A model for estimating peak skin dose in CT

Abstract A model to estimate the peak skin dose (PSD) delivered to a patient by a computed tomography (CT) scanner has been developed to assist in determining the likelihood of acute radiation injury from a CT examination. This model relates the PSD to the device-reported CT Dose Index (CTDIvol) by accounting for a variety of radiographic technique, scanner, and patient factors. It includes a novel method for estimating dose contributions as a function of patient or phantom size, scanner geometry and physical measurement of lateral and depth-based beam profiles. Physical measurements of PSD using radiochromic film on several phantoms have been used to determine needed model parameters. The resulting fitted model was found to agree with measured data to a standard deviation of 5.1% for the data used to fit the model, and 6.8% for measurements that were not used for fitting the model. Two methods for adapting the model for specific scanners are provided, one based on local PSD measurements with radiochromic film with another using CTDIvol measurements. The model, suitably adapted, may be applied to individual patients for accurate assessment of their PSD which is an accepted indicator of acute radiation injury.