Alternative Isotope Options for Amyloidosis Imaging: A Technologist's Perspective.

The recent pyrophosphate shortages can limit the availability of 99mTc-pyrophosphate scans for cardiac amyloidosis. However, another radiotracer is available: 99mTc-hydroxymethylene diphosphonate (HMDP). 99mTc-HMDP, widely available in the United States for bone scanning, has effectively been used in Europe to diagnose transthyretin amyloidosis. 99mTc-HMDP and 99mTc-pyrophosphate have comparable blood clearance and sensitivity. The imaging protocols for 99mTc-HMDP and 99mTc-pyrophosphate are similar, except 99mTc-HMDP is imaged 2-3 h after injection and whole-body imaging is optional. The interpretation is also essentially the same; however, caution is needed because of the high soft-tissue uptake with 99mTc-HMDP, which can affect heart-to-contralateral-lung ratios.