Dose Course Book

Dose to phantom to dose to water in water

The formalism to convert ionisation measured in a phantom to dose in water requires:

• Data on phantom material (available)

• Chamber perturbation factors (not widely available)

• Phantom conversion factor can be determined experimentally

•

Epoxy resin based solid phantoms

shown to be equivalent to within 1% to water

To choose a suitable water- equivalent solid phantom for dosimetry:

•the

depth scaling factor

needs to be close to unity; namely the material needs to have

effective mass attenuation coefficient close to that of water

•the

phantom dose conversion factor (fluence scaling factor)

to be close to unity