Related Experiment Video
Updated: Jan 16, 2026
X-ray Dose Reduction through Adaptive Exposure in Fluoroscopic Imaging
Published on: September 11, 2011
Evaluation of image quality in mobile cone-beam CT with dose modulation using automatic exposure control: A phantom
Keita Okazaki1, Wenchao Cao1, Reza Taleei1
1Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
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.
More Related Videos
06:33Construction of a Preclinical Multimodality Phantom Using Tissue-mimicking Materials for Quality Assurance in Tumor Size Measurement
Published on: July 29, 2013
07:57Positron Emission Tomography-based Dose Painting Radiation Therapy in a Glioblastoma Rat Model using the Small Animal Radiation Research Platform
Published on: March 24, 2022
