Abstract
Objective: Tc-99m-pyrophosphate has been used to evaluate amyloid transthyretin (ATTR) cardiac amyloidosis. Quantitative evaluation is widely performed by calculating the heart-to-contralateral lung (H/CL) ratio, but bone lesions may reduce measurement accuracy. We investigated the accuracy of the PYP-ROI software, developed by our group, in addressing the errors caused by bone lesions when measuring the H/CL ratio.
Methods: This retrospective study comprised 17 patients (mean age: 70.7 ± 13.9 years; male:female ratio 13:4) who underwent pyrophosphate scintigraphy to diagnose cardiac amyloidosis during March 2021–November 2021 and in whom cardiac amyloidosis was excluded clinically. None of the participants had rib fractures or other bone lesions. Simulated rib fractures were created, and the H/CL ratio was determined for various pathologies. The differences between these values and the H/CL ratios obtained from the original images were compared.
Results: Based on our findings, which confirmed the software’s utility, we recommend the following steps for imaging analysis. First, the accumulation in the fracture should be eliminated, by manual calculations in the absence of a removal function. Second, compensation for the removed part should be calculated using the average count of the surrounding area. Third, if the fracture accumulation is weaker than the sternal accumulation, the fracture should be included in the measurement. Fourth, if fracture uptake is clearly higher than sternal uptake, the impact is significant.
Conclusions: This study supports the utility of removing or compensating for the accumulation in rib fractures using PYP-ROI software. However, verification in larger clinical studies is required.