Search PubMed⌕ Search

Biomedical subjects

E A Zerhouni

Publications and source records attributed to E A Zerhouni.

At least 19 recordsLinked to original sources
PubMed1997

Fast 23Na magnetic resonance imaging of acute reperfused myocardial infarction. Potential to assess myocardial viability.

BACKGROUND: The ability of the myocyte to maintain an ionic concentration gradient is perhaps the best indication of myocardial viability. We studied the relationship of 23Na MRI intensity to viability and explored the potential of fast-imaging techniques to reduce 23Na imaging times in rabbits and dogs. METHODS AND RESULTS: Eighteen rabbits underwent in situ coronary artery occlusion and reperfusion. The hearts were then either imaged following isolation and perfusion with cardioplegic solution (n = 6), imaged in vivo (n = 6), or analyzed for 23Na content and relaxation times (n = 12). Normal rabbits (n = 6) and dogs (n = 4) were imaged to examine the effect of animal size on 23Na image quality. 23Na imaging times were 7, 11, and 4 minutes for isolated rabbits, in vivo rabbits, and in vivo dogs, respectively. Infarcted, reperfused regions, identified by triphenyltetrazolium chloride staining, showed a significant elevation in 23Na image intensity compared with viable regions (isolated, 42 +/- 5%, P < .02; in vivo, 95 +/- 6%, P < .001), consistent with increased tissue sodium content. Similarly, 23Na MR spectroscopy showed that [Na+] was higher in nonviable than viable myocardium (isolated, 99 +/- 4 versus 61 +/- 2 mmol/L; in vivo, 91 +/- 2 versus 38 +/- 1 mmol/L; P < .001 for both). Image signal-to-noise ratios were higher in dogs than rabbits despite shorter imaging times, primarily due to larger voxels. CONCLUSIONS: Following acute infarction with reperfusion, a regional increase in 23Na MR image intensity is associated with nonviable myocardium. Fast gradient-echo imaging techniques reduce 23Na imaging times to a few minutes, suggesting that 23Na MR imaging has the potential to become a useful experimental and clinical tool.

Animals↗
PubMed1997

Benign and malignant musculoskeletal masses: MR imaging differentiation with rim-to-center differential enhancement ratios.

PURPOSE: To assess the diagnostic potential of the rim-to-center differential enhancement ratio in the magnetic resonance (MR) imaging differentiation of benign from malignant musculoskeletal masses. MATERIALS AND METHODS: Dynamic gadolinium-enhanced fast multiplanar spoiled gradient-recalled acquisition in the steady state imaging was performed to evaluate 17 one and soft-tissue masses (10 malignant, seven benign) in 14 patients. The rim-to-center differential enhancement ratio was determined from images at the maximal enhancement rate. The difference in differential enhancement ratios between benign and malignant masses was evaluated and compared with the maximum rate of enhancement for each mass. RESULTS: Nine of 10 malignant masses showed rapid rim enhancement with delayed central fill-in. This enhancement pattern was absent in benign masses. The average rim-to-center differential enhancement ratio was 0.64 +/- 0.26 for malignant masses and -0.16 +/- 0.33 for benign masses (P < .001). This difference was statistically significant. The average maximum rate of enhancement was 3.41%/sec +/- 2.20 for malignant masses and 2.74%/sec +/- 2.46 for benign masses (P > .05). CONCLUSION: Intratumoral enhancement patterns of malignant and benign masses differ because of differences in vascular architecture. These preliminary results suggest that the rim-to-center differential enhancement ratio has potential as an additional parameter for the MR imaging differentiation of indeterminate musculoskeletal masses.

Adolescent↗
PubMed1996

Pencil excitation with interleaved fourier velocity encoding: NMR measurement of aortic distensibility.

A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of pulse-wave velocity in the aorta. A cylinder of magnetization is excited along the aorta, with Fourier-velocity encoding and readout gradients applied along the cylinder axis. Cardiac gating and data interleaving improve the effective time resolution to as high as 3 ms. Wave velocities are determined from the position of the foot of the flow wave in the velocity profiles. Evidence of helical flow distal to the aortic arch can be seen in normal subjects, while disturbed flow patterns are visible in patients with aneurysms and dissections.

Adult↗
PubMed1996

High resolution intravascular MRI and MRS by using a catheter receiver coil.

