Experimental measurement of radiation dose in a dedicated breast CT system

TL;DR

This study improves dose measurement methods in dedicated breast CT using smaller TLDs and new phantoms, introduces a weighted CT dose index for glandular dose assessment, and finds the system delivers lower radiation doses than traditional mammography.

Contribution

It introduces a novel dose measurement approach with improved phantoms and the first use of weighted CT dose index for glandular dose in breast CT.

Findings

CTDIw overestimates glandular dose but is practical for clinical use.

Dose in the studied DBCT system is lower than in conventional mammography.

Monte Carlo simulations validated measurement methods.

Abstract

Radiation dose is an important performance indicator of a dedicated breast CT (DBCT). In this paper, the method of putting thermoluminescent dosimeters (TLD) into a breast shaped PMMA phantom to study the dose distribution in breasts was improved by using smaller TLDs and a new half-ellipsoid PMMA phantom. Then the weighted CT dose index (CTDIw) was introduced to average glandular assessment in DBCT for the first time and two measurement modes were proposed for different sizes of breasts. The dose deviations caused by using cylindrical phantoms were simulated using the Monte Carlo method and a set of correction factors were calculated. The results of the confirmatory measurement with a cylindrical phantom (11cm/8cm) show that CTDIw gives a relatively conservative overestimate of the average glandular dose comparing to the results of Monte Carlo simulation and TLDs measurement. But with better practicability and stability, the CTDIw is suitable for dose evaluations in daily clinical practice. Both of the TLDs and CTDIw measurements demonstrate that the radiation dose of our DBCT system is lower than conventional two-view mammography.