الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
The aim of this work is to compare the role of MRI in comparison to CT in diagnosis of various mediastinal masses as well as staging of bronchial carcinoma. Normal mediastinal MRI anatomy , pathology & different MRI and CT appearance of various mediastinal vascular and non vascular masses were disscssed in detail. This study included 110 patients, 30 females and 80 males. Our cases are classified into 3 groups according to the final diagnosis ; vascular masses ; non vascular masses and bronchial carciboma. The first group in our series is the vascular masses. It included I patients, 6 females and 15 males with the age ranging from 28 to 74 years. It inculded 5 patients with aortic anewysm and 16 patients with aortic dissection. MRI was done in all cases whereas CT was done in 12 cases only. Both MRI and CT are atraumatic , safe and highly sensitive methods to identify aortic aneurysms and classifY aortic dissection. However some pitfalls can reduce the diagnostic accuracy of CT, insufficient opacification of the aorta , its inability to depict abnonnalities of the aortic valve and limitation of direct imaging in only axial plane. MRI is the imaging method of choice for mediastinal vascular masses , since it is completely non invasive and provides clear identification of vessels without the need for adminstration of intra venous. contrast medium. The results of our study indicate that the combined use of the SE sequences and MR angiography is very accurate for evaluation of the typicaJ and atypical pattern of dissection.Anatomic abnormalities are best seen on the images obtained with electro-cardio gated spin-echo techniques, whereas MR angiography provides functional information and helps to differentiate slow flow from thrombus. Moreover MRimaging with its muJtipJanar imaging capabilities