Cerenkov-free Scintillation Dosimeter for use in External Beam Radiotherapy. David R. McKenzie 1 , Natalka Suchowerska 1,2 , Jamil Lambert 1,2 , YongBai Yin 1 , Sue Law 1 , 1 Royal Prince Alfred Hospital, Sydney, Australia 2 University of Sydney, Sydney, Australia. SUMMARY
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Cerenkov-free Scintillation Dosimeter for use in External Beam Radiotherapy
David R. McKenzie1,Natalka Suchowerska1,2 , Jamil Lambert1,2, YongBai Yin1, Sue Law1,
1Royal Prince Alfred Hospital, Sydney, Australia
2University of Sydney, Sydney, Australia
We have shown that Cerenkov light can be reduced to a negligible level in scintillation dosimetry by using an air core light guide to transport the scintillation light signal out of the radiation primary beam. This novel design has favourable characteristics for megavoltage photon and electron beam dosimetry, with high spatial resolution and fast readout speed, critical for applications such as stereotactic radiosurgery and IMRT.
AIR CORE SCINTILLATION DOSIMETER
Current methods of transmitting the scintillation light to a remote detector use a solid core optical fibre. When exposed to radiation, these fibres generate an unwanted Cerenkov light as a background. The background can exceed the scintillation signal at characteristic angles.
Our new scintillation dosimeter design does not produce any Cerenkov signal in the air core. This design has a small detection volume which is tissue equivalent, it is energy and dose rate independent and provides real time dose readings with high reproducibility and linearity.
CERENKOV SIGNAL – ANGULAR DEPENDENCE
Figure 1. Experimental design
FIELD SIZE DEPENDENCE
Figure 3. Measured % depth dose
The Air core scintillation dosimeter eliminates Cerenkov background light and is tissue equivalent. This feature, combined with its other characteristics of dose rate independence, high spatial resolution, energy independence and fast response, make the Air core scintillation dosimeter a promising new tool for complex dosimetry applications, such as IMRT and stereotactic radiosurgery.
Lambert J, YinY., McKenzie D., Suchowerska N., Cerenkov free scintillation dosimetry in external beam radiotherapy with an air core light guide, Physics in Medicine and Biology(53) 3071-3080, 2008
Elsey, J, McKenzie, DR, Lambert, J, Suchowerska, N, Law, S, Fleming, S Optimal Coupling of Light from a Cylindrical Scintillator into an Optical Fibre, Applied Optics, 46 397-404, 2007
SH Law, N Suchowerska, DR McKenzie, SC Fleming, T Lin, The transmission of Čerenkov radiation in optical fibers, Optics Letters 32, (10), 1205-1207, 2007
Law, SH, Fleming, SC, McKenzie, DR, Suchowerska, N, Transmission of Čerenkov radiation generated in the core of an optical fiber, Applied Optics 32 2007