Geometric distortion in clinical MRI systems - Part II: correction using a 3D phantom

In this paper, we present the correction of the geometric distortion measured in the clinical magnetic resonance imaging (MRI) systems reported in the preceding paper (Part 1) using a 3D method based on the phantom-mapped geometric distortion data. This method allows the correction to be made on phantom images acquired without or with the vendor correction applied. With the vendor's 2D correction applied, the method corrects for both the residual geometric distortion still present in the plane in which the correction method was applied (the axial plane) and the uncorrected geometric distortion along the axis non-nal to the plane. The evaluation of the effectiveness of the correction using this new method was carried out through analyzing the residual geometric distortion in the corrected phantom images. The results show that the new method can restore the distorted images in 3D nearly to perfection. For all the MRI systems investigated, the mean absolute deviations in the positions of the control points (along x-, y- and z-axes) measured on the corrected phantom images were all less than 0.2 mm. The maximum absolute deviations were all below similar to0.8 mm. As expected, the correction of the phantom images acquired with the vendor's correction applied in the axial plane performed equally well. Both the geometric distortion still present in the axial plane after applying the vendor's correction and the uncorrected distortion along the z-axis have all been restored. (C) 2004 Elsevier Inc. All rights reserved.

An editor's view of telemedicine

Should an editor hold a view about telemedicine, or should an editor be entirely disinterested? The editorial role has been defined by the International Committee of Medical journal Editors and a long list of editorial responsibilities has been set out by the World Association of Medical Editors. This represents something of a counsel of perfection, although clearly an editor should not have a personal view, in the sense of promoting telemedicine or dismissing it. Since telemedicine editors are almost bound to be active in research, they should take particular care with manuscripts involving their own work, for example standing aside from the editorial process and delegating editorial decisions to other members of the editorial staff. At the beginning of the 1990s, there were few publications about telemedicine in the peer-reviewed literature. The subsequent years have seen a rapid growth in numbers of articles and the emergence of two specialist journals. These are all healthy signs. However, there have been remarkably few studies of telemedicine's cost-effectiveness, which must represent a sign of its immaturity. On balance, the evidence seems to indicate that telemedicine research is in a healthy state.