Organ and effective doses from verification techniques in image-guided radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy
• Radiation Dosimetry

Background:

• Image-guided radiotherapy (IGRT) is crucial for accurate treatment delivery.
• Verification imaging techniques in IGRT contribute to patient organ doses.
• Understanding these doses is essential for optimizing radiation safety in oncology.

Purpose of the Study:

• To evaluate organ doses and effective doses from three IGRT verification techniques.
• To compare doses from kilovoltage (kV) cone beam CT (CBCT), kV imaging, and megavoltage (MV) imaging.
• To assess doses for pelvis and head and neck (H&N) treatment sites.

Main Methods:

• Organ doses were measured using thermoluminescent dosemeters in a male anthropomorphic Rando phantom.
• Dose evaluations were performed for CBCT scans, two orthogonal kV images, and two orthogonal MV images.
• Prostate and H&N radiotherapy doses were assessed for comparative analysis.

Main Results:

• Pelvis kV imaging resulted in the lowest organ doses (0.05-1%) compared to CBCT (1-6%) and MV imaging (1-10%) relative to prostate radiotherapy.
• Maximum effective doses for pelvis imaging were 5.6 mSv (CBCT), 0.8 mSv (kV), and 11.9 mSv (MV).

Conclusions:

• Different IGRT verification methods yield varying organ and effective doses.
• kV imaging appears to deliver lower doses compared to CBCT and MV imaging for pelvis verification.
• Further research is needed to optimize IGRT protocols for dose reduction.