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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 631 records · Page 35Linked to original sources
PubMedDate not supplied

Cine gradient refocused echo (GRE) imaging of intravascular masses: differentiation between tumor and nontumor thrombus.

Spin echo MR imaging has not permitted reliable differentiation between intraluminal blood clot and tumor thrombus. This study assessed the role of ECG referenced repetitive gradient refocused echo (cine GRE) imaging for the differentiation of intravascular tumor from blood clot. Cine GRE images were reviewed in 23 patients, 11 of whom had intravascular tumor and 12 of whom had intravascular blood clots. Percentage contrast between the lesion and skeletal muscle as the reference tissue was determined from a subjective review of the images and objective signal intensity measurements. Intravascular clots were found to be lower in signal intensity than muscle (mean -55 +/- 29%). Intravascular tumors showed higher signal intensity relative to muscle (mean +17 +/- 9%) with the exception of myxomas (n = 2), which had signal intensity values relative to muscle as low as clots (mean -41 +/- 17%). Three masses in the inferior vena cava were composed of central tumor and peripheral clot; the two components could be differentiated with cine GRE imaging. Cine GRE imaging provides adequate signal intensity differences to visualize intravascular masses and helps to differentiate intravascular clot from tumor thrombus. However, if the tumor contains substantial amounts of iron, then the signal is also low and consequently clot and thrombus may not be distinguishable. This can occur in some atrial myxomas.

Diagnosis, Differential↗
PubMedDate not supplied

Pulmonary artery dissection: MR findings.

We report a case of pulmonary artery dissection imaged by MR. Dissection of a markedly dilated pulmonary artery is a rare and usually fatal complication of chronic pulmonary arterial hypertension. The diagnosis is made at autopsy, with only two cases having previously been documented (by Doppler echocardiography) during life. The hallmark of an arterial dissection is the finding of an intimal flap and a false lumen. In our case, spin echo MR imaging failed to show either the intimal flap or any intraluminal signal defects. The dissection was presumably obscured by nonhomogeneous intraluminal signal caused by the slow blood flow associated with severe pulmonary arterial hypertension. Cine MR imaging, however, demonstrated different signal intensity within the true and false lumens of the dissection, thereby outlining the intimal flap between the two channels.

Adult↗
PubMedDate not supplied

MRI and ultrasound detection of asymptomatic thyroid nodules in hyperparathyroidism.

A retrospective MRI and ultrasound (US) study of 50 patients with hyperparathyroidism and no history of thyroid disease was done. The purpose was to compare the sensitivity of both methods in the detection of asymptomatic thyroid nodules, as well as to determine the prevalence of thyroid abnormalities in patients with hyperparathyroidism. All the patients underwent MR and 33 were also studied by high-resolution US. Magnetic resonance imaging was performed on a 1.5 T unit, using T1-(500-700/20) and T2-(2,000/20 and 70) weighted images. Axial sections (5 mm with a 1 mm interval between them) were obtained along the neck. Ultrasonography was performed using a 10 MHz linear array transducer. The prevalence of thyroid nodules was 46% in the 50 patients studied by MR imaging. In the subgroup of patients studied by both methods, US depicted nodules in 48% of patients, and MR depicted nodules in 45%. Magnetic resonance imaging and US detected a high frequency of thyroid nodules in patients with hyperparathyroidism. This high frequency makes the detection of an intrathyroidal parathyroid adenoma problematic.

Adult↗
PubMedDate not supplied

Airway obstruction by right aortic arch with right-sided patent ductus arteriosus: demonstration by MRI.

An unusual cause of airway obstruction was demonstrated by MRI in two infants with congenital heart disease. The two infants experienced airway obstruction caused by a right aortic arch with right-sided patent ductus arteriosus. The diagnosis was established by MRI prior to surgery; angiography did not demonstrate the critical relationship between the large ductus and the airway. Axial, sagittal, and coronal MRI displayed the right arch, dilated ductus, and the compression of the proximal right bronchus and distal trachea by the ductus. Surgical findings confirmed the MR diagnosis. Thus, MRI can be used to localize the site of airway obstruction and to demonstrate unusual types of vascular anomalies.

