Basic evaluation of a novel 4D target and human body phantom.

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Stereotactic body radiation therapy (SBRT) requires accurate target verification.
• Current phantoms lack patient-specific tumor dynamics simulation capabilities.
• There is a need for advanced phantoms for customized validation in radiation therapy.

Purpose of the Study:

• To develop and evaluate a novel 4D dynamic target phantom (multi-cell 4D phantom).
• To assess the basic quality and dynamic reproducibility of the multi-cell 4D phantom.
• To enable patient-specific validation for radiation therapy of moving targets.

Main Methods:

• Developed a multi-cell 4D phantom with soft tissue, bones, lungs, and target components based on male CT data.
• Investigated phantom performance, including CT numbers, geometric movement amplitudes, and errors.
• Assessed dynamic reproducibility through repeated measurements and stability tests.
• Performed end-to-end tests using Gafchromic film for gamma analysis.

Main Results:

• Phantom CT numbers closely matched human data.
• Maximum geometric amplitudes were within millimeters (e.g., 4.57 mm lateral).
• Geometric errors were low (e.g., 0.40 mm cranio-caudal).
• Abdominal surface movements were stable for 60 seconds with high reproducibility (r > 0.97).
• End-to-end tests achieved a gamma pass rate of >= 98% (2 mm/3%).

Conclusions:

• The multi-cell 4D phantom demonstrates satisfactory precision for radiation therapy verification.
• The phantom shows high reproducibility in simulating target movements.
• While current tumor movement reproducibility is limited, the device is promising for treating moving targets.
• This phantom offers a valuable tool for customized validation in radiation oncology.