Evaluation of the diagnostic value of dual-time-point, multi-parameter 99mTc-PYP imaging in diagnosing Transthyretin Cardiac Amyloidosis.

Objective To assess the clinical value of dual-time-point planar imaging and SPECT/CT tomographic imaging of 99mTc-PYP in diagnosing transthyretin cardiac amyloidosis (ATTR-CA), and to compare the diagnostic performance of different imaging time points and methods. Methods A retrospective analysis of 98 suspected CA patients (ATTR-CA 12; AL-CA 23; non-CA 63). Early imaging at 1 h and delayed imaging at 3 h included planar and tomographic imaging. Evaluations used the Perugini visual grading, heart-to-contralateral lung uptake ratio (H/CL), and tomographic semi-quantitative scoring. Pathology biopsy and genetic testing served as the gold standard. Sensitivity, specificity, and accuracy were compared across methods. Results Delayed tomographic imaging for ATTR-CA achieved a sensitivity of 100.0%, specificity of 96.5%, and accuracy of 96.9%, the best among all methods. The earliest Perugini scoring method had the lowest accuracy (80.6%), and early imaging using the H/CL method had the lowest diagnostic sensitivity (58.3%). SPECT/CT imaging at 3 h provides significant incremental diagnostic value compared to planar imaging and offers the greatest benefits, Cases that were missed during the initial review have been reclassified.Delayed imaging was superior to early imaging overall, and tomographic imaging significantly reduced false positives caused by blood-pool artifacts. Conclusion Dual-time-point 99mTc-PYP imaging with tomographic imaging can significantly improve the diagnostic accuracy for ATTR-CA, with delayed SPECT/CT performing best. For cases with atypical early imaging or diagnostic difficulty due to blood-pool tracer distribution, when Perugini grade is 2, early H/CL ≤ 1.5 or delayed H/CL ≤ 1.3, or in highly suspected cases where early imaging provides insufficient diagnostic evidence, routine inclusion of delayed SPECT/CT in the imaging workflow for suspected ATTR-CA is recommended to optimize subtyping and guide subsequent therapy.