International Psychogeriatrics

Research Article

A comparison of 99mTc-exametazime and 123I-FP-CIT SPECT imaging in the differential diagnosis of Alzheimer's disease and dementia with Lewy bodies

Sean J. Collobya1 c1, Michael J. Firbanka1, Sanjeet Pakrasia1, Jim J. Lloyda2, Ian Drivera3, Ian G. McKeitha1, E. David Williamsa4 and John T. O'Briena1

a1 Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, U.K.

a2 Regional Medical Physics Department, Royal Victoria Infirmary, Newcastle upon Tyne, U.K.

a3 Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, U.K.

a4 Regional Medical Physics Department, Sunderland Royal Hospital, Sunderland, U.K


Background: The aim of this study is to investigate the diagnostic value of perfusion 99mTc-exametazime single photon emission computed tomography (SPECT) in the diagnosis of dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) in comparison with dopaminergic 123I-2β-carbomethoxy-3β-(4-iodophenyl)-n-(3-fluoropropyl) nortropane (FP-CIT) SPECT imaging.

Methods: Subjects underwent 99mTc-exametazime scanning (39 controls, 36 AD, 30 DLB) and 123I-FP-CIT scanning (33 controls, 33 AD, 28 DLB). For each scan, five raters performed visual assessments blind to clinical diagnosis on selected transverse 99mTc-exametazime images in standard stereotactic space. Diagnostic accuracy of 99mTc-exametazime was compared to 123I-FP-CIT results for the clinically relevant subgroups AD and DLB using receiver operating characteristic (ROC) curve analysis.

Results: Inter-rater agreement for categorizing uptake was “moderate” (mean κ = 0.53) for 99mTc-exametazime and “excellent” (mean κ = 0.88) for 123I-FP-CIT. For AD and DLB, consensus rating matched clinical diagnosis in 56% of cases using 99mTc-exametazime and 84% using 123I-FP-CIT. In distinguishing AD from DLB, ROC analysis revealed superior diagnostic accuracy with 123I-FP-CIT (ROC curve area 0.83, sensitivity 78.6%, specificity 87.9%) compared to occipital 99mTc-exametazime (ROC curve area 0.64, sensitivity 64.3%, specificity 63.6%) p = 0.03.

Conclusion: Diagnostic accuracy was superior with 123I-FP-CIT compared to 99mTc-exametazime in the differentiation of DLB from AD.

(Received February 11 2008)

(Revised April 30 2008)

(Revised May 19 2008)

(Accepted May 21 2008)

(Online publication August 27 2008)


c1 Correspondence should be addressed to: Dr. Sean J. Colloby, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, U.K. Phone: +44 191 248 1321; Fax: +44 191 248 1301; Email: