Accurate machine-specific reference and small-field dosimetry for a self-shielded neuro-radiosurgical system

Area of Science:

• Medical Physics
• Radiotherapy
• Radiation Oncology

Background:

• The ZAP-X system is a novel stereotactic radiosurgery platform for intracranial lesions.
• Its unique features necessitate thorough characterization for safe and effective clinical use.

Purpose of the Study:

• To precisely measure the radiation output of the ZAP-X system, particularly for small field sizes.
• To provide recommendations for accurate small field dosimetry quantification.

Main Methods:

• Six detector types (diodes, scintillator, ionization chambers, alanine) were used to measure relative output factors from 4 to 25 mm field sizes.
• Absolute dose was determined using TG-51 dosimetry and alanine measurements.

Main Results:

• MicroSilicon diodes, microDiamond detectors, and W2 scintillators showed consistent output factors within 1.0% for field sizes down to 4 mm.
• Ionization chambers (A1SL, A16) provided consistent results for fields larger than 10 mm.
• Alanine dosimetry results were within 1.2% of ion chamber measurements for absolute dose.

Conclusions:

• MicroSilicon diodes, microDiamond detectors, and W2 scintillators are suitable for ZAP-X small field dosimetry (<10 mm).
• Ionization chambers are appropriate for larger fields.
• Alanine dosimetry serves as a reliable verification method for absolute dose measurements.