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  4. 2D Optically Stimulated Luminescence Dosimetry Using Al2O3: Use of Tikhonov Regularization and Initial Tests in MRI Guided Radiotherapy

2D Optically Stimulated Luminescence Dosimetry Using Al2O3: Use of Tikhonov Regularization and Initial Tests in MRI Guided Radiotherapy

N Shrestha1*, L Placidi2 , D Cusumano3 , L AZARIO4 , E Yukihara5 , (1) Oklahoma State University, Stillwater, OK, (2) Fondazione Policlinico Universitario Agostino Gemelli, Roma, ,(3) Fondazione Policlinico Universitario Agostino Gemelli, Roma, ,(4) Fondazione Policlinico Universitario Agostino Gemelli, Roma, ,(5) Oklahoma State University, Stillwater, OK

Presentations

(Wednesday, 7/17/2019) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 4

Purpose: The objective of this work is to evaluate the use of Tikhonov regularization to improve 2D dosimetry using Al₂O₃-based optically stimulated luminescence (OSL) films and report initial IMRT dose verification tests in MRI-guided radiotherapy.

Methods: Tikhonov regularization was first tested in 1D-simulated profiles and simple 2D images obtained using Al₂O₃:C and Al₂O₃:C,Mg films. The films were then used to obtain the dose map of an intensity modulated radiation therapy (IMRT) plan delivered by a MRidian device (ViewRay Inc., OH, USA). Gamma analysis was performed comparing the obtained dose maps with the treatment planning system planned dose maps, using different gamma criteria.

Results: Tikhonov regularization significantly improves the signal-to-noise ratio (SNR) of the images both in simulation and in actual measurements by at least a factor of 2. Gamma criteria of 3% and 3 mm and 2% - 2 mm results in a passing rate of 98% and 95% respectively. The application of Tikhonov regularization did not improve the gamma analysis results.

Conclusion: The implementation of Tikhonov regularization in pixel bleeding algorithm of the OSL films improves the SNR in the OSL signal. Tikhonov regularization did not have significant improvement in the gamma analysis of the IMRT plans due to high delivered dose. The results from the gamma analysis shows the potential of using Al₂O₃ OSL films for IMRT dose verification in the MRI guided radiotherapy. For future work we will investigate the application of the Tikhonov regularization in more complex IMRT plans irradiated with low doses and sharp dose gradients

Funding Support, Disclosures, and Conflict of Interest: partially funded by Landauer Inc.

Keywords

Radiation Dosimetry

Taxonomy

TH- Radiation dose measurement devices: OSL

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