Several systems available for monitoring blood pressure. They include Millar probes (Millar Mikro-Tip®, Millar Sensors Systems, ADInstruments Ltd., Oxford, UK), fibre optic transducer, (which are most suitable for MRI imaging (e.g. Samba Preclin catheter®; Samba Sensors AB, Västra Frölunda, Sweden) and pressure transducers (TSD104A blood pressure transducer; Biopac Systems, Inc., Goleta, CA, USA). The perivascular flow probes (Transonic Systems, Inc., Ithaca, NY, USA) provide good precision blood pressure measurements for small animal vessels (0.25 mm) without the need to expose the lumen of the vessels, although the procedure still requires surgical exposure of the vessels to localise and fix the transducer around the vessel wall . Indirect blood pressure method (non-invasive) involves inflating a cuff around the tail which works as a pressure transducer measuring the blood flow in the tail artery.