Qualitative (QL) and 3D quantitative (QN) analysis of 123Ioflupane SPECT in differential diagnosis of cognitive disorders (CD)

Objectives To investigate the usefulness of QL and QN analysis of 123Ioflupane SPECT in CD differential diagnosis.

Methods We studied 56 consecutive patients, with CD for 12-48 mths with doubtful International Clinical Criteria for Alzheimer’s Disease (AD) and Lewy Body Dementia (LBD); CT/MR were non specific. All patients underwent Brain SPECT, 3-4 hrs after 148 MBq 123Ioflupane i.v. injection. SPECT images were evaluated by both QL and QN, the latter by a new dedicated software (NEUROTRANS 3D; Segami Corp.) which define striatal dopaminergic activity as Binding Potentials (BP) applying attenuation and partial volume effect corrections by degrading Talairach atlas. Caudate and putamen BP normal value (cut off of 3.3) was previously calculated in 20 sex-age matched normal subjects.

Results QL was pathological in 19/56 (33.9%) cases (Group A) with low tracer uptake in 10/38 (26.3%) caudate and in 27/38 (71%) putamen; in this Group, QN showed BP values <3.3 in 23/38 (60.5%) caudate and in 38/38 (100%) putamen and >3.3 in the remaining 15 caudate (39.5%). QL was normal in 37/56 (66.1%) patients (Group B) with BP >3.3 in 74/74 (100%) caudate and in 69/74 (93.2%) putamen and<3.3 in the remaining 5 (6.8%). BP mean values of caudate (2.25±0.61) and putamen (1.38±0.45) of Group A were significantly (p<0.000001) lower than controls (caudate and putamen mean values: 4.9±0.71 and 4.6±0.67, respectively), while they were not statistically different in Group B. Globally, QL and QN were concordant in classifying AD in 32 cases (57.1%) and LBD in 19 (33.9%). The tests were discordant in 5 further pts (9.0%) in whom only QN correctly classified LBD.

Conclusions Our study confirm 123Ioflupane SPECT usefulness in CD differential diagnosis, especially in discriminating LBD from AD. Moreover, in our cases, QN with BP calculation proved more reliable than QL, especially in the early phase of the disease, better defining dopamine transporter uptake