Repeatability of quantitative MR fingerprinting for T₁ and T₂ 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 T₁ and T₂ 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 T₁ and T₂ maps. Regions of interest (ROIs) across three tissue types (bone metastasis, bone, muscle) were drawn on two separate acquisitions. Repeatability of T₁ and T₂ was assessed using Bland-Altman plots, together with repeatability (r) and intraclass correlation (ICC) coefficients. Mean T₁ and T₂ 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 T₁ measurements was 6.9% (bone metastasis), 32.6% (bone), 5.8% (muscle) and 21.8%, 32.2%, 16.1% for T₂ measurements. The ICC of T₁ was 0.97 (bone metastasis), 0.94 (bone), 0.96 (muscle); ICC of T₂ was 0.94 (bone metastasis), 0.94 (bone), 0.91 (muscle). T₁ values in bone metastasis were higher than in bone (p < 0.001). T₂ 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 T₁ and T₂ 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 T₁ measurements in bone metastasis and muscle was better than for T₂.

Clinical relevance MR fingerprinting allows repeatable T₁ and T₂ 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.