A new technique for visualization of interventional devices using MR is presented. A prototype catheter was equipped with a thin copper wire loop, leading from the proximal end to the tip and back. A small current (10-150 mA) through these two parts of a wire induces a local magnetic field along the catheter. Introduction of this catheter into the main magnetic field of the MR imager locally disturbs the homogeneity of the magnetic field. Image locations within the locally induced fields appear dark due to signal loss, and the extent of this effect can be varied during the procedure by simply adjusting the current. Different dedicated wire configurations allow visualization of the catheter in its whole length or in parts, i.e., with markers for balloons. Fast gradient echo sequences that provide a bright signal from inflowing blood are used for rapid imaging.

Gadolinium-enhanced excretory MR urography performed after low-dose diuretic injection is a promising and accurate alternative to conventional excretory urography for imaging the morphology of the urinary tract.

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Precise placement of the Tulip filter is feasible by either access route and the device appears mechanically stable. Further observations are needed to confirm that safe filter removal is practical up to 10 days after its insertion.

Patients suspected of having esophageal perforation and who have unremarkable findings at esophagography with water-soluble contrast media need to undergo follow-up esophagography with a barium-containing contrast medium. The use of a digital fluoroscopy unit does not obviate the follow-up examination.

Muscle cross-section areas were measured by magnetic resonance imaging (MRI) in the thigh of a human cadaver, the results being compared with those obtained by photography of corresponding anatomic macroslices. A close correlation was found between MRI and photographic evaluation, differences between the methods ranging from nil to 9.5%, depending on the scan position and the muscle groups. In vivo MRI measurements were performed on 12 female and 16 male students, the objectivity, the test-retest reliability and the variability of the MRI measurements being studied by fixing the scan position either manually or by coronary scan. The latter method appeared to be more objective and reliable. The coefficients of variation for muscle cross-section areas measured by MRI were in the range of those for the planimetry of given cross-section areas. Allowing for differentiation between several small muscle bundles in a given area, MRI proved to be a suitable method to quantify muscle cross-sections for intra- and interindividual analysis of muscle size.

Gadolinium-DTPA (diethylenetriaminepentaacetic acid)-cascade-polymer, a potential new blood pool contrast agent for magnetic resonance (MR) imaging, was compared with a known blood pool agent, Gd-DTPA-polylysine, in an animal model. The relative signal intensities of liver, renal cortex, pancreas, and trunk muscle were assessed in 12 pigs between 4 seconds and 120 minutes after injection of a 20 mumol/kg dose of each contrast agent, by using a FLASH (fast low-angle shot) sequence. Except for muscle, all tissues showed visible enhancement after injection of either contrast agent. After injection of Gd-DTPA-polymer, enhancement patterns in the liver, renal cortex, and pancreas were similar to those seen after injection of Gd-DTPA-polylysine. No statistically significant differences in enhancement between the two contrast agents were found at any time point. The authors conclude that the contrast kinetics of Gd-DTPA-cascade-polymer are similar to those of Gd-DTPA-polylysine and that this agent may also be used as a blood pool contrast agent for MR imaging.

Cross sectional echocardiography from a suprastemal approach usually allows visualisation of the aortic arch and its branches and detects aortic coarctation.i Image quality is often poor, however, (particularly in older patients) after coarctation repair because of the small acoustic window and the long distance between the transducer position and the isthmic region.78 Furthermore, assessment by ultrasound is disappointing because the acoustic window is inadequate when a prosthetic vascular conduit is used for surgical correction of coarctation.9 Recent studies cast doubt on the reliability of measurements of luminal diameter by cross sectional echocardiography without additional colour Doppler flow mapping, which enhances the contrast between the vessel lumen and its wall.1' Several groups have reported on the usefulness of MRI in detecting morphological anomalies of the great vessels, especially in aortic coarctation."1-13Diminished pulses in the lower limbs after coarctation repair suggests restenosis or persisting stenosis. Gradients can be measured from blood pressures in the upper and lower limbs. Flow velocities in the descending aorta distal and proximal to the isthmic region can be measured throughout the cardiac cycle by Doppler ultrasound and it has become clear that not only Doppler determined velocities in the descending aorta but also the flow profile are important in the assessment of the functional state after coarctation repair. 1416 We have evaluated whether the morphological situation after surgical repair of aortic coarctation can be properly demonstrated and measured by MRI and cross sectional echocardiography. We compared morphometric data with the functional data obtained by oscillometric measurement of blood pressure and Doppler ultrasound measurements.