Dementia is a clinical diagnosis based on significant and persisting deficits of intellectual function, usually memory. Diagnostic imaging techniques for morphologic examinations (eg, CT and MR imaging) and for functional examinations (eg, SPECT and PET) are now used widely for supporting the diagnosis of dementia. The PET done with radiopharmaceutical [18F]fluorodeoxyglucose can detect any abnormal regional glucose metabolism in patients with dementia and is the most widely available & useful biomarker for dementia diagnosis. However, to exclude several pathologies such as subdural hematoma, vascular dementia, normal pressure hydrocephalus, and brain tumors, a thorough clinical examination is usually followed by MR imaging because FDG-PET alone cannot detect these diseases.
PET and MRI done together with simultaneous PET/MRI offers the best possible technique that offers the best of both to detect, differentiate, suggest any comorbidity and may also be used to follow response to stem cell therapy.
Encephalitides: MR is the best available imaging modality for encephalitis however, false negatives can occur in first few days of opportunistic infections, paraneoplastic limbic encephalitis and autoimmune encephalitis where there may not be any detectable abnormality on MRI.18F-FDG can be used as a problem-solving tool in such clinically suspected cases of encephalitis.
In the following cohort of cases, the PET/MRI findings in various types of dementia and encephalitis are depicted highlighting the importance of FDG PET and MR in their differential diagnosis.
65 year male with progressive dementia.
Axial T1 (A, B) and FLAIR (C, D) images show generalized cerebral atrophy more marked in the frontal and temporal lobes including bilateral hippocampal atrophy (arrows in B) with dilatation of bilateral Sylvian fissures and ventricles.
Qualitative and quantitative comparative analysis to a standard age-matched database using the SCENIUM software shows moderate to marked FDG hypometabolism (blue color, arrowheads) involving bilateral frontotemporal regions also showing a negative standard deviation on quantitative analysis consistent with Fronto – Temporal Dementia.
This short PET-MRI Scan case was compiled by Dr. Sangeeta Taneja and Dr. Amarnath Jena (Nuclear Medicine Physician at PET-Suite @ Indraprastha Apollo Hospital, Sarita Vihar).
Read More about PET-MRI Scan at House Of Diagnostics in Delhi and NCR.
The Simultaneous PET-MRI Scan is currently offered at PET-Suite at Apollo Hospital, Sarita Vihar.