Mediastinal chyloma, a roentgenographic sign of chylous fistula.
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Chylothorax↗
Biomedical subjects
C B Higgins
Publications and source records attributed to C B Higgins.
Dual effects of gadodiamide injection in depiction of the region of myocardial ischemia.
The high safety index of the nonionic magnetic resonance (MR) contrast agent gadodiamide injection permits a wide dose range without induction of hemodynamic effects. The wide dose range might confer a diagnostic advantage by providing both T1 enhancing and magnetic susceptibility effects for demarcating pathologic regions. The dual utility of this contrast agent for T1 and T2 enhancement in creating differential contrast between normal and acutely ischemic myocardium was explored. MR imaging was initiated 20-40 minutes after occlusion of the left coronary artery in two groups of rats: Group 1 (n = 8) received 0.3 mmol/kg gadodiamide injection before and after acquisition of T1-weighted images; group 2 (n = 10) received 0.5 mmol/kg before and after acquisition of T2-weighted images. Postcontrast T1-weighted images showed clear delineation of the ischemic region as a relatively low-signal-intensity area for 15 minutes. On postcontrast T2-weighted images, the ischemic region appeared as a relatively high-signal-intensity area for 60 minutes. These effects were obtained with doses of gadodiamide injection that have safety indexes greater than those of gadopentetate dimeglumine.
Animals↗
Contrast media for cardiothoracic MR imaging.
Contrast media have been used for the study of disease of the thorax. Most experience has consisted of the use of MR contrast media for improving the delineation of acute myocardial infarction, for demarcating the area of acute myocardial ischemia, and for demonstrating the area of potentially jeopardized myocardium after acute coronary occlusion. Contrast agents demonstrate the ischemic or jeopardized area as a zone of decreased signal intensity to normal myocardium. On the other hand, the magnetic susceptibility agents demonstrate the ischemic or jeopardized area as a zone of increased signal intensity to normal myocardium. Little experience exists concerning the use of MR contrast media for enhancing mediastinal and lung masses. The few reports to date demonstrate that contrast media can improve the conspicuity of thoracic masses. A new nonionic contrast medium, gadodiamide injection, has been shown to considerably increase S/N and C/N of thoracic masses. Further studies are necessary to define the role of MR contrast media in the evaluation of myocardial ischemia and thoracic masses in clinical practice.
Animals↗
Flow pattern analysis in the abdominal aorta with velocity-encoded cine MR imaging.
The sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% +/- 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.
Adult↗
First pass of an MR susceptibility contrast agent through normal and ischemic heart: gradient-recalled echo-planar imaging.
Gradient-recalled echo-planar magnetic resonance (MR) imaging was used to monitor the first pass of a magnetic susceptibility contrast agent through the heart of normal rats and rats subjected to 60-minute occlusion of the anterior branch of the left main coronary artery. Each animal (six normal and six ischemic) received four doses (0.05, 0.1, 0.15, and 0.2 mmol/kg) of Dy-DTPA-BMA [diethylenetriaminepentaacetic acid-bis(methylamide)] administered as a bolus volume of 1.0 mL/kg. In both normal and ischemic rats, signal intensity in nonischemic myocardium was reduced by the contrast agent in a dose-dependent manner. Signal intensity in the ischemic zone was reduced much less, so that at a contrast agent dose of 0.1 mmol/kg or greater the ischemic zone was clearly defined as a high-intensity zone on echo-planar images. Plots of the change in the apparent T2* relaxation rate (delta R2*) during the peak bolus effect versus injected dose were well fit by straight lines for normal, nonischemic, and ischemic myocardium but not for blood in the left ventricle. No difference was seen between myocardial response in normal animals and in nonischemic regions in animals with coronary artery occlusion. These findings suggest that the contrast agent-induced changes in tissue T2* are monoexponential and support the idea that data derived from contrast transit studies may be useful for calculation of myocardial blood flow.
Animals↗
Contribution of MR imaging in ischemic heart disease.
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Contrast Media↗
Contrast media for MR imaging of the heart.
The role of contrast media for quantitative characterization of ischemic myocardial events with magnetic resonance (MR) imaging has advanced considerably in the past few years. Contrast material-enhanced MR imaging is useful for identifying and sizing myocardial infarcts and for distinguishing between occlusive and reperfused myocardial infarcts. Recent results suggest that contrast-enhanced MR imaging can also be used to identify areas of cell death in regions of reperfused myocardial infarction. With the aid of MR contrast media, fast MR imaging techniques may be useful in estimating regional myocardial perfusion. Although no simple relationship between signal intensity and concentration exists, contrast-enhanced MR perfusion imaging can demonstrate the presence and relative severity of hypoperfused myocardium. Combining myocardial perfusion imaging with the anatomic and functional information provided by other MR imaging techniques could make MR imaging a comprehensive noninvasive means of evaluating ischemic cardiac disease.
