Figure 1

Definition of parameters in MRI measurements. (a) Axial section of MRI on T2 showing the maximum area of the prostate. A dashed-yellow line ‘BC’ indicates the maximum length of the width of the prostate at the section showing the maximum area of the prostate. The line is extended where it crosses the lateral edge of the obturator internus muscle. Point A and D were defined as the point crossing the lateral edge of the obturator internus muscle. ‘Prostate-muscle index (PMI)’ was defined as the sum of distance 'AB + CD' shown in a yellow line with arrowheads. (b) Sagittal section of MRI on T2 showing the pelvic cavity. ‘Anteroposterior diameter of the pelvic inlet (API)’, ‘pelvic depth (PD)’, and ‘anteroposterior diameter of the pelvic outlet (APO)’ were defined as the ‘diameter from the sacral promontory to the most superior aspect of the pubic symphysis’ (mm), ‘diameter from the sacral promontory to the most inferior point of the pubic symphysis’ (mm), ‘diameter from the inferior aspect of the pubic symphysis to the tip of the coccyx’ (mm). (c, d) Axial section of MRI onT2 showing the measurement of ISD and ASP. ‘Interspinous distance (ISD)’ was defined as ‘the narrowest distance between tips of the ischial spines’ (mm). ‘Angle of the symphysis pubis (ASP)’ was also measured. P: prostate, Fe: femoral bone, Pu: pubic bone, R: rectum, ObM: obturator internus muscle, Bl: bladder.