99m Technetium-pyrophosphate SPECT/CT with novel semiautomated quantification has excellent diagnostic accuracy for detecting cardiac transthyretin amyloidosis.

OBJECTIVE

This study aimed to assess the diagnostic accuracy of a novel semiautomated method to calculate relative myocardial wall uptake (RCU) of 99m Technetium-pyrophosphate SPECT/CT in suspected cardiac transthyretin amyloidosis (ATTR).

METHODS

Prospective analysis of 108 participants with suspected ATTR. Using novel software, we quantified radiopharmaceutical uptake in the wall of each chamber of the heart at 3 h, calculating RCU for combined ventricular (RCU-V) and whole-heart (RCU-W) measures as a ratio over physiological blood-pool activity. Optimal RCU cut-off ratios were determined using a documented clinical diagnosis of ATTR amyloidosis as the reference standard.

RESULTS

The RCU-V method with a cut-off ratio of 1.2 achieved a sensitivity of 100% [95% confidence interval (CI): 90-100%], specificity of 99% (95% CI: 95-100%), and accuracy of 99% (95% CI: 96-100%). The RCU-W method required a higher cut-off ratio of 1.4 to achieve a comparable specificity of 99%.

CONCLUSION

This novel SPECT/CT quantification software using the RCU-V method significantly improves diagnostic accuracy for cardiac ATTR and represents an advance compared to existing planar nuclear imaging assessment techniques.