Detecting low blood concentrations in joints using T1 and T2 mapping at 1.5, 3, and 7 T: an in vitro study

Abstract

Background Intra-articular blood causes irreversible joint damage, whilst clinical differentiation between haemorrhagic joint effusion and other effusions can be challenging. An accurate non-invasive method for the detection of joint bleeds is lacking. The aims of this phantom study were to investigate whether magnetic resonance imaging (MRI) T1 and T2 mapping allows for differentiation between simple and haemorrhagic joint effusion and to determine the lowest blood concentration that can be detected. Methods Solutions of synovial fluid with blood concentrations ranging from 0 to 100% were scanned at 1.5, 3, and 7 T. T1 maps were generated with an inversion recovery technique and T2 maps from multi spin-echo sequences. In both cases, the scan acquisition times were below 5 min. Regions of interest were manually drawn by two observers in the obtained T1 and T2 maps for each sample. The lowest detectable blood concentration was determined for all field strengths. Results At all field strengths, T1 and T2 relaxation times decreased with higher blood concentrations. The lowest detectable blood concentrations using T1 mapping were 10% at 1.5 T, 25% at 3 T, and 50% at 7 T. For T2 mapping, the detection limits were 50%, 5%, and 25%, respectively. Conclusions T1 and T2 mapping can detect different blood concentrations in synovial fluid in vitro at clinical field strengths. Especially, T2 measurements at 3 T showed to be highly sensitive. Short acquisition times would make these methods suitable for clinical use and therefore might be promising tools for accurate discrimination between simple and haemorrhagic joint effusion in vivo.

7 T Musculoskeletal MRI

“…The 7 T longitudinal magnetization relaxation times (T1) of musculoskeletal tissues were reported to be moderately longer (20% to 60%) than corresponding T1 times at 3 T, with a particularly large increase in synovial fluid, 32 as shown in Table 1. The relaxation times and relative changes of the synovial fluid and other fluids strongly depend on macromolecular content and viscosity 33–36 . Interestingly, an opposite trend for hip cartilage T1 values, assessed with the dual flip-angle method, was also published 21 .…”

“…The relaxation times and relative changes of the synovial fluid and other fluids strongly depend on macromolecular content and viscosity. 33 – 36 Interestingly, an opposite trend for hip cartilage T1 values, assessed with the dual flip-angle method, was also published. 21 Increased T1 times may result in longer scan times compared with 3 T examinations; however, so far such differences are masked in most situations by different choice of acceleration factors and by specific absorption rate (SAR) limits at 7 T.…”

Right and left ventricular blood pool T2 ratio on cardiac magnetic resonance imaging correlates with hemodynamics in patients with pulmonary hypertension

“…The higher the blood oxygen saturation is, the higher the intracellular hemoglobin content is, and the blood T2 will increase. Thus, T2 is sensitive to blood oxygenation and the alteration of blood oxygen saturation will affect the blood T2 value [14,[19][20][21]. Previous studies quantified the relationship between blood T2 value and blood oxygen saturation by the Luz-Meiboom chemical exchange model, which showed a positive correlation between blood T2 value and blood oxygen saturation.…”

Influence of saturation effects on biexponential liver intravoxel incoherent motion

“…The saturation effects may have a larger influence in the MS setting when much shorter TRs are used. A lower TR results in a reduced blood signal due to the relatively long T 1 time of blood [27][28][29][30][31][32] in comparison to liver tissue. On the other hand, blood could only flow into a few adjacent slices at shorter TR, which could reduce the saturation effect.…”