Repeatability of quantitative MR fingerprinting for T and T measurements of metastatic bone in prostate cancer patients.

Objectives: MR fingerprinting (MRF) has the potential to quantify treatment response. This study evaluated the repeatability of MRF-derived T and T 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 and T maps. Regions of interest (ROIs) across three tissue types (bone metastasis, bone, muscle) were drawn on two separate acquisitions. Repeatability of T and T was assessed using Bland-Altman plots, together with repeatability (r) and intraclass correlation (ICC) coefficients. Mean T and T 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 measurements was 6.9% (bone metastasis), 32.6% (bone), 5.8% (muscle) and 21.8%, 32.2%, 16.1% for T measurements. The ICC of T was 0.97 (bone metastasis), 0.94 (bone), 0.96 (muscle); ICC of T was 0.94 (bone metastasis), 0.94 (bone), 0.91 (muscle). T values in bone metastasis were higher than in bone (p < 0.001). T 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 and T 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 measurements in bone metastasis and muscle was better than for T. Clinical relevance MR fingerprinting allows repeatable T and T 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.