Brain and Bone (image) Radiological Society of North America Caption (a) Axial T2-weighted image shows brain and bone antero¬posterior distance (APD). (b) Coronal T2-weighted image shows brain and bone biparietal diameter (BPD), interhemispheric distance (IHD), right superior extra-axial distance (RSAD). Credit Radiological Society of North America Usage Restrictions May be used with credit Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.