Potentially important diagnostic information about atherosclerosis can be obtained by using magnetic resonance imaging and spectroscopy techniques. Because critical vessels such as the aorta, coronary arteries, and renal arteries are not near the surface of the body, surface coils are not adequate to increase the data quality to desired levels. A few catheter MR receiver coil designs have been proposed for imaging the walls of large blood vessels such as the aorta. These coils have limited longitudinal coverage and they are too thick to be placed into small vessels. A flexible, long and narrow receiver coil that can be placed on the tip of a catheter and will enable multi-slice high resolution imaging of small vessels has been developed. The authors describe the theory of the coil design technique, derive formulae for the signal-to-noise ratio characteristics of the coil, and show examples of high resolution cross-sectional images from isolated human aortas acquired by using this catheter coil. In addition, high resolution in vivo rabbit aorta images were obtained as well as a set of spatially resolved chemical shift spectra from a dog circumflex coronary artery.

Animals↗
PubMed1996

Peripheral primitive neuroectodermal tumors. CT and MRI evaluation.

The clinical, radiographic, and pathologic features of 17 patients with documented peripheral primitive neuroectodermal tumor (PNET) were evaluated in a retrospective study. The age at diagnosis ranged from 9 months to 46 years (median, 15.8 years). Primary sites of involvement were the abdomen (n = 8), extremities (n = 5), chest (n = 1), temporal bone (n = 1), maxilla (n = 1), and diploe (n = 1). At the time of diagnosis, six patients had distant metastases; all of these patients died, with an average survival of 8.8 months. Radiologic workup included standard radiographs, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy. The radiographic appearance of these tumors was not specific for differentiation of PNETs from other types of bone and soft tissue tumors. The typical appearance resembled large non-calcified, soft tissue masses with cystic or necrotic areas. Heterogeneous enhancement with intravenous contrast agents was evident on CT, as was an intermediate signal intensity on Tl-weighted images and hyperintense signal on T2-weighted and STIR sequences. After gadolinium administration, variable enhancement was seen. MRI and CT were useful in predicting resectability, in detecting distant metastases, and in the evaluation of response to treatment. Surgery was performed in all cases, either for definitive diagnosis or for therapy. All patients received combined chemotherapy and radiotherapy and five patients received autologous bone marrow transplantation. Clinical follow-up was obtained over a mean period of 3 years (range 1 day to 6 years). Prognosis was poor with a median survival of 3.4 years. Our experience in 17 patients with peripheral neuroectodermal tumors indicates that although their radiologic features are non-specific, they should be included in differential diagnosis of soft tissue tumors of aggressive behavior, especially in a young age group. CT and MRI are useful in delineating the extent and resectability of tumor and in monotoring treatment.

Adolescent↗
PubMed1996

MRI of avascular necrosis of bone.

Avascular necrosis (AVN) is characterized by death of both trabecular bone as well as bone marrow elements. Weight-bearing bone becomes mechanically weakened and may eventually collapse, secondarily leading to osteoarthritis and debilitating pain. Early diagnosis and treatment of this entity are crucial because it affects relatively young individuals, and treatment options for advanced disease are limited. Magnetic resonance imaging (MRI) has emerged as the modality of choice for the evaluation of avascular necrosis of bone. We will discuss applications of MRI for early diagnosis, for monitoring therapy, and for its potential role in assessing individuals at risk of AVN. Although bone scintigraphy using single photon emission computed tomography (CT) may be nearly as accurate as MRI, MRI offers a more specific diagnosis in the patient who presents with hip pain of uncertain etiology. In addition, lesion size and location can be more easily assessed on magnetic resonance images, and this has been shown to relate to prognosis and need for treatment. We will review the pathophysiologic mechanisms of AVN and the current use of MRI in the diagnosis of this condition.

Contrast Media↗
PubMed1996

Fluid-fluid levels in injured knees: do they always represent lipohemarthrosis?

PURPOSE: To determine if fluid-fluid levels on horizontal-beam radiographs of posttraumatic knee joints always represent lipohemarthrosis. MATERIALS AND METHODS: The files of 41 patients with tibial plateau fracture were reviewed retrospectively. Twelve with fluid-fluid levels on radiographs who underwent computed tomography (CT) or magnetic resonance (MR) imaging were selected; CT attenuation and MR signal intensity patterns were used to assess fluid-fluid levels. Simulated hemarthrosis and lipohemarthrosis underwent plain radiography, CT, and MR imaging. RESULTS: Eight patients showed no evidence of fat in the supernatant fluid with either CT (n = 7) or CT and MR imaging (n = 1). Fluid levels resulted from blood separating into cellular elements and supernatant serum. Four patients showed evidence of lipohemarthrosis with either CT (n = 3) or MR imaging (n = 1); in one of these patients, a double fluid-fluid level could be demonstrated retrospectively on plain radiographs. CONCLUSION: Single fluid-fluid levels in posttraumatic knee joints do not necessarily represent a lipohemarthrosis. Double fluid-fluid levels are a more specific finding.

Hemarthrosis↗
PubMed1996

Quantitative cardiac perfusion: a noninvasive spin-labeling method that exploits coronary vessel geometry.

