The impact of head miscentering on the eye lens dose in CT scanning: Phantoms study

Abstract

The aim of this study was to evaluate the eye lens dose due to miscentering, either above or under the isocenter, and to assess the possibility of eye lens dose reduction by using miscentering phenomenon. We used two types of phantoms (head CTDI and adult anthropomorphic phantoms) and two types of detectors (pencil ionization chamber and radiophotoluminescence detectors). Measurements using the head CTDI phantom and pencil ionization chamber were performed at the upper peripheral hole of the CTDI phantom, whereas measurements using RPL detectors were performed on the surface of the eyes of the anthropomorphic phantom. Each measurement was performed with position phantoms at the isocenter and also at the positions ±2, ±4, and ±6 cm under and above the isocenter. The impact of miscentering on noise was also observed. Our results show that the dose to the eye decreases with increasing position of the phantoms from the isocenter, and increases with decreasing position of the phantoms from the isocenter. Miscentering above the isocenter can potentially reduce the dose to the eye lens, which is a sensitive organ to ionizing radiation.