Conversion coefficients for the estimation of effective dose in cone-beam CT

Area of Science:

• Medical Physics
• Radiology
• Diagnostic Imaging

Background:

• Cone-beam CT (CBCT) is widely used in dentistry and medicine.
• Accurate estimation of effective dose from CBCT is crucial for radiation safety.
• Dose-Area Product (DAP) is a measurable quantity that can be used to estimate effective dose.

Purpose of the Study:

• To determine the conversion coefficients (CCs) for estimating effective dose from DAP values in CBCT.
• To investigate how CCs vary across different CBCT imaging modes and anatomical regions.

Main Methods:

• A CBCT scanner with four fields of view (FOV) was utilized.
• DAP values were measured using a DAP meter across C, P, I, and D modes with standard and low-dose settings.
• Effective doses were measured using an adult male head and neck phantom and thermoluminescent chips.
• Linear regression analysis was performed to calculate CCs for each CBCT examination.

Main Results:

• Conversion coefficients (CCs) ranged from 0.038 to 0.146 µSv/mGycm².
• CCs varied significantly based on the imaging mode (C, P, I, D) and the irradiated region (maxilla, mandible).
• The highest CC was observed for the D mode at the mandibular molar (0.146 µSv/mGycm²).

Conclusions:

• The study established specific CCs for a fixed 80 kV CBCT device, applicable to different imaging modes and anatomical sites.
• These CCs are essential for accurate effective dose assessment in CBCT procedures.
• The findings highlight the importance of considering imaging parameters and target region when estimating patient radiation dose from CBCT.