Quantifying ventilation change due to radiation therapy using 4DCT Jacobian calculations

Area of Science:

• Pulmonary imaging
• Radiation oncology
• Medical physics

Background:

• Four-dimensional computed tomography (4DCT) enables regional ventilation assessment.
• Image registration techniques are crucial for analyzing ventilation changes over time.
• Understanding radiation therapy's impact on lung function is vital for treatment planning.

Purpose of the Study:

• To investigate the impact of radiation therapy (RT) on regional lung ventilation.
• To determine if radiation-induced ventilation changes depend on pre-treatment ventilation.
• To correlate ventilation changes with radiation dose using 4DCT.

Main Methods:

• Acquired 4DCT scans from 12 subjects (pre- and post-RT).
• Generated pre- and post-RT ventilation maps using image registration and Jacobian determinant.
• Calculated voxel-wise ventilation change as a function of dose and pre-RT ventilation.

Main Results:

• Lung regions receiving >20 Gy showed a significant 3.3% decrease in ventilation.
• High pre-RT ventilation regions experienced a greater decline (4.8%) compared to low-ventilation regions (2.4%) after RT.
• Ventilation reduction was dose-dependent and more pronounced in regions with higher baseline ventilation.

Conclusions:

• Radiation therapy leads to significant reductions in lung ventilation.
• Ventilation changes are dependent on both radiation dose and pre-RT lung function.
• Lung tissue with higher pre-RT ventilation is more susceptible to ventilation reduction post-RT.