Image Quality Indicator (IQI) in RT is meant to assess quality of radiograph w.r.t. the desired performance standard of desired visibility wire or hole type. If you can identify the desired wire and/or hole that means your radiograph is of good quality. Now to my opinion this performance qualification does not implies equivalent guareentee for Defect Detectability but in fact it gives us a reliable comfort for defect identification. But many technician has an understanding that if you can get the desired wire or hole you must and must will get the same defect detectability. A discussion sought for. regards DM