Scattered Radiation Level During Computed Tomography Fluoroscopy

CB Chan, LK Chan, HS Lam

Hong Kong J Radiol 2002;5:19-23

Objective: To assess the scattered radiation dose to personnel during CT fluoroscopy using phantom measurements.

Materials and Methods: Scattered radiation levels (normalised by mA and scan time) were measured at different distances from the isocentre of the CT scanner with different kV settings and slice thicknesses using supplied head and body phantoms in three configurations (head front side and back side; body front side). The effect of varying the phantom effective thickness on scattered radiation dose was also evaluated using a plain phantom.

Results: For each configuration, the scattered radiation dose at each applied tube potential was linearly related to the distance from the isocentre when the slice thickness and phantom effective thickness were constant. In the body front side configuration (the only one tested), doubling the slice thickness approximately doubled the scattered radiation level. The scattered radiation dose at each kV setting was also linearly related to the phantom effective thickness when the distance from the isocentre and slice thickness were fixed.

Conclusion: The results of this study (in the form of the linear equations obtained) enable the scattered radiation dose to be estimated based on the distance from the isocentre and kV setting of a particular CT scanner and scanning configuration, and can be used to develop guidelines for radiation protection management.