Single- Versus Dual-Time-Point Imaging for Transthyretin Cardiac Amyloid Using 99mTc-Pyrophosphate
Wesley Ng1,2, Kunthi Pathmaraj3,4,5, Natalia Kovaleva3
1Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Victoria, Australia; wesley.ng@austin.org.au.
Journal of Nuclear Medicine Technology
|April 22, 2025
Summary
Single-time-point 99mTc-pyrophosphate scintigraphy is accurate for diagnosing cardiac transthyretin amyloidosis. Early imaging is preferred, with delayed scans used only if results are equivocal.
Area of Science:
- Nuclear medicine
- Cardiology
- Radiology
Background:
- 99mTc-pyrophosphate scintigraphy is valuable for diagnosing cardiac transthyretin amyloidosis.
- Optimal imaging time points for this diagnosis remain unclear.
- Recommendations for imaging timing have varied over time.
Purpose of the Study:
- To determine if single- or dual-time-point imaging is necessary for reporting cardiac amyloidosis.
- To identify the most appropriate single time point if only one is used.
- To compare the diagnostic accuracy of single versus dual time points.
Main Methods:
- Retrieved cardiac amyloid scans using 99mTc-pyrophosphate from 2017-2023.
- Included static views and SPECT/CT images at 1-hour (early) and 3-hour (delayed) time points.
- Three nuclear medicine physicians independently reviewed scans, using dual-time-point reports as the reference standard.
Main Results:
- 70 patients were included in the study.
- Single-time-point imaging demonstrated high sensitivity, accuracy, and specificity for diagnosis.
- All readers reached agreement, with only 4 out of 140 scans classified as equivocal.
Conclusions:
- Single-time-point imaging is as accurate as dual-time-point imaging for diagnosing cardiac transthyretin amyloidosis.
- Early imaging (1-hour post-injection) is the preferred single time point.
- Delayed imaging (3-hour post-injection) is recommended only when early imaging results are equivocal.