Airway Obstruction↗
PubMedDate not supplied

Right ventricular diastolic filling: evaluation with velocity-encoded cine MRI.

Abnormal flow velocity curves across the tricuspid valve (TV) and in the superior vena cava have been described in patients with abnormal right ventricular (RV) relaxation or restriction and with pericardial diseases by means of Doppler echocardiography. In this study, various imaging planes and strategies of velocity-encoded cine (VEC) MR for measurement of peak E and peak A velocities and the E/A ratio across the TV were evaluated and compared to Doppler measurements in 10 normal volunteers. In addition, VEC-MR velocity measurements were performed in the superior vena cava. Peak E and peak A velocities derived from three-dimensional VEC-MR phase images were slightly higher than velocities derived from two-dimensional VEC images. Higher velocities were measured by VEC-MR in the vertical long-axis plane compared with the horizontal long-axis plane. Excellent correlations (r > 0.89) were found between E/A ratios derived by VEC-MR and Doppler echocardiography. The interobserver variability for VEC-MR measurements was in the range of 2%. The VEC-MR depicted normal superior vena cava velocity curves in every volunteer. These results indicate that VEC-MR may offer a highly reproducible means of assessing abnormal filling properties of the RV.

Adult↗
PubMedDate not supplied

Enhancement of thoracic masses using nonionic MR contrast agents.

OBJECTIVE: This study evaluated the effect of a new nonionic MR contrast medium, gadodiamide injection (Omniscan; Sanofi-Winthrop), on enhancement of thoracic masses on T1-weighted SE images. MATERIALS AND METHODS: Gadodiamide injection was administered intravenously at a dose of 0.2 mmol/kg to 26 patients with thoracic masses. The T1-weighted images with and without fat suppression and T2-weighted images obtained before contrast medium injection were compared with T1-weighted images obtained at 5, 30, and 45 min and a T1-weighted fat-suppressed image at 10 min after administration of the contrast medium. Enhancement of the thoracic masses and image quality were quantified by measuring signal intensity, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) using muscle and fat as reference tissues. RESULTS: The SNR of the masses increased significantly (p < 0.001) following contrast material injection both on standard T1-weighted sequences and on T1-weighted fat-suppressed images when compared with the precontrast T1-weighted images with and without fat suppression. The CNR (reference tissue muscle) improved significantly (p < 0.001) after contrast medium injection and persisted for 45 min on T1-weighted images compared with those prior to contrast medium. However, there was no significant difference in CNR between the T2-weighted images obtained before and the T1-weighted images obtained after contrast agent administration. On the other hand, the SNR of contrast-enhanced images was significantly better than that of the T2-weighted images. When fat was used as a reference tissue, CNR of the thoracic masses decreased significantly. CONCLUSION: This study shows that gadodiamide injection caused significant enhancement of thoracic masses on T1-weighted images, which rendered high signal intensity to the masses similar to the appearance on T2-weighted images. In comparison with the T2-weighted images, SNR was significantly improved.

Adolescent↗
PubMedDate not supplied

MRI of tracheal and esophageal compression following surgery for congenital heart disease.

OBJECTIVE: Magnetic resonance imaging has proven to be a useful diagnostic tool for the evaluation of various types of vascular rings and congenital heart disease. We report two cases showing the accuracy of MRI in detecting post-surgical complications in patients with these conditions. MATERIALS AND METHODS: The two cases reported here demonstrate the use of MRI to show the altered vascular anatomy and the mechanism of tracheal and/or esophageal compression. RESULTS: In the first case, MRI demonstrated narrowing of the right pulmonary artery due to a dilated and posteriorly displaced ascending aorta with residual coarctation, and esophageal compression by an aberrant left subclavian artery. In the second case, MRI demonstrated esophageal compression by a posteriorly displaced ascending aorta. CONCLUSION: We conclude that MRI is an effective noninvasive method for assessing the results and complications of surgical correction of aortic abnormalities.

Aorta↗
PubMedDate not supplied

Use of cine gradient echo (GRE) MR in the imaging of cardiac hemochromatosis.