Animals↗
First-pass contrast-enhanced inversion recovery and driven equilibrium fast GRE imaging studies: detection of acute myocardial ischemia.
The purpose of this study was (1) to monitor the dynamic effects of T1-enhancing and magnetic susceptibility contrast material on normal canine myocardium using inversion recovery (IR)- and driven equilibrium (DE)-prepared fast gradient-recalled echo (GRE) sequences and (2) to determine the relative value of T1-enhancing and magnetic susceptibility contrast material in detecting regions of ischemia in the same animal. Normal dogs (n = 5) and dogs with acute occlusion of the left anterior descending (LAD) coronary artery (n = 11) were studied using a 1.5-T MR imager. ECG-gated fast IR-prepared GRE images were acquired using TI/TR/TE of 700/7.0/2.9 msec and a flip angle of 7 degrees. Fast DE-prepared GRE images were obtained using a flip angle of 12 degrees and a DE delay/TR/TE of 60/10.2/4.2 msec. Sequential images were acquired to monitor transit of 0.05 mmol/kg gadodiamide injection and 0.2 and 0.4 mmol/kg sprodiamide injection. On slice-nonselective IR fast GRE images, gadodiamide caused significant enhancement of the normal myocardium and the left ventricular (LV) chamber blood. In dogs with LAD occlusion, the ischemic region was defined as an area of low signal intensity (SI). On DE-prepared GRE sequences, administration of sprodiamide resulted in a substantial decrease in signal from normal myocardium and LV chamber blood in normal dogs. In animals subjected to LAD occlusion, this contrast medium produced a transient decrease in SI from normal myocardium (P < .05) and no significant change in SI from ischemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
Persistent/recurrent hyperparathyroidism: a comparison of sestamibi scintigraphy, MRI, and ultrasonography.
For patients with persistent or recurrent hyperparathyroidism, parathyroid imaging is indicated to confirm the presence of abnormal parathyroid gland(s) and identify their location. These imaging techniques are being modified constantly and newer methods have been developed. Sestamibi scintigraphy, MRI and sonography were compared in 23 patients with persistent or recurrent hyperparathyroidism. Preoperative 99m-Technetium Sestamibi (MIBI), MRI and ultrasonographic (US) studies of 23 patients with 25 histopathologically confirmed abnormal parathyroid glands were compared, using independent prospective interpretations. All patients had been operated upon previously for hyperparthytroidism. Accuracy of various combinations of MRI, MIBI, and US also were calculated. The results are shown for all abnormal glands (n =25); sensitivities and accuracies were 88 and 84% for MRI, 80 and 80% for MIBI, and 58 and 44% for US. For only parathyroid adenomas (n = 18), sensitivities and accuracies were 89 and 89% for MRI, 94 and 94% for MIBI, and 58 and 39% for US. Finally, for parathyroid hyperplasia (n = 7 glands in five patients), sensitivities and accuracies were 83 and 71% for MRI, 43 and 43% for MIBI, and 57 and 57% for US. Either MIBI or MRI results were significantly better for detecting abnormal parathyroid glands than US (P < 0.01), but MRI and MIBI were not statistically different. Combining MRI and MIBI produced a combined accuracy of 92%, whereas combining either of these tests with US did not improve on the accuracy of either test alone. In conclusion, for patients with persistent or recurrent hyperparathyroidism, MRI and MIBI are equally accurate for detecting abnormal parathyroid glands, and the combination of both tests may be more accurate than either test alone.
Adenoma↗
Cardiovascular applications of magnetic resonance flow and velocity measurements.
With recent developments of MR techniques for blood flow measurements, qualitative and quantitative information on both flow volume and flow velocity in the major vessels can be obtained. MR flow quantitation uses the phase, rather than the amplitude of the MR signal, to reconstruct the images. Previous validation studies have demonstrated the accuracy of the phase shift techniques for measuring flow velocities. This technique is now being applied successfully in the cardiovascular system to quantify global and regional ventricular function, valvular heart disease, pulmonary artery disease, thoracic aortic disease, congenital heart disease, and ischemic heart disease.
Blood Flow Velocity↗
Improved reproducibility in measuring LV volumes and mass using multicoil breath-hold cine MR imaging.
