Comparison of PET template-based and MRI-based image processing in the quantitative analysis of C11-raclopride PET

Abstract

BackgroundQuantitative measures of 11C-raclopride receptor binding can be used as a correlate of postsynaptic D2 receptor density in the striatum, allowing 11C-raclopride positron emission tomography (PET) to be used for the differentiation of Parkinson’s disease from atypical parkinsonian syndromes. Comparison with reference values is recommended to establish a reliable diagnosis. A PET template specific to raclopride may facilitate direct computation of parametric maps without the need for an additional MR scan, aiding automated image analysis.MethodsSixteen healthy volunteers underwent a dynamic 11C-raclopride PET and a high-resolution T1-weighted MR scan of the brain. PET data from eight healthy subjects was processed to generate a raclopride-specific PET template normalized to standard space. Subsequently, the data processing based on the PET template was validated against the standard magnetic resonance imaging (MRI)-based method in 8 healthy subjects and 20 patients with suspected parkinsonian syndrome. Semi-quantitative image analysis was performed in Montreal Neurological Institute (MNI) and in original image space (OIS) using VOIs derived from a probabilistic brain atlas previously validated by Hammers et al. (Hum Brain Mapp, 15:165–174, 2002).ResultsThe striatal-to-cerebellar ratio (SCR) of 11C-raclopride uptake obtained using the PET template was in good agreement with the MRI-based image processing method, yielding a Lin’s concordance coefficient of 0.87. Bland-Altman analysis showed that all measurements were within the ±1.96 standard deviation range. In all 20 patients, the PET template-based processing was successful and manual volume of interest optimization had no further impact on the diagnosis of PD in this patient group. A maximal difference of <5% was found between the measured SCR in MNI space and OIS.ConclusionsThe PET template-based method for automated quantification of postsynaptic D2 receptor density is simple to implement and facilitates rapid, robust and reliable image analysis. There was no significant difference between the SCR values obtained with either PET- or MRI-based image processing. The method presented alleviates the clinical workflow and facilitates automated image analysis.

Striatal Dopamine D2/D3 Receptor Availability Varies Across Smoking Status

“…Furthermore, MRI images were not available for all participants, thus limiting our capacity to coregister images and determine striatal ROIs. However, we and others have shown that MRI coregistration does not improve quantification of [ 11 C]raclopride binding (Kuhn et al, 2014;Wang et al, 1997). To minimize the acute effects of nicotine on [ 11 C]raclopride binding, smokers were allowed to have a last cigarette 42.5 h before PET scanning.…”

Partial volume correction in quantitative amyloid imaging

“…In our implementation, a brain tissue mask is generated based on FreeSurfer segmentation, a CSF dilution factor is calculated for each region, and the raw time activity curve for each region is corrected by this dilution factor before BP ND is calculated. The second method is based on computation of the regional spread function (RSF) (Rousset et al, 2008; Rousset et al, 1998), which has also been extensively applied in PET imaging analysis (Kim et al, 2013; Kuhn et al, 2014; Le Pogam et al, 2011). Our implementation of RSF PVC also included additional ROIs outside the brain (hence, not defined by FreeSurfer) to account for tracer uptake in non-brain tissue.…”

Non-invasive Imaging and Analysis of Cerebral Ischemia in Living Rats Using Positron Emission Tomography with ¹⁸F-FDG

“…By standardizing the volumes to be quantified across hemispheres of the brain and across multiple animals, this method generates consistent measurements of decreased tissue glucose uptake. Note that other PET tracers with brain uptake, like 11 C-raclopride for D2 receptors, may be used with this protocol as well 21 . Finally, we describe a method to visualize an ischemic stroke in a rat brain within its skeleton with high anatomical accuracy in three dimensions.…”