Efficacy of myocardial washout of ⁹⁹ᵐTc-MIBI/Tetrofosmin for the evaluation of inflammation in patients with cardiac sarcoidosis: comparison with ¹⁸F-fluorodeoxyglucose positron emission tomography findings

Objective Both myocardial perfusion scintigraphy and ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) are useful for the diagnosis of cardiac sarcoidosis (CS). However, the association between the washout of ⁹⁹ᵐTc-labeled tracer and FDG PET has not been established. This study aimed to evaluate the association between the washout of ⁹⁹ᵐTc-labeled tracer and FDG PET findings in patients with CS. Methods We retrospectively analyzed 64 patients (65.0 ± 11.2 years, 53% male) with suspected CS who underwent myocardial single-photon emission computed tomography (SPECT) with ⁹⁹ᵐTc-labeled tracer and FDG PET. The SPECT images were acquired at 15 min (early images) and 3 h (delayed images) after injection and scored visually using a 17-segment model with a 5-point scoring system. The washout score was defined as the difference between the early and delayed total defect scores. FDG positivity was considered as focal or focal on diffuse patterns on visual assessment, and FDG uptake was quantified by measuring the standardized uptake value (SUV) of each of the 17 segments. Results The washout score was significantly higher for the CS group than for the non-CS group (3.0 [−1.0–5.0] vs. 0.0 [−0.5–1.0], p = 0.010). Receiver operating characteristic analysis showed that a washout score of ≥ 2 had the best accuracy for detecting CS (88% sensitivity and 56% specificity) and FDG positivity (71% sensitivity and 89% specificity). In the segment-based analysis of 833 segments from 49 patients, excluding 15 patients with diffuse FDG uptake, the median SUVs for FDG uptake for the washout scores of ≤ 0, 1, and 2 were 2.3 (1.8–3.6), 4.2 (2.9–7.8), and 8.3 (6.5–9.4), respectively (p