There is a generally recognized need for improvement in quality of fast cardiac MR images. Consequently, breath-hold cine MR images were obtained with multiple surface coils connected to phased array receivers, and C/N, intra-observer and inter-observer variabilities for LV volumes and mass were evaluated. Two sets of short-axis images of the LV, one with multiple surface coils and another with a body coil, were acquired in eight subjects with a fast cine MR sequence using k-space segmentation (TR/TE = 7/2.2 msec, temporal resolution = 56 msec). C/N with multicoil imaging was 32.2 +/- 7.6 (mean +/- SD), significantly higher than that with a body coil (11.0 +/- 3.3, P < .01). The mean percentage differences in intra-observer and inter-observer measurements with multicoil imaging were significantly better than those with a body coil. In conclusion, multicoil imaging provides significant gain in C/N on breath-hold cine MRI of the heart. In addition, intra-observer and inter-observer reproducibilities are improved with multicoil imaging.
Adult↗
Breath-hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts.
Breath-hold velocity-encoded cine MR (VENC-MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC-MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath-hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath-hold VENC-MR sequence with K-space segmentation and view-sharing reconstruction (TR/TE = 16/9 msec, VENC = 100 cm/s). In 10 native IMA, nonbreath-hold VENC-MR images were acquired as well for comparison. Breath-hold VENC-MR imaging showed significantly higher systolic and diastolic peak velocities in native IMA (43.1 cm/second +/- 15.0 and 10.0 cm/second +/- 4.8), in comparison to those of nonbreath-hold VENC-MR imaging (27.6 cm/second +/- 10.2 and 7.3 cm/second +/- 3.9, P < .05). The diastolic/systolic peak velocity ratio in the IMA grafts (.88 +/- .41) was significantly higher than that in native IMA (.24 +/- .08, P < .01). Interobserver variability in the flow velocity measurement was less than 4%. Breath-hold VENC-MR imaging demonstrated higher peak flow velocity in the IMA than nonbreath-hold VENC-MR imaging. This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts.
Adult↗
Evaluation of the effects of intravascular MR contrast media (gadolinium dendrimer) on 3D time of flight magnetic resonance angiography of the body.
The aims of this preliminary study were to establish the efficacy and minimum effective dose of TG(5)(FdDO3A)(52) gadolinium dendrimer for contrast-enhanced, three-dimensional (3D) time of flight (TOF) magnetic resonance angiography (MRA) of the body. In a dose ranging study in eight rabbits (Group A), each of two animals received 0.03; 0.02; 0.01; or 0.005 mmol/kg of the agent for 3D-TOF MRA of the pelvic circulation in the axial and coronal planes. An additional nine animals (Group B) received a dose of 0.02 mmol/kg for 3D-TOF MRA of the mediastinum, abdomen or of the lower limbs. Quantitative and qualitative analyses of the images from Group A demonstrated a dose-related reduction in saturation effects and improved visualization of vascular structures, with maximal augmentation of the contrast-to-noise ratio (CNR) at 0.03 mmol/kg. The dose of 0.02 mmol/kg was found to be the minimal effective dose at the three vascular regions.
Animals↗
MR imaging characterization of postischemic myocardial dysfunction ("stunned myocardium"): relationship between functional and perfusion abnormalities.
Stunned myocardium has been detected in patients treated successfully with thrombolytic agents. The hypothesis of this study was that fast gradient echo (GRE) imaging could be used to characterize the regional functional and perfusion abnormalities that are indicative of myocardial stunning. This study was designed to monitor and correlate the extent of wall thickness and perfusion abnormalities as determined by fast (segmented k space) cine and contrast enhanced GRE imaging, respectively. Dogs were subjected to left circumflex (LCX) coronary artery occlusion (15 min) followed by 30-minute reperfusion (n = 8). Perivascular flow probes were used to continuously measure flow in left anterior descending (LAD) and LCX coronary arteries. Short-axis inversion recovery prepared fast GRE and cine images were acquired at baseline, at occlusion, and at 1, 10, and 30 minutes of reflow. Regional signal intensity and percent systolic wall thickening were determined at 26 equally spaced circumferential positions to compare the extent of functional and perfusion abnormalities. During occlusion and reperfusion, the ischemic region was demonstrated on contrast-enhanced images as a hypointense and hyperintense region, respectively. During occlusion, the extent of the perfusion defect (32% +/- 2% of the circumference of the equatorial slice) correlated closely (r = .74) with the extent of contractile dysfunction (35% +/- 2%). After reperfusion, there was transient recovery in the percent wall thickening (26% +/- 4% vs 36% +/- 4% normal), coinciding with the reactive hyperemic response, but this was followed by a significant decline in wall thickening at 10 minutes (19% +/- 4%) and 30 minutes (12% +/- 2%). Fast MR imaging may be useful to monitor postischemic myocardial abnormalities after thrombolytic therapy and the response to pharmacologic interventions.
Animals↗
Measurement of collateral blood flow in a porcine model of aortic coarctation by velocity-encoded cine MRI.
