements with an electronic cursor. Time-intensity curves demonstrated peak enhancement of all abdominal organs during or immediately after bolus injection of gadopentetate dimeglumine. MR enhancement patterns included visualization of renal cortical nephrogram and heterogeneous enhancement of the spleen during the bolus phase of contrast material administration. Peak enhancement of normal liver was 72%; spleen, 172%; pancreas, 82%; adrenal gland, 85%; and kidney, 291%. This study established reference data regarding abdominal organ enhancement that will be useful as dynamic gadolinium-enhanced MR imaging becomes clinically implemented.

Abdomen↗
PubMed1991

Normal rotator cuff: MR imaging with conventional and fat-suppression techniques.

The signal intensity and morphologic characteristics of the rotator cuff and surrounding structures at magnetic resonance (MR) imaging were investigated with five pulse sequences in 15 asymptomatic subjects. In all subjects, a focal region of relative increased signal intensity corresponding to the critical zone was observed in the supraspinatus tendon just proximal to its insertion. Soft-tissue signal intensity (isointense with muscle) was also located between the supraspinatus tendon and underlying joint capsule, interposed between the conjoined leaves of the supraspinatus and infraspinatus tendons, and superolateral to the conjoined cuff tendon, near its insertion. These regions were most conspicuous and most clearly defined with fat-suppression imaging. Small amounts of fluid were observed within the joint space and its recesses, the bicipital tendon sheath, and the subacromial-subdeltoid bursa. These and other MR imaging findings of this study previously have been regarded as indicative of rotator cuff abnormalities. These results will help refine the criteria for diagnosis of rotator cuff disorders with MR imaging.

Adult↗
PubMed1991

Hyperintense basal ganglia on T1-weighted MR images in patients receiving parenteral nutrition.

Patterns of intracranial signal intensity on magnetic resonance (MR) images were studied in nine patients undergoing long-term total parenteral nutrition therapy. The duration of therapy ranged from 5 months to 11 years (mean, 5.3 years). Symmetric increased signal intensity on T1-weighted MR images (hyperintense relative to white matter) was observed in the basal ganglia of all patients, without corresponding abnormality on T2-weighted images. Analysis of signal-intensity characteristics and distribution pattern suggests that the basis for these changes may be deposition of intravenously administered paramagnetic trace elements, especially manganese, and/or an astrogliotic reaction to such deposition.

Basal Ganglia↗
PubMed1991

Perfluoroctylbromide as a gastrointestinal contrast agent for MR imaging: use with and without glucagon.

The utility of perfluoroctylbromide (PFOB) as a gastrointestinal contrast agent for magnetic resonance (MR) imaging was evaluated with MR examinations performed in 30 subjects (16 healthy volunteers and 14 patients). Transaxial T1-, proton density-, and T2-weighted MR images were acquired in each subject before and after the administration of PFOB. The healthy volunteers each underwent two sets of post-PFOB MR examinations, one before and one after glucagon administration. The degree of bowel marking, clarity of bowel-wall visualization, ability to distinguish bowel from adjacent parenchymal organs, and severity of phase-encoding artifacts were independently analyzed by two reviewers. Oral administration of PFOB significantly (P less than .001) increased the percentage of bowel loops with low signal intensity. Subcutaneous administration of glucagon significantly (P less than .001) increased the clarity of bowel-wall visualization on post-PFOB MR studies. The severity of phase-encoding artifacts did not change substantially after administration of PFOB or glucagon.

Adult↗
PubMed1990

Rapid acquisition spin-echo (RASE) MR imaging: a new technique for reduction of artifacts and acquisition time.

