Performance Validation of In-House Developed Four-dimensional Dynamic Phantom.

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Analysis

Background:

• Four-dimensional (4D) imaging in radiotherapy is crucial for accurately targeting moving tumors.
• Developing reliable phantoms for quality assurance (QA) of 4D imaging is essential.
• In-house developed dynamic phantoms require rigorous validation before clinical use.

Purpose of the Study:

• To validate the performance characteristics of an in-house developed four-dimensional (4D) dynamic phantom (FDDP).
• To assess the FDDP's accuracy in measuring target motion parameters.
• To evaluate the FDDP's suitability for quality assurance in 4D radiotherapy imaging.

Main Methods:

• The FDDP featured three target inserts (1.0-2.0 cm diameter) with sinusoidal motion (0.5-1.5 cm amplitude, 0.2-0.25 Hz frequency).
• Motion parameters were measured manually and using the Real-Time Position Management (RPM) system.
• Static, free-breathing, and 4D CT scans were acquired; volumes (V_Static, V_FB, V_4D, ITV_MIP) were calculated and compared.

Main Results:

• Motion amplitude and frequency measurements showed good agreement between manual, RPM, and phantom data.
• The measured target length in motion closely matched the theoretical length (within 1.0 mm).
• The similarity between different volume calculations (V_FB vs. V_4D, V_FB vs. ITV_MIP) decreased with increasing displacement.

Conclusions:

• The FDDP demonstrated acceptable mechanical and imaging performance.
• The phantom is suitable for quality assurance of 4D imaging processes in radiotherapy.
• FDDP provides a reliable tool for validating 4D CT data acquisition and analysis.