RT - Journal Article T1 - A new approach to contrast enhancement in MAGICA gel dosimeter image with MRI technique JF - Int-J-Radiat-Res YR - 2008 JO - Int-J-Radiat-Res VO - 6 IS - 3 UR - http://ijrr.com/article-1-485-en.html SP - 151 EP - 156 K1 - Gel dosimeter K1 - MAGICA K1 - resolution K1 - MRI K1 - R2 map. AB - parameters that have to be measured in gel dosimetry. However, the resolution in gel is strongly dependant on gel composition. Selection of optimum method in dose response readout and proper values of parameters can result in noise reduction as well as improvement of contrast, and spatial resolution considerably. Materials and Methods: MAGICA polymer gel dosimeters were manufactured and irradiated to different doses using a 60Co therapy unit. Imaging was performed in a 0.5T MRI with 8 echoes in air and water as a hydrogenous environment. Imaging condition was kept constant, as much as possible, in both imaging modalities. Results: Images obtained from these two procedures were compared quantitatively. R2- dose curves have three different sections, sensitivity obtained in these three sections were 1.039, 1.671, 1.260 Gy-1S-1 and 1.032, 1.729, 1.37 Gy-1S-1 for water and air respectively. Calibration errors were investigated and graphically were compared in two different methods. Conclusion: Imaging in water medium for doses lower than 17 Gy led to a small reduction in spatial resolution was exchanged to a considerable increase of contrast in R2 map. For doses higher than17 Gy, imaging in water or air was preferred depending on the importance of contrast or spatial resolution. Iran. J. Radiat. Res., 2008 6 (3): 151-156 LA eng UL http://ijrr.com/article-1-485-en.html M3 ER -