Feasibility of CBCT-based proton dose calculation using a histogram-matching algorithm in proton beam therapy.

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Image-Guided Radiation Therapy

Background:

• Cone-beam computed tomography (CBCT) is used for image-guided radiation therapy.
• Accurate proton dose calculation is crucial for effective proton beam therapy.
• Hounsfield unit (HU) variability in CBCT can impact dose calculation accuracy.

Purpose of the Study:

• To validate the use of histogram matching with CBCT for precise proton dose calculation.
• To assess the impact of modified CBCT (mCBCT) on dosimetric accuracy in proton therapy.
• To compare the accuracy of dose calculations between standard CBCT and mCBCT techniques.

Main Methods:

• CBCT data from phantoms and head and neck cancer patients were modified using histogram matching.
• Two types of modified CBCT (mCBCT-RR, mCBCT-DIR) were generated using rigid and deformable image registration.
• Proton dose calculations were evaluated by comparing dosimetric parameters (D2%, D98%, Dmean) for target volumes and organs at risk.
• Proton ranges and gamma passing rates were compared against planning CT data.

Main Results:

• Modified CBCT (mCBCT) demonstrated improved accuracy in proton dose calculations compared to standard CBCT.
• Average dose and proton range differences were smaller for mCBCTs.
• Average gamma passing rates were higher for mCBCTs (e.g., 94.1% for mCBCT-DIR vs. 87.8% for CBCT).

Conclusions:

• Histogram matching is an effective algorithm for improving CBCT accuracy in proton dose calculations.
• Modified CBCT techniques enhance the reliability of dose calculations in proton beam therapy.
• This method holds promise for improving image-guided proton therapy outcomes.