A robotically assisted 3D printed quality assurance lung phantom for Calypso

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Respiratory motion significantly impacts radiation dose delivery to thoracic and upper-abdominal tumors.
• Current quality assurance (QA) phantoms for internal surrogate motion tracking systems like Calypso are limited for lung applications.
• This limitation necessitates the development of specialized QA solutions to meet AAPM TG142 testing requirements.

Purpose of the Study:

• To design and develop a novel 3D-printed motion phantom for evaluating the Calypso system in lung cancer radiotherapy.
• The phantom aims to simulate true lung motion by allowing Calypso beacons to move in multiple directions.
• This addresses the need for specialized QA tools for lung-based Calypso applications.

Main Methods:

• A 3D-printed phantom with three independent arms for Calypso transponders was designed and constructed.
• A 4-axis robotic arm simulated respiratory motion, guided by a four-dimensional CT (4DCT) scan.
• Treatment plans were delivered to assess dosimetric accuracy and temporal accuracy of the Calypso system during simulated breathing.

Main Results:

• Dosimetric accuracy was found to be within 2%, meeting TG142 tolerances.
• Temporal accuracy for beam-on was greater than the 100 ms TG142 tolerance.
• Temporal accuracy for beam-hold was less than the 100 ms TG142 tolerance.

Conclusions:

• The developed robotic QA phantom provides a dedicated solution for Calypso system testing in lung radiotherapy.
• This phantom facilitates commissioning and acceptance testing, enhancing the reliability of Calypso for lung treatments.
• It enables more accurate evaluation of motion management strategies in radiation oncology.