3 Dimensional Conformal Radiation Therapy (3D-CRT)
Conventional radiation therapy is delivered with rather broad radiation beams with a uniform intensity. A more advanced approach is called Three Dimensional Conformal Radiation Therapy which contours the radiation beam to the irregular shape and size of an individual’s tumor. This computer based modality allows radiation oncologists to substantially improve the precision of radiation delivered to tumors and to decrease the dose to the surrounding normal tissues.
Permanent tumor control of tumors such as prostate and lung cancer can be achieved only by using very high doses to the tumor. Unfortunately, this can result in damage to the surrounding normal tissues. 3D conformal treatment planning allows us to shape the high dose region around the tumor while sparing much of the normal tissues.
Three-dimensional treatment planning usually begins with the patient obtaining a special imaging study such as a CT scan, MRI, or PET/CT scan to create a detailed 3 dimensional representation of the tumor and surrounding organs. A computer will then compile these CT images into a “virtual patient.” Your physician will then identify the tumor volume as well as the other organs whose dose tolerance will put constraints on the treatment planning process. Once this is done, the anatomic and tumor volumes are assembled in the computer to produce a 3D model of the patient. Your Radiation Oncologist then has an excellent view of your anatomy in three dimensions and can decide on the most optimal way to tailor the radiation beam to the size and shape of your tumor while at the same time avoiding as much of the normal tissue as possible. The field shaping is done with multi-leaf collimators or custom fabricated field shaping blocks. With such sophisticated and precise treatment planning the dose to the normal tissues surrounding the tumors is reduced which decreases the risks of complications.