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Commissioning and Evaluation of the NanoDot OSLD as In-Vivo Dosimeter for Intrabeam Radiotherapy

P Yan

P Yan1*, R Shih2 , (1) Columbia University Medical Center, New York, NY, (2) Columbia University, New York, New York


SU-I-GPD-T-304 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: There is a growing need for an accurate and clinical applicable in-vivo dosimetry technique for the Intra Operative Radiation Therapy (IORT). The nanoDot offer a potential solution for this purpose. The purpose of this investigation was to commission and evaluate the nanoDot as in-vivo dosimeter for ZEISS IntraBeam system.

Methods: First, the calibration curves were generated for spherical applicators with diameters ranging from 2cm to 4.5cm. The nanoDot was attached to the surface of spherical applicator and measured inside the water phantom. The surface dose from 0.1Gy to 25Gy was measured. Then the dose was measured at different depths: 1.5cm, 3.5cm and 6cm with the nanoDot rotated from 0° to 90° with 15° increments. We also tested the dose response with different water equivalent materials.

Results: The standard deviation of nanoDot measurements were within 2 percent. The angular dependence is within 1 percent at the depth 6.5cm. However the dosimetry reading is dramatically increased at 90° when the nanoDot was closer to the surface of applicator. At the depth 3.5cm, the reading at 90° is about 5 percent higher than the reading at 0°. At the depth 1.5cm, the reading at 90° is about 12 percent higher than the reading at 0°. The angular dependence is within 3 percent for the degrees less than 75° at any depth. The reading with bolus insert is within 1 percent comparing to water. However the reading with solid water phantom insert is only 56 percent of the reading with water.

Conclusion: The nanoDot is a suitable in-vivo dosimeter for IntraBeam. However, we should avoid the placement of nanoDot at the degree larger than 75° to the surface of applicator. The lower reading of solid water phantom is due to the photoelectrical effect of higher physical density for low energy X-ray.

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