Breast dose reduction with organ-based, wide-angle tube current modulated CT

Abstract

This study aimed to estimate the organ dose reduction potential for organ-dose-based tube current modulated (ODM) thoracic computed tomography (CT) with a wide dose reduction arc. Twenty-one computational anthropomorphic phantoms (XCAT) were used to create a virtual patient population with clinical anatomic variations. The phantoms were created based on patient images with normal anatomy (age range: 27 to 66 years, weight range: 52.0 to 105.8 kg). For each phantom, two breast tissue compositions were simulated: [Formula: see text] and [Formula: see text] (glandular-to-adipose ratio). A validated Monte Carlo program (PENELOPE, Universitat de Barcelona, Spain) was used to estimate the organ dose for standard tube current modulation (TCM) (SmartmA, GE Healthcare) and ODM (GE Healthcare) for a commercial CT scanner (Revolution, GE Healthcare) using a typical clinical thoracic CT protocol. Both organ dose and [Formula: see text]-to-organ dose conversion coefficients ([Formula: see text] factors) were compared between TCM and ODM. ODM significantly reduced all radiosensitive organ doses ([Formula: see text]). The breast dose was reduced by [Formula: see text]. For [Formula: see text] factors, organs in the anterior region (e.g., thyroid and stomach) exhibited substantial decreases, and the medial, distributed, and posterior region saw either an increase of less than 5% or no significant change. ODM significantly reduced organ doses especially for radiosensitive superficial anterior organs such as the breasts.

Keywords: computed tomography; organ dose; organ dose based tube current modulation; tube current modulation.

Fig. 1

Frontal view of the female XCAT phantoms.

Fig. 2

BMI of the 21 patients modeled in this study.

Fig. 3

Illustration of the dose reduction zone (red) for organ-dose-based tube current modulation.

Fig. 4

Standard attenuation-based tube current modulation profile (${\mathrm{mA}}_{\mathrm{TCM}}$) and organ-dose-based tube current modulation profile (${\mathrm{mA}}_{\mathrm{ODM}}$) for a sampled scan length of a sample XCAT phantom. The shaded region represents the dose reduction zone of ODM.

Fig. 5

(a) Breast dose and (b) $h$ factors for TCM and ODM scans.

Fig. 6

Dose distribution plots of (a) TCM, (b) organ-dose-based TCM (ODM) scheme, and (c) ODM with same ${\mathrm{CTDI}}_{\mathrm{vol}}$ as in (a) for a sample XCAT phantom.

Fig. 7

Cross-patient averaged (a) organ dose and (b) ${\mathrm{CTDI}}_{\mathrm{vol}}$-normalized-organ dose coefficients ($h$ factors) differences simulated by ODM versus TCM. Negative numbers indicate that dose reduced with ODM compared to TCM.

Fig. 8

Contribution of effective dose, as a percentage of TCM effective dose under TCM, ODM (same ${\mathrm{CTDI}}_{\mathrm{vol}}$ as TCM), and ODM.