The rapid acquisition spin-echo (RASE) technique combines a short repetition time, a short echo time, and a single excitation pulse sequence with half-Fourier data sampling. This allows for acquisition of 11 strongly T1-weighted sections during a single 23-second breath-holding period. Measurements obtained from volunteers and with phantoms reveal that RASE images have a lower signal-to-noise ratio and contrast-to-noise ratio than do conventional multiacquisition spin-echo (SE) images due to reduced data acquisition. However, liver-spleen contrast and spatial resolution are not affected. Moreover, contrast-to-artifact (C/A) measurements are 77% greater with RASE. When normalized for imaging time, all parameters are significantly higher with RASE, with a C/A per unit time that was 338% higher. Randomized, blinded review of RASE and SE sequences from 20 patients was conducted to evaluate qualitative performance. Excellent to good performances for phase-encoding artifact reduction, edge sharpness, and overall image quality were recorded for 89%, 88%, and 86% of RASE examinations, respectively, versus 41%, 59%, and 47% of conventional SE examinations, respectively. All results were statistically significant with P less than .001. RASE is an easily implemented imaging technique that utilizes widely available existing technology. Its major benefits relate to significant reduction in imaging time, elimination of respiratory artifacts, and the potential for performing dynamic contrast material-enhanced screening examinations.

Abdomen↗
PubMed1990

Normal signal-void patterns in cardiac cine MR images.

The diagnosis of valvular regurgitation and stenosis with cardiac cine magnetic resonance (MR) imaging is based on observation of localized regions of signal void. However, areas of signal void frequently are present in patients without cardiac abnormalities and may closely resemble signal-void areas that occur secondary to valvular pathologic conditions. Twenty healthy volunteers were prospectively evaluated with gradient-echo cine MR imaging to determine the frequency, distribution, and timing of appearance of regions of signal void in the healthy population. The most frequent sites included the regions adjacent to the atrioventricular valves, the left ventricular outflow tract, atrial appendages, and areas of venous inflow, including the coronary sinus, superior vena cava, and pulmonary veins. Awareness of normal signal-void areas and their characteristics is critical in the assessment of cardiac cine MR examinations.

Adult↗
PubMed1990

Renal masses: evaluation with gradient-echo Gd-DTPA-enhanced dynamic MR imaging.

Dynamic contrast material-enhanced gradient-echo magnetic resonance (MR) imaging was performed on 15 patients with 18 renal masses (seven simple renal cysts, nine renal cell carcinomas, one angiomyolipoma, and one oncocytoma). Fifteen sequential images were obtained while the patients held their breath during a 2.5-3.5-minute interval during and immediately after the intravenous administration of gadolinium diethylenetriaminepentaacetic acid (DTPA); delayed images were also obtained for 15 minutes. Time-intensity curves showed that renal cortical enhancement reached maximal intensity 80 seconds after the injection of Gd-DTPA. Medullary enhancement reached maximal intensity at 120 seconds. None of the simple renal cysts showed enhancement; each cyst displayed a signal intensity less than that of the renal cortex on precontrast images. All renal cell carcinomas were isointense with the renal cortex and demonstrated variable enhancement. Three patterns of enhancement were observed: predominantly peripheral, heterogeneous, and homogeneous. Both the angiomyolipoma and the oncocytoma showed brisk, homogeneous enhancement. This MR imaging technique appears to be useful in the detection and characterization of simple renal cysts and solid neoplasms.

Adenoma↗
PubMed1990

Thoracic aortic dissection: pitfalls and artifacts in MR imaging.

Results of 53 thoracic magnetic resonance (MR) imaging examinations were reviewed to determine the prevalence and severity of artifacts and pitfalls that may occur in the evaluation of acute aortic dissection. Grade 1 artifacts and pitfalls were mimics of aortic dissection on individual images but could be demonstrated not to represent a dissection when other images from the same sequence were evaluated. Grade 2 artifacts and pitfalls required the use of images from other planes or sequences to distinguish them from a dissection. Grade 3 artifacts and pitfalls could not be distinguished from a dissection without the use of other imaging modalities. Of the 53 cases examined, 34 (64%) had artifacts or pitfalls of grade 1 or higher, 10 (19%) had artifacts or pitfalls of grade 2 or higher, and one case (2%) had grade 3 artifacts or pitfalls. Sixteen cases had more than one artifact or pitfall. Pitfalls and artifacts that mimic aortic dissection occur in a significant percentage of thoracic MR imaging examinations. An awareness of their existence, knowledge of normal anatomy, the use of axial images in all cases with the addition of images in other planes as needed, rotation of phase and frequency gradients as needed, and clinical correlation may avert misinterpretation in nearly all cases.

Aortic Dissection↗
PubMed1990

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis.

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.

Adolescent↗
PubMed1990

Magnetic resonance imaging of congenital heart disease.

