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C E Spritzer

Publications and source records attributed to C E Spritzer.

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

Cine phase-contrast magnetic resonance imaging for analysis of flow phenomena in experimental aortic dissection.

Using a 1.5 T magnetic resonance imaging (MRI) system, cine phase-contrast and magnitude images were obtained in three phantoms that simulated different anatomic configurations of aortic dissection. The dissection phantoms were made of compliant materials, and pulsatile flow was used in all experiments. Phantoms differed only in the location of the fenestration between the true and false lumens (I: an upstream "entry" only, II: both upstream "entry" and downstream "re-entry," and III: a downstream "entry" only). Flow jets, flap motion, and wave propagation were clearly visualized in cine MR images of each phantom, and quantitatively analyzed with reference to the stimulated cardiac cycle of the pump. Flow in the false lumen was always bidirectional. Upstream and downstream flow waves collided and dispersed within the false lumen. Flow through the false lumen was the same in phantoms I and II, and least in phantom III. The average area of the true lumen was largest in phantom III and smallest in I. Phantom I had the highest overall flow rate in the false lumen and greatest change in false lumen size during the cardiac cycle, while the downstream "entry" phantom had the lowest of both parameters. Flow phenomena in aortic dissections can be studied by cine phase-contrast MRI.

Aortic Dissection↗
PubMed1991

Imaging of the renal arteries: value of MR angiography.

We compared the efficacy of MR angiography with that of conventional angiography for visualizing the renal arteries and detecting renovascular disease. Thirty-three MR angiographic studies, consisting of axial two-dimensional (2-D) phase-contrast, coronal 2-D phase-contrast, and coronal 2-D time-of-flight acquisitions, were performed within 48 hr of conventional arteriography. The studies were done to evaluate possible renovascular hypertension (n = 25) or potential donor nephrectomy (n = 8). The three MR image sets were interpreted independently, in random order by three observers, with regard to the number of renal arteries, degree of vessel visualization, arteriovenous overlap, and presence of renovascular disease. A fourth interpretation was based on the combined axial and coronal phase-contrast image sets. Evaluation was limited to the proximal 35 mm of each renal artery. Renal artery visualization and detection of renovascular disease were more complete with coronal phase-contrast (80% sensitivity, 91% specificity) than with time-of-flight (53% sensitivity, 97% specificity) images. Combined axial and coronal phase-contrast images permitted visualization of the proximal 35 mm of all dominant renal arteries and detection of 13 of 15 stenoses (87% sensitivity, 97% specificity). Our data suggest that biplanar MR angiography has considerable potential as a noninvasive screening technique for the evaluation of renovascular disease.

Angiography↗
PubMed1991

Preliminary experience with magnetic resonance imaging in patients with third-trimester bleeding.

Fifteen patients with third-trimester bleeding, in whom transabdominal ultrasound had failed to identify a definitive source of bleeding, underwent magnetic resonance imaging (MRI). Magnetic resonance imaging correctly identified three cases of placenta previa. In four patients, intrauterine blood was identified in hematomas. One hematoma was associated with a previa, two progressed to acute abruptions, and one was associated with a clot at the marginal cord insertion. Blood was seen leading away from the placenta in a case that progressed to an acute abruption. It was also seen in the region of the cervix in two patients with placenta previa. One patient had a normal MRI but had a fresh clot at delivery, which presumably formed after the imaging. In the remaining seven patients, MRI scans were negative and the placentas were normal at delivery. Our preliminary results suggest that MRI is helpful in evaluating patients with unexplained third-trimester bleeding.

Abruptio Placentae↗
PubMed1990

Detection, characterization and functional assessment of reperfused Q-wave acute myocardial infarction by cine magnetic resonance imaging.

The capability of dynamic gradient-refocused magnetic resonance imaging (cine MRI) to detect, localize and functionally assess acute myocardial infarction (AMI) in 25 patients at a mean time interval of 7 days after AMI was evaluated. Fifteen asymptomatic volunteers were also examined to determine the specificity of the observations. Upon presentation, each patient received intravenous thrombolytic therapy, underwent immediate cardiac catheterization and had percutaneous transluminal coronary angioplasty performed when coronary reperfusion was absent. Twenty-four of the patients had documented coronary reperfusion at a mean interval of 259 +/- 129 minutes. Global ejection fraction and regional wall motion abnormalities were evaluated at 7 days by cine MRI, left ventriculography and radionuclide angiography. Twenty patients with both an absolute decrease in myocardial signal and a matched regional wall motion abnormality had AMI properly identified by cine MRI. In contrast, the finding of both decreased signal intensity and a matched regional wall motion abnormality was absent in the group of asymptomatic volunteers. The ejection fraction by cine MRI correlated better with the ejection fraction by left ventriculography (r = 0.94, standard error of the estimate = 3.6) than did the ejection fraction by radionuclide angiography (r = 0.82, standard error of the estimate = 5.8). The regional wall motion concordance rate in comparison to left ventriculography was similar for both cine MRI (69%) and radionuclide angiography (65%). These findings suggest that cine MRI may play an important role in the future detection and functional characterization of AMI.

