الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
Computed tomography CT has been widely used in radiotherapy planning since it provides electron density map which is required for accurate dose calculations, Nevertheless, due to its inherent poor soft-tissue contrast, accurate localization of the tumor in brain could be quite uncertain, Magnetic resonance imaging MRI with its better soft-tissue contrast and ability to acquire images in any oblique sections make MRI appropriate for brain tumor localization. So, it is expected that it will be more beneficial if the two modalities are used together (by the fusion process) for planning of brain tumors. But what is the role of that mixing ((CT-MR) Fusion)? What are the real results? And what is the risk level of using CT alone for radiotherapy treatment planning of brain tumors? These were our purposes of this study.
This work was carried out at clinical oncology and nuclear medicine at Mansoura University, Mansoura Scan Center, and Ayadi Almostkbal Oncology Center in Alexandria (AAAOC). A total of 34 patients with astrocytoma tumors (grade II, grade III and (GBM) glioblastoma multiform) were prepared for standard RT treatment. The CT scanner (GE Healthcare, Bright Speed) was used. Each patient was scanned in treatment position, with an immobilization applied. CT data were then exported from CT and imported to the RT treatment planning system. The MR data sets were obtained by 0.2 Tesla signal profile. Patients were immobilized in supine position with the same thermoplastic mask as that used during CT scan, where, the patients were scanned according to the standard diagnostic protocol, and images were transferred to the RTP workstation for treatment planning.
CT-MRI Image Fusion technique is more precise than either by CT alone in defining the PTV of 3-dimensional conformal radiotherapy for astrocytoma. Avery accurate delineation of the treatment targets based on the MRI images should be carried out for minimizing the risks of geographical misses and, thereby, enable delivery of the desired (prescribed) doses to the tumor volume(s). Also CT-MRI fusion can reduce the uncertainty of PTV delineation in radiation treatment planning for glioma patients after operation. Fusion allows to defining smaller more accurate volumes which may decrease dose to normal tissues and improve tumor coverage. Results show the optimal modality for planning astrocytoma is CT-MRI Fusion.