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Introduction of intensity modulated radiation therapy

Article information

J Korean Med Assoc. 2011;54(11):1172-1178
Publication date (electronic) : 2011 November 15
doi : https://doi.org/10.5124/jkma.2011.54.11.1172
Yong Chan Ahn, MD
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Corresponding author: Yong Chan Ahn, ahnyc@skku.edu
Received 2011 September 09; Accepted 2011 September 23.

Abstract

The role of radiation therapy (RT) in cancer management has grown remarkably during the past few decades. For successful RT, the most important factor is highly conformal radiation delivery focused to the tumor-bearing region while minimizing the surrounding normal tissue damage. RT has evolved from 2-dimensional and 3-dimensional techniques to intensity modulated RT (IMRT) along with the development of computer science and mechanical engineering. IMRT is a special form of 3-dimensional conformal RT techniques, by which the intensities of radiation coming though the beamlets are modulated so that conformal radiation dose distribution around the tumor-bearing region is achieved. IMRT has been covered by the Korean health insurance system since July 2001. The basic principles and process of IMRT are introduced.

Keywords: Intensity-modulated radiation therapy; Radiotherapy

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Article information Continued

Copyright © 2011 Korean Medical Association

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Figure 1

Figure 1

Intensity modulated radiation therapy using the linear accelerator with multi-leaf collimator system. The shape and the intensity of radiation coming through the multi-leaf collimator are modulated to achieve a highly conformal radiation dose distribution around the target region, while limiting the radiation doses to the surrounding normal organs below the acceptable tolerance limits.

Figure 2

Figure 2

The design of tomotherapy. The radiation intensity is modulated while the megavoltage X-ray tube is continuously rotating, and the patient's couch is moving. CT, computed tomography.

Figure 3

Figure 3

An example case of nasopharynx cancer treated by tomotherapy. The radiation doses to the gross tumor volume (GTV), clinical target olume (CTV), and the normal organs (parotid glands, brainstem) are optimized.

Table 1

Definitions of terms used in radiation therapy planning

Table 1

GTV, gross tumor volume; MRI, magnetic resonance imaging; CT, computed tomography; PET, positron emission tomography; CTV, clinical target volume; ITV, internal target volume; PTV, planning target volume; OAR, organ at risk..