A study on adaptive IMRT treatment planning using kV cone-beam CT

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Tumor size changes during radiotherapy necessitate adaptive radiotherapy (ART).
• On-board cone-beam CT (CBCT) offers potential for ART in head and neck and prostate cancer patients.
• Assessing CBCT's accuracy for ART is crucial for treatment adaptation.

Purpose of the Study:

• To investigate the feasibility and usefulness of on-board cone-beam CT (CBCT) for adaptive radiotherapy (ART).
• To evaluate CBCT for patients with bulky head and neck tumors treated with intensity-modulated radiation therapy (IMRT).
• To assess CBCT for prostate cancer patients with potential target position variations.

Main Methods:

• Compared dosimetric and geometric accuracy of conventional CT and CBCT using a phantom.
• Acquired patient planning CT and CBCT images before treatment and at mid-course.
• Calculated dose-volume histograms (DVHs) by applying IMRT plans to CBCT images.

Main Results:

• CBCT-based DVHs showed excellent agreement with planning CT-based DVHs in phantom and patient studies.
• Minimum, maximum, and mean doses agreed well between CT and CBCT.
• Patient study showed 1-3% agreement in doses for targets and normal tissues calculated on CBCT versus planning CT.

Conclusions:

• CBCT images can accurately predict dosimetric outcomes for ART.
• CBCT is feasible for assessing dosimetric changes due to tumor shrinkage and geometry variations.
• CBCT shows potential as a valuable tool for online ART, though re-planning may still require planning CT.