Performance of a PTW 60019 microDiamond detector in a 1.5 T MRI-linac

Area of Science:

• Medical physics
• Radiation oncology
• Detector physics

Background:

• Accurate dosimetry is crucial for magnetic resonance linacs (MRI-linacs).
• The PTW 60019 microDiamond is a promising detector for small-field dosimetry due to its characteristics.
• Characterization in a 1.5 T magnetic field is essential before MRI-linac implementation.

Purpose of the Study:

• To fully characterize the PTW 60019 microDiamond detector's performance in a 1.5 T magnetic field.
• To assess its suitability for MRI-linac commissioning and quality assurance.

Main Methods:

• Standard detector testing techniques adapted for MRI-linac capabilities.
• Evaluation of detector warmup, constancy, linearity, field size dependence, leakage, and effective point of measurement.
• Assessment of angular dependence in a 1.5 T magnetic field.

Main Results:

• Detector performance metrics (warmup, constancy, linearity, leakage) were within acceptable tolerance.
• Measurements showed consistency with ion chamber data for medium fields.
• Effective point of measurement determined at 0.80 ± 0.23 mm below the surface.
• Angular dependence showed variations up to 9.7% in the 1.5 T field, with a maximum impact of 0.6% within the expected usage range.

Conclusions:

• The PTW 60019 microDiamond detector is suitable for measuring small radiation fields in a 1.5 T magnetic field.
• It is appropriate for MRI-linac commissioning and quality assurance, with considerations for angular dependence in large fields.
• Correction factors may be needed for patient-specific QA at varying gantry angles.