Poster - 24: Characterization of the energy dependence of high-sensitivity MCP-N TLD and Al2O3:C OSLD in-vivo dosimetry systems for 40–100 kVp energies

Authors

  • Poirier Yannick,

    1. Tom Baker Cancer Centre, Calgary AB, University of Calgary, Calgary AB, Tom Baker Cancer Center/University of Calgary, Calgary AB
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  • Kuznetsova Svetlana,

    1. Tom Baker Cancer Centre, Calgary AB, University of Calgary, Calgary AB, Tom Baker Cancer Center/University of Calgary, Calgary AB
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  • Barajas Eduardo Villarreal

    1. Tom Baker Cancer Centre, Calgary AB, University of Calgary, Calgary AB, Tom Baker Cancer Center/University of Calgary, Calgary AB
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Abstract

Purpose:

To characterize the energy dependence of high-sensitivity MCP-N TLD and Al2O3:C OSLD dosimetry systems at low (40–100 kVp) energies for in-vivo dosimetry.

Methods:

We assessed the variation of response with energy of two detectors in the 40–100 kVp energy range: high-sensitivity MCP-N TLDs (LiF:Mg,Cu,P) and OSLDs (Al2O3:C).

The detectors were irradiated with an XRad 320ix biological irradiator under reference conditions. The delivered dose was 10 cGy for 7 beam qualities ranging from 40–100 kVp, 1.7–4.0 mm Al, and effective energies 26.9–37.9 keV.

Both sets of detectors were also irradiated under reference conditions at 6 MV using a Varian Clinac 21Ex to assess the change in response from high-energy beams.

Results:

The MCP-N high-sensitivity TLDs were relatively insensitive to energies in the kV range, as their response varied by ±5%, i.e. well within the reproducibility limits of these detectors. However, the OSLDs exhibited a linearly-decreasing response with energy with a response 18.7% higher at 40 kVp than at 100 kVp for the same nominal dose.

Compared to the 6 MV beams used in conventional radiotherapy, OSLDs responded 3.3–3.9 times higher depending on beam quality while the MCP-N TLD response was unchanged within experimental uncertainty.

Conclusions:

Unlike the more commonly used TLD-100, the high-sensitivity MCP-N TLDs exhibit little to no energy response. OSLDs are shown to be highly energy-dependent, both from MV to kV and within the kV range.

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