Evaluation of SCALE PET Software for Quantitative Brain PET Analysis in Alzheimer's Disease

1. Study Overview This study is a single-center, retrospective, rater-blinded, crossover reader study. The primary objective is to evaluate the efficacy of 'Neurophet SCALE PET', a medical image analysis software, in assisting clinicians with the quantitative analysis of amyloid-beta (Aβ) positivity on brain PET scans. The study will compare the performance of readers when they use the software (SW-assisted) versus when they do not use it (unassisted). 2. Data Collection and Reference Standard The investigators will retrospectively collect medical data from a total of 194 patients (97 Aβ-positive and 97 Aβ-negative cases). Data Sources: De-identified data will be obtained from Ajou University Hospital and the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. 3. Study Procedures (Reader Study) The reader study consists of two main reading sessions separated by a 4-week washout period to minimize memory bias and order effects. Four readers will be randomly assigned to two groups (Reader Group 1 and Reader Group 2). * Session 1: Reader Group 1 will evaluate Case Group A with SW assistance and Case Group B without assistance. Reader Group 2 will evaluate Case Group B with SW assistance and Case Group A without assistance. * Washout Period: A 4-week interval will be implemented between sessions. * Session 2: The conditions will be swapped following a crossover design. Readers will re-evaluate the same cases under the opposite condition (assisted vs. unassisted) compared to Session 1. During each session, readers will rate Aβ positivity on a 5-point scale (1: Definitely negative, 2: Probably negative, 3: Equivocal, 4: Probably positive, 5: Definitely positive) and record their diagnostic confidence level on a 3-point scale (1: low confidence, 2: moderate confidence, 3: high confidence). 4. Statistical Analysis The efficacy of the software will be assessed by comparing the diagnostic performance between the SW-assisted and unassisted conditions. * Primary outcomes: Differences in readers' sensitivity and specificity for Aβ positivity classification. * Secondary Outcomes: Differences in diagnostic accuracy (AUC), the number of cases rated as "equivocal," rater confidence levels, and inter-rater agreement.