Validation of the Mobius system for patient-specific quality assurance using introduced intentional errors

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Model-based verification software like Mobius3D/MobiusFX aid in patient-specific quality assurance for radiation therapy.
• These tools analyze linear accelerator log files and perform independent dose calculations on patient CT data.

Purpose of the Study:

• To evaluate the Mobius system's efficacy in detecting linear accelerator delivery errors.
• To compare Mobius's error detection capabilities against measurement-based systems: ArcCHECK and 3DVH.

Main Methods:

• Investigated 50 treatment plan deliveries, including 3 original and 47 with introduced errors.
• Compared Mobius system performance with ArcCHECK and 3DVH systems using gamma passing rates and error detectability metrics.
• Assessed detection limits for specific delivery errors like collimator rotation, MLC offset, and jaw offset.

Main Results:

• Mobius system showed comparable gamma passing rates and error detectability to the ArcCHECK system.
• The 3DVH system generally exhibited lower sensitivity in detecting errors compared to Mobius and ArcCHECK.
• Mobius successfully detected delivery errors as small as 2° collimator rotation, 1 mm MLC offset, and 10 mm collimator jaw offset.

Conclusions:

• The Mobius system is a reliable tool for detecting linear accelerator delivery errors, performing comparably to the ArcCHECK system.
• Mobius demonstrates significant potential for enhancing patient-specific quality assurance in radiation therapy.
• The study highlights Mobius's ability to identify subtle mechanical and rotational errors in treatment delivery.