MRI has assumed an important role in the noninvasive evaluation of patients with congenital cardiac lesions. In this article, the authors examine basic technical considerations, an approach to analysis of MR images in congenital heart disease patients, and review major applications of MRI as they apply to patients with congenital heart disease.

Heart Defects, Congenital↗
PubMed1989

The gastric air-fluid sign: aid in CT assessment of gastric wall thickening.

The differentiation of apparent gastric wall thickening due to incomplete gastric distention from true pathologic wall thickening can be difficult on computed tomographic (CT) scanning. We have observed a transition in gastric wall thickening that is often present at or slightly above the gastric air-fluid or air-contrast level. The apparently thickened gastric wall in the dependent portion of the stomach undergoes an abrupt change to normal thickness at or above the air-fluid level. Review of CT scans in 259 patients without known or suspected gastric pathologic conditions revealed this finding, termed the "gastric air-fluid sign," in 57 patients (22%). While not considered diagnostic, the presence of this sign may allow for a greater degree of confidence in the CT assessment of gastric wall thickening in an appropriate clinical setting.

Contrast Media↗
PubMed1989

Evaluation of pulmonary arterial morphology in cyanotic congenital heart disease by magnetic resonance imaging.

Before and after surgical therapy, the anatomy of the pulmonary arteries in cyanotic congenital heart disease is often distorted. Pulmonary arterial anatomy was evaluated by magnetic resonance imaging (MRI) and angiography in 20 patients, ages 3 months to 20 years, with cyanotic heart disease associated with decreased pulmonary blood flow. Excellent correlation between MRI and angiographic estimates of pulmonary artery diameter was obtained (main pulmonary artery, r = 0.96; right pulmonary artery, r = 0.93; left pulmonary artery, r = 0.96). A similar excellent correlation (kappa = 0.83) was found in the assessment of the presence and severity of proximal pulmonary arterial stenoses. However, stenoses in the peripheral pulmonary arteries visualized with angiography were missed with MRI. MRI and angiography showed complete agreement in determining the patency of 11 surgical shunts. MRI did not demonstrate all of the systemic collateral vessels present with angiography, and the distal connections of collaterals were not detected with MRI. MRI is comparable to angiography in the evaluation of central pulmonary arterial anatomy over a wide range of ages. These findings suggest an important role for noninvasive MRI in the serial evaluation of pulmonary artery morphology in patients with cyanotic congenital heart disease before and after surgical repair.

Adolescent↗
PubMed1989

Tetralogy of Fallot: MR findings.

Surgical treatment of patients with tetralogy of Fallot requires accurate definition of all anatomic structures, particularly the central pulmonary arteries. Magnetic resonance (MR) images of 22 patients with tetralogy of Fallot were studied to assess their usefulness in providing information regarding the spectrum of anatomic abnormalities in this condition. MR findings were compared with information obtained at catheterization (in 16 patients) and at surgery (in nine patients), both of which were performed within 3 months of MR imaging. Ventricular chamber enlargement and wall hypertrophy were clearly delineated in most of the 17 patients who were examined before definitive surgical repair, and ventricular septal defects were visualized in all 17. Palliative systemic-to-pulmonary shunts were visualized in 11 patients and could be evaluated for patency. Most important, the morphology and size of the right ventricular outflow tract and central pulmonary arteries could be accurately assessed. Pulmonary artery measurements obtained from MR images demonstrated excellent correlation with angiographic measurements. In six patients examined after complete surgical repair, MR images accurately reflected changes in pulmonary artery outflow tract morphology and complications, such as residual pulmonary artery stenosis and thrombosis. The findings suggest that MR imaging can complement or obviate catheterization in the evaluation of tetralogy of Fallot with regard to suitability for definitive surgical repair.

Adult↗
PubMedDate not supplied

MR imaging evaluation of knee collateral ligaments and related injuries: comparison of T1-weighted, T2-weighted, and fat-saturated T2-weighted sequences--correlation with clinical findings.

