The need of standardization and of large clinical studies in an emerging indication of [¹⁸F]FDG PET: the autoimmune encephalitis

Excerpt

[¹⁸F]FDG PET is currently the most commonly used functional imaging method for the in vivo investigation of regional brain metabolism in clinical practice. PET/CT scanners are widely available in Europe, in the US, in Australia, and most of the rest of the world [1] and the clinical role of [¹⁸F]FDG brain PET can be regarded as established for a number of diagnostic challenges in Neurology and Psychiatry [2]. In particular, [¹⁸F]FDG PET plays a major role in the early and differential diagnosis of neurodegenerative dementias and Parkinsonian syndromes by showing disease-specific patterns of hypometabolism [3]. For a substantial period of time, however, the lack of standardisation in reading images and reporting results, as well as the lack of large studies in homogeneous patient cohorts, has delayed a wider routine clinical use of [¹⁸F]FDG PET [4]. This is particularly true in the field of inflammation/infection imaging despite initial attempts to standardize this methodology between the European Association of Nuclear Medicine (EANM) and the American Society of Nuclear medicine and Molecular Imaging (SNMMI) [5]. In the last decade, thanks to the synergistic efforts of the neuroimaging and neurological communities across different countries, larger data sets and functional imaging repositories have become available. This allowed for assessing the clinical value of [¹⁸F]FDG PET as well as that of other imaging biomarkers in the field of neurodegenerative diseases [6‐8]. The added value of this large multi-center approach has gained attention in the US for PET imaging in other indications as well, for example, through the National Oncologic PET Registry (NOPR) and more recently the Imaging Dementia Evidence for Amyloid Scanning (IDEAS) clinical trials. Similarly, software based semi-quantitative approaches have increasingly been used both in the context of published group analyses as well as in clinical practice, thus testifying that objective measures can be incorporated and added to the traditional analysis approach in nuclear medicine, i.e., visual reading [9‐11]. …