Performing clinical 18F-FDG-PET/MRI of the mediastinum optimising a dedicated, patient-friendly protocol. Issue 8 (August 2019) - Peerlings, Jurgen
Abstract : Objective: To construct a mediastinal-specific fluorine-18-fluorodeoxyglucose ( 18 F-FDG)-PET/MR protocol with high-quality MRI of minimal acquisition-time and comparable diagnostic value to 18 F-FDG-PET/computed tomography (CT). Materials and methods: Fifteen healthy participants received PET/MRI and 10 patients with mediastinal tumours (eight non-small-cell lung, two oesophageal cancer) received 18 F-FDG-PET/MRI immediately after 18 F-FDG-PET/CT. Sequences volume interpolated breath-hold examination (T1-VIBE) and Half-Fourier acquisition single-shot turbo spin echo (T2-HASTE) were optimised by varying the parameters: breath-hold (BH, end-expiration), fat suppression (spectral adiabatic inversion recovery), and ECG-triggering (ECG, end-diastole). Image quality (IQ) of each sequence-variation was qualitatively scored by medical experts and quantitatively assessed by calculating signal-to-noise ratios, contrast relative to muscle, standardized-uptake-value, and tumour-to-blood ratios. Patient comfort was evaluated on patients' experience. Diagnostic accuracy of 18 F-FDG-PET/MRI was compared to 18 F-FDG-PET/CT, in reference to histopathology/cytopathology. Results: ECG-triggered T1-VIBE images showed the highest signal-to-noise ratio ( P < 0.01) and the largest contrast between mediastinal soft-tissues, regardless of BH or free-breathing acquisition. IQ of ECG-triggered T1-VIBE scans in BH were scored qualitatively highest with good reader agreement ( κ = 0.62). IQ of T2-HASTE was not significantly affected by BH acquisition ( P > 0.9). Qualitative IQ of T1-VIBE and T2-HASTE declined after spectral adiabatic inversion recovery fat-suppression. All patients could maintain BH at end-expiration and reported no discomfort. Diagnostic performance of 18 F-FDG-PET/MR was not significantly different from 18 F-FDG-PET/CT with comparable staging, standardized-uptake-values, and tumour-to-blood ratios. However, T-status was more often over-staged on 18 F-FDG-PET/CT, while N-status was more frequently under-staged on 18 F-FDG-PET/MR. Conclusion: ECG-triggered T1-VIBE sequences acquired during short, multiple BHs are recommended for mediastinal imaging using 18 F-FDG-PET/MR. With dedicated protocols, 18 F-FDG-PET/MRI will be useful in thoracic oncology and aid in diagnostic evaluation and tailored treatment decision-making. Abstract : Supplemental Digital Content is available in the text.