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↗

PubMedDate not supplied

A new model for occluding the left coronary artery in the rabbit without thoracotomy.

A small, nonmagnetic coil was fluoroscopically guided into the left circumflex coronary artery (LCXA) at the midventricular level via the left femoral artery in seven rabbits. Coronary artery occlusion was confirmed by intracoronary contrast injection, electrocardiographic changes, akinesis of the posterolateral wall distal to the occluded area, and histopathological staining of the myocardium. This new model of a closed-chest coronary artery occlusion in the rabbit may be suitable for acute ischemic myocardium studies that do not require reperfusion.

Animals↗

PubMedDate not supplied

MRI of postoperative maxillary cysts.

OBJECTIVE: The purpose of this study is to review the MR characteristics of postoperative maxillary cysts (POMC). MATERIALS AND METHODS: The MR findings in 24 patients with 38 surgically confirmed POMC were retrospectively reviewed. RESULTS: Of 32 cysts detected by MRI, 31 cysts (96.9%) were well demarcated. Nineteen cysts (59.4%) were smooth and the others (40.6%) were irregular. Thirty cysts (93.8%) had signal intensities ranging from that of muscle to that of subcutaneous fat on T1-weighted imaging. On T2-weighted imaging 16 homogeneous (50.0% and 5 inhomogeneous (15.6%) cysts showed signal intensities equal to or higher than subcutaneous fat. The peripheral rims of 11 ring-like cysts (34.4%) also showed signal intensities equal to or higher than subcutaneous fat on T2-weighted imaging. Nine patients (37.5%) had multiple cysts. Their characteristic high signal intensities or ring-like patterns on T2-weighted imaging and well-demarcated margins enabled them to be discriminated from other tumors of the maxillary sinus, such as carcinoma. CONCLUSION: MR imaging is useful for diagnosis of POMC.

Female↗

PubMedDate not supplied

Effects of meal intake on the flow velocity in the superior mesenteric artery: evaluation with 2D phase mapping MRI.

OBJECTIVE: Reliable results in MR flow measurements have been reported in humans. The current study was performed to evaluate the effects of a meal intake on the flow velocities in the superior mesenteric artery (SMA) and aorta by using 2D phase-mapping MRI. MATERIALS AND METHODS: A constant flow phantom generating 0-150 cm/s of flow velocities was constructed to evaluate the accuracy of MR flow measurements. Eleven healthy volunteers underwent serial MRI once before and three times after a mixed meal intake (700 kcal). RESULTS: Reliable MR flow measurements were validated in the constant flow phantom. In the healthy volunteers, the SMA and aorta had triphasic flow velocity waveforms in one cardiac cycle. Ingestion of a mixed meal increased flow velocities in the SMA. Peak velocities were observed at 20 min after the meal. The aortic flow velocities were unaffected by the meal. CONCLUSION: A 2D phase-mapping MR technique is feasible to evaluate the SMA and aortic flow velocities. Evaluation of the flow velocities in the SMA may contribute to understanding intestinal as well as hepatic conditions in humans.

Adult↗

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↗