Early Timepoint 99mTc-DPD Whole Body Scintigraphy and Quantitative SPECT/CT Imaging for Diagnosis of Cardiac ATTR Amyloidosis

Background:

Cardiac amyloidosis is a progressive myocardial disease ultimately leading to heart failure. Standard diagnostic workup includes ^99mTc-DPD scintigraphy performed after 2.5 – 3 h. The purpose of this study is to compare early (1 h after injection) to late imaging of ^99mTc-DPD scintigraphy and SPECT for the detection of CA. Early imaging could improve patient comfort and examination efficiency.

Methods & Results:

50 patients undergoing ^99mTc-DPD scintigraphy and SPECT for suspected cardiac transthyretin amyloidosis (ATTR-CA) were included. Imaging was performed at both 1 hour and 2.5–3 h post-injection. Tracer uptake was assessed visually (Perugini score), semi-quantitatively (e.g., heart-to-mediastinum ratio, HMR), and quantitatively (e.g., maximum standardized uptake value, SUV_max). ATTR-CA was diagnosed in 28 % of patients. Median visual Perugini score was significantly higher for early imaging (0.5 vs. 0, p<0.001). Findings were validated using an external validation cohort. Intraclass correlation coefficients between early and late imaging were very good. Visual evaluation of early imaging demonstrated comparable sensitivity, specificity, and overall diagnostic accuracy to late imaging. HMR and SUV_max from early imaging showed highest diagnostic accuracy. No false-negative results were observed. Visual evaluation using the Perugini score was slightly less consistent between readers in early than in late imaging, with lower inter-observer agreement at 1 h.

Conclusion:

Early ^99mTc-DPD imaging provides diagnostic performance equivalent to conventional late imaging while substantially enhancing patient comfort and workflow efficiency. Adoption of early imaging protocols, complemented by quantitative and semi-quantitative analysis, may streamline CA diagnostics, enabling timely diagnosis and treatment.