Advancing dosimetry in cone-beam computed tomography: methodologies and key findings

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Dosimetry

Background:

• Cone-beam computed tomography (CBCT) is essential in radiology and radiotherapy.
• Accurate dose assessment in CBCT is hindered by wide X-ray beams and nonstandardized protocols.

Purpose of the Study:

• To investigate a practical method for obtaining reference Computed Tomography Dose Index (CTDI) measurements on a CBCT system.
• To adapt existing dosimetry formalisms for CBCT by generating a narrow beam using an external tungsten slit.

Main Methods:

• Utilized a tungsten slit to create a narrow beam compatible with standard dosimetry.
• Performed computed tomography air-kerma index measurements with a 10-cm pencil ionization chamber.
• Derived a conversion factor between CTDI and dose-area product (DAP) using a head phantom.

Main Results:

• Successfully implemented a method for reference CTDI measurements on a CBCT system.
• Determined the effective beam width and characterized the system's geometric behavior.
• Established a CTDI-DAP conversion factor for a head phantom, demonstrating feasibility and limitations.

Conclusions:

• The proposed method provides a practical approach for standardized dose assessment in CBCT.
• The findings offer experimental data and geometric information crucial for future Monte Carlo simulations.
• This research contributes to improving the accuracy and standardization of CBCT dosimetry.