Patient dose and image quality for computed tomography in several Dutch hospitals

In several Dutch hospitals a survey of computed tomography (CT) techniques was performed at 14 CT scanners. In this survey the computed tomography dose index (CTDI) was measured free-in-air with a pencil type ionisation chamber. These measurements yield dose values related to a single CT scan of one slice whilst radiation exposure of patients due to a complete CT examination should preferably be expressed in terms of organ and tissue doses or effective dose. Organ and effective doses were derived by application of published organ dose conversion factors. Effective doses varied from 0.7 mSv to 2.2 mSv for head scans, from 6.0 mSv to 13 mSv for chest scans and from 7.1 mSv to 21 mSv for standard abdomen scans. The survey also included the assessment of parameters related to image quality i.e. high contrast resolution and noise (standard deviation, ω, of Hounsfield units) associated with the CT scanners and protocols at the different locations. Image quality in terms of noise or resolution and effective dose did not reveal a significant correlation for the different CT scanners. (Author)