Texture feature by FDG PET can predict events of cardiac sarcoidosis

Purpose: FDG PET plays a significant role in the assessment of cardiac sarcoidosis (CS). Texture analysis has a possibility to assess FDG cardiac uptake in depth. Our aim was to investigate whether texture analysis applied to myocardial FDG uptake has a prognostic value in patients with CS.

Methods: We retrospectively analyzed patients who were diagnosed as CS based on Japanese Society of Sarcoidosis and Other Granulomatous disorders (JSSOG) guideline. Patient who had already oral steroid treatment prior to the FDG PET/CT scan was excluded. A total of 62 patients given over 18 hours fasting prior to FDG injection were studied. The median age of the patients was 64 (interquartile range, 55-71) years and 14 patients (22.5%) were men. Approximately 4.5 MBq/kg (body weight) of FDG was intravenously administrated under a resting condition. A static PET scan was performed 60 min after the administration of FDG. All PET/CT imaging was performed using a Biograph 64 TruePoint TrueV scanner (Siemens Japan, Tokyo). Semi-quantitative FDG PET parameters such as maximal standard uptake value (SUVmax), cardiac metabolic volume (CMV) and cardiac metabolic activity (CMA) were estimated as previously reported (ref 1). Texture features were computed using polar map images (ref 1). Among the several textural features, Homogeneity, Entropy and high gray-level run emphasis (HGRE) were selected as they were found to be robust with respect to the delineation method and were not highly correlated one with another (ref 2). The primary endpoint of this study was composite of major adverse cardiac events (MACE) such as all cause death, sustained VT (SVT), ventricular fibrillation (VF), advanced atrioventricular (AV) block, and hospitalization due to worsening of heart failure. In patients with implantable cardiac defibrillators (ICDs), device interrogation records were used to identify any ventricular arrhythmias requiring cardioversion or anti-tachycardia pacing. We analyzed the effects of FDG PET parameters on MACEs among patients with CS. Multivariate analysis was performed with a selection of variables among gender, New Your Heart Association (NYHA) classification, left ventricular ejection fraction (LVEF), steroid treatment after PET scan, SUVmax, CMV, CMA and texture features identified as significant on univariate analyses (P < 0.05) using Cox proportional-hazards regression model with likelihood ratio test.

Results: During the median of 3.1 years (interquartile range, 2.1 - 4.7 years) of follow-up, MACE occurred in 15 patients. Age, LVEF, the frequency of male and diabetes mellitus showed no significant difference between the patients with and without MACE. No significant differences were found in SUVmax, CMV, CMA, Homogeneity and Entropy, however, HGRE was significantly higher in the patient with MACE compared to the patient without MACE (1078 [914-1532] vs. 838 [706-1056], P = 0.004). Kaplan-Meier curves constructed from HGRE values showed the statistical significance by log-rank test (P < 0.05) (Figure). A univariate analysis showed that NYHA classification (hazard ratio [HR]; 1.7, 95% confidential interval [CI]; 1.0-2.9, P = 0.048), LVEF (HR; 0.96, 95% CI 0.9-1.0; P = 0.026) and HGRE (HGRE/100 - HR; 1.15, 95% CI; 1.02-1.27, P = 0.022) were significantly associated with MACE. Multivariate Cox proportional hazard regression analysis demonstrated that HGRE was the significant predictor of MACE (P < 0.05).

Conclusions: Textural feature obtained with FDG PET/CT can provide independent prognostic information complementary to semi-quantitative assessment for patients with CS. Reference 1. Manabe O et al. Use of ¹⁸F-FDG PET/CT texture analysis to diagnose cardiac sarcoidosis. Eur J Nucl Med Mol Imaging. 2018 Oct 16. doi: 10.1007/s00259-018-4195-9. 2. Orlhac F et al. Tumor texture analysis in 18F-FDG PET: relationships between texture parameters, histogram indices, standardized uptake values, metabolic volumes, and total lesion glycolysis. J Nucl Med. 2014 Mar;55(3):414-22.

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