This case report describes the MR appearance of cardiac iron deposition using spin echo and cine gradient echo imaging (GRE) in a young man with secondary hemochromatosis. The ratio of the signal intensity of left ventricular myocardium to skeletal muscle was abnormally low on both spin echo and GRE compared with normal. The abnormally low myocardial signal was most severe on the cine gradient echo sequence. Cine GRE can be used to establish the diagnosis of cardiac iron deposition.

Adult↗
PubMedDate not supplied

MRI vs echocardiography in the evaluation of the Jatene procedure.

OBJECTIVE: Effective, noninvasive imaging studies are essential in the long-term assessment of patients who have had surgical correction of congenital heart disease. The initial study in most patients is echocardiography. The objective of the current study was to define the additional information that might be provided by MRI in comparison to echocardiography. MATERIALS AND METHODS: Electrocardiogram-gated MRI was used to evaluate 12 patients (mean age 4.5 years) who had undergone the Jatene (arterial switch) procedure for transposition of the great arteries. Magnetic resonance imaging and two-dimensional echocardiography were compared for their ability to demonstrate common complications of this procedure, namely, focal stenoses of the aortic and pulmonary anastomoses, right ventricular outflow tract, and both branch pulmonary arteries. RESULTS: A total of 24 focal stenoses were detected by MRI and echocardiography. The MR detected 22 of these (92%) and echocardiography detected 14 (58%). Ten of 17 stenoses involving the branch pulmonary arteries were identified only by MR. CONCLUSION: These results indicate that MRI is effective in evaluating post-operative complications of the pulmonary arteries in patients who have undergone the Jatene procedure and can provide information additive to echocardiography in these patients.

Anastomosis, Surgical↗
PubMedDate not supplied

Assessment of popliteal arterial occlusive disease with 2D time-of-flight MRA.

OBJECTIVE: The purpose of this study was to evaluate both morphology and blood flow in peripheral arteries with occlusive lesions using MR angiography (MRA) and velocity-encoded cine MRI. MATERIALS AND METHODS: Two-dimensional time-of-flight MRA and velocity-encoded cine MRI were performed in nine patients with peripheral arterial occlusive disease. Findings on MR angiograms were verified by conventional angiography. RESULTS: All the stenotic lesions in the popliteal arteries were depicted by MRA. The degree of the stenoses in the artery was overestimated by MRA. Major collateral circulations were demonstrated. Velocity-encoded cine MRI provided flow velocity information on the arteries above and below the stenoses. The flow velocity waveform was monophasic above and below the stenosis. The peak systolic velocity in the artery below the stenosis was reduced compared with that above the stenosis (p < 0.05). CONCLUSION: The combination of MRA and velocity-encoded cine MRI has clinical potential for the evaluation of peripheral arterial occlusive disease.

Adult↗
PubMedDate not supplied

Evaluation of thoracic aortic dissection using breath-holding cine MRI.

OBJECTIVE: Our goal was to determine if breath-hold cine MRI in transaxial planes can be used for the evaluation of thoracic aortic dissection instead of conventional cine MRI since rapid imaging is required in this clinical setting. MATERIALS AND METHODS: Twelve patients with thoracic aortic dissection were imaged using a 1.5 T imager. Breath-hold images were acquired with fast cine MR sequence (TR/TE = 9/2.8, 20 degrees flip angle) using segmented k-space data acquisition. Conventional non-breath-hold cine MR images (TR/TE = 22/7.5, 35 degrees flip angle, 2 averages) were taken with flow and respiratory compensation. RESULTS: Sharpness of edges of the vessels on fast cine MR images was better than that on conventional cine MR images in 34 (57%) of 60 images. Inhomogeneous blood signal in aortic lumen due to motion artifacts was found in 2 (3%) of fast cine MR images and in 15 (25%) of conventional cine MR images. The contrast-to-noise ratios of fast cine MR images were significantly better than those of conventional cine MR images (26.4 +/- 9.1 vs. 18.5 +/- 10.1; p < 0.05) when the region of interest for noise was placed to include ghosting artifacts. CONCLUSION: Breath-hold cine MRI is a rapid technique that gives high quality images of thoracic aortic dissection and can provide a diagnosis in < 10 min of imaging time.

