They hold potential for detecting changes of low-volume, low-velocity blood flow in small vessels such as those of the synovium in arthritic joints [51]. Positron emission tomography [PET] is a technique that uses molecules labelled with isotopes that emit positrons from their nucleus. The most commonly used tracer is 2-deoxy-2-(18F) fluoro-p-deoxyglucose (FDG) [52]. After intravenous injection, FDG is taken up by the cells according to their level of glucose metabolism. Animal models have demonstrated that FDG uptake by tumours

is not only due to the tumour cells themselves, but also due to the inflammatory cells appearing in association with tumour growth or necrosis. Based on this concept, an on-going study (unpublished data) has demonstrated the feasibility of using PET to

detect arthritis-related inflammation prior to visualization by morphologic imaging in a rabbit model of blood-induced AZD5363 mouse arthritis. Preliminary results of this study showed that the number of bleeding events would influence the degree of inflammatory changes and consequently, the FDG uptake in affected knees. These data demonstrated that the increased glucose Venetoclax supplier metabolism of many inflammatory cell types and the FDG uptake by inflammatory tissues are the basis for the potential use of FDG-PET in the detection and monitoring of chronic arthropathic processes in haemophilia. Dual-echo steady-state imaging  Dual-echo steady-state (DESS) imaging results in images with higher T2* weighting, which has bright cartilage signal and bright synovial fluid. This technique has proved useful for assessing

cartilage morphology in osteoarthritis [53] and holds potential for the assessment of cartilage abnormalities in haemophilic arthropathy. Driven equilibrium Fourier transform and fluctuating equilibrium  Driven equilibrium Fourier transform (DEFT) and fluctuating equilibrium MRI SPTLC1 (FEMR) are techniques that depend on the ratio of T1/T2 in a given tissue [54,55]. These techniques produce contrast by enhancing the signal from synovial fluid rather than attenuation of cartilage signal as in T2-weighted sequences. DEFT and FEMR show much greater cartilage to fluid contrast than spoiled gradient-recalled (SPGR), proton-density spin-echo (PD-SE) or T2-weighted fast-spin-echo (FSE) sequences [56]. Sodium MRI  This technique is based on the ability of sodium imaging to depict regions of proteoglycan depletion [57]. High sodium concentration is seen throughout the normal cartilage. This method shows promise in being sensitive to early decreases in proteoglycan concentration in arthritis. T1 mapping  Gadolinium-DTPA-enhanced T1 imaging is also a technique sensitive to the cartilage proteoglycan content [58]. In this technique, the negative charge of the paramagnetic contrast agent distributes into the cartilage inversely to the fixed charge density of glycosaminoglycans [58].