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A Novel Quantification Method for Low-Density Gel Dosimeter Publisher Pubmed



Nedaie HA1, 2 ; Pak F3 ; Vaezzadeh V2 ; Eqlimi E1 ; Takavar A1 ; Saligheh Rad HR1, 4 ; Mosleh Shirazi MA5 ; Mirheydari M6
Authors
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Authors Affiliations
  1. 1. Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
  2. 2. Department of Radiotherapy Oncology, Cancer Research Centre, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
  3. 3. Department of Radiation Science, School of Allied Medical Sciences, Tehran University of Medical Sciences, West Taleghani Avenue, Poursina Street, Tehran, 14174, Iran
  4. 4. Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran
  5. 5. Department of Radiotherapy and Oncology, Medical Imaging Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
  6. 6. Department of Physics, Kent State University, Kent, OH, United States

Source: Journal of Cancer Research and Therapeutics Published:2018


Abstract

Aim: Low signal-to-noise ratio (SNR) images of lung-like (low-density [LD]) gel dosimeters, compared to unit-density (UD) gels, necessitate the use of different quantification methods. Setting and Design: In this study, a new method is introduced based on noise correction and exponential (NCEXP) fitting. The feasibility of NCEXP method for quantifying dose absorption in LD gels is evaluated. Materials and Methods: Sensitivity, dose resolution, detectable dynamic range, and correlation of the calibration curve for both UD and LD gel dosimeters are the parameters, which we analyze to investigate the consequences of new method. Results of NCEXP method are compared to maximum likelihood estimation of rician distribution (MLE-R) and variable echo number (VAREC) quantification methods. Results: Dose response of LD gel dosimeter shows wider detectable dynamic range as compared to UD gel. Using NCEXP method for both LD and UD dosimeter gels, a more sensitive calibration curve with a superior dose resolution is obtained. The advantage of new quantification method is more significant for LD dosimeter gel analysis, where SNR decreases as a result of higher absorbed doses (≥10 Gy). Despite the inverse effect of the VAREC method on detectable dose range of UD gel, no specific changes are observed in dynamic dose range of LD gel dosimeter with different quantification methods. The correlations obtained with different methods were approximately of the same order for UD and LD gels. Conclusion: NCEXP method seems to be more effective than the MLE-R and VAREC methods for quantification of LD dosimeter gel, especially where high-dose absorption and steep-dose gradients exist such as those in intensity-modulated radiation therapy and stereotactic radiosurgery. © 2016 Journal of Cancer Research and Therapeutics.
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