Harmonization of PET imaging biomarkers is a critical step in multi-center studies to enable accurate statistical between-groups comparisons by reducing the bias introduced by inter-site imaging protocols and inter-scanner variability.

With this aim, the use of Hoffman phantoms was a pioneering approach aimed at bringing Hoffman phantom images from different scanner models to a common spatial resolution. Despite the Hoffman-based approach having resulted in a useful tool for large studies, it is logistically challenging and costly to implement in the complex settings of multi-center clinical trials.

Overview of our Hoffman phantom-free approach for estimating spatial resolution in PET images. The logarithmic intensity plots are used for estimating the spatial resolution of PET images. Then, a mathematical formula gives the kernel size to blur the image to the pre-defined common target resolution.

Rather than using Hoffman phantom images as a surrogate, we introduce an approach, called SPITFIRE™, that estimates the spatial resolution directly from the actual human brain PET images.