Practical approaches to four-dimensional heavy-charged-particle lung therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Four-dimensional (4D) CT imaging captures respiratory motion for lung cancer treatment.
• Compensating boli are crucial for accurate dose delivery in 4D radiotherapy.
• Clinical implementation of 4D charged-particle lung therapy requires efficient bolus design algorithms.

Purpose of the Study:

• To develop and evaluate new design algorithms for compensating boli in 4D charged-particle lung therapy.
• To compare the dosimetric and time efficiency of different bolus design strategies.

Main Methods:

• Acquired 4D CT data from eight lung cancer patients.
• Developed six compensating boli based on Gross Tumor Volume (GTV) and Internal Target Volume (ITV) from 4D CT and image-processed 3D CT data (TMIP/TAIP).
• Calculated carbon beam dose distribution over time for each bolus type and compared with ungated/gated strategies.

Main Results:

• GTV-4DCT bolus delivered >95% prescribed dose but required excessive contouring time.
• ITV-TMIP and ITV-TAIP boli were time-efficient but led to unacceptable normal tissue dose and target underdosing.
• ITV-4DCT bolus provided dose distribution similar to GTV-4DCT bolus with significantly reduced practitioner time.

Conclusions:

• The ITV-4DCT bolus design is time-efficient and offers a high-quality dose distribution.
• ITV-4DCT bolus represents a practical and effective alternative for 4D charged-particle lung therapy implementation.