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External Beam Radiation Therapy

Receive Advanced Radiation Treatments — 3-D Conformal RT, IMRT, IGRT and SBRT — in a Setting Close to Home

Say the words “radiation therapy,” and most people think of external beam radiation therapy. It is sometimes called traditional radiation therapy and dates back to the 1950s. At Central Maryland Radiation Oncology, we offer today’s leading-edge treatments of this “traditional” radiation therapy. CMRO offers patients the same state-of-the-art external beam technologies that are available at the larger academic medical centers in downtown Baltimore, right here in your Columbia community.

External beam therapy is given by a linear accelerator. This machine is sometimes called a linac (pronounced lie-knack) for short. You lie still on a treatment bed while the linac rotates around you. The machine creates high-energy X-ray beams that are aimed through skin and tissue to reach their target — the cancer tumor.

Over the years, University of Maryland and Johns Hopkins radiation oncologists have helped develop ways to better direct radiation to tumors. Along with knowledge from other leaders in the field, they use this know-how to reduce radiation on healthy cells.

External beam radiation treatment is planned by a team of experts — radiation oncologists, physicists and dosimetrists. They use their clinical expertise and the latest technology tools available to precisely determine:

• the size and shape of the radiation beam
• how strong the beam should be
• where the beam should be directed with pinpoint accuracy

Special Forms of External Beam Radiation Therapy

Depending on the type of cancer and the tumor’s location, the treatment team might use a special form of external beam therapy.

3-D Conformal Radiotherapy (3-D CRT)

Three-dimensional conformal radiation therapy, or 3-D CRT, is the art of shaping the radiation beams to match the tumor. Covering the tumor with radiation is the first half of this strategy. The other half of 3-D CRT is avoiding as many healthy cells as possible from the radiation beam.

It starts with good images of the tumor. Doctors use imaging tests such as CT (computed tomography), MRI (magnetic resonance imaging) and PET (positron emission tomography) to see the tumor. These images are taken from all angles and show the size and shape of the tumor and nearby areas. Based on these images, treatment is planned so that radiation is fully directed at the exact, 3-D area of the tumor, and healthy areas are minimally exposed to radiation. 

Intensity Modulated Radiation Therapy (IMRT)

Intensity modulated radiation therapy, or IMRT, is a form of 3-D CRT. IMRT changes the intensity of the X-ray beams during treatment. Because the linac rotates around you, it delivers radiation from many different directions or angels. Doctors use IMRT to direct the beam lower or higher at each of these angles. The result is that radiation can be stronger in some directions and weaker in others. In this way, your care team can direct more radiation to cancer cells and less to healthy cells.

IMRT is useful in protecting certain tissues from too much radiation. For patients with tumors near vital organs, IMRT may be a recommended treatment option. In other cases, IMRT allows a higher dose of radiation to be safely directed at the tumor.

Image Guided Radiation Therapy (IGRT)

Image guided radiation therapy, or IGRT, involves imaging the target area right before treatment. This helps the care team confirm that the radiation beam will be delivered to the right area. If the tumor has moved, however, the radiation beam can be adjusted.

IGRT is especially helpful for treating tumors that move while patients are breathing. It can also be helpful with tumors that can be in a different place when you have a full or empty stomach or bladder, for example. IGRT helps ensure that the tumor receives the radiation beams rather than normal cells.

Stereotactic Body Radiation Therapy (SBRT) and Stereotactic Radiosurgery (SRS)

Stereotactic body radiation therapy (SBRT, sometimes known as SABR) and stereotactic radiosurgery (SRS) are technically forms of external beam radiation therapy. However, they involve very high doses of radiation that make them different from traditional radiation therapy. Unlike traditional therapy given in small doses, five days a week for several weeks, SBRT and SRS involve just a few treatments. Patients often have just one to five stereotactic radiation treatment sessions. For more information about SBRT and SRS at Central Maryland Radiation Oncology, see our Stereotactic Radiation Therapy page.

For Advanced External Beam Radiation Therapy in Howard County, call us for a consultation at 443-546-1300.