Nuclear medicine

The study find that the computed tomography (CT); and magnetic resonance imaging (MRI); are routinely use in the evaluation of memory clinic patients. Therefore Hybrid PET/MR systems now allow simultaneous PET and MRI imaging within the duration of the PET emission scan. Brain imaging plays a pivotal role in the evaluation of patients with cognitive complaints.

The evaluation of patients

Structural imaging using compute tomography (CT); or magnetic resonance imaging (MRI) is recommend in all patients in order to exclude potentially reversible causes of dementia, to demonstrate presence of vascular disease or characteristic patterns of regional atrophy. Magnetic resonance imaging (MRI) is often consider superior to CT in dementia imaging; in particular for demonstrating vascular lesions and for identifying additional pathology; e.g. microbleeds and white matter lesions.

Radionuclide studies using 18F-fluoro-deoxy-glucose (FDG) positron emission tomography (PET) imaging of glucose metabolism or single photon emission tomography (SPECT); imaging of cerebral perfusion has been shows to provide valuable information of neuronal function and integrity; and FDG PET has been shows to be superior to both perfusion SPECT and MRI hippocampal volume measurements for detection of Alzheimer’s disease.

A multimodal approach combining FDG PET and MRI providing complementary information may thus be optimal; and co-registration with structural imaging is recommend when evaluating FDG PET in order to correctly assess structural correlates of FDG PET abnormalities.

Patterns of regional atrophy

Currently; FDG PET can be obtained on standard PET/CT and read with CT acquire separately ; (or in the same scanning session) or with separately obtained MRI. With the introduction of hybrid PET/MRI systems, the added diagnostic value of MRI may now also be include in a single imaging procedure.

Hybrid PET/MRI systems are becoming increasingly available and the potential clinical and research applications have been the subject of a number of recent reviews. However; PET/MRI is still a new technology and its potential clinical use is not address in current guidelines.

Potential clinical use

Studies on routine clinical use of hybrid FDG PET/MRI in a mixed memory clinic population are sparse, and no previous studies have investigated how PET/MRI; compares to PET/CT in terms of diagnostic information including interpretation of FDG PET; clinical diagnosis and patient management. When implementing the PET/MRI system for clinical routine at our institution, we initially used the system for FDG PET only.

In order to complete the scan within the recommended PET duration of 10 minutes; the MRI protocol was limited to T2 and 3D T1 weighted MRI not intended for diagnostic purposes; and clinical CT obtained elsewhere was used. These data provide the opportunity to retrospectively investigate the diagnostic yield of a time efficient combined FDG PET/MRI protocol compared to separate PET and CT in clinical routine.