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Biomedical subjects

N M Rofsky

Publications and source records attributed to N M Rofsky.

At least 55 records · Page 3Linked to original sources
PubMed1997

Peripheral vascular disease evaluated with reduced-dose gadolinium-enhanced MR angiography.

PURPOSE: To demonstrate the utility of low-dose gadolinium-enhanced magnetic resonance (MR) angiography of two consecutive anatomic areas for assessment of peripheral vascular disease. MATERIALS AND METHODS: Fifteen patients underwent gadolinium-enhanced MR angiography for evaluation of lower extremity peripheral vascular disease after conventional digital subtraction angiography (DSA). MR angiography was performed with three-dimensional coronal gradient-echo acquisitions before and during administration of gadopentetate dimeglumine. Two separate, contiguous areas were studied with separate doses of 0.075 and 0.1 mmol/kg gadopentetate dimeglumine. MR angiography findings were compared with DSA findings; DSA was the standard of reference. Treatment options were determined first with MR angiograms and then with DSA images. RESULTS: For distinguishing greater than 50% stenosis from 50% or less stenosis, gadolinium-enhanced MR angiography yielded a sensitivity of 97%, a specificity of 96%, and an accuracy of 97%. In 146 (97%) of 150 anatomic segments, there was essential or total agreement on treatments determined with MR angiography and DSA. In two cases (one case of vascular stent placement and one case of surgical anastomosis), extent of disease was overestimated with MR angiography. The MR study of one infrapopliteal area was insufficient for evaluation. CONCLUSION: Accurate gadolinium-enhanced MR angiography of multiple peripheral vascular areas of the lower extremities can be performed in most patients with less than 0.2 mmol/kg contrast material.

Aged↗
PubMed1997

MR imaging in the evaluation of small (< or =3.0 cm) renal masses.

The use of MR imaging in evaluating renal tumors has expanded beyond the established utility for patients with renal insufficiency and allergy to iodinated contrast. MR imaging is increasingly relied on for the evaluation of small renal lesions. The use of gadolinium chelate contrast agents, high performance MR systems, and optimized techniques is essential. This article details our experience using MR to evaluate small renal tumors and reviews the clinical issues pertinent to the management of these lesions.

Adenoma↗
PubMed1996

Dysplastic nodules and hepatocellular carcinoma: thin-section MR imaging of explanted cirrhotic livers with pathologic correlation.

PURPOSE: To evaluate detection and characterization of hepatocellular nodules in fresh whole explanted cirrhotic livers at thin-section magnetic resonance (MR) imaging. MATERIALS AND METHODS: T1-weighted spin-echo and T2-weighted fast spin-echo MR imaging (5-mm-thick sections) were performed in a head coil at 1.5 T in the whole cirrhotic livers of 28 consecutive patients within 4 hours of explantation. MR imaging findings were correlated with findings at pathologic examination, and new international terminology was used to classify the hepatocellular nodules. RESULTS: At pathologic examination, 42 suspect (other than regenerative) nodules were identified in 11 patients. MR imaging depicted 41 of 42 (98%) of these nodules (five of five hepatocellular carcinomas [HCCs {diameter, > or = 2 cm}], 10 of 10 small HCCs [diameter, < 2 cm], two of two dysplastic nodules with subfoci of HCC, three of three high-grade dysplastic nodules, and 21 of 22 low-grade dysplastic nodules. Lesions demonstrated the following combinations of signal intensity characteristics on thin-section T1- and T2-weighted images, respectively: HCC, hyperintense, hypointense (n = 3); hyperintense, hyperintense (n = 1); hypointense, isointense (n = 1). Small HCC, hyperintense, hypointense (n = 7); hypointense, hyperintense (n = 2); hyperintense, hyperintense (n = 1). Both dysplastic nodules with subfoci of HCC, hyperintense, hypointense. All seven nonsiderotic low-grade dysplastic nodules, hyperintense, hypointense. All 14 siderotic low-grade dysplastic nodules, hypointense, hypointense. All three high-grade dysplastic nodules, hyperintense, hypointense. CONCLUSION: The variable signal intensity characteristics of HCCs made reliable diagnosis impossible, but the thinsection unenhanced in vitro MR images were sensitive for detection of HCCs and dysplastic nodules in cirrhotic livers.

