Dose calculation with a cone beam CT image in image-guided radiation therapy

Area of Science:

• Medical Physics
• Radiotherapy
• Image Processing

Background:

• Kilovoltage cone-beam CT (CBCT) is used for target verification in radiation therapy.
• CBCT image quality limitations prevent direct use in dose calculations, unlike multi-slice CT (MSCT).
• Accurate daily dose verification requires reliable dose calculation methods using available imaging data.

Purpose of the Study:

• To develop and validate a new method for dose calculation using CBCT and MSCT images.
• To improve the accuracy of daily dose distribution verification in radiation therapy.
• To overcome the limitations of using degraded CBCT images directly for dose calculations.

Main Methods:

• Segmentation of CBCT and MSCT images into lung, bone, and soft tissue regions using histogram analysis.
• Assigning representative CT numbers from MSCT to corresponding regions in CBCT images.
• Calculating dose distribution using the modified CBCT images.

Main Results:

• The proposed method produced dose distributions similar to the initial dose plan.
• The method demonstrated superiority over conventional techniques in distance-to-agreement and gamma analyses.
• Dose-volume histogram analysis confirmed the accuracy of the proposed method.

Conclusions:

• The developed method enables accurate dose calculation using modified CBCT images.
• This approach enhances the reliability of daily dose verification in radiation therapy.
• The findings suggest improved accuracy and consistency in radiotherapy treatment delivery.