Adult↗
PubMed1990

Rapid MR imaging of blood flow with a phase-sensitive, limited-flip-angle, gradient recalled pulse sequence: preliminary experience.

To assess blood flow rapidly, a limited-flip-angle, gradient recalled pulse sequence was modified to acquire two views at the same phase-encoding step in successive repetitions. One view is obtained with first-moment flow compensation, while the second view is obtained with selectable flow encoding (non-zero first moment) along one direction. Blood flowing along the encoded direction acquires a phase difference between the two views, resulting in signal dependent on both direction and speed of flow. Stationary tissues undergo no phase change. Therefore, the phase shift between the two views produces an image that spatially renders flow direction and velocity. With a 24-msec repetition time, a 256 X 128 matrix, and two excitations, data acquisition is completed in 13 seconds per location (both a magnitude image and a flow image are produced at each location). Images generated with flow phantoms confirmed the accuracy of this method. Preliminary clinical evidence in 23 human subjects suggests that this method is useful in evaluating portal hypertension, distinguishing arterial from venous flow, distinguishing between slow flow and clot, and confirming the presence of clot. This method appears to be a fast, easy way to assess blood flow in large vessels.

Adolescent↗
PubMed1990

Deep venous thrombosis: experience with gradient-echo MR imaging in 66 patients.

The medical records of 66 patients who underwent evaluation for possible deep venous thrombosis (DVT) by means of gradient-echo (GRE) magnetic resonance (MR) imaging were reviewed. Confirmatory venograms were obtained in 26 patients; in the other 40, the accuracy of GRE MR imaging was assessed by means of clinical follow-up, which ranged from 1 to 23 months (mean, 7.7 months). Findings in GRE MR images were negative in 42 patients (64%) and positive in 24 patients (36%). In patients who underwent confirmatory venography, the sensitivity of GRE MR imaging was 100% and the specificity was 92.9%. No patient with a negative GRE MR study developed DVT or pulmonary emboli during the follow-up period. Although seven patients in this group died, the single autopsy showed no evidence of pulmonary embolism, and no clinical evidence existed to suggest that pulmonary embolism was the cause of death in any of the other six patients. It is concluded that GRE MR imaging is an accurate, noninvasive means of detecting DVT.

Adolescent↗
PubMed1990

Hepatic hemangiomas vs metastases: MR differentiation at 1.5 T.

We retrospectively studied the value of MR imaging at 1.5 T in distinguishing hepatic hemangiomas (n = 15) from metastases (n = 15) by using (1) lesion/liver signal-intensity ratios, (2) contrast/noise ratios, and (3) T2 relaxation time on long TR/TE spin-echo (SE) sequences. Lesion/liver margin sharpness, lesion shape, and overall lesion morphologic pattern were evaluated also. Univariate logistic regression analysis of the quantitative data showed that T2 was the only statistically significant (p less than .02) variable for distinguishing a hemangioma from a metastasis. A receiver-operator-characteristic plot of T2 produced an area of 0.80 (+/- 0.08). T2 values for these lesions still overlapped with those for metastases. Morphologically, hemangiomas were sharply marginated (80%), rounded or oval (93%), homogeneous, hyperintense lesions (73%), whereas metastases were poorly marginated (66%) and inhomogenous (67%) lesions. The marked, hyperintense appearance was present in 27% of metastases. Retrospective, multivariate logistic regression analysis of T2 and the presence of hyperintense morphology did not improve results based on T2 alone. Morphologic criteria are helpful in differentiation, as some metastases have a prolonged T2 and are not homogenous, hyperintense lesions. In cases where T2 or morphology are equivocal, other diagnostic tests may help confirm the MR findings. We currently use a T2 of greater than 88 msec and the presence of hyperintense morphology to diagnose hemangiomas. Despite both quantitative and qualitative analysis, data for these hemangiomas and metastases still overlap.

Adult↗
PubMed1990

Assessing the patency of mediastinal and thoracic inlet veins: value of MR imaging.

