 I am Dr. Sindhu Paul Kavilakat, consultant radiation oncologist working at Manipal Hospital Bangalore. So, before going to discuss what is 3D CRT, first we should realize that all tumors are not regular. They come in different size and shapes. So, 3D CRT uses three-dimensional imaging modalities like CT scan, MRI or PET scans to show size, shape and location of the tumor. 3D CRT uses these imaging modalities and highly sophisticated computer softwares to generate a three-dimensional representation of the tumor as well as the adjacent vital organs. This enables the radiation oncologist to tailor the radiation beams, size and shape of the radiation beams to fit to the tumor target. Since the radiation beams are precisely directed, the adjacent normal healthy tissues receives less amount of radiation. So, this technique 3D CRT or three-dimensional conformal radiation therapy is used in the treatment of various cancers, mainly cancer of the uterine cervix or cancer of the lower uterus, cancer of the rectum or motion passage.