Radiation Therapy IMRT/IGRT

Basics about Radiation Therapy

Varian iX Linear Accelerator with On-Board Imaging (OBI) – External Beam Radiation Therapy

Radiation therapy is a type of treatment that uses high doses of radiation to eradicate, stop or slow the growth of cancer cells.  It is one of the most common treatments for cancer, either by itself or along with other forms of treatment.  At low doses, radiation is used as an x-ray to see inside your body and take images, such as your teeth at the dentist office or broken bones.  Radiation used in cancer treatment works in much the same way, except that it is given at much higher energy.

External beam radiation therapy is a local treatment, meaning that the radiation is aimed only at a specific part of your body.  It comes from a machine outside your body that aims the radiation at your cancer cells.  For example, if you have prostate cancer, you will get radiation in the pelvis area only and not the rest of your body.  We use On-Board Imaging (OBI) to take x-rays of your internal anatomy to see exactly where to aim the radiation beam for daily treatment.

Many people with cancer need radiation therapy.  In fact, more than half of people with cancer receive radiation therapy.  Sometimes, radiation therapy is the only kind of cancer treatment people need.

Most people get external beam radiation therapy once a day, 5 days a week, Monday through Friday.  Treatment lasts for 2 to 10 weeks, depending on the type of cancer you have and the goal of your treatment.  Each treatment lasts about 15 – 30 minutes. 

Three Dimensional Conformal Radiation Therapy (3D CRT) 

Three dimensional conformal radiation therapy is also called 3D CRT.  3D CRT is a process during which images obtained using CT (computed tomography) and/or MRI (magnetic resonance imaging) are used to create detailed, accurate, three-dimensional representations of a tumor and any surrounding organs. The information taken from these scans is fed directly into the radiotherapy planning computer, so doctors can see the treatment area in 3 dimensions. The dosimetrist then designs radiation beams that follow the shape of the tumor more closely, so the radiation beam spares healthy tissue as much as possible.

Of course, doctors have always tried to avoid affecting as much healthy tissue as possible with radiotherapy. But the main benefit with conformal radiotherapy is that it is more precise, as it allows doctors to plan in 3D. Conformal radiotherapy can give a better chance of killing the cancer by delivering a higher dose of radiation straight to the tumor. Less healthy tissue is included in the radiotherapy field and so you are likely to have fewer long term side effects. If doctors took too much of the surrounding area out of the radiotherapy treatment field, there could be a risk of cancer cells being missed. But radiation oncologists are extremely precise in keeping the right balance between keeping all the cancer inside the radiation treatment field, while as much healthy tissue as possible is kept out.

This is an example of a 50 year old female with left breast cancer in the upper outer quadrant.  She chose to have breast conservation therapy, lumpectomy followed by 3D CRT external beam radiation therapy.  She had a total of 33 treatments to the left breast.  She handled treatment extremely well with very minimal side effects.  The highlighted area above shows the exact area of the body being treated with radiation therapy.  The rest of the body receives very minimal dose.

Intensity-Modulated Radiation Therapy (IMRT)

A Multileaf Collimator (MLC) is used to shape the beams in delivery of Intensity Modulated Radiotherapy.

 A Multileaf Collimator (MLC) is used to shape the beams in delivery of Intensity Modulated Radiotherapy.

SmartBeam IMRT is a type of radiation treatment involving varying (or modulating) the intensity of the radiation beam (in this case, X-rays), through the use of a multileaf collimator. It is a form of radiation therapy that uses computer generated images to plan and then deliver more tightly focused radiation beams to cancerous tumors than is possible with conventional radiotherapy. With this capability, clinicians can deliver a precise radiation dose that conforms to the shape of the tumor, while significantly reducing the amount of radiation to surrounding healthy tissues.  Consequently, the technique can increase the rate of tumor control while greatly reducing adverse side effects. Intensity-modulated radiation therapy (IMRT) is the most technologically advanced and most precise method of external beam radiation therapy available.  IGRT takes this technology one step further.  It delivers high doses of radiation directly to the treatment area while sparing surrounding healthy tissue through the use of daily imaging.

This is a 71 year old gentleman with adenocarcinoma of the prostate.

This is a 71 year old gentleman with adenocarcinoma of the prostate.  This patient decided to undergo radiation instead of surgery for his cancer treatment. He received an IMRT treatment to the prostate which aloud us to increase the dose to the prostate significantly while sparing dose to the rectum and bladder. His prostate gland is highlighted in red. This patient has been through with his radiation treatment for two years now and has no detectable PSA.

Image-Guided Radiation Therapy (IGRT)

IGRT (Image Guided Radiation Therapy) is a type of treatment that uses x-rays daily before treatment to look internally at the cancer site.

We have a Clinac iX medical linear accelerator from Varian Medical Systems, for treating cancer with Dynamic Targeting image-guided radiotherapy (IGRT).  This new robotic and automated technology combines a state-of-the-art treatment machine with sophisticated digital imaging, and tracking and monitoring tools, enabling doctors to deliver the most accurate treatments possible, even when treating tumors that move as the patient breathes.  We are proud to bring this advanced and sophisticated technology to the Greater Austin area.

  This highly advanced system incorporates a high-quality imaging device that enables clinicians to position patients very precisely and to deliver the radiation dose directly to a targeted area with sub millimeter accuracy, guided by three-dimensional images of the patient’s anatomy.  The system’s versatility makes it appropriate for treating a wide range of abnormalities, from small metastases to large tumors, even in cases where the tumor is close to critical structures like the spinal cord or the optic nerve.  Altogether, these tools deliver extremely precise treatments with better outcomes and fewer side-effects.

The Clinac iX with its On-Board Imager device is visually compelling.  Housed in a specially designed vault visible through closed circuit television, the machine stands approximately nine feet tall and rotates 360 degrees around the patient to deliver radiation from several angles.  The On-Board Imager is attached to the machine on a pair of robotic arms that extend out on either side of the patient to generate anatomical images that will guide the treatment.  Sophisticated image-matching software shows patient anatomy on computer monitors outside the treatment room.