“…Sometimes this is called the test-retest performance. It has been measured for many parameters, for example spectroscopy (Charles et al, 1996;Marshall et al, 1996;Simmons et al, 1998;Bartha et al, 2000;Chard et al, 2002), dynamic Gd imaging (Buckley, 2002;Galbraith et al, 2002;Padhani et al, 2002), fMRI (Tegeler et al, 1999;Loubinoux et al, 2001), tissue volume (Fox and Freeborough, 1997;Lemieux et al, 2000;Cardenas et al, 2001;Gasperini et al, 2001), lesion volume (Grimaud et al, 1996;Vaidyanathan et al, 1997;Rovaris et al, 1998;Filippi et al, 1998b), lesion counting (Rovaris et al, 1999;Wei et al, 2002), spinal cord cross-sectional area (Leary et al, 1999) and clinical scores (Cohen et al, 2000). Its value depends on the method used to measure the parameter, and is often very sensitive to the precise details of the data collection procedure (such as patient positioning and pre-scan procedure) and data analysis (particularly ROI placement).…”