Dementia

Ian Law¹

¹University of Copenhagen, Denmark

Synopsis

The benefits of PET/MRI in dementia is still in development. There is no firm evidence to suggest added value of this hybrid technique for dementia work-our over sequential scanning besides convenience for patient and clinician.

Introduction

Commercially available integrated PET/MRI has been in clinical use for 7 years. Although being the cause of considerable excitement, the exact role and benefits of the technique have not been firmly defined. Given the key role that MRI has in the diagnostic evaluation of diseases of the brain dementia is an obvious clinical target to consider.

To date PET/MRI using [18F]-fluorodeoxyglucose (FDG) or an amyloid tracer is a practical clinical tool in the evaluation of dementia and allows for a fast, condensed, and well-accepted high-quality imaging protocol with interpretation effectively supported by statistical tools, but besides the convenience for the patient of having a single imaging session, there is no firmly established additive effect of PET/MRI over MRI and PET. One important reason of this is that many of the potentially advanced MRI techniques (e.g. arterial spin labelling) are not in end stage development and have not demonstrated robust performance in a routine clinical setting. Other important issues is establishing a standard for PET attenuation correction in MRI. At the moment there are at least 38 published methods.

Future perspective

The outperformance of PET and MRI by PET/MRI for clinical use is contingent on a closer integration of the two techniques into products that is dependent on simultaneity. This could be in applications that depend on measurements where the variability between sequential MRI and PET is sufficiently large to impact results, e.g. in kinetic PET modelling that require a perfusion measure, or in the estimation of an image derived input function, where accurate alignment of arteries are needed, or in the addition of an accurate and robust global or regional perfusion or oxygen metabolism measure, that may scale the regional distribution measures obtained by PET. However, these methods are still under development and the clinical use of these applications are theoretical and need to be tested in large clinical studies.

Acknowledgements

No acknowledgement found.

References

Ladefoged CN, Law I, Anazodo U et al. A multi-centre evaluation of eleven clinically feasible brain PET/MRI attenuation correction techniques using a large cohort of patients. Neuroimage. 2017;147:346-359.

Henriksen OM, Larsen VA, Muhic A et al. Simultaneous evaluation of brain tumour metabolism, structure and blood volume using [F]-fluoroethyltyrosine (FET) PET/MRI: feasibility, agreement and initial experience. Eur J Nucl Med Mol Imaging. 2016;43:103-112.

Barthel H, Schroeter ML, Hoffmann KT, Sabri O. PET/MR in Dementia and Other Neurodegenerative Diseases. Semin Nucl Med. 2015;45:224-233.

Anazodo UC, Finger E, Kwan BYM et al. Using simultaneous PET/MRI to compare the accuracy of diagnosing frontotemporal dementia by arterial spin labelling MRI and FDG-PET. Neuroimage Clin. 2018;17:405-414.

Proc. Intl. Soc. Mag. Reson. Med. 26 (2018)