Magnetic resonance imaging of acute myocardial ischemia using a manganese chelate, Mn-DPDP.

Nine adult rats underwent occlusion of the left coronary artery (LCA) to assess the ability of a manganese chelate of N, N'-Bis (pyridoxal-5-phosphate) ethylenediamine-N, N'-diacetic acid (Mn-DPDP), to delineate acute myocardial ischemia. Hemodynamic effects of the contrast medium were tested in the isolated rat heart. Gated transaxial images of the heart at the mid-ventricular level were obtained using a 2 Tesla magnet. A TE of 20 msec and a TR of 1 R-R interval (approximately 250 msec) were used. Images were taken prior to injection of 400 mumol/kg of Mn-DPDP, 2 minutes after injection, and then at 15 minute intervals for one hour. The time between LCA occlusion and injection of contrast averaged 95 minutes. The signal intensity (SI) of normal myocardium was increased by 125 +/- 9% immediately after injection, and did not significantly vary over one hour. SI of ischemic myocardium increased by only 16 +/- 14% immediately after injection, gradually rising to 44 +/- 13% after one hour. Visual discrimination between normal and ischemic myocardium was obtained throughout the study. The percent contrast between normal and ischemic myocardium was 47.2 +/- 6% at 2 minutes after injection, gradually decreasing to a final value of 31.3 +/- 4%. No hemodynamic effects were produced in the isolated heart using concentrations in the perfusate several-fold higher than those expected to be produced by the intravenous injection of 400 mumol/kg Mn-DPDP. Mn-DPDP shows the potential for delineation of the jeopardy area resulting from coronary occlusion for at least one hour after injection of the agent.

Upper extremity DVT. Correlation of MR and nuclear medicine flow imaging.

The purpose of this study is to determine correlation between MR and nuclear medicine flow studies in the evaluation of upper extremity deep venous thrombosis. We retrospectively reviewed MR and radionuclide venography images obtained in 10 patients with suspected upper extremity venous thrombosis. In nine cases there was complete agreement in the identification of thrombus. In one case, MR images failed to identify a thrombus in the axillary vein adjacent to a port-a-cath. Good correlation between MR and radionuclide venography images in evaluation of upper extremity DVT is present in the majority of cases.

MR imaging-guided focused ultrasound surgery of fibroadenomas in the breast: a feasibility study.

PURPOSE: To test the feasibility of noninvasive magnetic resonance (MR) imaging-guided focused ultrasound surgery (FUS) of benign fibroadenomas in the breast. MATERIALS AND METHODS: Eleven fibroadenomas in nine patients under local anesthesia were treated with MR imaging-guided FUS. Based on a T2-weighted definition of target volumes, sequential sonications were delivered to treat the entire target. Temperature-sensitive phase-difference-based MR imaging was performed during each sonication to monitor focus localization and tissue temperature changes. After the procedure, T2-weighted and contrast material-enhanced T1-weighted MR imaging were performed to evaluate immediate and long-term effects. RESULTS: Thermal imaging sequences were improved over the treatment period, with 82% (279 of 342) of the hot spots visible in the last seven treatments. The MR imager was used to measure temperature elevation (12.8 degrees -49.9 degrees C) from these treatments. Eight of the 11 lesions treated demonstrated complete or partial lack of contrast material uptake on posttherapy T1-weighted images. Three lesions showed no marked decrease of contrast material uptake. This lack of effective treatment was most likely due to a lower acoustic power and/or patient movement that caused misregistration. No adverse effects were detected, except for one case of transient edema in the pectoralis muscle 2 days after therapy. CONCLUSION: MR imaging-guided FUS can be performed to noninvasively coagulate benign breast fibroadenomas.