 I am Dr. Sindhu Paul Kavilakat, consultant radiation oncologist working at Manipal Hospital, Bangalore. So, IMRT or Intensity Modulated Radiation Therapy is one of the most advanced forms of 3D CRT. In IMRT, each radiation beam is subdivided into hundreds of small beams or which are known as beamlets. Entity of or strength of each of these beamlets can be modulated or modified by using various beam modifying devices known as multi-leaf collimeters or MLCs. So, IMRT is of particularly it is valuable or useful in treating some targets with either a concave or complex shape or with close proximity to radio sensitive nearby structures. This technique is mainly useful in situations either we have to give a very high dose of radiation to the tumor or target, example carcinoma prostate or prostate cancer or where we have to restrict dose to adjacent critical radio sensitive vital organs, example as in head and neck cancer where the spinal cord will be coming in close proximity to the tumor or target. IMRT can be delivered by two mechanisms either the MLCs can move and treat this is known as a dynamic mode also known as a sliding window mode or MLCs will remain static will acquire some specific shapes and treat which is known as a static or segmented MLC technique. IMRT can also be used for intensity modulated arc treatment as well.