Nuclear medicine

The study find that the positron emission tomography/magnetic resonance imaging PET/MRI is a promising diagnostic imaging tool for the diagnosis of dementia, as PET can add complementary information to the routine imaging examination with MRI. The purpose of this study was to evaluate the influence of MRI-based attenuation correction (MRAC) on diagnostic assessment of dementia with [18F]FDG PET. Quantitative differences in both [18F]FDG uptake and z-scores are calculate for three clinically available (DixonNoBone, DixonBone, UTE) and two research MRAC methods; (UCL, DeepUTE) compared to CT-based AC (CTAC).

PET/MRI is a promising diagnostic

Furthermore; diagnoses based on visual evaluations were made by three nuclear medicine physicians and one neuroradiologist (PETCT, PETDeepUTE, PETDixonBone, PETUTE, PETCT + MRI, PETDixonBone + MRI). In addition; pons and cerebellum are compare as reference regions for normalization. Magnetic resonance imaging (MRI) is today the preferred imaging modality in the clinical workup of suspected neurodegenerative disease due to the high spatial resolution and high soft tissue contrast.

MRI can identify atrophy in dementia and exclude other diseases like vascular disease; cerebral amyloid angiopathy, brain tumors, and traumatic as well as inflammatory brain changes. Positron emission tomography (PET) with fluorodeoxyglucose ([18F]FDG) is however increasingly used to support the clinical diagnosis of patients with suspected dementia; as hypometabolism in certain brain regions can help identify specific types of dementia; including Alzheimer’s disease (AD) and frontotemporal dementia (FTD). PET has a higher sensitivity for detecting early metabolic changes, which takes place prior to the morphological changes visible on MRI.

Inflammatory brain changes

Hybrid PET/MRI systems have opened up the opportunity for simultaneous PET/MRI acquisitions, enabling fast and convenient examinations for patients with dementia. The information from PET and MRI is complementary; and detection of dementia with the combination of [18F]FDG PET and MRI is more accurate than with either of the imaging modalities alone. As a complement to the visual assessment of hypometabolism in PET images performed by nuclear medicine physicians; PET data can be compared to databases of age-matched healthy controls.

Z-score maps are then calculate, which represents the number of standard deviations (σ) separating the [18F]FDG uptake of the patient and the average of the healthy controls; where moderate hypometabolism is define as a z-score between − 2 σ and − 3 σ, and severe hypometabolism for a z-score below  3 σ. A prerequisite for using such quantitative comparisons clinically is quantitatively accurate PET images, which are heavily dependent on attenuation correction (AC). AC is one of the most important corrections that needs to be performed on PET images; but is still challenging when using a PET/MRI system.