Technical Note: Patient-weight dependence of the effective dose conversion coefficients for diagnostic x-ray imaging procedures.

Purpose: The aim of this study was to provide a method and reference data for the evaluation of the weight dependence of the conversion coefficients from air collision kerma integrated over beam area to the effective dose for patients undergoing diagnostic x-ray examinations.

Method: A simple physics-based analytical model was developed in order to calculate the weight dependence of the effective dose conversion coefficients based on existing values of the conversion coefficients between patient effective dose and air collision kerma integrated over beam area calculated by the Monte Carlo method on the base of computational MIRD-5-type stylized models.

Results: The analytical expressions that make possible taking into account a patient's weight when assessing the effective dose were presented. The following categories of diagnostic x-ray examinations are considered: CT; plain radiography; cardiac angiography; fluoroscopy. The results indicate that the weight dependence of the effective dose conversion coefficients for different categories of diagnostic x-ray examinations has the same form. Correction factor for evaluation of the new value of the effective dose conversion coefficient for a patient with weight W when we know its value for a standard patient with weight W depends on the ratios of their weights (W /W ) and fractions of the incident energy which is imparted to a patient.

Conclusions: The paper presents an approach and necessary data for the estimation of the weight dependence of the effective dose conversion coefficients for patients undergoing different diagnostic x-ray examinations.