sir i ama23 yr old physiotherapy student of 160cm 55 kg wt, i am having severe back pain worsening during night,and on certain positions radiating to my left leg down to my ankles for about six months now ..i have edema on my left ankle and knee ...yesterday i got my urine tested and had rbc 1-2,albumin-slight ,epithelial cells-1-2,pus cells 1-2...due to this persisting back pain doctor suggested an mri spine how much is this relevant at this point of time and why?