SBRT 2016

Dosimetry of Small Fields

 Measurement of small photon beams is complicated by  loss of lateral electronic equilibrium,  volume averaging,  detector-interface artifacts,  collimator effects,  and detector position-orientation effects

 Recommendation: use an appropriate dosimeter with a spatial resolution of approximately 1 mm or better (stereotactic detectors)  Collimator with a diameter of 5 mm => dose falloff over a radius of 2.5 mm  Thickness of 1 euro coin is 2.3 mm!