ASSESSMENT OF OVERRANGING AS A FUNCTION OF PITCH, COLLIMATION AND ROTATION TIME FOR THREE OF THE MOST RECENT AND WIDESPREAD CT SCANS IN FRANCE

Abstract Purpose: to assess overranging (OR) as a function of pitch, collimation and rotation time for three commonly used CT models in France. Methods: OR was measured using XR-SP2 Gafchromic films (Ashland, USA) and computed from exposure data for three widely used CT models in France. The impact of collimation, pitch and rotation time on OR was analyzed while comparing the three CT models. Results: for a typical head protocol, measured OR was found to be equal to 1.64 cm for CT scan A, 0.5 cm for CT scan B and 3.44 cm for CT scan C. OR values were respectively of 4.47, 3.24 and 7.81 cm for the typical chest protocol and the 3 CT models. OR was lowest at pitch values