Contributions of imprecision inPET‐MRIrigid registration to imprecision in amyloidPETSUVRmeasurements

Abstract

Quantitative measurement of β‐amyloid from amyloid PET scans typically relies on localizing target and reference regions by image registration to MRI. In this work, we present a series of simulations where 50 small random perturbations of starting location and orientation were applied to each subject's PET scan, and rigid registration using spm_coreg was performed between each perturbed PET scan and its corresponding MRI. We then measured variation in the output PET‐MRI registrations and how this variation affected the resulting SUVR measurements. We performed these experiments using scans of 1196 participants, half using 18F florbetapir and half using 11C PiB. From these experiments, we measured the magnitude of the imprecision in the rigid registration steps used to localize measurement regions, and how this contributes to the overall imprecision in SUVR measurements. Unexpectedly, we found for both tracers that the imprecision in these measurements depends on the degree of amyloid tracer uptake, and thus also indirectly on Alzheimer's disease clinical status. We then examined common choices of reference regions, and we show that SUVR measurements using supratentorial white matter references are relatively resistant to this source of error. We also show that the use of partial volume correction further magnifies the effects of registration imprecision on SUVR measurements. Together, these results suggest that this rigid registration step is an attractive target for future work in improving measurement techniques. Hum Brain Mapp 38:3323–3336, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Accuracy of rigid registration between amyloid / tau PET and MRI based on normalized mutual information

“…Therefore, it is reasonable that MRI was more correctly registered to amyloid negative images than to amyloid positive images. Schwarz et al [12] indicated that Alzheimer's disease had a larger registration error than the control group in amyloid PET images, and our results are consistent with their report.…”

“…It is important to understand the registration accuracy in order to use the software appropriately because PET images change a lot depending on not only the choice of tracers but also disease progression in dementia PET. One study about registration accuracy of amyloid PET and MRI using SPM has been reported by Schwarz CG, Jones DT, Gunter JL, Lowe VJ, Vemuri P, Senjem ML, et al [12]. They analyzed the registration accuracy for some groups classified by clinical disease severity.…”

Regional amyloid accumulation and cognitive decline in initially amyloid-negative adults

“…Finally, we used a reference region previously shown to provide the most stable reference over time: the average of both the whole cerebellum and the cerebral white matter. 31 A partial volume correction with the method of Muller-Gartner et al 32 was tested but was found to add error, particularly due to limitations in coregistering PET to MRI, 33 and therefore the data presented are not partial volume corrected.…”

White Matter Reference Region in PET Studies of 11C-Pittsburgh Compound B Uptake: Effects of Age and Amyloid-β Deposition

“…The benefit of WM over the cerebellum as a reference region is that there is a larger region over which to average the signal, potentially leading to less noise. WM measurements may also be more resistant to small degrees of misregistration during image quantification (12). In addition, the cerebellar signal is collected at the edge of the scanner field of view where sensitivity is lower (8,9).…”