Quantitative and compositional magnetic resonance imaging study of bone marrow oedema-like lesions in knee osteoarthritis

Abstract

Background: Bone marrow oedema-like lesions (BMLs) detected on magnetic resonance imaging are common in patients with knee OA and have been linked with pain and disease progression. A number of MRI sequences have been used to assess BML size, however there are few data directly comparing sequences and the optimum approach remains unknown. Structural change within BMLs, including an increase in water content, offers a potential alternative approach to the assessment of BMLs using novel compositional MRI methods. Aim: The overall aim of the thesis was to evaluate the performance of different MRI sequences in the assessment of bone marrow lesions (BMLs) in knee osteoarthritis and to investigate the role of novel compositional MRI methods (mDixon Quant fat fraction and T1 mapping) for BML assessment. Methods: BML volumes were compared using STIR, PDFS, contrast enhanced T1-w FS, GE T1-w FS and 3D GE mDixon Quant water-only images obtained from patients with knee OA. In a separate study of OA patients, fat fraction was determined using 3D GE mDixon Quant imaging in both normal marrow and BMLs and change in fat fraction over an 8-week period using image registration was compared with change in BML volume. A series of fat-water-bone (FWB) phantoms comprising different fat fractions were made and imaged using 3D mDixon Quant imaging and T1 mapping (Single slice inversion recovery, SSIR and variable flip angle, VFA) and results compared with MR Spectroscopy. A preliminary study of SSIR T1-based measurements in a small number of knee OA subjects was also performed. Results: Reliability of the assessment of BML size was excellent for STIR, PDFS, contrast enhanced T1-w FS and 3D GE mDixon Quant water-only sequences. There was little difference in BML size assessed using the different sequences apart from the 3D FS GE T1-w sequence which was much less sensitive. Fat fraction from 3D GE mDixon Quant images was significantly lower in BMLs compared to non-BML marrow in subjects with knee OA and change in fat fraction correlated with change in BML size over time. In-vitro fat fraction values from mDixon Quant imaging were similar to those obtained using MR spectroscopy. There was a strong correlation between SSIR and VFA T1 estimates in the phantom. SSIR T1-based measurements of BMLs showed differences compared to marrow without BML in knee OA subjects. Conclusion: Most conventional fluid sensitive MRI sequences are reliable and sensitive for assessment of BML size. 3D gradient echo Dixon imaging appears a promising technique for the assessment of BMLs in osteoarthritis, allowing both volumetric and compositional assessment, despite previous concerns about gradient echo imaging in the literature. T1 mapping holds promise as a novel approach to imaging BMLs but is less feasible and less well validated than Dixon imaging.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Terence O'Neill (Supervisor) & Richard Hodgson (Supervisor)