How can the air kerma strength of a brachytherapy source be measured?

Measuring the air kerma strength of a brachytherapy source is most accurately achieved using a calibrated well-type ionization chamber. This device is specifically designed for brachytherapy sources and provides precise measurements of the ionization produced in air by radiation emitted from the source. The well-type chamber has a geometry that allows it to effectively measure low-energy radiation, which is characteristic of many brachytherapy isotopes.

The calibrated nature of the well-type ionization chamber ensures that the measurements are standardized and reliable, accounting for factors such as energy dependence and sensitivity, which can vary with different radiation types and energies. When measuring air kerma strength, it is essential to use a device that not only accurately detects ionization but also provides a calibration factor that relates the ionization detected to the air kerma strength of the source.

In contrast, using a standard ionization chamber may not be suitable for all brachytherapy sources because it may not be specifically calibrated for the energy range of the isotopes commonly used in brachytherapy. Calculating the air kerma strength from the dose delivered is indirect and does not provide the direct measurement that a well-type chamber does, which is critical for determining the source strength accurately. Similarly, while handheld devices can measure