MOESM1 of Human jugular vein collapse in the upright posture: implications for postural intracranial pressure regulation

Additional file 1: Figure S1. Illustration of how IJV cross-sectional area (area within manually drawn circumference) was assessed and the ellipse major and minor axes (straight lines) were estimated in the ultrasound images. The upper image shows a measurement in supine and the lower a measurement at 16° upper body tilt (half-sitting).