Aged↗
PubMedDate not supplied

MRI of primary malignant cardiovascular tumors.

PURPOSE: The purpose of this study was to describe the MR features of primary malignant cardiac tumors, which may aid in differentiation from primary benign cardiac tumors. METHOD: Seven patients with primary malignant cardiac tumor were imaged with MR. All studies were performed on a 1.5 T MR imager using variable combinations of SE T1-weighted cine gradient MR and post-Gd-DTPA SE T1-weighted MR with fat saturation sequences. The following features were analyzed on images: length of attachment to cardiac structures, size of tumors, involvement of more than one chamber, extension to pericardium or beyond the heart, and necrosis of the mass. RESULTS: All cases had a wide point of attachment. Six of the seven tumors were large in size and occupied almost the entire cardiac chamber. There was involvement of more than one cardiac chamber or great vessel in three patients. Pericardial or extracardiac extension occurred in four and two patients, respectively. Tumor necrosis was evident in two patients. All patients had at least one of these signs of malignant tumor. CONCLUSION: Primary malignant cardiac tumors have distinctive MR features that can be used to differentiate them from primary benign cardiac tumors.

Heart Neoplasms↗
PubMedDate not supplied

MRI of supracristal ventricular septal defects.

The MR features of two cases of supracristal ventricular septal defect are described. In both patients, axial SE T1-weighted images demonstrated a defect between the base of the aorta and the upper posterior aspect of the right ventricular infundibulum. Cine MRI in the two cases showed left-to-right shunting with a flow jet in the distal right ventricular outflow tract that propagated into the main pulmonary artery. Both patients had prolapse of the right sinus of Valsalva, and one had aortic insufficiency.

Adult↗
PubMedDate not supplied

Identification of pulmonary vein stenosis after radiofrequency ablation for atrial fibrillation using MRI.

Pulmonary vein stenosis is one of the frequent complications after radiofrequency ablation for atrial fibrillation. MRI plays an important role in depicting the pathoanatomic structure of the pulmonary veins, and measuring the blood flow velocity in the pulmonary veins before and after therapy, and is superior to transesophageal echocardiography for this purpose.

Aged↗
PubMedDate not supplied

Coronary flow reserve: assessment by magnetic resonance imaging.

Coronary angiography has been the standard method for quantifying the severity of coronary artery stenosis, however its physiological relevance by angiography is imperfect. At present velocity-encoded cine phase contrast MRI is a non invasive technique that can provide accurate assessment of coronary flow volume and coronary flow reserve, validated in animal and human studies by Doppler flow measurement. MRI may be recognized as a comprehensive, widely available technique independent of any nuclear tracer or contrast media, for evaluation of the presence and physiological significance of a variety of heart diseases which compromise coronary flow reserve.

Animals↗
PubMedDate not supplied

Cardiac tumors: assessment with Gd-DTPA enhanced MR imaging.

Previous studies have shown the value of MR imaging for the identification of cardiac masses. The distinction of intramural tumors from normal myocardium may be equivocal because of the similarity of signal intensity between tumor and normal myocardium on ECG-gated SE images. The purpose of this study was to assess the role of Gd-DTPA for improving the contrast between cardiac tumors and myocardium. Four patients with established or suspected cardiac tumors were imaged with a 1.5 T imager. The T1-weighted images (TR = RR interval, TE = 20-30 ms) were obtained before and immediately after the intravenous injection of Gd-DTPA, at a dosage of 0.1 mmol/kg. Tumors were identified in three patients. All tumors were isointense to the myocardium in precontrast images but demonstrated differential enhancement relative to myocardium after the administration of Gd-DTPA. Two tumors were hyperintense relative to myocardium, and the third was mostly hypointense, surrounded by a hyperintense rim. In the remaining case, no tumor was found and the myocardium was homogeneously enhanced on postgadolinium images. Gadolinium DTPA can produce differential enhancement of tumor from normal myocardium and therefore demonstrate intramural masses.

Aged↗