Advanced Physics for Brachytherapy 2018

Experimental dosimetry:

Use of a detector (dosimeter) providing a measurable signal that is of a known relationship with the absorbed dose in its volume

• The relationship between signal and dose is known for absolute dosimeters (calorimeters, ion chambers & Fricke gels) • All other dosimeters must be calibrated relative to an absolute one in a beam quality Q 0 , to obtain the absorbed dose sensitivity :

M

Q

(

) 0( )0 QwD

Q

) 0( , =

S wAD

or equivalently the calibration coefficient :

0( QwD

)0( )

N

QwAD

)0( =

,

QM

• Dose to a medium in the absence of the detector (water) is of interest • The calibration must be traceable to international standards

* The terminology used in this lecture is that introduced in: Rogers & Cygler (Eds), Clinical dosimetry measurements in radiotherapy (2009 AAPM Summer School), Monograph No. 34, Medical Physics Publishing 2011