Types of Radiotherapy

The Difference Between Alpha, Beta and Gamma Radiation

Radiation Therapy for Cancer?

 

Radiation therapy, the use of high-energy particles or waves, such as x-rays, gamma rays, electron beams, or protons, has long been used to treat cancer. From as early as the 20th Century, physicians have given regular doses of radiation to greatly improve the patient’s chance for cure. From physicists Wilhelm Roentgen

Marietta Blau, Nuclear Physicist 1925 who first discovered the X-ray, to Marietta Blau, who contributed significantly to the fast development of medical and industrial applications of radiation, especially alpha radiation.

Image 1 - Marietta Blau, Jewish Nuclear Physicist 1925

At its basic form, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Alpha, beta and gamma radiation are all types of ionizing radiation – a type of radiation that carries enough energy to detach electrons from atoms or molecules.

 

Dependent on the radiation type, its source, speed, and size provide a good indicator for understanding how far each type of radiation can travel and the associated damage it can cause to cells. For this reason, it is highly important that methods of cancer treatment are adapted to utilize the advantageous properties of different radiation types.

Image 2 - Range of Alpha, Beta and Gamma Radiation

For example, gamma radiation has a very long range that can penetrate the human body unhindered and can travel several hundred meters in the air. In contrast, alpha radiation has a very short range traveling only a few centimeters in air. In fact, alpha particles are stopped by a thin sheet of paper or by the skin, see Image 2.

 

The long range of gamma radiation to penetrate through tissue makes it highly suitable for external beam radiation therapy, that directs high-energy rays from outside the body into the tumor, without the need for surgery.

 

However, when using external-beam radiation healthy tissues are unavoidably exposed to radiation. For this reason, advances in cancer radiation therapy have aimed to provide new ways to both lower the dose to produce the same therapeutic response, while providing a more targeted and localized activity for improved patient outcomes and reduced cost.

 

The unique properties of alpha radiation compared to beta and gamma radiation, are making it a highly effective treatment approach for localized and targeted radiation therapy. See Table 1 to understand the characteristics of the different radiation types.

Table 1 - Comparative characteristics between alpha, beta and gamma radiation

LET

When considering radiation effectiveness, a good measurement is to look at the radiation’s linear energy transfer (LET). LET is defined as the average amount of energy that is lost (and deposited) per unit path-length as a charged particle travels through a given material; in other words, in cancer treatment, the capability of the radiation to efficiently kill the tumor cells and its range inside the tissue.

 

Low LET radiation types such as X-rays, gamma rays and beta particles deposit a relatively small quantity of energy. On the other hand, high-LET particles, including protons and alpha particles, deposit more energy on the targeted areas and therefore are significantly more effective in killing cancer cells.

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