Simulation study on the conversion between CT and CBCT dose quantities via the effective dose

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Dosimetry

Background:

• Cone-beam computed tomography (CBCT) is increasingly used for tasks traditionally performed by computed tomography (CT).
• Dosimetric quantities like dose-area product (DAP) and dose-length product (DLP) are not mutually convertible between CBCT and CT.
• This lack of convertibility complicates dose comparisons in clinical studies and the application of diagnostic reference levels (DRLs).

Purpose of the Study:

• To investigate the conversion of DAP to DLP and vice versa via effective dose (E).
• To establish common diagnostic reference levels (DRLs) for both CT and CBCT imaging tasks.

Main Methods:

• Monte Carlo simulations were used for dose calculations.
• Simulations covered four head and four trunk scan regions applicable to both CT and CBCT.
• Conversion coefficients (k=DAP/DLP) were calculated for each region.

Main Results:

• Calculated conversion coefficients (k) varied by anatomical region.
• Examples include: cranium 30(4) cm, thorax 78(12) cm, and pelvis 70(12) cm.
• These coefficients provide a basis for inter-modality dose comparison.

Conclusions:

• The study provides essential conversion coefficients for DAP and DLP between CT and CBCT.
• These findings facilitate the establishment of unified diagnostic reference levels (DRLs).
• Enables more accurate dose assessment and comparison across different imaging techniques.