Carcinoma, Hepatocellular↗
PubMed1996

Breath-hold single-dose gadolinium-enhanced three-dimensional MR aortography: usefulness of a timing examination and MR power injector.

PURPOSE: To determine the usefulness of a timing examination performed with 1 mL gadopentetate dimeglumine administered with a magnetic resonance (MR) power injector at single-dose three-dimensional (3D) MR aortography. MATERIALS AND METHODS: 3D fast imaging with steady-state precession (repetition time [msec]/echo time [msec] = 5.0/2.0, with 50 degrees flip angle) was performed in 30 patients after administration of 0.1 mmol/kg gadopentetate dimeglumine. In 15 inpatients, a power injector was used and a timing examination was performed (experimental group). In 15 outpatients, manual injection was used and a timing examination was not performed (control group). In the timing examination, 1 mL gadopentetate dimeglumine was followed with 15 mL saline, both at 2 mL/sec, during axial turbo fast low-angle shot imaging (11/4.2/300 [inversion time ¿msec¿], with a 15 degrees flip angle); one image was obtained every 2 seconds for 60 seconds. Aortic signal-to-noise ratios (S/Ns) and contrast-to-noise ratios (C/Ns) were determined on images obtained in the two groups. RESULTS: In the timing examinations, aortic S/N increased significantly (902% +/- 517 [P < .001]) and was sufficient to help determine the timing of arterial enhancement. Findings on experimental images were superior to those on control images (S/N, 29.8 vs 20.5 [P = .003]; C/N, 23.8 vs 12.8 [P < .001], respectively). The time to perform procedures and calculations at the timing examination added a mean of 4.5 minutes to each examination. CONCLUSION: The combined use of a power injector and a timing examination improved S/Ns and C/Ns at breath-hold single-dose gadolinium-enhanced 3D MR aortography.

Aged↗
PubMed1996

Nonspecificity of short inversion time inversion recovery (STIR) as a technique of fat suppression: pitfalls in image interpretation.

Short inversion time inversion recovery (STIR) and the rapid acquisition with relaxation enhancement (RARE) version of STIR are commonly used pulse sequences that are sensitive enough to detect a broad range of pathologic conditions. In addition to suppressing the signal from fat, the STIR sequence achieves additive T1-weighted, T2-weighted, and proton density-weighted contrast to facilitate lesion conspicuity [1, 2]. Fat suppression with STIR sequences is based on short T1 relaxation rates and therefore is not tissue specific. The signal from any tissue with a short T1, similar to that of fat, may be nulled as well. The signal from tissues that accumulate paramagnetic contrast agents also may be suppressed with STIR sequences when an appropriate degree of T1 shortening results.

Adipose Tissue↗
PubMed1996

Image subtraction in gadolinium-enhanced MR imaging.

Image subtraction in gadolinium-enhanced MR imaging is a broadly applicable postprocessing technique that can be used with any field strength and T1-weighted sequence. This technique is typically a quick and efficient means of obtaining fat suppression that avoids the limitations of incomplete fat saturation due to field inhomogeneity and increased imaging times associated with conventional fat-suppression techniques. In particular, image subtraction may be valuable on lower strength magnetic field systems that lack effective chemical-shift fat-suppression techniques. Because source data are viewed in conjunction with subtracted images, image subtraction is unlikely to introduce errors in interpretation. By performing unenhanced and enhanced sequences in a manner amenable to image subtraction, radiologists should find this technique to be a useful and almost cost-free option.

Aged↗
PubMed1996

Mangafodipir trisodium injection (Mn-DPDP). A contrast agent for abdominal MR imaging.

Mangafodipir trisodium (Mn-DPDP) is one of several recently developed targeted hepatobiliary agents. Contrast-to-noise measurements have shown favorable results for Mn-DPDP-enhanced MR as compared with nonenhanced T1- and T2-weighted images. An improved capability for lesion detection and the ability to characterize tumors of hepatocellular origin have been demonstrated. The prolonged enhancement obtained with Mn-DPDP provides an extended window of time during which effective contrast is maintained as compared with traditional extracellular contrast agents. This report details the experimental and initial clinical experience with Mn-DPDP-enhanced MR imaging of the abdomen.

Adrenal Gland Diseases↗
PubMed1995

Multiple breath-hold averaging (MBA) method for increased SNR in abdominal MRI.

Breath-holding during MR imaging eliminates respiratory motion artifacts but places a major time constraint on data acquisition. This constraint limits image signal-to-noise ratio and hence spatial resolution. A new method, multiple breath-hold averaging, is presented that overcomes these time limitations. Several images are acquired in sequential breath-hold periods, separated by periods of normal breathing, and averaged. This averaged image shows the expected increase in SNR with surprisingly little blurring due to misregistration. SNR improvements can be traded for increased spatial resolution. The MBA methodology can also be applied to 3D data acquisitions, dynamic contrast acquisitions, and image subtractions.

Abdomen↗
PubMed1995

CT and MRI of diffuse liver disease.

CT and MRI contribute important information to the clinical evaluation of diffuse liver disease. In some cases, these modalities can establish a diagnosis that was not ascertained histologically, which is often the case when sampling errors prevent a definitive tissue diagnosis. Characteristic alterations of liver attenuation on CT, signal changes on MRI, and morphological changes appreciated with both modalities can be used to diagnose fatty infiltration, some parenchymal deposition diseases, and cirrhosis. Furthermore, hepatocellular disease can be confirmed in the setting of indeterminate clinical and laboratory findings. Significant overlap in the imaging findings of this wide range of disorders continues to limit specificity; however, at a minimum, these techniques provide a rapid means to a noninvasive evaluation that often guides clinical decisions. Faster scanning techniques available with CT and MRI may provide additional information by assessing contrast dynamics. This review of CT and MRI in diffuse liver disease considers the diagnostic utility and clinical implications of these modalities. Pathological findings relevant to imaging considerations are discussed.

Fatty Liver↗
PubMed1995

Effect of magnetic resonance exposure combined with gadopentetate dimeglumine on chromosomes in animal specimens.

RATIONALE AND OBJECTIVES: We tested for the presence of a form of unstable chromosomal damage--anaphase bridges--that might result from the combined exposure to gadopentetate dimeglumine and magnetic resonance (MR) imaging in rats. METHODS: Fifty-four male Sprague-Dawley rats, along with appropriate controls, were exposed either to MR imaging alone, gadopentetate dimeglumine alone, or a combination of the two. After exposure, partial hepatectomies were performed to induce a vigorous mitotic response in the regenerating liver stump. Twenty-eight to 30 hr after partial hepatectomy, tissue specimens from regenerating liver were removed and analyzed microscopically for the presence of anaphase bridges. RESULTS: No anaphase bridges were detected in any of the animals, including those exposed to gadopentetate dimeglumine and MR imaging. CONCLUSION: Using anaphase bridge formation as an indicator, exposure to MR imaging alone, gadopentetate dimeglumine alone, or a combination of the two under the conditions used in this experiment did not cause detectable unstable chromosomal damage.

Anaphase↗
PubMed1995

MR angiography of the hand and wrist.

MR angiographic techniques that visualize the arterial anatomy of the hand and wrist currently are available. Further refinements are necessary to ensure that diagnostic studies are routine. In my experience, the most detailed anatomy is obtained with gadolinium-enhanced 3-D sequences. The specific role of MR angiography of the hand and wrist has yet to be defined. Currently, it is used in my practice as a screen for certain vascular disorders and in those patients in whom the risk/benefit considerations of conventional arteriography are deemed unacceptable to the referring surgeon. Future applications may include a quantitative component. This information could prove beneficial in the serial follow up of patients with vasospastic disorders that require intermittent vasodilator therapy. It is hoped that quantitative information might provide a means to direct therapy prior to the onset of debilitating symptoms. Clinical efficacy must be established with comparative studies to the reference standard of conventional angiography. If reliable MR angiography can be obtained with sufficient information for clinical decision making, it is likely that it will have a cost and safety advantage over conventional angiography.

