Underestimated Centiloid Values in Amyloid PET: A Technical Report on Clinically Relevant Quantification Errors.

Area of Science:

• Neurology
• Radiology
• Pharmacology

Background:

• Quantitative amyloid positron emission tomography (PET) interpretation with the Centiloid scale is crucial for guiding anti-amyloid therapy.
• Discrepancies between visual and quantitative PET assessments can lead to clinical misjudgments.

Purpose of the Study:

• To highlight a case where quantitative amyloid PET (Centiloid) underestimated cortical amyloid deposition.
• To investigate the impact of reference region selection on Centiloid values.

Main Methods:

• Analysis of an 18F-florbetapir PET scan with visually evident cortical amyloid.
• Comparison of Centiloid values derived from different cerebellar reference regions (whole cerebellum vs. gray matter).

Main Results:

• A visually positive amyloid PET scan resulted in a Centiloid value of 0 when using the whole cerebellum as a reference.
• Using cerebellar gray matter as a reference yielded higher Centiloid values compared to the whole cerebellum.

Conclusions:

• Centiloid underestimation can occur due to reference region selection, potentially excluding patients from vital anti-amyloid therapies.
• Clinical interpretation of Centiloid values requires caution, corroboration with visual reads, and harmonization of methods is needed.