1. Dr Hussein Farghaly PSMMC
Radionuclide Brain Imaging
Lecture 5
Dr Hussein Farghaly
PSMMC
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2. Dementia: An acquired syndrome characterized by:
Short-term memory impairment AND
At least one of the following:
Aphasia - language impairments
Apraxia - motor memory impairments
Agnosia - sensory memory impairments
Abstract thinking / Exec. function impairments
Impairment in social and/or occupational fn
Not explainable by another disorder

4. Causes of Dementia
Dementia is a manifestation of many diseases. Only about 10% of dementias, such as those caused by vitamin B12 or thyroid hormone deficiency, are treatable

5. Causes of Dementia Alzheimer Disease (50-70%) Vascular dementia (15%)
Frontotemporal dementia (5-10%)
Lewy Body disease (25%)
Normal Pressure Hydrocephalus (NPH)
Depression
Intracranial Mass

6. Diagnosis of Dementia
The clinical diagnosis is often difficult and delayed, and anatomical imaging modalities such as CT and MRI may not reveal changes such as atrophy until the end stages of disease.
SPECT and PET, on the other hand, have been shown useful in early diagnosis of Alzheimer disease. In addition, these functional modalities show promise for the identification of subjects early before damage is too severe for therapy to have any benefit.
Although PET has higher sensitivity and higher resolution than SPECT, the overall patterns seen in dementia are similar for both rCGM and rCBF.
In general, the types of dementia can be characterized as posterior, frontotemporal, or vascular.
The posterior dementias include Alzheimer disease, Lewy body disease, and Parkinson dementia.
Pick disease is the classic frontotemporal dementia.

7. Alzheimer’s Disease (AD)
Progressive neurodegenerative disorder
deterioration in cognition, function, and behavior
Most common cause dementia in elderly
4 million in U.S.
30 million worldwide
Female to male 3:1
$100 billion per year in U.S.

8. Pathology and Etiology
Initial damage of neurons in temporal lobes and later in neocortex
Extracellular beta amyloid plaques and intracellular neurofibrillary tangles (tau protein)
Plaque buildup induces inflamation causing injury in hippocampus and cerebral cortex

9. Clinical Diagnosis Accuracy can exceed 90%
Detailed history, physical, mental status examination, and neurologic assessment
Rule out hypothyroidism, vitamin B12 deficiency, reversible causes of dementia

10. Imaging Studies
Stuctural: CT and MR recommended for routine evaluation of AD
Functional: PET and SPECT demonstrate physiologic changes in brain

11. MR vs. CT Low specificy and sensitivity MR preferred over CT
Assess degree of Medial Temporal Lobe Atrophy
Amygdala, Hippocampus, Parahippocampal gyrus
Rule out other causes dementia

12. AD vs. Other Dementias
NPH: holoventricular enlargement out of proportion to sulcal enlargement; dementia, apraxia, incontinence
Generalized atrophy: sulcal and ventricular findings concordant
Vascular dementia: multiple areas of high signal intensity on MR; stepwise decline, smokers, HTN, diabetes

13. Functional Imaging Modalities
SPECT and PET
Vascular dementia
Frontotemporal dementia
Lewy Body
depression

14. SPECT imaging
Brain uptake of technetium 99m-based lipid-soluble radionuclide
89% sensitivity and 80% specificity for AD
Bilateral posterior perfusion abnormality associated with AD
Frontal perfusion deficit associated with frontotemporal dementia
Patchy uptake pattern associated with vascular dementia

15. SPECT imaging

16. Alzheimer Disease VS. Lewy Body diseaseAD LB
Comparison of posterior dementias on Tc-99m HMPAO. Top row: Alzheimer disease generally begins near the superior convexity and involves the parietal and temporal regions laterally (arrows), sparing the occiput and cerebellum (arrowhead). Bottom row: Lewy body disease involves the medial occipital region (arrows) and usually has more caudal extension than Alzheimer disease.
Nuclear Medicine: The Requisites textbook

17. PET imaging FDG and blood flow
Deficits in temporoparietal metabolism seen in patients with AD
Sparing of basal ganglia, thalamus, cerebellum, and primary sensorimotor complex
Sensitivity 87-96%, 73% specificity

18. Alzheimer disease
(A) Transaxial PET images reveal decreased metabolism to the temporal parietal cortex beginning high in the posterior parietal region with sparring of the basal ganglia, thalamus, and cerebellum.
Nuclear Medicine: The Requisites textbook

19. (B) Tc-99m HMPAO SPECT shows that although Alzheimer disease is classically described as a symmetric process, it may be quite asymmetric, as seen in the left posterior parietal region.
Nuclear Medicine: The Requisites textbook

20. (C) As Alzheimer disease becomes more severe it is more diffuse on this SPECT study.
Nuclear Medicine: The Requisites textbook

21. PET imaging
Frontotemporal dementias: decreased uptake in frontal and anterior temporal regions
Depression: normal scan
Vascular: patchy defects in central white matter
Lewy body: deficits in occipital lobes and cerebellum

22. Frontotemporal Dementia

23. Frontotemporal dementia
sparing posterior parietal regions. A, Frontal hypometabolism on PET can be due to many causes and changes visible long before MRI
Nuclear Medicine: The Requisites textbook

24. AD

25. MID

26. FTD

27. Amyloid PET imaging New tracer for PET
Carbon-11 (C-11)-labeled Pittsburgh
compound B (PiB), Ab—or amyloid PET
[F-18]florbetapir, achieved approval by the U.S. Food and Drug Administration in April 2012
Targets amyloid beta senile plaques and neurofibrillary tangles
Long retention times in hippocampus

28. References
Jack CR et al. MR Imaging-Based Volume Measurements of the Hippocampal Formation and Anterior Temporal Lobe: Validation Studies. Neuroradiology. Volume 176. No. 1; pp
Lehericy et al. Magnetic Resonance Imaging of Alzheimer’s Disease. Eur Radiol (2007) 17:
Petrella, et al. Neuroimaging and Early Diagnosis of Alzheimer Disease: A Look to the Future. Radiology 2003; 226:
Zakzanis, Graham, and Campbell. A Meta-Analysis of Structural and Functional Brain Imaging in Dementia of the Alzheimer’s Type: A Neuroimaging Profile. Neuropsychology Review, Vol. 13, No. 1, March 2003.