Calibration of ionization chamber for ¹⁸F and ⁶⁸Ga

Area of Science:

• Nuclear Physics
• Radiochemistry
• Metrology

Background:

• Accurate radionuclide calibration is essential for medical imaging and research.
• Maintaining primary activity standardization requires regular recalibration of measurement systems.
• Positron emitters and short half-life radionuclides present unique calibration challenges.

Purpose of the Study:

• To determine calibration factors for a pressurized 4π-ionization chamber for (18)F and (68)Ga.
• To address critical aspects of calibrating ionization chambers for short-lived positron-emitting isotopes.
• To ensure the continuity of primary activity standardization results from 2011.

Main Methods:

• Utilized a pressurized 4π-ionization chamber coupled to a Keithley 6517A electrometer.
• Employed a custom LabVIEW program for precise control of the ionization chamber system.
• Investigated critical parameters including timing, current measurement, background radiation, and radioactive decay.
• Performed measurements using a (226)Ra check source for system validation.

Main Results:

• Established calibration factors for (18)F and (68)Ga using the described ionization chamber system.
• Identified and quantified the impact of timing, background, and decay on measurement accuracy.
• Demonstrated the feasibility of calibrating for short half-life positron emitters.

Conclusions:

• The study successfully determined calibration factors for (18)F and (68)Ga, vital for accurate activity measurements.
• The findings provide a comprehensive understanding of the challenges and solutions for calibrating ionization chambers with positron emitters.
• This work supports the ongoing primary activity standardization efforts at LNMRI.