Vol.5 No.4 2013

Research paper−228−Synthesiology - English edition Vol.5 No.4 pp.228-240 (Mar. 2013) manner. The typical period required for the development of a radiation dose standard is approximately 3–5 years. Here, by fully utilizing existing research facilities and technologies, the period from the commencement of development to dissemination was reduced to approximately 1.5 years. Moreover, a widely available calibration service system was established rapidly by utilizing the standard in the current quality control system for mammography. In this paper, we describe the scenario established by AIST for developing the mammography X-ray standard and improving the reliability of X-ray dose evaluation in mammography quality control.2 Background of the research and development2.1 Expansion of mammography in societyThe age-adjusted incidence rateTerm 1 and the age-adjusted mortality rateTerm 2 for breast cancer has been increasing steadily in recent years.[1] Because the prognosis of breast cancer is good when treated early, early detection leads to a decrease in mortality. The rapid increase in the number of breast cancer patients was seen much earlier in Europe and in the US than in Japan. Since mammography was introduced as a screening methodology for the early detection of breast cancer, the mortality rate of breast cancer has decreased.[2]In Japan, in addition to visual inspection and palpation, mammography was introduced for breast cancer screening beginning in 2000. The Ministry of Health and 1 IntroductionOwing to the recent increase in mortality due to breast cancer, mammography was introduced in Japan from 2000 to ensure early detection of breast cancer. After its introduction, the number of mammography examinees has increased, and this number surpassed 2.5 million people in fiscal year (FY) 2009. To effectively diagnose breast cancer, high quality diagnostic images and excellent interpretation techniques (e.g., the ability to discern lesions on diagnostic images) are required. However, to ensure patient safety, mammography must be performed with a minimum yet appropriate X-ray dose. The maintenance and improvement of mammography quality control are mainly conducted by academic societies and industries. Further improvement in the reliability of mammography X-ray dose assessment was demanded by the societies and industries involved because of the large discrepancy between the radiation quality (energy spectrum) for mammography and the calibration reference field, and this difference might affect the sensitivity of the dosimeters. Therefore, to manage this issue, the National Institute of Advanced Industrial Science and Technology (AIST) set out to develop and disseminate the national standard for X-ray dose based on mammography X-rays.Measurement standards become meaningful only when they are used widely in society, and it is therefore important to meet the social demand for such standards in a timely - Establishment of X-ray dose standards for mammography and construction of a calibration service system-Breast X-ray screening (mammography) was introduced in 2000 to detect breast cancer at an early stage. Since then, the number of examinees has increased steadily. The X-ray dose must be optimized to obtain high-quality images that ensure diagnosis reliability without compromising safety. Mammography utilizes low-energy X-rays with a special energy spectrum for breast cancer screening. This X-ray energy spectrum is significantly different from the reference X-ray spectrum used to calibrate dosimeters. Members of industry and academia were concerned about the reliability of dose evaluation for mammography quality control. Thus, the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) has established an X-ray dose standard based on the X-ray energy spectrum for mammography and has disseminated this standard to industry. NMIJ has succeeded in rapidly establishing this standard by making the utmost use of existing research equipment and technology, and by utilizing the standard in the existing mammography quality control system. Moreover, it created a research and development (R&D) scenario beforehand considering both domestic and international situations regarding mammography dosimetry that has enabled rapid and extensive dissemination of the standard with international consistency.Dose standards for safe and secure breast cancer screeningKeywords : Mammography, dosimetry standard, calibration, dosimeter, reliability[Translation from Synthesiology, Vol.5, No.4, p.222-233 (2012)]Takahiro Tanaka*, Tadahiro Kurosawa and Norio SaitoNational Metrology Institute of Japan, AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba 305-8568, Japan *E-mail : Original manuscript received January 31, 2012, Revisions received August 7, 2012, Accepted August 15, 2012


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