In the treatment of cancer radiotherapy plays an important role and nearly 70% of all patients with solid tumors require radiation at some point of their treatment. Radiotherapy is effective when delivered accurately as only then will the treatment be successful in eliminating the tumor but also reduce side effects resulting from the normal tissue toxicity. Recent technological advances have helped in developing precision based machines and, the Image guided radiation therapy (IGRT) that uses

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... equent imaging during a course of radiation therapy improves the accuracy of the delivery of treatment. In this study an attempt is made to quantitatively analyse the patient positioning errors, target localisation, treatment verification and monitoring with the 2D-2D fusion using the Brain Lab Exac-Trac system in head and neck sites and pelvic sites. The analysis was done for definitive radiotherapy using IMRT and 3 dimensional conformal radiations.