Dispersion patterns of scattered radiation exposure on phantom in CT fluoroscopy

Abstract

Introduction

Working with CT fluoroscopy for diagnoses and therapeutics potentially exposes radiology nurses to ionising radiation. This study aims to estimate the dispersion patterns of scattered radiation doses received by operators during CT fluoroscopy.

Methods

An anthropomorphic phantom was exposed to radiation through constant CT fluoroscopy workflow and protocols. Images were obtained per exposure without gantry tilt, 30° gantry tilt in the caudal and 30° in cranial directions. A survey meter was used to detect the scattered radiation doses, which were recorded in millisieverts per hour (mSv/h) with specific distances from the phantom's isocentre in x- (lateral from the isocentre), y- (above the isocentre), and z-directions (anterior and posterior from the isocentre). A survey was conducted to record the most preferred self-positioning of the staff nurses during the procedures. Logarithmic transformation was performed to normalise the measured dose values. The correlation between the radiation dose fall off with distances to the isocentre was evaluated. A generalised linear mixed model (GLMM) was conducted to examine the effects of gantry tilt, height from the floor, and absolute distances from the isocentre on the dose reduction, accounting for variability between the cluster positions.

Results

Heatmaps of the dose dispersion pattern were produced, showing that there were moderate negative correlations between scattered radiation and distances to the isocentre. The GLMM analysis showed that gantry tilt, height from the floor, and absolute distance from the isocentre were significant predictors of Log D variation (p < 0.001). Higher Log D values were associated with a 0^o gantry tilt and 30^o cranial tilt, as well as heights of 102 cm and 142 cm compared to 182 cm. Pairwise comparisons indicated significant differences in Log D across gantry tilts and heights, with interaction effects showing a monotonic reduction in Log D from 0° to 30° cranial and caudal tilts, particularly at 142 cm and 182 cm heights. The majority of the staff nurses would station themselves closest to the isocentre during the procedure.

Conclusion

This study highlights the influence of gantry tilt, height, and distance from the isocentre on scattered radiation distribution during CT fluoroscopy. The heatmap from this study could be used as a guide for staff nurses to position themselves in the CT room during imaging procedures and support a radiation-safe working environment.