To assess the accuracy of MR imaging in the evaluation of patients with suspected thoracic venous obstruction, hospital records and MR studies of 31 such patients were reviewed. Gradient-recalled echo, spin-echo, or cine MR techniques were used. In 26 of the 31 patients, venous obstruction was confirmed by CT, venography, sonography, surgery, or autopsy. Causes included tumor invasion, compression of veins, coagulopathy, or indwelling catheters. MR detected an abnormality of the superior vena cava in all 16 cases in which it was seen on other tests. Abnormality of the internal or external jugular veins was detected in all six cases in which other studies were abnormal. Abnormality of veins in the shoulder region was detected by MR in 10 of 12 patients in whom such disease was seen on other tests. The two interpretive errors were caused by nonocclusive clot, short (less than 2-cm) occlusions, and metallic artifact. Overall, MR correctly identified abnormality in 32 of 34 vessels (sensitivity, 94%). In all cases, a negative MR study was found to be a true negative (no false positives in 42 normal vessels; specificity, 100%). We conclude that MR is an accurate means of assessing patency of the thoracic inlet and mediastinal veins. Its noninvasive nature and multiplanar capability contribute to its usefulness in this clinical setting.

Adolescent↗
PubMed1990

Practical aspects of vascular imaging using MRI.

MRI is an accurate means of noninvasively assessing vascular abnormalities. However, multiple potential pitfalls exist. In order to minimize error, a knowledge of the flow phenomena seen on various pulse sequences, along with an understanding of pulse sequence modifications that alter these flow phenomena, is necessary. With such an understanding, the current utility of MRI for solving commonly encountered clinical problems of the vascular tree is addressed. Emphasis is placed on a "how-I-do-it" approach, realizing that the reader will make modifications where necessary due to differences in hardware, software, and experience. As appropriate, references to the literature are made in an attempt to justify the use of MRI for the particular problems being discussed.

Blood Vessels↗
PubMed1990

Magnetic resonance imaging of the femoral head after acute intracapsular fracture of the femoral neck.

In fifteen patients who had a subcapital fracture of the femoral neck (twelve displaced fractures and three non-displaced fractures), magnetic resonance imaging of the femoral head was done with two-dimensional Fourier transform spin-echo technique within forty-eight hours of injury. The magnetic resonance image did not show avascular necrosis of the femoral head in any of the patients. In eleven patients, there was a decreased signal at the base of the femoral head, immediately adjacent to the fracture. This decreased signal corresponded to a recognized band of necrosis and hemorrhage next to the site of the fracture and was not related to the viability of the femoral head. No other changes were seen on the images. We concluded that this type of magnetic resonance imaging is inadequate to determine the viability of the femoral head within forty-eight hours after a patient sustains an acute intracapsular fracture of the femoral neck.

Aged↗
PubMed1989

MR fluoroscopy: initial clinical studies.

Magnetic resonance (MR) fluoroscopy is a method for high-speed MR image acquisition with the goals of short acquisition time per image (500 msec or less), high image rate (10 images or more per second), and high-speed image reconstruction (150 msec or less from data acquisition to image display). The authors present their results with the first two goals in volunteers. MR fluoroscopic image data were acquired with a limited flip angle pulse sequence with reduced repetition times (TRs) and fewer phase encodings used per image. The sequence was applied continuously, and images were formed by updating one set of data with data from the most recently taken measurements. Sample head images were generated with TR/echo times as small as 11/5.5 msec and 48 phase encodings for a total acquisition time of about 500 msec. Images were acquired while the volunteer flexed his head. Artifacts from the motion became less evident on images as progressively shorter acquisition times were used.

Brain↗
PubMed1989

Herniation pits of the femoral neck: appearance at MR imaging.

Herniation pits of the femoral neck are benign lesions recognized because of their characteristic appearance and location on plain radiographs. The appearance of this lesion in seven magnetic resonance (MR) examinations of the hips in five patients is described. MR revealed a well-marginated, round to oval defect in the superior lateral quadrant of the femoral neck with anterior cortical extension in all cases. With T1 weighting the signal intensity within each lesion was uniformly low. All but one case revealed a peripheral margin of absent signal intensity on T2-weighted and out-of-phase images. The MR appearance and location are sufficiently characteristic to allow identification of this lesion and aid in differentiating it from pathologic processes such as avascular necrosis, with which it may be confused.

Adult↗
PubMed1989

Cine-gradient-refocused MR imaging of central pulmonary emboli.

