Conformal radiation therapy: A procedure that uses computers to create a 3-dimensional picture of the tumor in order to target the tumor as accurately as possible and give it the highest possible dose of radiation while sparing normal tissue as much as possible. It is also known as 3-D or conformational radiation therapy. Conventional radiation therapy directs x-rays not only at the tumor but also unavoidably at nearby healthy tissue. Conformal radiation is meant to deliver a higher dose of radiation to the cancer without causing so much damage to surrounding tissues. Conformal radiation therapy is in use to treat prostate cancer and is under study with other types of cancer including lung cancer, brain tumors and cancer of the head and neck.