Ian R. Young

Use of multicoil arrays for separation of signal from multiple slices simultaneously excited

Increased acquisition efficiency has been achieved by exciting several slices simultaneously. The mixed data were unfolded to produce separate slices using the spatial encoding information inherent in a multicoil receiver system. Each coil yields a linear combination of signals from all excited slices weighted by the sensitivity of each coil. A matrix inversion provides a solution to unfold these images. J. Magn. Reson. Imaging 2001;13:313–317.

Two methods for semi-automated quantification of changes in ventricular volume and their use in schizophrenia

Two semi-automated methods for quantification of ventricular volume change from baseline and follow-up magnetic resonance imaging scans have been developed. Technique 1 employs direct segmentation of the ventricles from both the scans using thresholding and contour extraction. Technique 2 operates on difference images produced by voxel based intensity subtraction of the baseline from the registered follow-up images. Here, all voxels with intensities above a noise threshold and in a restricted area are monitored to compute volumetric changes. In phantom measurements the first technique was accurate to 0.0046%, the second to 0.167% of the phantom volume. Results from normal volunteers was that the average ventricular volume changed by 1.52% and 1.54% for images acquired within 9 months using techniques 1 and 2, respectively. With schizophrenic patients mean change of 10.78% and 9.43% were found employing the first and second procedures, respectively. All measurements agreed with a radiologists visual grading of the changes. Robust, objective, fast, easy-to-use, and fairly accurate procedures have been developed and validated to quantify volumetric changes.

Notes on current safety issues in MRI.

The present unsatisfactory state of the worldwide regulatory system for whole body magnetic resonance is explored. The priorities of a number of the most important regulators are outlined, and the differences between factors affecting the safety of patients on the one hand, and of those operating equipment on the other, are discussed. At the end, a strategy is outlined for obtaining the data needed to establish new, more firmly based, limits of operation. A prime factor in getting this data will be collaboration between the regulators, users of equipment, and manufacturers. A measure of urgency is desirable as the longer the present situation is allowed to persist the greater the risk that the stresses already present in it will become intolerable. Copyright

Pre‐polarized saline: an in vivo feasibility study of a potential contrast agent

The potential for using pre‐polarized liquids as contrast agents in vivo is investigated and the feasibility of the method demonstrated. In this study we show the enhancement obtained following intravenous delivery of pre‐polarized saline into the antecubital vein of a volunteer. This form of contrast agent provides signal gain on time scales commensurate with its T1 and allows repeated doses to be administered, thus making alternate acquisitions of data with and without enhancement practicable. Copyright