Standardization of 99mTechnetium pyrophosphate imaging methodology to diagnose TTR cardiac amyloidosis
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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).
KeywordsATTR-CA 99mTc-PYP standardized imaging protocol non-invasive amyloidosis amyloid
CA transthyretin cardiac amyloidosis
Heart failure preserved ejection fraction
Technetium-99m 3,3-diphosphono-1,2-propanodicarboxylic acid
The authors would like to acknowledge Ketan Bhatia and Amsala Robi. Additionally, we would like to thank all the patients who participated in the study and contributed to our efforts to improve the management and treatment of cardiac amyloidosis.
M.S.M.’s institution, Columbia University Medical Center, receives funding for research and serving on advisory boards and DSMBSs from Pfizer, Inc, Alnylam Pharmaceuticals Inc, ISIS Pharmaceuticals, and Prothena Inc.
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