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Radiosurgery for Beginners

Last updated: 2/24/18

Radiosurgery is a medical technique that involves using precisely targeted beams of radiation to attack brain tumor cells. So, although the word "surgery" is part of its name, no sharp instruments are involved in these processes. The radiation damages the DNA of the targeted cells, which keeps them from dividing. This keeps the tumor from growing.

There are some important advantages when this technique is employed instead of traditional surgery:
A. Only local anesthesia is required, and the patient remains conscious during the treatment.

B. This means that often radiosurgery can be an outpatient procedure, meaning that no overnight hospital stay is necessary.

C. Because it is noninvasive and painless, patients are frequently able to return to their normal activities within a day or two.

D. Sometimes tumors are located in places inside the brain such that traditional surgery is impossible; in these cases radiosurgery may be the only way to get at the tumor.

E. Tumor cells are more sensitive to radiation than normal healthy cells, and this is one of the reasons radiosurgery is effective.

A good brief introduction to radiosurgery can be found on YouTube, at:

There are four kinds of radiosurgery:

  • Gamma Knife
    Multiple beams of radiation from three directions converge on the tumor site. This is all made possible by a computerized treatment plan created for each patient, to ensure that the full impact of the beams reaches the tumor only, while other surrounding parts of the brain get much smaller doses. The precise name for this approach is "Stereotactic Radiosurgery." For more information check out this 8-minute video on YouTube:
  • Linear Accelerator (Linac)
    These machines are not used only on the brain. They can also be used to treat tumors elsewhere in the body. And they are used to treat larger tumors. For more information check out this 8-minute video on YouTube:

    Please note that CyberKnife is the brand name for a specialized radiation delivery system based on Linac. The main difference is that the linear accelerator is mounted on a robotic arm, and this offers more flexibility in how the radiation beam can be delivered. For example the machine can be moved around the patient's head to deliver radiation to the tumor from many different angles, while healthy brain cells get a minimal amount of radiation, as the machine moves around the patient's head.

  • Intensity Modulated Radiation Therapy (IMRT)
    This is an advanced type of photon (X-ray) therapy that was originally used in prostate surgery, but also now is used to treat brain tumors. It uses special software to control a linear accelerator so that the dose of radiation delivered is based on the tumor's size, shape and location. This allows higher doses of radiation to be delivered to tumor cells while reducing radiation exposure to healthy tissue.

  • Particle Beam Therapy (also called Proton Radiotherapy)
    Other types of radiosurgery use photons, while this newer technology uses protons. For more information check out this 3-minute video on YouTube:

Single-dose RadioSurgery (SRS) typically delivers the whole dose of radiation in a single session, although the dose may sometimes be repeated, when necessary.

By contrast, Fractionated Stereotactic Radio Surgery (FSRS) is used to deliver smaller doses of radiation over a period of days, and from different angles. Normal brain tissue can tolerate a number of smaller doses of radiation better than one large one. This is one major reason FSRS is used.

For an excellent discussion about choosing the most appropriate treatment read "Radiation Therapy: Which type is right for me"

All of these techniques have the same goal, which is to deliver appropriately high doses of radiation to tumor cells, to keep them from dividing, while at the same time seeing that nearby healthy cells get the minimum amount of radiation possible. So it is very important that the patient's head be kept still during treatment sessions.

One common way this is accomplished is to fit a "Frame" to the patient's head. The frame is attached to the head at four points, using pins. The patient receives four local anesthetic doses ahead of time, one at each of the four locations of the pins. During treatment sessions the frame is anchored, keeping the patient's head immobilized.

Another way is to have a mask made from plastic. The mask wraps around the patient's head and is connected to a frame, which in turn is anchored to the machine. This immobilizes the patient's head, without having anything physically connected to the head.

A good 4-minute video on the use of Frames in Radiosurgery can be viewed at:

A newer approach is called "Frameless Radiosurgery." It uses a pre-planned computerized guidance system to deliver the radiation to its target, without a frame being used. This is much more comfortable for the patient, of course.

A three-minute video on "Frameless Stereotactic Guidance System" can be viewed at:

There are a number of companies which supply all of the devices to the medical world on which these technologies are based. And of course each vendor wants us all to believe that a) their type of radiosurgery is the best, and b) their particular machine is the best available device for that type of radiosurgery.

Trusting your medical team with this decision is likely to be the best way to proceed here, since these technologies are all VERY TECHNICAL. But do bear in mind that in the same way that the vendors can be biased, medical practitioners can also be biased towards or away from any particular solution.This may make getting a second opinion a critically important part of your strategy.

This article is only a very brief introduction. For a much more detailed explanation, particularly of the origins and history of the various types of radiosurgery, read this article:

George Bigham
February 24, 2018

The primary sources for this article include:

  1. Radiosurgery for brain tumors
  2. Stereotactic Radiosurgery Overview
  3. Other Malignant Tumors
  4. Stereotactic Radiosurgery and Stereotactic Body Radiotherapy (SBRT)
  5. Radiosurgery and Radiotherapy
  6. Stereotactic radiosurgery
  7. CyberKnife
  8. Stereptactoc Radiosurgery Overview
  9. IMRT for brain cancer

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