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

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Oncology

Background:

• Mobile cone-beam CT (CBCT) integration in brachytherapy enhances applicator placement verification and adaptive planning.
• Sufficient image quality is crucial for delineating targets and organs at risk in brachytherapy.
• Evaluating automatic exposure control (AEC) is vital for balancing image quality and patient radiation dose.

Purpose of the Study:

• To assess the performance of AEC in a mobile CBCT system for brachytherapy.
• To determine the impact of AEC settings on image quality and radiation dose.

Main Methods:

• The Elekta ImagingRing CBCT system was used with Medium Dose Limit (MDL) and Ultra-High Dose Limit (UHDL) protocols.
• A two-layer mAs modulation process with preset and real-time AEC adjustments was employed.
• Image quality metrics including noise, NPS, MTF, HU linearity, UI, and CNR were analyzed.

Main Results:

• AEC effectively modulated x-ray tube current based on phantom attenuation.
• The UHDL protocol showed superior noise reduction compared to MDL.
• Spatial resolution (MTF) was preserved in the MDL protocol, and HU linearity remained consistent (R² > 0.993).

Conclusions:

• AEC in mobile CBCT optimizes radiation dose and image quality by adjusting tube current.
• The MDL protocol provides a viable option for brachytherapy, reducing radiation exposure while maintaining image quality.
• The UHDL protocol maximizes noise reduction at the highest tube current settings.