Choice of the measuring quantity for therapy-level dosemeters

Area of Science:

• Medical Physics
• Radiology
• Dosimetry

Background:

• The transition to International System (SI) units in radiology necessitates changes in radiation measurement quantities.
• The quantity 'exposure' presents inconvenient conversion factors for calculating absorbed dose in SI units.
• Current primary standards in radiology are based on exposure, creating a challenge for immediate SI unit adoption.

Purpose of the Study:

• To discuss the challenges and recommend a path forward for dosimetry in radiology.
• To evaluate the use of intermediate quantities like kerma versus a direct transition.
• To propose a standardized approach for calibrating therapy-level dosemeters.

Main Methods:

• Discussion of expert opinions on dosimetry quantity selection.
• Analysis of conversion factors between exposure, kerma, and absorbed dose.
• Evaluation of practical implications for primary, secondary, and field instruments.

Main Results:

• Abandoning 'exposure' for therapy-level dosemeters is probable due to cumbersome SI unit conversions.
• A direct calibration in 'absorbed dose in water under specified conditions' is favored over intermediate kerma quantities.
• The transition requires careful management of conversion factors between different standards and instruments.

Conclusions:

• The study recommends a full transition to calibrating field instruments in terms of absorbed dose in water.
• This approach simplifies dosimetry and aligns with SI unit principles.
• Addressing the interface between existing exposure standards and new absorbed dose calibrations is crucial.