Experimental Performance Assessment of SPM for SPECT Neuroactivation Studies Using a Subresolution Sandwich Phantom Design

Abstract

The validity domain of voxel-based statistical analysis of SPECT neuroactivation studies with statistical parametric mapping (SPM) has been investigated by a limited number of theoretical and simulation studies. In this work, an experimental setup is described with an assessment of its activation detection performance together with the influence of acquisition and processing parameters. A subresolution sandwich phantom was constructed using a printed high-resolution digital Hoffman phantom with a (99m)TcO(4)-ink mixture. Activations of 8, 16, and 24 mm diameter, with an intensity ranging from 5 to 60%, were constructed in the right frontal cortex, anterior and posterior cingulate, and left striatum. Triple-headed SPECT acquisitions were carried out using both fan-beam and parallel beam geometry. The impact of activation characteristics (size, intensity and location), study size, physical degradation factors, and reconstruction technique were studied using SPM99 in a group comparison design with correction for multiple comparisons. For a 15 x 15 design, all 24-mm activations of 5% intensity were detected for the fan-beam data. Decreased focus or study size, lower SPECT resolution, absence of scatter, and attenuation correction resulted in an increase in minimally detectable activation. For a single study referred to 15 control studies, only 24-mm activation foci with a minimal intensity of 10% were detected in the optimal configuration. This approach allows experimental parameter optimization of SPM-based group or single-subject SPECT activation studies compared to normal data, as used in clinical applications. In principle, these findings can be extended to SPECT receptor studies or PET data.

Type 1 cannabinoid receptor mapping with [18F]MK-9470 PET in the rat brain after quinolinic acid lesion: a comparison to dopamine receptors and glucose metabolism

“…It is known that there is a higher physiologic interindividual variability of absolute regional [ 18 F]MK-9470 determinations in the human brain, in the order of several tens of per cent [14,57]. Relative measurements have the advantage of being much more sensitive, allowing changes of 5-10% to be measured using SPM [58], as proven here.…”

Anterior Cingulate and Subgenual Prefrontal Blood Flow Changes Following Tryptophan Depletion in Healthy Males

“…On the other hand, the above factors do not invalidate the positive findings of the study. When appropriate correction for multiple comparisons is made, false-positive clusters would appear to be extremely well controlled for in voxelbased statistical analysis of SPECT neuroactivation studies with SPM (Van Laere et al, 2002). In addition, the rCBF changes associated with RTD may possibly vary with the magnitude of the depletion of brain Trp (and subsequent 5-HT) achieved in a given study.…”

“…For each subject, the second image was realigned to the first (using a sixparameter rigid body transformation with least-squares cost function) and both images were normalized to a standard SPECT template space based on the atlas of Talairach and Tournoux (1988). Spatially normalized images were then smoothed to approximately twice the FWHM system resolution (Van Laere et al, 2002) using an isotropic (18 mm FWHM) Gaussian filter to reduce the error variance associated with individual variability in gyral anatomy, to improve the signal-to-noise ratio, and to precondition the data to fit the Gaussian distribution more closely. Global flow differences were normalized voxel-by-voxel to a mean of 50 ml/dl/min by proportional scaling, and the gray matter threshold was set at 80% of the maximum voxel value in the volume.…”

Influences of Age and Length of Education on rCBF-SPECT in Healthy Elderly: Diagnostic Implications for Dementia

“…The image matrices were 128 × 128 pixels and the spatial resolution of the system (FWHM) at a 100 mm distance from the camera is 6.9 mm. The transmission dependent convolution subtraction method with one iteration [46,47], was used for scatter correction before reconstruction. The images were prefiltered with a 2D Hanning filter with a cut-off frequency of 1.0 cm -1 and reconstructed into transaxial slices with the iterative orderedsubsets ML-EM (OSEM) [48] algorithm using 8 iterations and a subset of 4 images.…”

“…Calculations were performed in Matlab 6.5.1 (Mathworks Inv., Sherborn, Mass., US). Before the statistical analysis, the rCBF-SPECT data were normalized to the MNI SPECT template (SPM2) and smoothed with a 12 mm FWHM 3D Gaussian filter kernel [47]. The confounding effect of varying global activity was removed by proportional scaling to a global value of 50 ml/min per 100 g and a standard level of grey matter threshold of 0.8 was used to exclude voxels of minor interest in the analysis.…”