Contrast induced myocardial signal reduction: effect of lanthanide chelates on ultra high speed MR images.

The myocardial MR signal reduction associated with an intravenous bolus of Gd-DTPA and Dy-DTPA was studied in a canine model. Imaging was performed with a high speed echo-planar type imaging system (Instascan, Advanced NMR Systems, Inc.).

Nonaxial whole-body instant imaging.

We demonstrate that whole-body, single-shot imaging is practical for imaging out of the central plane, including oblique axes. The technique is illustrated by images of the heart in the cardiac long- and short-axis and by coronal images of the brain. Secondary gradients can produce additional image distortion and ghosting in these images.

Functional cerebral imaging by susceptibility-contrast NMR.

In vivo measurement of cerebral physiology by dynamic contrast-enhanced NMR is demonstrated. Time-resolved images of the cerebral transit of paramagnetic contrast agent were acquired using a new ultrafast NMR imaging technique and a novel mechanism of image contrast based on microscopic changes in tissue magnetic susceptibility. Global hypercapnia in dogs was used to establish the relationship between susceptibility-induced signal change and brain blood volume, and the response of gray and white matter to this microvascular stimulus was measured.

Sensory stimulation by time-varying magnetic fields.

When two human volunteers were imaged with magnetic field gradient dB/dt of 61 T/s RMS, the subjects reported, to our surprise, feeling muscular twitches synchronous with gradient pulses over repeated experiments. No adverse or sustained effects were seen. Experiments in a canine, intended to assess the safety of MR imaging with dB/dt of up to 66 T/s RMS, failed to induce detectable changes in the electrocardiogram or to show any signs of gross response to gradient pulsing.