Experimental validation of a comprehensive fluoroscopy peak skin dose model using four different computational phantoms.

Abstract

Background: Accurately determining the Peak Skin Dose (PSD) delivered to the patient during Fluoroscopically Guided Interventional Procedures (FGIP) is crucial for assessing potential radiation-induced skin injuries and determining the necessary follow-up care for exposed patients.

Purpose: This study evaluates the accuracy of PSD estimation model for FGIPs using mathematical and anthropomorphic computational phantoms that mimic the dimensions of the imaged patient and provides their description.

Methods: The modeling of the FGIP and calculation of peak skin dose involved extracting geometric parameters like primary and secondary angulation, fields sizes, and table shifts, as well as dosimetric parameters such as tube voltage, Air Kerma, Kerma Area Product, and additional filtration of the FGIP stored in a dose tracking system. Computational phantoms were employed to represent the patient anatomy and their axes scaled to match the patient dimensions. The first, a hybrid computational human phantom (HCHP) was developed using Rhinoceros 6.0, generating a 3D surface skin model derived from an adult International Commission on Radiological Protection (ICRP) reference voxel-male-phantom. Three other computational (mathematical) phantoms with cylindrical, ellipsoidal, and semi-ellipsoidal geometries were created using MATLAB software and employed to calculate PSD. Dose-distribution mapping was performed on all phantoms using MATLAB software, following the guidelines outlined in the summary of a joint report by AAPM TG357 and EFOMP by Andersson et al. To improve the PSD model accuracy, measured Kerma correction factors (KCF) that account for backscatter and table attenuation were incorporated for all radiation fields. Two FGIPs were conducted utilizing a male anthropomorphic phantom. Thermoluminescent Dosimeters (TLD) were strategically positioned in a grid pattern on the posterior surface of the phantom to serve as reference measurements. Traditional methods, in which all fields overlap, intersect the table and phantom, were also used to calculate the PSD. The resulting skin doses, derived from the HCHP, mathematical phantoms, and traditional methodologies, were then compared against the corresponding reference measurements for a comprehensive evaluation.

Results: The results showed that the PSD calculations obtained through the HCHP, cylindrical, ellipsoidal, and semi-ellipsoidal phantoms were 3.163, 3.085, 2.952, and 3.095 Gy, respectively, for the first FGIP and 3.728, 3.722, 3.598, 3.720 Gy, respectively, for the second FGIP. In comparison, the measured PSD using TLDs was 3.161 and 3.713 Gy for the first and second FGIP. The use of the HCHP-introduced PSD differences of 0.1% and 0.4%, and the mathematical phantoms yielded differences of -2.4% and 0.3%, 6.6% and -3.1%, and -2.1% and 0.2% for the cylindrical, ellipsoidal, and semi-ellipsoidal phantoms, respectively for each FGIP. The traditional approach yielded a difference of -19.1% and -6.4%.

Conclusions: Modeling the FGIP with the use of computational phantoms accurately reflects patient anatomy and can be useful in evaluating radiation PSD from FGIPs. The traditional methods yielded a greater difference against our fluoroscopy PSD measurements, while the use of the HCHP resulted in superior though practically comparable accuracy in calculating PSD to using computational phantoms, with added computational power and time needed to create a patient-based human model.