Brain structure localization in positron emission tomography: comparison of magnetic resonance imaging and a stereotactic method

Age-related shift in brain region activity during successful memory performance

Coregistered positron emission tomography (PET)/magnetic resonance imaging (MRI) was used to characterize brain function in 70 volunteers, aged 20-87 years, during a verbal memory task. Frontal activity showed an age-related decline that remained significant after statistical control for sulcal atrophy. Analyses of young and old subgroups matched for memory scores revealed that young good performers activated frontal regions, whereas old good performers relied on occipital regions. Although activating different cortical regions, good performers of all ages used the same cognitive strategy semantic clustering. Age-related functional change may reflect dynamic re-allocation in a network of brain areas, not merely anatomically fixed neuronal loss or diminished capacity to perform.

A reference method for correlation of anatomic and functional brain images: validation and clinical application

We describe a reference device that provides accurate correlation between anatomic and functional brain images. The reference device, which generates fiduciary reference points on sequential scan planes, is positioned adjacent to the canthomeatal line of the subject and held in place by a glasses-like framework anchored to the external auditory meatus. The reference system was tested on 17 subjects undergoing 99mTc hexamethylpropylene amine oxime ([99mTc]HMPAO) brain single-photon emission computed tomography (SPECT) and cranial computed tomography (CT) scans. The centers of the caudate nuclei, thalami, brain stem, and cerebellar vermis were identified independently on CT and SPECT. The average difference +/- 1 SD between structure locations (x, y, and z) on SPECT and CT were calculated as 1.86 +/- 1.5, 2.16 +/- 1.4, and 1.83 +/- 1.9 mm, respectively. The clinical application of the method is showed by coregistration of images from SPECT to MRI. An example of sequential [99mTc]HMPAO brain SPECT scan sections precisely coregistered with MRI scan sections oriented parallel to and sequentially above the canthomeatal line illustrates the correlation between regional cerebral blood flow (rCBF) tracer activity on SPECT and normal anatomic structures. Test-retest activation paradigms in brain SPECT requires precise SPECT-to-SPECT image coregistration to evaluate changes in rCBF during activation. Precisely coregistered rest, 48-hour repeat rest [99mTc]HMPAO SPECT studies are shown to illustrate the normal intrasubject variability of tracer uptake. An example of the usefulness of image coregistration for evaluation of viable residual brain tumor and its application to tumor biopsy is presented. An example of developmental abnormalities identified by [99mTc]HMPAO brain SPECT is illustrated by a case of autistic disorder. An example of image coregistration in stroke and evaluation of cerebrovascular disease with Diamox (Lederle Laboratory Division, Pearl River, NY) cerebrovasculature stress testing is presented. The usefulness in epilepsy using a protocol whereby the tracer is injected during the ictal phase of seizure is presented. We conclude that the reference system provides an accurate, rapid, and noninvasive patient-specific method for correlating brain structure with brain function.

Validation of a reference method for correlation of anatomic and functional brain images

We describe a reference device that provides accurate correlations between anatomic and functional brain images. The reference device, which generates fiduciary reference points on sequential scan planes, is positioned adjacent to the orbitomeatal line of the subject, and held in place by a framework anchored to the external auditory meatus. The reference system was tested on 17 subjects undergoing Tc-99m-hexamethylpropyleneamine oxime (Tc-99m-HM-PAO) brain single photon emission computed tomography (SPECT) and cranial computed tomography (CT) scans. The centers of the caudate nuclei, thalami, brain stem, and cerebellar vermis were identified independently on CT and SPECT. The average difference +/- 1 sd between structure locations (x, y, and z) on SPECT and CT were calculated as 1.86 +/- 1.5, 2.16 +/- 1.4, and 1.83 +/- 1.9 mm, respectively. The relevance of the method to clinical applications is illustrated by the localization of a recurrent viable glioma and an epileptogenic focus. This reference system provides an accurate, rapid, and noninvasive patient-specific method for the correlation of brain structure with brain function.