The objectives of this study were to compare the ability of T1-weighted (T1W), proton density/T2-weighted (PD/T2W), and fat saturation (FS) PD/T2W magnetic resonance (MR) sequences for depiction of the knee collateral ligaments and related injuries, and to compare MR findings with clinical findings. Ten subjects with normal knee ligaments and 64 patients with suspected collateral ligament injuries underwent coronal T1W, PD/T2W, and FS PD/T2W imaging. Abnormalities ranged from edema surrounding the collateral ligaments (grade I) to complete disruption of ligamentous fibers (grade III). FS PD/T2W images improved definition of the medial collateral ligament (MCL) and lateral collateral ligament (LCL) compared with other sequences in 78% and 81% of patients, respectively. While the apparent grade of collateral ligament injury was similar with all pulse sequences in most patients, depiction of such injury was usually most conspicuous on FS PD/T2W images (MCL, 92% of patients; LCL, 38% of patients). In no patients were clinically diagnosed collateral ligament injuries undetected or understaged with MR imaging. MR findings indicated higher-grade MCL and LCL injuries than did clinical examination in 24 and 15 patients, respectively.

Adipose Tissue↗
PubMedDate not supplied

Hepatic T2-weighted MRI: a prospective comparison of sequences, including breath-hold, half-Fourier turbo spin echo (HASTE).

The purpose of this study was to quantitatively compare the hepatic contrast characteristics of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences with breath-hold T2-weighted images acquired with half-Fourier turbo spin echo (HASTE). Forty-five patients were examined with a phased-array surface coil. Nineteen patients had focal hepatic lesions, including eight malignant tumors, 10 cavernous hemangiomas, and one hepatic adenoma. Twenty-six patients had no focal hepatic lesions. T2-weighted images with comparable TE were acquired with CSE, FSE, and HASTE pulse sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for liver, spleen, and lesions were measured. FSE demonstrated significantly better quantitative performance than CSE for liver-spleen CNR (P .0084). No statistically significant difference was demonstrated between FSE and CSE for liver or spleen SNR. FSE demonstrated clear scan time and resolution advantages over CSE. HASTE performed significantly poorer than CSE and FSE for liver-spleen CNR (P < .0001), liver SNR (P = .0002 for CSE and P < .0001 for FSE), and spleen SNR (P < .0001). Optimized FSE images with a short echo train length performed comparably to CSE images of equivalent TE. Liver-lesion CNR was suppressed on HASTE images, suggesting that long echo train length FSE sequences could diminish solid lesion detection compared to CSE and short echo train length FSE.

Adenoma, Liver Cell↗
PubMedDate not supplied

Interactive multiplanar reformation of conventional two-dimensional MR images.

In this report, we describe a new application for three-dimensional computer image processing that can provide for improved depiction of anatomical structures on routine nonvolumetric magnetic resonance (MR) examinations. The technique can be applied to standard two-dimensional MR images of the brain, spine, musculoskeletal system, and body including those obtained with relatively thick slices and with an intersection gap. This report demonstrates use of the reformation technique to establish retrospectively the symmetry in bilateral structures that were displayed out of alignment due to suboptimal patient positioning or patient motion during image acquisition and to improve the depiction of anatomical structures that were oriented out of the plane of original image acquisition. This method can be performed interactively in near real time, requires no increase in patient examination time, and has potential application throughout the body.

Artifacts↗
PubMedDate not supplied

Neurodegenerative diseases of childhood: MR and CT evaluation.

To evaluate the diagnostic utility of MR and CT in neurodegenerative diseases of childhood, we examined 63 children (MR in 44, CT in 53) carrying diagnoses of Leigh disease (14 patients), various metabolic diseases (13 patients), leukodystrophies (13 patients), other specific degenerative diseases (10 patients), and unclassified neurodegenerative disorders (13 children). Magnetic resonance yielded positive findings in 86% and CT in 81%. Lesion extent and conspicuity were consistently greater with MR. The high frequency of abnormalities detected on MR, and to a lesser extent on CT, helps distinguish children with neurodegenerative diseases from those with nonprogressive idiopathic movement disorders. The most common abnormalities included signal alterations (MR) or decreased attenuation (CT) of the basal ganglia and cerebral white matter, as well as local or generalized brain atrophy. Although considerable overlap was present, the findings showed four general patterns that may assist in tentative classification of patients with nonspecific clinical and laboratory findings.

Adolescent↗