The Centiloid Project: Standardizing quantitative amyloid plaque estimation by PET

Abstract

Although amyloid imaging with PiB-PET, and now with F-18-labelled tracers, has produced remarkably consistent qualitative findings across a large number of centers, there has been considerable variability in the exact numbers reported as quantitative outcome measures of tracer retention. In some cases this is as trivial as the choice of units, in some cases it is scanner dependent, and of course, different tracers yield different numbers. Our working group was formed to standardize quantitative amyloid imaging measures by scaling the outcome of each particular analysis method or tracer to a 0 to 100 scale, anchored by young controls (≤45 years) and typical Alzheimer’s disease patients. The units of this scale have been named “Centiloids.” Basically, we describe a “standard” method of analyzing PiB PET data and then a method for scaling any “non-standard” method of PiB PET analysis (or any other tracer) to the Centiloid scale.

Amyloid imaging in cognitively normal older adults: comparison between 18F-flutemetamol and 11C-Pittsburgh compound B

“…To investigate the prevalence and the meaning of these cases with sufficient power a joint longitudinal approach including different centres would be necessary. In such an approach a standardized quantification of amyloid deposition, such as centiloid scale [24], would facilitate the comparison. Values close to threshold probably explain the higher rate of discordance in visual reads in our study compared to what has been found in AD and MCI [10,11].…”

Standardized Expression of 18F-NAV4694 and 11C-PiB β-Amyloid PET Results with the Centiloid Scale

“…Lack of standardization prevents the application of universal cut points for diagnostic and prognostic purposes (18) and limits comparison of the relative effectiveness of therapies that claim to reduce Ab burden (17).…”

“…An international working party of Ab imaging researchers has developed a method to standardize quantitative PET measures of Ab binding by scaling the outcome to the centiloid scale (18). This scale has a zero-centiloid point that corresponds to the mean result from scans of young adults who, based on age, are reasonably assumed to be free of Ab plaques.…”

“…Users can confirm that they are applying the method correctly by comparing their own results for the validation scans to the results supplied with the validation scans before analyzing their own scans. It is then possible to derive an additional linear equation to convert the results from any in-house analysis method to centiloids by analyzing 11 C-PiB images that have been converted to parametric centiloid images by the standard centiloid method (18).…”

Establishing Amyloid PET Imaging Biomarkers: Ongoing Efforts

“…A method to unify amyloid PET analysis for different radiotracers has also been proposed. 6 One critical question that was not addressed in the current study by Nayate et al 3 is the accuracy of scan interpretation by using SUVr information. Presentation of the SUVr values at the time of scan interpretation improved interreader agreement.…”