A Chincarini1, E Peira2,3, M Corosu2, S Morbelli4,5, M Bauckneht4,5, S Capitanio4,5, M Pardini3,5, D Arnaldi3,5, C Vellani6, D D'Ambrosio7, V Garibotto8,9, F Assal8,10, B Paghera11, G Savelli12, A Stefanelli12, U P Guerra12, F Nobili3,5. 1. Istituto Nazionale di Fisica Nucleare (INFN), via Dodecaneso 33, I-16146, Genova, Italy. andrea.chincarini@ge.infn.it. 2. Istituto Nazionale di Fisica Nucleare (INFN), via Dodecaneso 33, I-16146, Genova, Italy. 3. Dept. of Neuroscience, Rehabilitation ,Ophthalmology, Genetics, Child and Maternal Health (DINOGMI), University of Genoa, Genova, Italy. 4. Nuclear Medicine Unit (DISSAL), University of Genoa, Genova, Italy. 5. Neurology Clinic, IRCCS Ospedale Policlinico San Martino, Genova, Italy. 6. Nuclear Medicine Unit of Pavia Institute, Istituti Clinici Scientifici Maugeri IRCCS, Pavia, Italy. 7. Medical Physics Unit of Pavia Institute, Istituti Clinici Scientifici Maugeri IRCCS, Pavia, Italy. 8. Faculty of Medicine, University of Geneva, Geneva, Switzerland. 9. Division of Nuclear Medicine and Molecular Imaging, University Hospitals of Geneva, Geneva, Switzerland. 10. Memory Clinic, University Hospitals of Geneva, Geneva, Switzerland. 11. Nuclear Medicine Unit, ASST Spedali Civili, Brescia, Italy. 12. Nuclear Medicine Unit, Fondazione Poliambulanza, Brescia, Italy.
Abstract
PURPOSE: To develop and validate a semi-quantification method (time-delayed ratio, TDr) applied to amyloid PET scans, based on tracer kinetics information. METHODS: The TDr method requires two static scans per subject: one early (~ 0-10 min after the injection) and one late (typically 50-70 min or 90-100 min after the injection, depending on the tracer). High perfusion regions are delineated on the early scan and applied onto the late scan. A SUVr-like ratio is calculated between the average intensities in the high perfusion regions and the late scan hotspot. TDr was applied to a naturalistic multicenter dataset of 143 subjects acquired with [18F]florbetapir. TDr values are compared to visual evaluation, cortical-cerebellar SUVr, and to the geometrical semi-quantification method ELBA. All three methods are gauged versus the heterogeneity of the dataset. RESULTS: TDr shows excellent agreement with respect to the binary visual assessment (AUC = 0.99) and significantly correlates with both validated semi-quantification methods, reaching a Pearson correlation coefficient of 0.86 with respect to ELBA. CONCLUSIONS: TDr is an alternative approach to previously validated ones (SUVr and ELBA). It requires minimal image processing; it is independent on predefined regions of interest and does not require MR registration. Besides, it takes advantage on the availability of early scans which are becoming common practice while imposing a negligible added patient discomfort.
PURPOSE: To develop and validate a semi-quantification method (time-delayed ratio, TDr) applied to amyloid PET scans, based on tracer kinetics information. METHODS: The TDr method requires two static scans per subject: one early (~ 0-10 min after the injection) and one late (typically 50-70 min or 90-100 min after the injection, depending on the tracer). High perfusion regions are delineated on the early scan and applied onto the late scan. A SUVr-like ratio is calculated between the average intensities in the high perfusion regions and the late scan hotspot. TDr was applied to a naturalistic multicenter dataset of 143 subjects acquired with [18F]florbetapir. TDr values are compared to visual evaluation, cortical-cerebellar SUVr, and to the geometrical semi-quantification method ELBA. All three methods are gauged versus the heterogeneity of the dataset. RESULTS: TDr shows excellent agreement with respect to the binary visual assessment (AUC = 0.99) and significantly correlates with both validated semi-quantification methods, reaching a Pearson correlation coefficient of 0.86 with respect to ELBA. CONCLUSIONS: TDr is an alternative approach to previously validated ones (SUVr and ELBA). It requires minimal image processing; it is independent on predefined regions of interest and does not require MR registration. Besides, it takes advantage on the availability of early scans which are becoming common practice while imposing a negligible added patient discomfort.