PURPOSE: To quantitate myocardial arterial perfusion with a noninvasive magnetic resonance (MR) imaging technique that exploits the geometry of coronary vessel anatomy. MATERIALS AND METHODS: MR imaging was performed with a spin-labeling method in six arrested rabbit hearts at 4.7 T. Selective inversion of magnetization in the short-axis imaging section along with all myocardium apical to that section produces signal enhancement from arterial perfusion. A linescan protocol was used for validation of flow enhancement. Flow was quantitated from two images and validated with spin-echo (SE) imaging. Regional perfusion defects were created by means of coronary artery ligation and delineated with gadolinium-enhanced imaging. RESULTS: Linescan estimates of T1 obtained at physiologic flows agreed with model predictions. Flow-induced signal enhancement measured on SE images also agreed with expected values. Finally, perfusion abnormalities created by means of coronary artery ligation were detected. CONCLUSION: This spin-labeling method provides quantitative estimates of myocardial arterial perfusion in this model and may hold promise for clinical applications.

Animals↗
PubMed1996

CT and MR imaging in the staging of colorectal carcinoma: report of the Radiology Diagnostic Oncology Group II.

PURPOSE: To prospectively evaluate the relative accuracy of computed tomography (CT) and magnetic resonance (MR) imaging in the staging of colorectal carcinoma. MATERIALS AND METHODS: CT and MR studies were independently interpreted in a group of 478 patients with colorectal carcinoma in a study conducted from 1989 to 1993. The accuracy of each modality was assessed in a subset of 365 patients with primary tumors with respect to staging of local extent of tumor, status of local-regional lymph nodes, and the presence of liver metastases. RESULTS: In the staging of local extent of tumor, CT is more accurate than MR imaging, particularly in the definition of penetration of the muscularis propria by rectal cancer (74% vs 58%). Accuracies of CT and MR imaging were equivalent in depiction of transmural extent in colon cancers. CT and MR imaging exhibited accuracies of 62% and 64% in assessment of lymph node involvement with sensitivities of 48% and 22%, respectively. The accuracy of MR imaging and of CT (85% for each) are better for evaluation of liver metastases; lower sensitivities (62% and 70%, respectively) than specificities (97% and 94%, respectively) were demonstrated for both modalities. CONCLUSION: CT was more accurate than MR imaging in detection and characterization of transmural penetration of rectal tumors. Recent technologic advances in MR imaging may affect these results.

Aged↗
PubMed1995

Physiological basis of myocardial contrast enhancement in fast magnetic resonance images of 2-day-old reperfused canine infarcts.

BACKGROUND: Contrast-enhanced fast magnetic resonance (MR) images of acute, reperfused human infarcts demonstrate regions of hypoenhancement and hyperenhancement. The relations between the spatial extent and time course of these enhancement patterns to myocardial risk, infarct, and no-reflow regions have not been well characterized. METHODS AND RESULTS: The proximal left anterior descending coronary artery was occluded in 11 closed-chest dogs for 90 minutes followed by 2 days of reperfusion. Regional blood flow was determined by use of radioactive microspheres. The animals were studied at the 2-day time point with contrast-enhanced fast MRI (Signa 1.5 T, General Electric). Thioflavin-S was administered to demarcate no-reflow regions. The hearts were then excised, sectioned into five base-to-apex slices, stained with 2,3,5-triphenyltetrazolium chloride (TTC), and photographed under room light (for TTC) and ultraviolet light (for thioflavin). The spatial extents of thioflavin-negative, TTC-negative, and risk regions were compared planimetrically with MRI hypoenhanced and hyperenhanced regions. The spatial locations of subendocardial hypoenhancement in MR images correlated closely with those of thioflavin-negative regions. Microsphere blood flow in these regions was significantly reduced compared with remote regions (0.37 +/- 0.09 versus 0.88 +/- 0.10 mL/min per gram, respectively, P < .001) and with baseline (0.37 +/- 0.09 versus 0.87 +/- 0.15 mL/min per gram, P < .01). The spatial extent of hyperenhancement was smaller than the risk region (r = .64, slope = 0.48, P < .001) but highly correlated with TTC-negative regions and were, on average, 12% larger (r = .93, slope = 1.12, P = .035). CONCLUSIONS: In contrast-enhanced MR images of 2-day-old reperfused canine infarcts, myocardial regions of hypoenhancement are related to the no-reflow phenomenon. Approximately 90% of the myocardium within hyperenhanced regions is nonviable.

Animals↗
PubMed1995

Regional heterogeneity of human myocardial infarcts demonstrated by contrast-enhanced MRI. Potential mechanisms.

