Document Type

Article

Publication Date

9-28-2025

Comments

This article is the author's final published version in Journal of Applied Clinical Medical Physics, Volume 26, Issue 10, October 2025, Article number e70248.

The published version is available at https://doi.org/10.1002/acm2.70248.

Copyright © 2025 The Author(s).

Abstract

BACKGROUND: The integration of mobile cone-beam computed tomography (CBCT) into brachytherapy workflows offers clinical advantages such as immediate verification of applicator placement and adaptive treatment planning. These benefits require sufficient image quality to delineate applicators, target volumes, and organs at risk. A systematic evaluation of automatic exposure control (AEC) settings, radiation dose, and image quality is essential to ensure clinically acceptable imaging while minimizing patient exposure.

PURPOSE: This study evaluates the characteristics of AEC and its impact on image quality and radiation dose in a mobile CBCT system used for brachytherapy.

METHODS: The Elekta ImagingRing CBCT system was used to scan a CatPhan phantom under two imaging protocols: Medium Dose Limit (MDL) and Ultra-High Dose Limit (UHDL). This system employs a two-layer mAs modulation process, consisting of preset mA values based on body mass index (BMI) and adjusted mA based on real-time AEC. A bolus was used to simulate larger patient sizes. Real-time x-ray tube current at 10 degrees intervals was recorded. Image quality was evaluated using image noise, noise power spectrum (NPS), modulation transfer function (MTF), Hounsfield Unit (HU) linearity, uniformity index (UI), and contrast-to-noise ratio (CNR) across different protocols.

RESULTS: AEC effectively modulated x-ray tube current in the MDL protocol after x-ray attenuation through the scanned phantom was measured. The UHDL protocol demonstrated greater noise reduction than the MDL. MTF values were comparable between protocols, indicating preserved spatial resolution in the MDL protocol. HU linearity was consistent across all protocols, with R

CONCLUSION: AEC in mobile CBCT optimized radiation dose and image quality by adjusting tube current based on attenuation. The MDL protocol reduced radiation exposure while maintaining image quality, making it a viable option for verifying applicator placement and treatment planning in brachytherapy. The UHDL protocol achieved noise reduction with the maximum available tube current.

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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PubMed ID

41016018

Language

English

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