Evaluation of image quality in mobile cone-beam CT with dose modulation using automatic exposure control: A phantom study

IF 2.2 4区医学 Q3 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Journal of Applied Clinical Medical Physics Pub Date : 2025-09-28 DOI:10.1002/acm2.70248

Keita Okazaki, Wenchao Cao, Reza Taleei, Firas Mourtada, Jun Li, Karen Mooney, Pramila Rani Anne, Yingxuan Chen

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引用次数: 0

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 R² > 0.993.

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.

Abstract Image

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使用自动曝光控制剂量调制的移动锥束CT图像质量评价：模拟研究。

背景：将移动锥束计算机断层扫描（CBCT）集成到近距离治疗工作流程中提供了临床优势，例如立即验证涂抹器放置和适应性治疗计划。这些好处需要足够的图像质量来描绘涂抹器、靶体积和有风险的器官。系统地评估自动曝光控制（AEC）设置、辐射剂量和图像质量对于确保临床可接受的成像，同时最大限度地减少患者的暴露是必不可少的。目的：本研究评估用于近距离治疗的移动CBCT系统中AEC的特征及其对图像质量和辐射剂量的影响。方法：采用Elekta ImagingRing CBCT系统在中剂量限（MDL）和超高剂量限（UHDL）两种成像方案下对CatPhan幻体进行扫描。该系统采用两层mAs调制过程，包括基于身体质量指数（BMI）的预设mA值和基于实时AEC的调整mA值。一丸是用来模拟更大的病人。实时记录每隔10度x射线管电流。通过不同协议的图像噪声、噪声功率谱（NPS）、调制传递函数（MTF）、霍斯菲尔德单位（HU）线性度、均匀度指数（UI）和噪声对比比（CNR）来评估图像质量。结果：经扫描体的x射线衰减后，AEC有效地调制了MDL方案中的x射线管电流。UHDL协议显示出比MDL更大的降噪效果。MTF值在协议之间具有可比性，表明MDL协议中保留了空间分辨率。各方案的HU线性一致，R2为> 0.993。结论：移动CBCT的AEC是基于衰减调节管电流来优化辐射剂量和图像质量的。MDL方案在保持图像质量的同时减少了辐射暴露，使其成为近距离治疗中验证涂抹器放置和治疗计划的可行选择。UHDL协议实现降噪与最大可用的管电流。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Applied Clinical Medical Physics 医学-核医学

CiteScore

3.60

自引率

19.00%

发文量

331

审稿时长

3 months

期刊介绍： Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission. JACMP will publish: -Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500. -Review Articles: Reviews of major areas or sub-areas in the field of clinical medical physics. These articles may be of any length and are peer reviewed. -Technical Notes: These should be no longer than 3000 words, including key references. -Letters to the Editor: Comments on papers published in JACMP or on any other matters of interest to clinical medical physics. These should not be more than 1250 (including the literature) and their publication is only based on the decision of the editor, who occasionally asks experts on the merit of the contents. -Book Reviews: The editorial office solicits Book Reviews. -Announcements of Forthcoming Meetings: The Editor may provide notice of forthcoming meetings, course offerings, and other events relevant to clinical medical physics. -Parallel Opposed Editorial: We welcome topics relevant to clinical practice and medical physics profession. The contents can be controversial debate or opposed aspects of an issue. One author argues for the position and the other against. Each side of the debate contains an opening statement up to 800 words, followed by a rebuttal up to 500 words. Readers interested in participating in this series should contact the moderator with a proposed title and a short description of the topic