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Dosimetric Characteristics Study of NanoDotâ„¢ for In-Vivo Dosimetry

a hussain

A Hussain1*, A Wasaye1 , R Gohar1 , L Rehman1 , S Hussein2 , (1) Department of Oncology, Aga Khan Univesity Hospital (AKUH), Karachi, Pakistan (2) Burnaby, BC, Canada


SU-E-T-120 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The purpose of the study was to analyze the dosimetric characteristics (energy dependence, reproducibility and dose linearity) of nanoDot™ optically stimulated luminescence dosimeters (OSLDs) and validate their potential use during in-vivo dosimetry, specifically TBI. The manufacturer stated accuracy is ±10% for standard nanoDot™.

Methods: At AKUH, the InLight microStar OSL dosimetry system for patient in-vivo dosimetry is in use since 2012. Twenty-five standard nanoDotâ„¢ were used in the analysis. Sensitivity and reproducibility was tested in the first part with 6MV and 18 MV Varian x-ray beams. Each OSLD was irradiated to 100cGy dose at nominal SSD (100 cm). All the OSLDs were read 3 times for average reading. Dose linearity and calibration were also performed with same beams in common clinical dose range of 0 - 500 cGy. In addition, verification of TBI absolute dose at extended SSD (500cm) was also performed.

Results: The reproducibility observed with the OSLD was better than the manufacturer stated limits. Measured doses vary less than ±2% in 19(76%) OSLDs, whereas less than ±3% in 6(24%) OSLDs. Their sensitivity was approximately 525 counts per cGy. Better agreement was observed between measurements, with a standard deviation of 1.8%. A linear dose response was observed with OSLDs for both 6 and 18MV beams in 0 - 500 cGy dose range. TBI measured doses at 500 cm SSD were also confirmed to be within ±0.5% and ±1.3% of the ion chamber measured doses for 6 and 18MV beams respectively.

Conclusion: The dosimetric results demonstrate that nanoDotâ„¢ can be potentially used for in-vivo dosimetry verification in various clinical situations, with a high degree of accuracy and precision. In addition OSLDs exhibit better dose reproducibility with standard deviation of 1.8%. There was no significant difference in their response to 6 and 18MV beams. The dose response was also linear.

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