Dr. Tsubokura's Radiation Lecture Vol.130

Author: Masaharu Tsubokura PhD.

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

259 Proton beams can reach the deep part of the body

The previous articles introduced how current cancer treatment consists of three standard therapies: surgery, anticancer drugs (chemotherapy), and radiation therapy. Moreover, using irradiation to treat cancer cells is one of the options as effective as surgery or chemotherapy.


Cancer treatment often involves radiotherapies using electromagnetic radiation such as X-rays and gamma rays, which are similar to the visible light and radio waves used in cell phones. Furthermore, radiotherapy also uses "particle radiation" such as proton beams. Particle radiation is made of atoms, protons, neutrons, and electrons, which make up all matter.


Proton beams are selected according to the type of disease and location of the lesions. However, it is not yet widely available in Japan. In Japan, insurance coverage for proton beam therapy is limited to only a few diseases, such as some pediatric diseases and prostate cancers.


There is one major difference between external radiation therapy using X-rays and proton beam therapy.


When X-rays are applied to the body from an external source, the nearby skin surface will receive the highest amount of radiation exposure. In contrast, the tissues located deep inside the body will receive less radiation exposure. That said, proton beams do not emit radiation near the body’s surface. Instead, a proton beam emits the largest energy and causes damage to the tissue when it stops completely at a designated depth after penetrating further in the body. This advantageous proton beam feature can minimize the radiation damage to the lesion's surrounding tissues or the body's surface area, and limit and concentrate the damage to the lesion.


260 Directly ingesting radioactive material as radiotherapy

The previous articles introduced how current cancer treatment consists of three standard therapies: surgery, anticancer drugs (chemotherapy), and radiation therapy. Moreover, using irradiation to treat cancer cells is one of the options as effective as surgery or chemotherapy.

    

The previous articles introduced radiotherapy using an external source that delivers radiation. In contrast, there are different radiotherapy types where a high dose of radiation is delivered by directly ingesting the capsule containing radioactive materials or by injection.


For example, radioactive iodine is used to treat Graves' disease, which is a disorder that results in the overproduction of certain hormones or a type of thyroid cancer that spreads to the rest of the body.


When iodine is consumed, the thyroid gland will uptake them. In other words, when you ingest the radioactive iodine capsule, the target therapy tissues, in this case the thyroid gland, will collect the radioactive iodine. Once the radioactive iodine is taken up by an overactive thyroid gland or thyroid cancer, it will emit beta rays and damage the tissues.


By the way, the radioactive iodine used in the internal radiation therapy explained above is also one of the radioactive materials that were spread to our living environment immediately after the 2011 Fukushima Daiichi nuclear power plant accident. Radioactive iodine has a half-life of 8 days, thus those that spread from the power plant after the accident no longer exist.


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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 5th and 12th 2020 was reproduced for MRIC Global under the author's permission.

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