The purpose of this study was to investigate the time course of development of collateral blood flow in an animal model of aortic coarctation. A juxtaductal aortic stenosis (model coarctation) was surgically created in five juvenile pigs. MRI was performed preoperatively, 1 to 2 days postoperatively, and 2 to 10 weeks postoperatively. Aortic blood flow was measured by velocity-encoded cine MR (VENC-MR). The percent change in aortic blood flow (delta BF) from proximal to distal descending thoracic aorta was calculated, and a multiple-comparison paired t test used to assess changes in delta BF over time. Invasive flow measurements were obtained in one animal before sacrifice using an ultrasonic probe. delta BF preoperatively was -2 +/- 8% (mean +/- SE). delta BF increased to 32 +/- 7% (mean +/- SE, P = .022) 2 days postoperatively and 55 +/- 19% (P = .032) 2 to 8 weeks postoperatively. Invasive measurements were in qualitative agreement with the VENC-MR data. VENC-MR is an accurate noninvasive method of measuring collateral blood flow in aortic coarctation. Recruitment and development of collateral flow pathways occur rapidly in an animal model.
Animals↗
Histologic confirmation of microvascular hyperpermeability to macromolecular MR contrast medium in reperfused myocardial infarction.
A macromolecular MR contrast medium (MMCM) designed to permit histochemical staining and specific tissue localization, albumin-(biotin)10-(Gd-DTPA)25 (Bio-Alb-Gd), was used in a rat model of reperfused myocardial infarction to confirm the presence and distribution of microvascular hyperpermeability. T1-weighted spin-echo images were acquired before and after administration of Bio-Alb-Gd. An avidin-biotin-complex (ABC) stain, specific for the biotinylated MR contrast medium, was used to define the MMCM distribution and to detect any regional change in microvascular permeability related to infarction. Immediately after Bio-Alb-Gd administration, the infarcted region was enhanced, with greatest signal intensity noted at the rim and less at the center. There was a gradual increase in signal intensity of the initially hypointense central region. The steady increase in signal intensity of the central region suggested convection transport of MMCM through the interstitial space and its influx into cellular compartment after leakage from the vascular compartment. Histologic findings confirmed regional microvascular hyperpermeability corresponding to the site of infarction and a predominant rim distribution of the MMCM. Bio-Alb-Gd was identified at high microscopic power in the intravascular, interstitial, and intracellular spaces at the periphery of reperfused infarcted myocardium. Bio-Alb-Gd can be used as an MR contrast medium in reperfused infarcted myocardium to confirm the existence and to localize altered microvascular permeability to macromolecules. Bio-Alb-Gd contrast technique removes all the ambiguity between the distribution of the MR or other imaging contrast agent and the distribution of the substrate for histochemical staining.
Albumins↗
Contrast-enhanced 3D-TOF MRA of peripheral vessels: intravascular versus extracellular MR contrast media.
MR contrast media have been used to improve MR angiography (MRA). Their effect has been particularly beneficial for extracranial MRA. This study evaluated the efficacy of a new formulation of ultrasmall superparamagnetic iron oxide particles (USPIO) on three-dimensional (3D) time of flight (TOF) MRA in the pelvis and lower limb circulation. Each of six dogs received 3 mg/kg of USPIO and .2 mmol/kg of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) bis-methylamide (BMA) by intravenous infusion on separate examinations. Precontrast and postcontrast 3D-TOF MRA images of the lower extremities were acquired over the course of 45 minutes postinjection. Signal intensity (SI) was measured on axial views along the external iliac, femoral, and popliteal arteries. USPIO provided clear demarcation of the major primary, secondary, and tertiary vessels and the improved contrast-to-noise ratio (CNR) was maintained for 45 minutes. Gd-DTPA-BMA provided less signal enhancement than USPIO. The increase in CNR with this agent had significantly declined by 15 minutes after injection. The major vessels could no longer be visualized at 30 and 45 minutes after injection of Gd-DTPA-BMA This study demonstrates the efficacy of USPIO as a contrast medium for 3D-TOF MRA. It was concluded that USPIO provided effective and persistent enhancement of the peripheral vessels.
Animals↗
Aberrant left coronary artery arising from the right sinus of Valsalva with a right coronary arteriovenous malformation.
An 11-year-old boy presented with myocardial ischemia and was found to have an aberrant left main coronary artery from the right sinus of Valsalva coursing between the aorta and pulmonary artery, as well as a small arteriovenous malformation from a right atrial branch of the right coronary artery to the right atrium. Distinctive echocardiographic findings were supported by angiographic and magnetic resonance imaging studies. Treadmill and scintigraphic stress testing were normal. Corrective surgery was accomplished by a modified technique to unroof the intramural proximal course of the left coronary artery, without postoperative complications. The anatomy and pathophysiology of this rare coronary lesion are reviewed.
Arteriovenous Malformations↗