Assessment of cardiac amyloidosis with 99mTc-pyrophosphate (PYP) quantitative SPECT
Chao Ren, Jingyun Ren, Zhuang Tian, Yanrong Du, Zhixin Hao, Zongyao Zhang, Wei Fang, Fang Li, Shuyang Zhang, Bailing Hsu, Li Huo
Abstract
Abstract Background 99m Tc-PYP scintigraphy provides differential diagnosis of ATTR cardiomyopathy (ATTR-CM) from light chain cardiac amyloidosis and other myocardial disorders without biopsy. This study was aimed to assess the diagnostic feasibility and the operator reproducibility of 99m Tc-PYP quantitative SPECT. Method Thirty-seven consecutive patients who underwent a 99m Tc-PYP thorax planar scan followed by SPECT and CT scans to diagnose suspected ATTR-CM were enrolled. For the quantitative SPECT, phantom studies were initially performed to determine the image conversion factor (ICF) and partial volume correction (PVC) factor to recover 99m Tc-PYP activity concentration in the myocardium for calculating the standardized uptake value (SUV) (unit: g/ml). SUV max was compared among groups of ATTR-CM, AL cardiac amyloidosis, and other pathogens (others) and among categories of Perugini visual scores (grades 0–3). The intra- and inter-operator reproducibility of quantitative SPECT was verified, and the corresponded repeatability coefficient (RPC) was calculated. Results The ICF was 79,327 Bq/ml to convert count rate in pixel to 99m Tc activity concentration. PVC factor as a function of the measured activity concentration ratio in the myocardium and blood-pool was [ y = 1.424 × (1 − exp(− 0.759 × x )) + 0.104]. SUV max of ATTR-CM (7.50 ± 2.68) was significantly higher than those of AL (1.96 ± 0.35) and others (2.00 ± 0.74) (all p < 0.05). SUV max of grade 3 (8.95 ± 1.89) and grade 2 (4.71 ± 0.23) were also significantly higher than those of grade 1 (1.92 ± 0.31) and grade 0 (1.59 ± 0.39) (all p < 0.05). Correlation coefficient ( R 2 ) of SUV max reached 0.966 to 0.978 with only small systematic difference (intra = − 0.14; inter = − 0.23) between two repeated measurements. Intra- and inter-operator RPCs were 0.688 and 0.877. Conclusions 99m Tc-PYP quantitative SPECT integrated with adjustable PVC factors is feasible to quantitatively and objectively assess the burden of cardiac amyloidosis for diagnosis of ATTR-CM.