A technique for quantifying the sensitivity of dosimetric tool gamma with 2D detector array in pretreatment IMRT...

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Intensity-modulated radiation therapy (IMRT) requires precise treatment plan transfer.
• Unexpected errors during plan transfer can compromise patient safety.
• Dosimetric verification tools are crucial for quality assurance.

Purpose of the Study:

• To evaluate the sensitivity of a 2D detector array and gamma analysis in detecting errors.
• To assess the impact of segment deletion errors in IMRT treatment plans.
• To investigate the effectiveness of verification methods under unexpected error conditions.

Main Methods:

• Seventeen head and neck cancer patient plans were used.
• Nine verification plans were created by deleting up to eight segments per field.
• A decrement factor (χ) quantified gamma passing rate decay.
• Analysis was performed with and without a region of interest (ROI).

Main Results:

• Linear regression slopes indicated sensitivity to errors, with higher values for increased sensitivity.
• The absolute values of slopes ranged from 0.015 to 0.030 depending on criteria and ROI selection.
• A threshold of 83.44% was identified for 2%/2 mm criteria equivalent to 3%/3 mm clinical practice.

Conclusions:

• The combination of a 2D detector array and gamma analysis demonstrated limited sensitivity.
• Detecting unprecedented segment deletion errors in IMRT plans proved challenging.
• Current verification methods may not fully capture all potential treatment plan deviations.