According to the study, researchers explained that under the conditions of high spatial resolution and voxelwise data analysis with a homogeneous tissue model, decreases the scan duration of L-[1-11C]leucine PET studies from 90 to 60 min, which has negligible effects on estimates of rates of cerebral protein synthesis (rCPS)

Fully quantitative measurement of regional rates of cerebral protein synthesis (rCPS) is now possible with the L-[1-11C]leucine positron emission tomography (PET) method.

The method has been developed and validated for use in human subjects. The biological process of protein synthesis is important to measure because it is an essential process for growth, maintenance, and function of living organisms. This is especially true in the central nervous system where de novo protein synthesis is involved in adaptive responses such as learning and memory and neural plasticity.

Measurements of rCPS in studies of awake age-matched healthy young men with the L-[1-11C]leucine PET method are reproducible and have low variability. rCPS are also unaffected by propofol anesthesia in healthy young men.

This latter finding suggested that subjects unable to tolerate the PET scanning procedures while awake, such as those with neurodegenerative or neurodevelopmental disorders, could be studied under sedation.

To examine effects of scan duration on estimates of regional rates of cerebral protein synthesis (rCPS), we reanalyzed data from thirty-nine previously reported L-[1-11C]leucine PET studies. Subjects consisted of 12 healthy volunteers studied twice, awake and under propofol sedation, and 15 subjects with fragile X syndrome (FXS) studied once under propofol sedation.

All scans were acquired on a high-resolution scanner. We used a basis function method for voxelwise estimation of parameters of the kinetic model of L-[1-11C]leucine and rCPS over the interval beginning at the time of tracer injection and ending 30, 45, 60, 75 or 90 min later.

For each study and scan interval, regional estimates in nine regions and whole brain were obtained by averaging voxelwise estimates over all voxels in the region. In all three groups, rCPS was only slightly affected by scan interval length and was very stable between 60 and 90 min.

Furthermore, statistical comparisons of rCPS between awake and sedated healthy volunteers provided almost identical results when they were based on 60 min scan data as when they were based on data from the full 90 min interval.

Statistical comparisons between sedated healthy volunteers and sedated subjects with FXS also yielded almost identical results when based on 60 and 90 min scan intervals. Researchers conclude that, under the conditions of the studies, scan duration can be shortened to 60 min without loss of precision.