Reducing radiation exposure to patients from kV-CBCT imaging

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Kilovoltage cone-beam computed tomography (kV-CBCT) is integral to modern radiation therapy for patient positioning.
• However, the radiation dose associated with kV-CBCT imaging requires careful consideration and optimization.

Purpose of the Study:

• To investigate and identify methods for reducing radiation dose delivered during kV-CBCT imaging procedures.
• To compare dose differences between different kV-CBCT acquisition parameters and hardware configurations.

Main Methods:

• Monte Carlo simulations were employed to calculate doses from kV-CBCT scans.
• Dose-volume histograms were used for dose analysis.
• Simulations modeled patient anatomy and CBCT acquisitions with varying gantry rotations (360° and 200°) and bow-tie filter types (half fan and full fan).

Main Results:

• Older OBI 1.3 systems delivered substantially higher doses (up to 15 times) compared to OBI 1.4.
• Reduced gantry rotations (200°) significantly lowered doses to critical structures like the eyes and spinal cord.
• Scan parameters and patient size influenced the delivered radiation dose, with smaller patients receiving higher relative doses.

Conclusions:

• Radiation dose from kV-CBCT can be effectively minimized through strategic adjustments.
• Key optimization strategies include reducing scan length and exposure settings.
• Selecting appropriate gantry rotation angles and utilizing the full fan bow-tie filter are crucial for dose reduction.