 Hello, everyone. Myself, Dr. Vindyaki, junior resident, department of radio diagnosis, Myself Medical College and Research Institute. Today, I'm presenting a paper on the role of multi-detector competitive tomography in characterization of midiastenal masses. Introduction, the midiastenal is strategically located from the thoracic inlet to the diaphragm. Midiastenal lesions include a wide spectrum of pathologies. These lesions are challenging problems, frequently faced by the radiologist and often a plain chest radiograph is inadequate for answering the queries posted by the physician. In past, patients had to undergo midiastenoscopy or thoracotomy to establish a diagnosis. Preoperative discrimination of midiastenal solid tumors based on imaging findings might be useful because thoracotomy could be avoided for certain lesions. Ultrasonography is not currently used in midiastenal mass evaluation because of the limitation due to inadequate acoustic window. Computed tomography is capable of defining the precise anatomical details and characterizing the nature, site and the extent of midiastenal lesions. With the high resolution multi-detector competitive tomography scans, it is easy to localize biopsy needles for diagnostic fine needle aspiration or core biopsy in both benign and malignant diseases. The midiastenal is divided into anterior, middle and posterior midiastenal for the ease of differential diagnosis of the midiastenal masses. Ames and objectives of our study was to characterize different midiastenal masses by multi-detector competitive tomography and to correlate the diagnosis with histopathology. We also aim to differentiate between the benign and malignant lesion based on imaging characteristics. Materials and methods with a sample size of 40, a hospital-based cross-sectional study was conducted on all patients referred to the department of radiodiagnosis, MMCRI, with a clinical or radiological suspicion of midiastenal mass. MBCD of the chest was performed, lesions were characterized based on location, attenuation characteristics and associated findings. Histopathology was performed wherever possible. Results. Lesions were most common between 46 to 60 years. 72% of the lesions were benign, most commonly distributed in the anterior compartment and had a well-defined margin. Most lesions showed soft tissue attenuation and heterogeneous contrast enhancement. Thymic lesions were most common in anterior compartment and neurogenic tumors in posterior compartment. The diagnostic accuracy over histopathology was 91% in our study. Coming to the few representative images, thymoma, it is the most common primary neoplasm of the thymos seen in 50 to 60 years. On contrastenal CT, we can see a well-defined soft tissue attenuation lesion in the anterior midiastenal. They usually shows cross asymmetry to one side of the midiastenal. 30% of the lesions can be locally aggressive or invasive. Thymic neuroendocrine tumor, most commonest is the atypical carcinoid. On contrastenal CT, they show heterogeneous enhancement with the areas of calcification, midiastenal invasion and distant metastasis. Teratomas, they show on post-contrast study, they show heterogeneous enhancement with areas of fluid-filled cyst, fat, soft tissue component and calcifications. Pericardial cysts. On contrastenal CT, they appear as a well-defined non-enhancing fluid attenuation lesion next to the pericardial. Lymphomas show homogeneously enhancing lesion in the anterior and middle midiastenum, encasing the vessels but not invading it. Ectopic thyroid in midiastenum is very rare and here we can see a well-defined heterogeneously enhancing lesion in the anterior midiastenum, which was histologically proven case of ectopic thyroid. Schwannomas are the most commonest nerve shift tumors. On contrastenal CT, they appear as heterogeneously enhancing lesions in the paraspinal region. However, the heterogeneous enhancement is because of the cystic and hemorrhagic areas within. Ganglion neuroma is more commoner in children older than 10 years and on contrastenal CT, we can see an elongated lesion in the posterior midiastenum and on contrast enhancement, we can see only slight to moderate enhancement. Discussion, our study compresses the total 40 cases out of which 29 were benign and 7 were malignant. This correlated with a study by Stroll et al, Benjamin et al, Hermit Kaur et al. In our study, midiastenal masses were common in 46 to 60 years of age. This correlates with a study by the Vinod et al, Singh et al and Armit et al. We found an equal incident of midiastenal masses among both sexes in our study, which correlates well with a study done by Vinod and Hermit Kaur et al. Comparing the compartment distribution with other study, we found that the anterior compartment was most common followed by posterior and the middle compartment. And comparing the accuracy of the MD CT with various studies, we found the similar rare results and the accuracy was about 91%. Concluding, although just radiograph forms the initial investigation, multi-detector CT forms the investigation of choice for evaluating specific cases of midiastenal masses. Post-processing techniques like MPR and VRT allow lesions to be analyzed in all three planes with good spatial resolution. Together with associated imaging features like encasement of vessels, classification, fat components, thyroid communication, et cetera, damaging characteristics and compartmental localization point towards a specific diagnosis and helps in the narrowing down of the differential diagnosis. Thus, CT in the hands of good radiologists will save the patient from unnecessary exposure to expensive and invasive procedures. These are my references. Thank you.