Fariba Farhadi Birgani - Department of Medical Physics, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Mohamad Javad Tahmasebi Birgani - Radiation Therapy and Medical Physics Department, Golestan Hospital, Jundishapur University of Medical Sciences, Ahvaz, Iran
Roghayeh Kamran Samani - Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
Fatemeh Maghsoodinia - Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.

Introduction: Nowadays, magnetic resonance imaging (MRI) in combination with computed-tomography (CT) is increasingly being used in radiation therapy planning. MR and CT images are applied to determine the target volume and calculate dose distribution, respectively. Since the use of these two imaging modalities causes registration uncertainty and increases department workload and costs, in this study, brain synthetic CT (sCT) and synthetic MR (sMR: sT۱w/sT۲w) images were generated using Atlas-based method; consequently, just one type of image (CT or MR) is taken from the patient. Material and Methods: The dataset included MR and CT paired images from ۱۰ brain radiotherapy (RT) patients. To generate sCT/sMR images, first each MR/CT Atlas was registered to the MR/CT target image, the resulting transformation was applied to the corresponding CT/MR Atlas, which created the set of deformed images. Then, the deformed images were fused to generate a single sCT/sMR image, and finally, the sCT/sMR images were compared to the real CT/MR images using the mean absolute error (MAE). Results: The results showed that the MAE of sMR (sT۱w/sT۲w) was less than that of sCT images. Moreover, sCT images based on T۱w were in better agreement with real CT than sCT-based T۲w. In addition, sT۱w images represented a lower MAE relative to sT۲w. Conclusion: The CT target image was more successful in transferring the geometry of the brain tissues to the synthetic image than MR target.

Computed Tomography Magnetic Resonance Imaging, Radiotherapy