Dementia is a complex syndrome affecting areas of cognition, problem-solving, memory amongst many others. Often times there is a significant overlap of clinical presentation of various dementia disorders.
Functional imaging can objectively diagnose, predict and differentiate various dementia disorders at a much higher sensitivity and specificity then conventional imaging. Nuclear medicine offers PET and SPECT imaging technology for the same.
This functional imaging modality is based on the utilisation of caused by the neurons. Areas showing abnormal function show a reduction in glucose utilisation and hence can be seen as an area of hypometabolism on the brain PET imaging.
Since functional changes proceed the development of structural changes, brain PET can pick abnormalities earlier then morphologic abnormalities.
Amongst the current available imaging modalies FDG brain PET is the most sensitive technique for evaluation of Alzheimer’s disease.
Patient’s clinical MCI progresses to develop frank Alzheimer’s disease while a small subgroup stays stable.
Subjects with clinical MCI and an abnormal abrain PET are 18 times more likely to develop frank Alzheimer’s disease in due course of me when compared with those subjects with normal Brain PET.
Movement disorders, typically Parkinson’s disease becomes overtly evident after over 50% neuronal loss on MRI Scan. Tc-TRODAT scan, which images the dopaminergic system, can objectively demonstrate dopaminergic deficit (which leads to Parkinson’s disease) much earlier during the course of disease, being the only imaging modality capable of doing so.
Combination of brain PET and Tc-TRODAT scan is valuable in the evaluation of Parkinson’s plus syndromes. These scans along with clinical neurologic evaluation provide the highest diagnostic yield in evaluation of movement disorders with dementia.
Tc-GHA SPECT study:
Based on the principle of blood-brain barrier breakage, this study reliably differentiates a post-
treatment inflammation versus a recurrence with the highest sensitivity.
Representative images from *literature:
Reference DOI: 10.4103/0972-3919.147525
Figure 8: A 30-year-old male with right frontal grade II
astrocytoma, primarily treated with radiotherapy, presented with
severe headache. Magnetic resonance imaging (a) was positive
for residual/recurrent tumor (arrow). 99m-technetium-glucoheptonate single photon emission computed tomography
(b) was also strongly positive for recurrent/residual tumor (arrow). However, on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (c) the recurrent/residual
lesion was hypometabolic (arrow).
Over 1/4th of the patients with epilepsy disorder evolve into refractory epilepsy. These patients can potentially be treated successfully with neurosurgical resection if the patient has a focal epileptogenic abnormality that is safe to remove FDG brain PET can identify the seizure focus.
At Infinity Medical Centre, we have a worked towards creating a multimodality imaging protocol that involves interictal FDG brain PET and MRI brain as one single study. This enables a perfect correlation between structural information by the MRI and functional information by the brain PET, enabling precise and more valuable information.