Value of cerebral blood flow quantification in the diagnosis of dementia
John J Zaknun1, Friedrich Leblhuber, Harald Schücktanz
1Nuclear Medicine Section, Division of Human Health, International Atomic Energy Agency, Wagramer Strasse 5, Vienna, Austria. J.Zaknun@iaea.org
Insights
Quantifying cerebral blood flow (CBF) with HMPAO-RNA SPECT improves dementia diagnosis. This simple, reproducible method aids in differentiating primary degenerative dementia from controls, offering a valuable tool for etiological classification.
Area of Science:
- Neuroimaging
- Nuclear Medicine
- Cerebrovascular Physiology
Background:
- Quantifying hemispheric cerebral blood flow (CBF) can enhance diagnostic accuracy when integrated with perfusion SPECT.
- Current diagnostic approaches for dementia may benefit from advanced imaging techniques for improved differentiation.
Purpose of the Study:
- To investigate the impact of mean CBF measurement on the differential diagnosis of dementia in a clinical setting.
- To assess the utility of HMPAO-RNA SPECT for differentiating dementia subtypes and controls.
Main Methods:
- Cerebral blood flow (CBF) was calculated using Patlak analysis of dynamic (99m)Tc-HMPAO SPECT imaging.
- Study included controls (n=34) and patients with probable dementia: primary degenerative aetiology (PDD, n=33) and vascular leuco-encephalopathy (vLEP, n=13).
- Age-dependent CBF differences were analyzed using ANCOVA, with P<0.05 considered significant.
Main Results:
- HMPAO-RNA SPECT demonstrated excellent inter-user reproducibility (<5% variation).
- Controls showed an age-dependent decrease in CBF. PDD patients exhibited significantly lower CBF than controls after age adjustment (P<0.001).
- ROC analysis revealed 93-94% sensitivity and 73-77% specificity for differentiating dementia from controls.
Conclusions:
- Routine quantification of mean CBF using HMPAO-RNA SPECT is a simple, reproducible addition to brain perfusion SPECT.
- This method provides an additional, cost-effective tool for the etiological classification of dementia without increasing radiation burden.
- Combined with regional perfusion data, it aids in differentiating dementia subtypes.
Background:
Quantifying hemispheric cerebral blood flow (CBF) may improve diagnostic accuracy when combined with perfusion SPECT.
Aim:
To explore the impact of measuring mean CBF on the differential diagnosis of dementia under clinical conditions.
Methods:
CBF was calculated from anterior planar dynamic images acquired over 100 s after i.v. bolus injection of 550 MBq of (99m)Tc-HMPAO using Patlak linearization of normalized time-activity curves derived from right and left hemispheric, and aortic ROIs. Regional perfusion was evaluated from SPECT imaging carried out 20 min later. ANCOVA was applied to compare age-dependent differences of CBF; model differences at P<0.05 were considered significant. Study populations consisted of controls, 34 patients with no focal or vascular abnormality or mood disorder and with normal MR or CT brain images (F:M, 16:18; age+/-SD; 54.3+/-20.2 years); and patients with probable dementia comprised two subgroups. The first consisted of 33 patients with primary degenerative aetiology (PDD) (DAT or mixed-type microvascular and DAT, Lewy body and fronto-temporal atrophy), F/M; 17:16, age+/-SD; 68.4+/-8.8 years. The second subgroup consisted of 13 patients with dementia related to subcortical microvascular leuco-encephalopathy (vLEP), M/F 7:6, age+/-SD; 71.7+/-12.6 years. Classification was mainly based on clinical findings according to DMS-IV criteria, combined with follow-up or functional and anatomical imaging.
Results:
Computation of CBF on 100 consecutive patients showed excellent inter-user reproducibility in trained hands (variation coefficient <5%). Mean CBF in controls showed an age dependent decrease, the first order linear regression was CBF(left)=58.9-0.2 x age (r=-0.648, P<0.001) and CBF(right)=57.9-0.02 x age (r=-0.645). In comparison to controls, a slightly more pronounced but statistically insignificant age-dependent decrease in mCBF was found in the vLEP group, CBF(left)=55.5-0.21 x age (r=-0.56) and CBF(right)=64.2-0.32 x age (r=-0.645). In the PDD group CBF, after adjusting for age, was significantly lower than control values (P<0.001); CBF(left)=37-0.025 x age and CBF(right)=39-0.057 x age. More importantly, better discrimination between PDD and controls in patients of younger age (45-65 years) was found. In older patients (65-85 years) overlap slightly increased. ROC analysis of the cohort of dement patients and controls older than 46 years revealed a 93-94% sensitivity and a specificity of 73% and 77% for the left and right hemispheres, respectively, at a CBF cut-off value of 39.5 ml.min(-1).100 g(-1).
Conclusion:
Routine quantification of mean CBF by HMPAO-RNA is a simple and reproducible method which can be easily added to the standard brain perfusion SPECT without additional cost or increasing patient's radiation burden. Combined with regional perfusion it provides an additional tool for the aetiological classification of dementia.
