Use of a 3D camera for automated patient positioning for chest-abdomen-pelvis CT scans: Effect on positioning accuracy and patient dose

Introduction

3D positioning cameras that automate the positioning of patients with respect to the CT isocentre have been developed and are in common use in CT departments. This study aimed to compare the performance of radiographers and a 3D camera system with respect to positioning accuracy and the effect on patient radiation dose for chest-abdomen-pelvis scans.

Methods

Patient positioning and dose data obtained from a dose management system was evaluated over a two-month period for patients positioned with (CAM_on) and without (CAM_off) the positioning camera. Median vertical and lateral offset values were compared between the groups whilst doses were evaluated as a function of patient water equivalent diameter (WED) for the thorax and abdomen-pelvis acquisitions for both cohorts.

Results

Radiographers demonstrated high levels of positioning accuracy, however significant improvements in median vertical offset were identified for the CAM_on cohort for both thorax (8 mm vs. 17 mm (p = 0.001)) and abdomen-pelvis (7 mm vs. 16 mm (p = 0.003)) scans. The percentage of patients positioned within 5 mm of the isocentre was 39.0% and 16.1% for the CAM_on and CAM_off cohorts. For CAM_off scans, 77.4% of patients were positioned below the isocentre, but this was reduced to 45.8% for CAM_on scans. No significant changes in dose as a function of WED were identified related to the camera use (thorax: p = 0.569, abdomen-pelvis: p = 0.760).

Conclusion

Use of a 3D camera delivered significant improvements in the accuracy and reproducibility of patient positioning when compared with radiographers.

Implications for practice

Improvements in positioning accuracy were observed at the research site and hence positioning camera use has the potential to become standard practice in CT to help ensure appropriate doses are delivered to patients according to their size.