Utilization of Radiation in Medical Fielｄ
Vice Director, Hiroshima High-Precision Radiotherapy Cancer Center

Masahiro Kenjo

On January 28, 1896, Röntgen exhibited a photograph of the hand of Kölliker taken using the X-rays
discovered the previous year, at a meeting of a society of physics held in Würzburg, Germany. This is theoldest existing evidence of the use of X-rays in medicine. The development of medicine in the TwentiethCentury and onwards is closely linked to the development of radiogenics.

In contemporary medicine, radiation is used in a variety of aspects. Diagnostic imaging uses radiationin units of millisieverts to perform chest X-rays, digestive tract imaging, X-ray CT, mammography and so on.
Nuclear medicine involves the introduction of isotopes into the body to perform scintigraphy for the bones andheart, FDG-PET examinations, treatment for thyroid cancer, and so on. Radiation is also used in units ofsieverts for treating cancers, either as external irradiation or interstitial irradiation.

Cancer, in the form of malignant
tumors, occurs due to the uncontrollable
proliferation of cells, leading to metastasis
from the original starting point to otherareas, ﬁnally becoming fatal. In many
developed countries malignant tumors are
one of the three leading causes of death,along with heart disease andcerebrovascular disease. One of the causes
leading to malignant tumors is radiation
exposure, yet at the same time
radiotherapy has an increasingly strong
track record against malignant tumors.
The progress of radiodiagnosis has led tothe capturing of changes in tumors in1

areas deep inside the body normallydiﬃcult to see with the naked eye. Early cancer detection leads to a rapid start of treatment with the potential
to cure it with less strain on the patient.

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The three main types of cancer
treatment are surgery, chemotherapy andradiotherapy. These three are used
separately, or if it is diﬃcult to gain a cure,they may be combined. Surgery is themost eﬀective method for lesions visible tothe naked eye, and has the advantage ofmaking it relatively easy to predict
post-treatment outcomes. Chemotherapy
can treat invisible lesions throughout thebody. Radiotherapy is used as a relatively
noninvasive local treatment.

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Radiotherapy irradiates tumor
cells with high-energy radiation to destroy
them by damaging their DNA. If a
suﬃcient dose of radiation is given, no cell
can survive. An important process inradiotherapy is the determination of thetarget volume and radiation dose, in otherwords the prescription. Putting theprescription into action is called
radiotherapy planning, and is usually
carried out based on diagnostic imaging of
the patient.
How to intensively deliverradiation to the cancer lesions is a key
question, but advances in diagnostic

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imaging and radiotherapy equipment havemade this possible. High-precision radiotherapy is the name of a recent type of radiotherapy realized using thismethod. In general it involves stereotactic body radiotherapy（SBRT）, intensity-modulated radiotherapy（IMRT）,and image-guided radiotherapy（IGRT）.In some cases all three are used together.

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Stereotactic body radiotherapy（SBRT）, also called pinpoint irradiation,
destroys cancer cells by administering asingle high dose radiation on the lesion
alone, directing several beams of radiation
with millimeter-level accuracy.
Intensity-modulated radiotherapy（IMRT）,
which is used for metastatic brain tumors,
early stage liver cancer or early stage lungcancer where there are only a few
relatively small cancers, divides theradiation into several beamlets,
individually adjusting the intensity of eachaccording to the shape of the tumor. Using
this technology limits the amount of4

radiation reaching the surrounding normal

tissues to protect them from damage while optimizing the delivery of the dose to the tumor, increasing theprobability of a cure. Image-guided radiotherapy（IGRT）takes CT or X-ray images immediately prior to eachtreatment session to conﬁrm the location of the tumor lesion, to correct the targeted location for delivery.
Image guidance allows the radiation to be targeted accurately each time on lesions that move around. Thesemethods make radiotherapy safer and more eﬀective.

The Hiroshima High-Precision
Radiotherapy Cancer Center（HIPRAC）
was opened in Hiroshima in October 2015.
HIPRAC provides high-precision
radiotherapy as a collaborative cancer
center that works in collaboration with anumber of designated regional cancer
centers and hospitals in Japan, including
Hiroshima University Hospital, Hiroshima
Prefectural Hospital, Hiroshima City
Hiroshima Citizens Hospital, Hiroshima
Red Cross Hospital & Atomic-Bomb
Survivors Hospital. It has three
radiotherapy units able to perform SBRT,IMRT, and IGRT.

5Through the incorporation ofcomputer technology, the ﬁeld of radiology continues to advance, playing a crucial role in today's medicine. It isimportant to continue to engage in the eﬀective utilization of radiation in medicine.

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