Blood Vessels↗
PubMed1993

Aortic aneurysm and dissection: normal MR imaging and CT findings after surgical repair with the continuous-suture graft-inclusion technique.

The normal range of postoperative imaging findings are described in 34 asymptomatic patients studied 5-66 months (mean, 28 months) after undergoing the continuous-suture graft-inclusion technique for repair of aortic aneurysms (n = 20) and dissections (n = 14) involving the ascending aorta. All 34 patients underwent magnetic resonance (MR) imaging, and 24 patients also underwent computed tomography (CT). Perigraft thickening was seen in 19 patients (56%) with MR imaging and in eight patients (33%) with CT. Flow outside the graft but contained within the native wrap was noted in five patients (15%) with MR imaging and in four patients (17%) with contrast material-enhanced CT. Thrombus was identified outside the graft and within the wrap in seven patients (21%) with MR imaging and in six patients (25%) with CT. Mass effect on the graft was depicted in four patients (12%) with MR imaging and in three patients (13%) with CT. Of the 14 patients who underwent repair of aortic dissections, an intimal flap was seen distal to the graft in seven of the 14 (50%) evaluated with MR imaging and in four of the 10 (40%) evaluated with contrast-enhanced CT. An accurate postoperative imaging evaluation requires precise knowledge of the surgical technique performed and its anatomic consequences.

Adolescent↗
PubMed1993

Hepatocellular tumors: characterization with Mn-DPDP-enhanced MR imaging.

Fifty-eight patients suspected of having focal hepatic disease were studied prior to and following the intravenous administration of manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate) (DPDP), a hepatobiliary magnetic resonance (MR) contrast agent. Four doses (3, 5, 8, or 10 mumol/kg) of Mn-DPDP were used to test the hypothesis that Mn-DPDP-enhanced MR imaging would display enhancement in tumors of hepatocellular origin. A total of 203 lesions were evaluated. Histologic proof was available in 32 cases, and in 26 cases lesions were evaluated on the basis of characteristic imaging findings. Statistical calculations for distinction of tumors of hepatocellular origin yielded a sensitivity of 100%, a specificity of 92.0%, an accuracy of 93.6%, a positive predictive value of 75.9%, and a negative predictive value of 100%. The authors conclude that the presence and patterns of enhancement at Mn-DPDP-enhanced MR imaging permit reliable distinction between hepatocellular and nonhepatocellular tumors.

Adult↗
PubMed1993

Surgical repair of type A aortic dissection by the circulatory arrest-graft inclusion technique in sixty-six patients.

During an 8-year period (1984 to 1991) 66 patients (mean age 59 years, range 26 to 84 years) with type A aortic dissection (60 ascending aorta tears, 6 arch tears; 35 acute, 31 chronic) had surgical repair by a continuous suture-graft inclusion technique. Hypothermic circulatory arrest (16 degrees C) was used in 58 patients (35/35 acute, 23/31 chronic; mean arrest time 26 minutes, range 10 to 55 minutes). Fifty-two patients had hemiarch repair and 6 had total arch replacement. Aortic valve disease necessitated treatment in 38 patients (1 valved conduit, 20 valve replacements, 17 valve repairs). Recently 11 patients had valve repair by reconstruction of the native aortic root, by means of techniques similar to those used for homograft valve insertion. Operative mortality was 9% (14% acute, 3% chronic). Stroke occurred in 2 patients (3%) and was fatal in both. Variables suggestive of increased operative risk by univariate analysis were acuteness (p = 0.12), visceral ischemia (p = 0.12), and preoperative shock (p = 0.13). No variable was significant by multivariate analysis. Overall actuarial survival at 48 months was 77%, with 3 late deaths from a ruptured distal aneurysm. Late computed tomography or magnetic resonance imaging scan was done in 28 patients at a mean interval of 33 months. These studies identified 1 patient with a pseudoaneurysm requiring reoperation and 3 patients with contained flow between the graft and the wrap. Three patients required late operation: 1 for pseudoaneurysm, 1 for arch dissection, and 1 for repair of a distal aneurysm.

Actuarial Analysis↗