Proton dose calculation on scatter-corrected CBCT image: Feasibility study for adaptive proton therapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Reconstruction

Background:

• Adaptive proton therapy requires accurate dose calculations.
• Cone-beam computed tomography (CBCT) is used for image guidance but suffers from scatter artifacts.
• Scatter correction is essential for reliable CBCT-based dose calculations.

Purpose of the Study:

• To assess the feasibility of proton dose calculation on scatter-corrected CBCT images.
• To evaluate the accuracy of a priori CT-based scatter correction (CBCTap) for adaptive proton therapy.

Main Methods:

• CBCT images were acquired from phantoms and a patient using an Elekta infinity linear accelerator.
• Two scatter correction techniques were applied: uniform (CBCTus) and a priori CT-based (CBCTap).
• Water equivalent path length (WEPL) and proton treatment plans were used to evaluate image accuracy against a reference CT (CTref).

Main Results:

• CBCTap significantly reduced WEPL errors (2.4 ± 2.0 mm) compared to uncorrected CBCT and CBCTus.
• CBCTap-based treatment plans achieved a high pass rate (96.0% ± 2.5%) in 3D gamma analysis.
• CBCTap demonstrated robustness against variations like rectal filling and weight loss.

Conclusions:

• A priori CT-based scatter correction is a promising technique for adaptive proton therapy.
• CBCTap enables equivalent proton dose distributions and WEPL compared to reference CT.
• This method enhances the accuracy of proton therapy dose calculations using CBCT.