Validation of a method for estimating peak skin dose from CT‐guided procedures

Abstract

A method for estimating peak skin dose (PSD) from CTDIvol has been published but not validated. The objective of this study was to validate this method during CT‐guided ablation procedures. Radiochromic film was calibrated and used to measure PSD. Sixty‐eight patients were enrolled in this study, and measured PSD were collected for 46 procedures. CTDIvol stratified by axial and helical scanning was used to calculate an estimate of PSD using the method [1.2 × CTDIvol(helical) + 0.6 × CTDIvol(axial)], and both calculated PSD and total CTDIvol were compared to measured PSD using paired t‐tests on the log‐transformed data and Bland‐Altman analysis. Calculated PSD were significantly different from measured PSD (P < 0.0001, bias, 18.3%, 95% limits of agreement, −63.0% to 26.4%). Measured PSD were not significantly different from total CTDIvol (P = 0.27, bias, 3.97%, 95% limits of agreement, −51.6% to 43.7%). Considering that CTDIvol is reported on the console of all CT scanners, is not stratified by axial and helical scanning modes, and is immediately available to the operator during CT‐guided interventional procedures, it may be reasonable to use the scanner‐reported CTDIvol as an indicator of PSD during CT‐guided procedures. However, further validation is required for other models of CT scanner.

A model for estimating peak skin dose in CT

“…Studies on CT skin dose have utilized various methods to measure surface dose, including the use of pencil chamber dosimeters [17], optically stimulated luminescence dosimeters [18], Monte Carlo simulation [19] and radiochromic film [14]. Overall, radiochromic film is the most well-suited to skin measurements, due to the physical conformance of the dosimeter to the surface, tissue equivalence, and capacity to localise and measure PSD in a single exposure.…”