BACKGROUND: Myocardial reperfusion is pivotal to the prognosis of patients with acute myocardial infarction. In these patients, coronary flow is generally assessed by angiography and tissue perfusion by tracer scintigraphy. This study was designed to examine whether magnetic resonance imaging (MRI) provides information on myocardial perfusion and damage beyond that supplied by angiography and thallium scintigraphy after acute myocardial infarction. METHODS AND RESULTS: Twenty-two patients with recent myocardial infarction had ECG, echocardiography, coronary angiography, and fast contrast-enhanced MRI. Twelve patients also had exercise thallium scintigraphy. Time-intensity curves obtained from infarcted and noninfarcted regions were correlated with coronary anatomy and left ventricular function. Two perfusion patterns were observed in infarcted regions by comparison with the normal myocardial pattern. All patients but 1 had persistent myocardial hyperenhancement within the infarcted region up to 10 minutes after contrast. In 10 patients, this hyperenhanced region surrounded a subendocardial area of decreased signal at the center of the infarcted region associated with coronary occlusion at angiography, Q waves on ECG, and greater regional dysfunction by echocardiography. Moreover, the extent and location of the MRI abnormalities correlated well with the extent and location of the fixed single-photon emission computed tomography thallium defects. CONCLUSIONS: Large human infarcts, associated with prolonged obstruction of the infarct-related artery, are characterized by central dark zones surrounded by hyperenhanced regions on MRI. Conversely, reperfused infarcts with less regional dysfunction have uniform signal hyperenhancement. The MRI hyperenhanced segment correlates well with the fixed scintigraphic defect in patients with acute myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1995

Effects of myocardial water exchange on T1 enhancement during bolus administration of MR contrast agents.

Interpretation of first-pass myocardial perfusion studies employing bolus administration of T1 magnetic resonance (MR) contrast agents requires an understanding of the relationship between contrast concentration and image pixel intensity. The potential effects of myocardial water exchange rates among the intravascular, interstitial, and cellular compartments on this relationship are controversial. We directly studied these issues in isolated, nonbeating canine interventricular septa. Myocardial T1 was measured three times/s during bolus transit of intravascular (albumin-Gd-DTPA and polylysine-Gd-DTPA) and extracellular (gadoteridol) contrast agents. For polylysine-Gd-DTPA, the peak changes in myocardial 1/T1 (delta R1) scaled nonlinearly with perfusate contrast concentration whereas a linear relationship would be expected for fast water exchange among the vascular, interstitial, and cellular compartments. For all agents, the peak delta R1 were much smaller than the values expected on the basis of fast myocardial water exchange. The data demonstrate that in isolated myocardial tissue, myocardial T1 enhancement during bolus administration of contrast can be strongly affected by myocardial water exchange for both intravascular and extracellular MR contrast agents.

Albumins↗
PubMed1995

Multi-shot EPI for improvement of myocardial tag contrast: comparison with segmented SPGR.

To assess the potential value of multi-shot EPI relative to segmented k-space SPGR for myocardial tagging, we measured tag contrast for both sequences in a phantom and human study and compared it with theoretical predictions. In the human heart, EPI tag contrast was three times that of SPGR at the end of systole. Tag duration was lengthened with EPI to at least 600 ms. In addition, the entire heart was examined in a total of 32 heartbeats with EPI versus 152 heartbeats with SPGR.

Algorithms↗
PubMed1995

A phased array coil for human cardiac imaging.

A prototype cardiac phased array receiver coil was constructed that comprised a cylindrical array and a separate planar array. Both arrays had two coil loops with the same coil dimensions. Data acquisition with the cylindrical array placed on the human chest, and the planar array placed under the back, yielded an overall enhancement of the signal-to-noise ratio (SNR) over the entire heart by a factor of 1.1-2.85 over a commercially available flexible coil and a commercially available four-loop planar phased array coil. This improvement in SNR can be exploited in cardiac imaging to increase the spatial resolution and reduce the image acquisition time.

Heart↗
PubMed1995

A magnetization-driven gradient echo pulse sequence for the study of myocardial perfusion.

A T1-weighted imaging pulse sequence for contrast-based studies of myocardial perfusion is presented and evaluated in phantoms and in vivo. The sequence is similar to spoiled gradient-recalled echo sequences except that nonselective preparatory RF pulses drive magnetization to steady state prior to image acquisition. Steady state is thus obtained in both tissue and blood resulting in a stable, homogeneous, and dark pre-contrast baseline. Tip angles and timings are chosen so that pixel intensity approximates a linear relation to 1/T1. The dynamic range of signal response to contrast agent concentration is greater than that of an inversion-recovery fast low angle shot sequence. The sequence proposed should be useful for myocardial perfusion studies.

Blood↗