Accuracy, repeatability, and reproducibility of T(1) and T(2) relaxation times measurement by 3D magnetic resonance fingerprinting with different dictionary resolutions

OBJECTIVES: To assess the accuracy, repeatability, and reproducibility of T(1) and T(2) relaxation time measurements by three-dimensional magnetic resonance fingerprinting (3D MRF) using various dictionary resolutions. METHODS: The ISMRM/NIST phantom was scanned daily for 10 days in two 3 T MR scanners using a 3D MRF sequence reconstructed using four dictionaries with varying step sizes and one dictionary with wider ranges. Thirty-nine healthy volunteers were enrolled: 20 subjects underwent whole-brain MRF scans in both scanners and the rest in one scanner. ROI/VOI analyses were performed on phantom and brain MRF maps. Accuracy, repeatability, and reproducibility metrics were calculated. RESULTS: In the phantom study, all dictionaries showed high T(1) linearity to the reference values (R(2) > 0.99), repeatability (CV < 3%), and reproducibility (CV < 3%) with lower linearity (R(2) > 0.98), repeatability (CV < 6%), and reproducibility (CV ≤ 4%) for T(2) measurement. The volunteer study demonstrated high T(1) reproducibility of within-subject CV (wCV) < 4% by all dictionaries with the same ranges, both in the brain parenchyma and CSF. Yet, reproducibility was moderate for T(2) measurement (wCV < 8%). In CSF measurement, dictionaries with a smaller range showed a seemingly better reproducibility (T(1), wCV 3%; T(2), wCV 8%) than the much wider range dictionary (T(1), wCV 5%; T(2), wCV 13%). Truncated CSF relaxometry values were evident in smaller range dictionaries. CONCLUSIONS: The accuracy, repeatability, and reproducibility of 3D MRF across various dictionary resolutions were high for T(1) and moderate for T(2) measurements. A lower-resolution dictionary with a well-defined range may be adequate, thus significantly reducing the computational load. KEY POINTS: • A lower-resolution dictionary with a well-defined range may be sufficient for 3D MRF reconstruction. • CSF relaxation times might be underestimated due to truncation by the upper dictionary range. • Dictionary with a higher upper range might be advisable, especially for CSF evaluation and elderly subjects whose perivascular spaces are more prominent. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00330-022-09244-x.