We studied the use of MR imaging with a limited-flip-angle, gradient-refocused pulse sequence to show central pulmonary emboli in 11 patients and to distinguish acute from chronic emboli. The central pulmonary vasculature was imaged by using a cine-limited-flip-angle (cine-MR) pulse sequence with 63/13 (TR/TE) and a 30 degrees flip angle (theta), as well as standard spin-echo sequences. Patients were selected on the basis of suspicion of central pulmonary embolism and correlative studies done within 24 hr of the MR examination. Correlations with other studies were based on the original MR report and blinded review of the MR images by two observers in consensus. Emboli were shown in all cases by cine-MR, and they corresponded to the locations of angiographic abnormalities and mismatched perfusion defects on scintigraphy. In three patients considered to have acute pulmonary embolus on the basis of angiography, the cine-MR studies were consistent with acute pulmonary embolus in two patients and chronic pulmonary embolus in one patient (however, in that patient pathologic examination showed chronic embolism). In one case in which angiography led to the diagnosis of acute and chronic pulmonary embolism, the cine-MR study showed acute embolism. In three patients thought to have chronic pulmonary embolus on the basis of angiography, the cine-MR study was interpreted as representing acute embolus in one patient and chronic embolus in two patients. In this highly selected, small group of patients, cine-MR imaging was accurate in showing central pulmonary embolism.

Acute Disease↗
PubMed1988

Fast limited flip angle MR subtraction angiography.

A fast MR angiography method is introduced that is capable of generating difference images of blood vessels in scan times of 10-20 s. This is an order of magnitude faster than many previous methods. The fundamental concept of this approach is to use cardiac gating and acquire several phase encodings at least twice during each cardiac cycle using limited flip angles (LFAs) and repetition times in the 20 to 50 ms range. The encodings acquired during diastole are subtracted from those acquired during systole to generate the difference image. The contrast in the difference image is due both to the influx of unsaturated spins and to the loss of phase coherence of systolic blood moving at high velocity along a magnetic gradient. The systolic peak of the cardiac cycle is determined during reconstruction by shifting the systolic and diastolic "windows" until the difference signal is maximized. Ghost artifacts due to pulsatile flow are eliminated by a phase reordering technique similar in concept to those developed for suppression of breathing artifacts. Arteries in thick slices are successfully imaged and initial in vivo results are presented.

Angiography↗
PubMed1988

Effects of turbulence on signal intensity in gradient echo images.

Although the appearance of laminar vascular flow in magnetic resonance (MR) images has been characterized, there is no general agreement about the effect of turbulent flow on MR signal intensity. This study uses a fast scan gradient echo pulse sequence to evaluate nonpulsatile turbulent flow in two different models. The first model simulated flow in normal vascular structure. It generated nonpulsatile, laminar and turbulent flow in straight, smooth-walled Plexiglas tubes. The second model simulated flow through a vascular stenosis. It generated nonpulsatile, laminar, and turbulent flow through an orifice. Velocities and flow rates ranged from low physiologic to well above the physiologic range (velocity = .3 to 280 cm/second, flow rate from .15 to 40 L/minute). Transition from laminar to turbulent flow was observed with dye streams. Turbulent flow in straight, smooth-walled vessels was not associated with a decrease in MR signal intensity even at the highest velocities and flow rates studied. The transition from laminar to turbulent flow through an orifice is not associated with a decrease in gradient echo signal intensity. As the intensity of the turbulent flow increases, however, there is a threshold above which signal intensity decreases linearly as turbulence increases (r = .97). This study suggests that flow in normal vascular structures should not be associated with decreased signal intensity in gradient echo images. Turbulent flow through areas such as valves, valvular lesions or vascular stenoses, may be associated with a decrease in gradient echo signal intensity.

Blood Flow Velocity↗
PubMed1988

Deep venous thrombosis evaluation with limited-flip-angle, gradient-refocused MR imaging: preliminary experience.

Sixteen patients (17 lower extremities) were prospectively examined with venography and limited-flip-angle, gradient-refocused magnetic resonance (MR) imaging for the presence or absence of deep venous thrombosis. Thrombosed vessels showed decreased-to-absent signal intensity, while patent vessels had high signal intensity. In 16 of 17 extremities, MR images allowed accurate detection and localization of the thrombi found with venography. In the remaining extremity, MR imaging allowed correct identification of thrombus in the iliac and femoral veins but incorrectly demonstrated clot in the calf and popliteal veins. MR imaging with limited-flip-angle, gradient-refocused pulse sequences appears to be a sensitive, noninvasive means of detecting deep venous thrombosis.

Female↗