Semi-quantitative evaluation of early phase 99mTc-DPD scintigraphy in patients with suspected cardiac amyloidosis

Scintigraphy using bone-avid tracers like 99mTc-diphosphono-propanodicarboxylic acid (99mTc-DPD), 99mTc-hydroxymethylene-diphosphonate (99mTc-HMDP), or 99mTc-pyrophosphate (99mTc-PYP) is a widely available and non-invasive imaging tool for diagnosis of cardiac amyloidosis. Visual evaluation and semi-quantitative image analyses reach excellent sensitivity and specificity results. For 99mTc-HMDP, high accuracy of early semi-quantitative parameters derived from imaging 10 min after tracer injection was described but never validated for other tracers. The aim of this study was to evaluate early semi-quantitative parameters in 99mTc-DPD scintigraphy. 122 patients (78 male / 44 female) with suspected cardiac amyloidosis who underwent 99mTc-DPD scintigraphy were retrospectively analysed. Early and late planar whole-body scintigraphy images were acquired 10 min (+ 5 min) and 2.5–3.5 h after tracer injection. Early cardiac 99mTc-DPD uptake was evaluated using the Heart/whole-body rectangular (H/WBr), Heart/whole-body profile (H/WBp), Heart/Skull (H/S), Heart/Mediastinum (H/M), Heart/Contralateral Lung (H/CL), Heart/Liver (H/L), and Heart/Pelvis (H/P) ratios. H/L was not correlated to the other parameters.Best results for prediction of Perugini ≥1 were achieved for H/M (sensitivity 69.6%, specificity 84.4%, accuracy 77.5%), best results for prediction of ATTR-CA for H/L (sensitivity 65.9%, specificity 88.6%, accuracy 80.8%). Adding the H/L to other parameters increased accuracy and specificity (best results for H/L+H/S: accuracy 83.3%, sensitivity 63.4%, specificity 93.7% to predict CA). Previous results for99mTc-HMDP were not confirmed; diagnostic precision of early 99mTc-DPD is not sufficient to replace late imaging in clinical routine. Early H/L is a novel, independent, and specific parameter which may be added to imaging protocols to increase the accuracy in combination with other imaging biomarkers