External reference markers for the correction of head rotation in brain single-photon emission tomography

On the incorporation of multi-modality image registration into the radiotherapy treatment planning process

A technique is presented that allows the direct use of physiological image sets in the radiation therapy treatment planning process. When fused to the treatment planning CT, physiological image studies may allow one to define physiological tumor subvolumes consisting of areas of possible chronic hypoxia, areas of high perfusion, areas of high diffusion, and areas containing high choline concentrations. These physiological tumor subvolumes could be selectively boosted to increase local control of malignant brain tumors once one has determined which of these physiological tumor subvolumes predicts for local tumor recurrence after conventional radiotherapy. In this technique a user assisted automatic registration technique is used that is based on an analytical estimate for the transformation matrix needed to register two rigid bodies. The only user input needed is three non-collinear points selected based on landmarks in the primary image and the corresponding three points in the secondary image. Since this registration technique uses two sets of at least three user-defined landmark points each of which has some selection error associated with it, the final registration will have an error that depends only on the selection error associated with the point sets. Since physiological image studies are acquired at the same setting as the T1- w MRI their spatial orientation with respect to the T1- w MRI is known. Therefore, the registration of multiple physiological image studies to the treatment planning CT can be accomplished by first correlating them to the T1- w MRI, and in a second step the T1- w MRI is then registered to the treatment planning CT. The desired registration of the physiological image studies to the treatment planning CT is then accomplished by simply composing the appropriate transformation matrices.

A survey of medical image registration

The purpose of this paper is to present a survey of recent (published in 1993 or later) publications concerning medical image registration techniques. These publications will be classified according to a model based on nine salient criteria, the main dichotomy of which is extrinsic versus intrinsic methods. The statistics of the classification show definite trends in the evolving registration techniques, which will be discussed. At this moment, the bulk of interesting intrinsic methods is based on either segmented points or surfaces, or on techniques endeavouring to use the full information content of the images involved.

In vivo evidence for the involvement of dopamine-D2 receptors in striatum and anterior cingulate gyrus in major depression

The dopaminergic system is a candidate neurotransmitter system thought to be involved in the pathogenesis of depression. This study addresses the issue whether the antidepressant efficacy of serotonin reuptake inhibition is related to changes in the cerebral dopaminergic system. Cerebral dopamine-D2 receptors were characterized in 13 patients with major depression using the dopamine-D2 receptor antagonist iodobenzamide and single photon emission tomography. Dopamine receptor binding was assessed twice, before and during serotonin reuptake inhibition. An increase in dopamine-D2 receptor binding during serotonin reuptake inhibition was found in striatum and anterior cingulate gyrus in treatment responders, but not in nonresponders. The increase in dopamine-D2 receptor binding correlated significantly with clinical recovery from depression as assessed with the Hamilton depression scale (r = 0.59 for right and left striatum respectively, P < 0.05; r = 0.79 for the anterior cingulate gyrus, P < 0.05 after Bonferroni correction). Qualitatively similar correlations were observed in the precentral gyrus, the medial frontal gyrus, the inferior frontal gyrus, and the frontal part of the opercular gyrus, but these correlations failed to reach statistical significance after correction for the effects of multiple testing. No such correlations were found in the superior frontal gyrus, the orbitofrontal gyrus, the gyrus rectus, the superior parietal gyrus, or the superior temporal gyrus. The data strengthen the concept that the striatum and the anterior cingulate gyrus are involved in mood regulation. Dopamine-D2 receptors may constitute a central role in this domain.