Measurement reproducibility of slice-interleaved T(1) and T(2) mapping sequences over 20 months: A single center study

BACKGROUND: Quantifying reproducibility of native T(1) and T(2) mapping over a long period (> 1 year) is necessary to assess whether changes in T(1) and T(2) over repeated sessions in a longitudinal study are associated with variability due to underlying tissue composition or technical confounders. OBJECTIVES: To carry out a single-center phantom study to 1) investigate measurement reproducibility of slice-interleaved T(1) (STONE) and T(2) mapping over 20 months, 2) quantify sources of variability, and 3) compare reproducibility and measurements against reference spin-echo measurements. METHODS: MR imaging was performed on a 1.5 Tesla Philips Achieva scanner every 2–3 weeks over 20 months using the T1MES phantom. In each session, slice-interleaved T(1) and T(2) mapping was repeated 3 times for 5 slices, and maps were reconstructed using both 2-parameter and 3-parameter fit models. Reproducibility between sessions, and repeatability between repetitions and slices were evaluated using coefficients of variation (CV). Different sources of variability were quantified using variance decomposition analysis. The slice-interleaved measurement was compared to the spin-echo reference and MOLLI. RESULTS: Slice-interleaved T(1) had excellent reproducibility and repeatability with a CV < 2%. The main sources of T(1) variability were temperature in 2-parameter maps, and slice in 3-parameter maps. Superior between-session reproducibility to the spin-echo T(1) was shown in 2-parameter maps, and similar reproducibility in 3-parameter maps. Superior reproducibility to MOLLI T(1) was also shown. Similar measurements to the spin-echo T(1) were observed with linear regression slopes of 0.94–0.99, but slight underestimation. Slice-interleaved T(2) showed good reproducibility and repeatability with a CV < 7%. The main source of T(2) variability was slice location/orientation. Between-session reproducibility was lower than the spin-echo T(2) reference and showed good measurement agreement with linear regression slopes of 0.78–1.06. CONCLUSIONS: Slice-interleaved T(1) and T(2) mapping sequences yield excellent long-term reproducibility over 20 months.