4DCT ventilation function image-based functional lung protection for esophageal cancer radiotherapy

Area of Science:

• Radiation Oncology
• Medical Imaging
• Pulmonary Medicine

Background:

• Four-dimensional computed tomography (4DCT) enables functional lung (FL) imaging for radiotherapy planning.
• Optimal functional lung thresholds for esophageal cancer patients remain unclear.
• Previous studies have not focused on esophageal cancer regarding functional lung imaging in radiotherapy.

Purpose of the Study:

• To investigate the correlation between functional lung dose-volume parameters and changes in pulmonary function tests (PFTs) after radiotherapy in esophageal cancer patients.
• To determine the optimal functional lung threshold for radiotherapy planning.
• To evaluate the efficacy of functional lung-sparing planning compared to conventional planning.

Main Methods:

• Generated functional lung images for 11 esophageal cancer patients using 4DCT.
• Correlated dose-volume parameters of FL (defined by various thresholds) with pre- and post-radiotherapy PFT metrics (FEV1/FVC).
• Developed and compared FL-sparing plans against conventional anatomical CT (non-sparing) plans.

Main Results:

• A significant positive correlation was found between FL dose-volume parameters (FL0.8, FL0.84, FL0.9) and the reduction in FEV1/FVC, with FL0.8-V30 showing the strongest correlation (r=0.819, P<0.01).
• FL-sparing plans demonstrated comparable target area conformity and homogeneity indices to non-sparing plans.
• FL-sparing planning significantly reduced mean lung dose (MLD), V10, and V20 for functional lung compared to non-sparing plans (P<0.05), with no significant differences in heart or spinal cord doses.

Conclusions:

• 4DCT-based functional lung irradiation dose in esophageal cancer is significantly associated with decreased FEV1/FVC.
• An optimal functional lung threshold defined by a Jacobian value ≤ 0.8 (approximately 21% of total lung volume) is proposed.
• FL-sparing planning effectively reduces functional lung dose without compromising target coverage, offering a potential improvement in radiotherapy for esophageal cancer.