Repeatability of quantitative MR fingerprinting for T1 and T2 measurements of metastatic bone in prostate cancer patients

Abstract Objectives MR fingerprinting (MRF) has the potential to quantify treatment response. This study evaluated the repeatability of MRF-derived T 1 and T 2 relaxation times in bone metastasis, bone, and muscle in patients with metastatic prostate cancer. Materials and methods This prospective single-centre study included same-day repeated MRF acquisitions from 20 patients (August 2019–October 2020). Phantom and human data were acquired on a 1.5-T MR scanner using a research MRF sequence outputting T 1 and T 2 maps. Regions of interest (ROIs) across three tissue types (bone metastasis, bone, muscle) were drawn on two separate acquisitions. Repeatability of T 1 and T 2 was assessed using Bland-Altman plots, together with repeatability (r) and intraclass correlation (ICC) coefficients. Mean T 1 and T 2 were reported per tissue type. Results Twenty patients with metastatic prostate cancer (mean age, 70 years ± 8 (standard deviation)) were evaluated and bone metastasis ( n = 44), normal-appearing bone ( n = 14), and muscle ( n = 20) ROIs were delineated. Relative repeatability of T 1 measurements was 6.9% (bone metastasis), 32.6% (bone), 5.8% (muscle) and 21.8%, 32.2%, 16.1% for T 2 measurements. The ICC of T 1 was 0.97 (bone metastasis), 0.94 (bone), 0.96 (muscle); ICC of T 2 was 0.94 (bone metastasis), 0.94 (bone), 0.91 (muscle). T 1 values in bone metastasis were higher than in bone ( p < 0.001). T 2 values showed no difference between bone metastasis and bone ( p = 0.5), but could separate active versus treated metastasis ( p < 0.001). Conclusion MRF allows repeatable T 1 and T 2 measurements in bone metastasis, bone, and muscle in patients with primary prostate cancer. Such measurements may help quantify the treatment response of bone metastasis. Key Points Question MR fingerprinting has the potential to characterise bone metastasis and its response to treatment. Findings Repeatability of MRF-based T 1 measurements in bone metastasis and muscle was better than for T 2 . Clinical relevance MR fingerprinting allows repeatable T 1 and T 2 quantitative measurements in bone metastasis, bone, and muscle in patients with primary prostate cancer, which makes it potentially applicable for disease characterisation and assessment of treatment response.