Organ doses from prostate radiotherapy and associated concomitant exposures.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiological Imaging

Background:

• Radiotherapy involves therapeutic irradiation alongside imaging for localization and verification.
• Increasing use of image-guided radiotherapy necessitates accurate dose assessment for critical organs.
• International Commission on Radiological Protection (ICRP) guidelines require justification of all radiation exposures.

Purpose of the Study:

• To measure organ and tissue doses from concomitant imaging (CT, portal imaging) during prostate radiotherapy.
• To quantify the contribution of these imaging doses to the total organ dose.
• To provide data for risk estimation and justification of imaging exposures in radiotherapy.

Main Methods:

• Used a realistic anthropomorphic phantom with thermoluminescent dosemeters.
• Irradiated the phantom using a standard prostate radical radiotherapy protocol.
• Measured doses from both therapeutic irradiation and concomitant CT/portal imaging exposures.

Main Results:

• Concomitant imaging contributed 5-10% to the total organ dose for most tissues outside the target volume.
• Bone surfaces received up to 20% of their total dose from concomitant imaging.
• These doses, while smaller than therapeutic doses, are significant and measurable.

Conclusions:

• Concomitant imaging represents a small but significant dose contribution in radiotherapy.
• Accurate dose estimation from imaging is essential for patient risk assessment and justification of exposures.
• Data can inform decisions regarding the number and type of verification imaging procedures used during treatment.