Standardization of 99m Technetium pyrophosphate imaging methodology to diagnose TTR cardiac amyloidosis

Technetium pyrophosphate (99mtc-pyp) imaging to diagnose transthyretin cardiac amyloidosis (attr-ca) has been increasingly utilized. the objective of this study is to provide a standardized 99mtc-pyp imaging protocol to diagnose attr-ca. 104 scans from 45 subjects with biopsy-proven attr-ca or light-chain cardiac amyloidosis (al) were assessed. multiple scans were obtained using different counts (750 vs 2000 k), times to acquisition (1 vs 2 to 4 hours), processing matrix (256 vs 128), and 99mtc-pyp dose. image quality and extracardiac activity was assessed. quantitative methods using heart-to-contralateral ratios (h/cl) and a visual semiquantitative scale were used to diagnose attr-ca.19 the correlation between h/cl ratios and reproducibility of semiquantitative visual scores, acquired using various imaging parameters, were evaluated. all imaging parameters had good to excellent image quality. 750 vs 2000 k counts, 1 hour acquisition and 256 matrix, had lower extracardiac activity (p = .00018). 10 mci of 99mtc-pyp v. higher doses showed excellent image quality and less extracardiac activity (p = .0015). correlation of h/cl ratios was strong (r ≥ 0.92) and reproducibility of semiquantitative visual scores was high (kappa = 95%). an imaging protocol using 750 k counts, 10 mci of 99mtc-pyp, and a 256 matrix was chosen as the standardized imaging protocol since it provided the shortest overall study time (1 vs 2 to 4 hours) and lowest radiation exposure (3 vs 8 to 10 msv).