Recent advances in PET-MRI for cardiac sarcoidosis

Abstract

The diagnosis of cardiac sarcoidosis (CS) remains challenging. While only a small fraction of patients with systemic sarcoidosis present with clinically symptomatic CS, cardiac involvement has been associated with adverse outcomes, such as ventricular arrhythmia, heart block, heart failure and sudden cardiac death. Despite the clinical relevance of having an early and accurate diagnosis of CS, there is no gold-standard technique available for the assessment of CS. Non-invasive PET and MR imaging have shown promise in the detection of different histopathological features of CS. More recently, the introduction of hybrid PET-MR scanners has enabled the acquisition of these hallmarks in a single scan, demonstrating higher sensitivity and specificity for CS detection and risk stratification than with either imaging modality alone. This article describes recent developments in hybrid PET-MR imaging for improving the diagnosis of CS and discusses areas of future development that could make cardiac PET-MRI the preferred diagnostic tool for the comprehensive assessment of CS.

Keywords: T1/T2 mapping; cardiac sarcoidosis; hybrid PET-MR; quantitative MRI; whole-heart imaging.

Figure 1

Combined ¹⁸F-FDG PET/MRI images showing short-axis slices including (A) native T1 map, (B) native T2 map, (C) LGE image, and (D) fused ¹⁸F-FDG PET and LGE image. (I) 67-year-old Male with cardiac and extra-cardiac sarcoidosis, with co-localized elevated T1 (green arrow), elevated T2 (black arrow), mid-wall LGE (red arrow) and focal FDG uptake (white arrow). With positive findings on both PET and MRI, the patient likely presents with active cardiac sarcoidosis. (II) 72-year-old Male with cardiac and extra-cardiac sarcoidosis, demonstrating slightly elevated T1 (green arrow) and corresponding mid-wall LGE (red arrow) at the inferolateral wall. No corresponding elevation of T2 or focal FDG uptake (white arrow) was observed, likely reflecting chronic, burnt-out cardiac sarcoidosis. Adapted from Cheung, E., et al. (2021). Combined simultaneous FDG-PET/MRI with T1 and T2 mapping as an imaging biomarker for the diagnosis and prognosis of suspected cardiac sarcoidosis. European Journal of Hybrid Imaging, 5(1) and the original ahs a CC BY 4.0 license, available here: https://ejhi.springeropen.com/articles/10.1186/s41824-021-00119-w#rightslink.