3D & 4D Conformal Radiation Therapy and Intensity Modulated Radiation Therapy (IMRT) 

Introduction
Advances in radiation treatment for cancer are made all the time.  There are various ways to treat cancer.  Surgery, chemotherapy, radiation, or a combination of treatments may be used.  Treatment depends on the type of cancer that you have and what kinds of treatment respond best to it.  Radiation treatment is highly successful for certain cancers.  3D & 4D Conformal Radiation Therapy and Intensity Modulated Radiation Therapy (IMRT) is a state-of-the-art radiation treatment that is associated with improved outcomes and less patient discomfort than older forms of radiation.

The goal of radiation therapy for cancer treatment is to reduce or to eliminate the tumor and spare as much healthy tissue and organ functioning as possible.  Radiation kills and disrupts the growth of cancer cells and radiated cancer cells are not able to repair themselves or replicate. 
 
Radiation often damages all cells, both healthy and cancerous, in the exposed area.  In the past, external sources of radiation therapy involved aiming high-beam energy rays at a treatment area.  Conventional radiation was associated with side effects and the loss of healthy tissue leading experts in the field to look for better ways to use radiation.
 
Today, sophisticated technology has refined the way that radiation treatment is delivered.  Modern radiation methods target the cancer more effectively, spare more healthy tissue, and are associated with fewer side effects and improved cure rates.  Some of the modern methods include three dimensional conformal radiation therapy (3D CRT), four dimensional conformal radiation therapy (4D CRT), and intensity modulated radiation therapy (IMRT).
 
State-of-the-art technology has advanced radiation methods to help make them more effective and tolerable.  Three dimensional conformal radiation therapy (3D CRT) maps a tumor with imaging scans before treatment.  Magnetic resonance imaging (MRI) scans, computed tomography (CT) scans, and positron emission tomography (PET) scans are used to produce images of a tumor and its surrounding tissue.  The images from the scans are combined with images combined in the treatment planning system (TPS).The TPS is used by the Physician, physicist, and dosimetrist  to design the optimal radiation treatment approach. It is then used to program the treatment machine and its Multileaf collimator(MLC). The MLC allows division of the standard rectangular beam into multiple (even hundreds) of beamlets. The programing allows these beamlets to open and close, thereby modulating the standard radiation output. This directs multiple beams of radiation to be targeted precisely at the tumor and spare as much healthy tissue as possible.
 
Four dimensional conformal radiation therapy (4D CRT) measures the motion of tumors during natural small movements that occur during treatment, such as breathing.  Four-dimensional CRT is especially useful when treating lung cancer.  The motion measurements are included in the treatment formula configurations.  This ensures that the tumor is targeted during motions and as much healthy tissue as possible is spared.
 
Intensity modulated radiation therapy (IMRT) is a refined type of 3D CRT.  CRT allows the radiation oncologists to sculpt the edges of a tumor sparing healthy tissue.  With IMRT, the radiation dose can be modified (modulated) during a treatment session.  In the past, radiation was delivered based on dose calculations to one point in the treatment field. IMRT allows calculation and delivery to virtually every point throughout the treatment region. Imrt modulates the treatment so the proper dose is more uniformly delivered to each area.

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Treatment
Before your radiation treatment begins, you will meet with your doctor for consultation and treatment simulation.  During the simulation, positioning devises will be made for your body.  A mold of a mask, sometimes referred to as a cradle, may be used to position your body during treatments.  X-rays and images of the tumor will be taken while you are positioned in the mold.  This allows your treatment team to pinpoint the tumor and mark the reference points on your skin with tiny tattooed dots. 
 
External radiation therapy is an outpatient procedure.  The treatment sessions are short.  It typically takes more time to position your body in the mold than it does to perform the treatment.  The actual treatment usually lasts just a few minutes.  Your doctor will determine how much treatment you need.  Treatment sessions are once or twice daily and last for upwards of two months.  Common side effects include feeling tired and experiencing some irritation in the treatment area.  Your doctor will let you know what to expect.  Be sure to share your concerns with your doctor and be sure to ask questions about your treatment and what to expect.

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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on April 13th, 2016. For information on iHealthSpot’s other services including medical website design, visit www.iHealthSpot.com.