4DCT and VMAT for lung patients with irregular breathing

Area of Science:

• Medical Imaging
• Radiation Oncology
• Radiotherapy Physics

Background:

• Irregular breathing patterns in lung cancer patients often preclude 4D CT (4DCT) use, limiting radiotherapy options.
• Accurate tumor motion and density representation are crucial for effective radiotherapy planning.

Purpose of the Study:

• To evaluate if 3D CT or 4DCT better represents tumor motion and average densities in irregular breathers.
• To determine if 4DCT allows for Volumetric Modulated Arc Therapy (VMAT) plans with acceptable dosimetric accuracy in irregular breathers.

Main Methods:

• Ten clinical breathing traces with irregularities were used with an anthropomorphic lung tumor phantom on a moving platform.
• 3D CT and 4DCT data (phase-resorted 4DCT-P and amplitude-resorted 4DCT-A) were acquired.
• Tumor motion, Hounsfield unit (HU) profiles, and VMAT plan dosimetric accuracy were assessed.

Main Results:

• 4DCT-P and 4DCT-A significantly reduced the difference in tumor motion range compared to 3D CT (p=0.005).
• 4DCT-P and 4DCT-A showed better agreement with expected tumor density profiles (lower AUC scores) than 3D CT (p=0.005).
• VMAT plans created with 4DCT-A and 4DCT-P achieved acceptable dosimetric accuracy, with 9/10 and 10/10 plans within 2.5% of expected dose, respectively.

Conclusions:

• 4DCT provides superior representation of tumor motion and average density compared to 3D CT, even with irregular breathing.
• 4DCT enables the delivery of VMAT plans with acceptable dosimetric accuracy for lung cancer patients with irregular breathing.
• The study supports the integration of 4DCT and VMAT for lung radiotherapy patients experiencing irregular breathing patterns.