Technical Note: A fast laser-based optical-CT scanner for three-dimensional radiation dosimetry

Autor: John Damilakis, Thomas G. Maris, Alex Papadakis, Giannis Zacharakis, C. Varveris, V. Papoutsaki, Jorge Ripoll
Rok vydání: 2011
Předmět:
Zdroj: Medical Physics. 38:830-835
ISSN: 0094-2405
DOI: 10.1118/1.3538924
Popis: Purpose: To introduce a novel laser-based optical-CT scanner for the readout of three-dimensional (3D) radiation dosimeters. Methods: The scanner employs a diode laser, a cylindrical lens, a motorized linear rail, a rotation stage, and a charge-coupled device camera. The scanner operates in a translate-rotate fashion and may be set up in two configurations depending on the orientation of the cylindrical lens. The attenuation coefficient versus dose response was determined for a normoxic N-vinylpyrrolidone based polymer geldosimeter. Cylindrical dosimeters, 2 cm diameter, were homogenously irradiated to known doses up to 60 Gy using a 6 MV linear accelerator. For a test irradiation, a 5 cm diameter dosimeter was irradiated along its cylindrical axis using a rectangular 1 cm × 1 cm irradiation beam. The dose readout of this scanner was compared to the corresponding readout of a common wide illumination and area detector optical-CT scanner. Results: The attenuation coefficient versus dose response of the laser-based system was found to be linear up to 60 Gy ( r 2 = 0.997 ) compared to the wide field illumination based optical-CT scanner, which exhibits linearity up to 32 Gy ( r 2 = 0.996 ) . The noise in the reconstructedattenuation coefficient maps was ± 7.2 × 10 − 2 mm − 1 versus ± 9.5 × 10 − 3 mm − 1 for the laser-based system and the wide field illumination system, respectively. Conclusions: We have developed a novel laser-based optical-CT scanner, which is capable of generating fast 3D dosimetric data using a scattering polymer geldosimeter. Our data demonstrate that the dose readout of this scanner preserves the advantage of existing laser-based optical-CT scanners in providing measurements, which are minimally affected by scattered light. For accurate reconstruction of the attenuation coefficients, noise reduction techniques need to be applied.
Databáze: OpenAIRE
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