Optimization of image quality and radiation dose using different cone-beam CT exposure parameters

Area of Science:

• Medical Imaging
• Radiology
• Orthopedic Imaging

Background:

• Cone-beam CT (CBCT) is increasingly used in orthopedics.
• Optimizing exposure parameters is crucial for balancing image quality and radiation dose.
• Latest generation CBCT systems offer advanced imaging capabilities for extremity applications.

Purpose of the Study:

• To investigate and optimize the impact of varying exposure parameters on image quality and radiation dose.
• To evaluate the performance of a latest generation orthopedic extremity CBCT system.
• To determine optimal settings for diagnostic image quality while minimizing radiation exposure.

Main Methods:

• 110 cadaver forearm scans were performed on a latest generation CBCT system.
• Scans were conducted before and after distal radius plate insertion for intra-individual comparison.
• Various combinations of tube voltage (kV) and tube current-exposure time product (mAs) were used, with dose metrics (DLP, CTDIvol) recorded.
• Subjective image quality was assessed by five blinded readers using Likert scales; objective image quality (SNR, CNR) was also analyzed.

Main Results:

• The manufacturer's standard protocol (90-kV, 5.0 mAs) resulted in the highest dose (DLP: 111.91 mGy*cm, CTDIvol: 4.49 mGy).
• Lower settings (70-kV, 2.0 mAs) significantly reduced dose (DLP: 20.34 mGy*cm, CTDIvol: 0.79 mGy).
• Higher tube voltage improved subjective cortical and cancellous bone depiction and overall image quality (p ≤ 0.038).
• Changes in tube current-exposure time product did not significantly alter image quality (p ≥ 0.063).
• Plate insertion reduced subjective overall image quality (p < 0.001) and objective SNR/CNR (p < 0.001).

Conclusions:

• Orthopedic extremity CBCT provides good image quality even at low exposure settings.
• Optimal subjective image quality was achieved with 85-kV / 4.7 mAs, yielding an 18.9% dose reduction compared to the manufacturer's protocol.
• The study highlights the potential for dose reduction without compromising diagnostic image quality in extremity CBCT.