Dr. Tsubokura's Radiation Lecture Vol.128

Author: Masaharu Tsubokura M.D., PhD.

Editors: Akihiko Ozaki M.D., PhD., Yuki Senoo

255 Difference between gamma ray and X-ray is source of origination

 The term “gamma ray” is often used in reference to measuring air radiation dose rate, whereas the term “X-ray” is commonly used in medicine, such as in “chest X-ray.”

What is the difference between these two types of radiation?

Let’s review what we have discussed in previous articles. Every single material in this world comprises numerous particles called protons, neutrons, and electrons. To be more precise, atoms consist of a nucleus made of protons and neutrons orbited by electrons. I assume many of you learned this in high school.

 When the number of protons, neutrons, and electrons in the nucleus is unbalanced, atoms become unstable, and they will try to make themselves stable again. To become stable, they get rid of the unnecessary protons, neutrons, electrons, and energy, a process known as radiation.

Both X-rays and gamma rays are types of radiation. However, the difference is in their origin. Gamma rays are emitted from the nucleus, situated at the center of the atom, whereas X-rays are produced outside of the nucleus.

The key difference between gamma rays and X-rays is how they are produced, and there is no distinction between these two types of radiation based on their energy level. Thus, in terms of their effects on the human body, there is no difference between X-rays and gamma rays.

256 Radiation therapy is an effective cancer therapy

 The current cancer treatment consists of three standard therapies: surgery, anticancer drugs (chemotherapy), and radiation therapy. Treating cancer by irradiation of cancer cells is one of the options that is effective as surgery or chemotherapy.

 Just as there are two types of radiation exposure, there are two types of radiation therapy: external beam radiation therapy and internal radiation therapy. External exposure refers to radiation directed from a large machine outside the body to the lesion inside the body.

 There are several types of radiation rays that can be applied to cancer cells. For treatment purposes, “electromagnetic radiation,” such as through X-rays and gamma rays, is often chosen. X-rays and gamma rays are often classified as being in the same group as the light we see and the radio waves from our cell phones. In addition, “particle radiation,” such as through proton beams and heavy particle beams (the particles themselves; a mass of protons, neutrons, and electrons; or a mass composed of a mixture of them), may also be applied to the body as therapy.

 The selection of therapy depends on the type of cancer cells and the location of the tumor in the body. However, all radiation therapy shares the same fundamental mechanism of action, which is damaging and killing cancer cells by radiation exposure.


The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 8th and 15th, December 2019 was reproduced for MRIC Global under the author's permission.

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