You are here: SSOM > Radiation Oncology> Services & Therapies > Intensity modulated radiation therapy (IMRT)

Services & Therapies
Intensity modulated radiation therapy (IMRT)

What is IMRT?
Intensity modulated radiation therapy (IMRT) is an advanced form of three-dimensional conformal radiotherapy (3DCRT). By using state-of-the-art software and hardware, it conforms the radiation dose exactly to the three-dimensional shape of the tumor. Hence, a higher radiation dose is delivered to the tumor while minimizing radiation exposure to surrounding normal tissues.

How does IMRT work?
IMRT uses the same medical linear accelerators that deliver x-ray beams in conventional radiotherapy. As a unique feature, it involves dynamic multi-leaf collimators (DMLC), computer-controlled devices that use 120 movable “leaves”. DMLC allow the intensity of radiation to vary within a single beam, in other words, to deliver higher radiation in some areas and lower radiation in others. To easily picture how DMLC work, imagine a showerhead with many nozzles, with the water representing radiation. Conventional radiotherapy techniques only allow a constant flow of water to be delivered through all nozzles, but with DMLC, individual nozzles may be turned off and on to deliver water at different intensities.

What are the advantages of IMRT?
IMRT has the potential to reduce treatment toxicity, i.e. fewer side effects compared with conventional radiotherapy techniques. Moreover, because the ratio of normal tissue dose to tumor dose is reduced to a minimum with the IMRT approach, higher and more effective radiation doses can safely be delivered to tumors, which can improve local control of a tumor. IMRT also has the ability to treat different regions of tumor simultaneously to different doses according to their importance. IMRT is particularly useful for head/neck, prostate and brain tumors where the target volume is in close proximity to critical healthy structures that must be protected.

What special procedures do I expect for IMRT treatment?
Procedures for IMRT are essentially the same as conventional radiotherapy, except that higher precision is required in imaging and positioning. Before planning treatment, a physical examination and medical history review will be conducted. Next, there is a treatment simulation session, which includes CT scanning and molding of a special device to maintain an exact treatment position. Treatment planning generally takes about a couple of weeks. Treatments are scheduled five days a week for six to eight weeks. Treatment with IMRT is slightly longer than that with 3DCRT, usually 10 to 20 minutes. You will not feel or sense anything out of the ordinary during treatment.