Imaging dose from cone beam computed tomography in radiation therapy

Area of Science:

• Medical Physics
• Radiology
• Radiation Oncology

Background:

• Historically, imaging dose in radiation therapy was considered negligible compared to therapeutic doses.
• The integration of volumetric imaging, such as cone beam computed tomography (CBCT), into linear accelerators for daily image-guided radiation therapy (IGRT) has increased patient imaging dose.
• This necessitates a re-evaluation of imaging dose magnitudes and their implications.

Purpose of the Study:

• To review the imaging dose delivered to patients during image-guided radiation therapy (IGRT) using current cone beam computed tomography (CBCT) technologies.
• To summarize methods for calculating CBCT imaging dose, including Monte Carlo (MC) simulations and treatment planning systems (TPS).
• To discuss dose reduction techniques and the relevance of metrics like CT dose index (CTDI) and effective dose in the context of CBCT.

Main Methods:

• Literature review of current methods and equipment for CBCT imaging in radiation therapy.
• Summary of dose calculation techniques, including Monte Carlo (MC) and treatment planning systems (TPS).
• Review of dose measurement protocols and dose reduction strategies.

Main Results:

• CBCT imaging significantly contributes to the total cumulative dose in IGRT.
• Various methods exist for calculating and measuring CBCT dose, with varying accuracy and complexity.
• Effective dose provides a standardized way to quantify the stochastic risk from imaging dose.

Conclusions:

• The increasing use of CBCT in IGRT requires careful consideration and management of the associated patient dose.
• Accurate dose calculation and measurement are crucial for optimizing imaging protocols.
• Further research into dose reduction techniques is essential to minimize risks while maintaining image quality for effective IGRT.