Optimising 99mTc-Pyrophosphate Scintigraphy Acquisition Protocols for Transthyretin Cardiac Amyloidosis Imaging

Abstract

The use of nuclear imaging in the detection of cardiac amyloidosis, particularly transthyretin (ATTR) amyloidosis, has become an essential aspect of its diagnosis. However, the necessity of imaging at both time points and the optimal time point remains a subject of debate.

This thesis investigates whether SPECT/CT in addition to planar imaging at one hour post injection provides sufficient diagnostic information to potentially eliminate the need for delayed imaging. The project begins with a review of cardiac amyloidosis, its subtypes, diagnostic approaches, and imaging protocols. A systematic literature review explores the diagnostic performance of early versus delayed imaging, focusing on sensitivity, specificity and clinical utility.

Finally, a reader study was conducted in which nuclear medicine physicians independently interpreted single-time-point scans, blinded to the timing of the imaging. Their interpretations were then compared with the original reports which had been generated using both imaging time points. ATTR cardiac amyloidosis was diagnosed based on clinical history, diagnostic test results, electronic medical records, and dual-time-point PYP scan reports. A case was considered positive if the diagnosis or treatment of ATTR cardiac amyloidosis was documented in the medical records.

The findings suggest that an imaging protocol which includes SPECT/CT at the early time point may offer comparable diagnostic accuracy to imaging acquired at both time points. The information provided by the acquisition of SPECT/CT, such as blood pooling and anatomical correlation, is essential for high diagnostic accuracy. The thesis concludes by discussing the implications for clinical practice, highlighting protocol simplification, reduced patient burden, reduced radiation exposure to staff members, and increased departmental efficiency.