Korean National Cancer Center Research Articles

Determination of distal dose edge location by measuring right-angled prompt-gamma rays from a 38 MeV proton beam

In clinical applications, it is very important to accurately determine the range of a proton beam in a patient. Recently, a prototype prompt-gamma scanning system, called a prompt-gamma scanner (PGS), has been constructed at Hanyang University in Korea with the collaboration of the Korean national cancer center (NCC), based on a series of Monte Carlo simulations. The PGS system is composed of a prompt-gamma collimator, a CsI(Tl) scintillation detector, a multi-channel analyzer (MCA), a precision movement system, and an integrated readout system. The prompt-gamma collimator is designed to effectively shield high-energy neutrons from the proton beam passage and subsequent capture gammas. The PGS system can be used to scan the distribution of the prompt gammas in the patient from the proton beam passage. The distribution of the prompt gammas can then be used to determine the proton beam range or the distal dose edge in the patient. In this study, the PGS system was tested with a 38 MeV proton beam at the Korea cancer center hospital (KCCH). The experiment was also simulated, using a Monte Carlo particle transport simulation code, MCNPX. Our result is very encouraging, showing that there is a clear correlation between the distribution of the prompt gammas and the location of the distal dose edge for the 38 MeV proton beam. According to our result, we believe that the location of the distal dose edge can be determined within 1–2 mm from the distribution of the prompt gammas.

National Guidelines for Breast Cancer Screening

Breast cancer is the school most common cancer in Korea women. The incidence of breast cancer is around 25 per 100,000 women, and more than 5,500 women are diagnosed as breast cancer annually. Epidemics show that the incidence and mortality of breast cancer are increasing due to rapid changes of women's life style and westernized food and so on. The risk factors for breast cancer include hormone-related factors (early menarche, late menopause, no or late birth, hormone replacement therapy) and genetic background. It is hard to change risk factors for breast cancer but early detection strategies are best for decreasing the mortality rate from breast cancer.Breast self examination, clinical breast examination, and mammography can be used for screening of breast cancer. Breast self examination is not sensitive enough to detect a small cancer but monthly exam makes women be awakening about breast cancer and feel changes of her breast. Meta-analysis shows annual mammography reduces breast cancer mortality around 35% in the ages over 50. Some randomized clinical trials also showed mortality reduction by mammography in the ages of 40s.Surprisingly, breast cancer is rapidly increasing in late thirties with a peak incidence in forties among Korean women. Whether the early peak makes mammography less accurate is controversial. However, data from qualified screening centers showed mammography has same sensitivity with that in westerns. Korean Breast Cancer Society and National Cancer Center organized the 1st Consensus meeting for the national guidelines for breast cancer screening on July 24, 2001. We recommend that women should have monthly self examination beginning at age 30, should receive biannual clinical breast exam from healthcare providers from age 35, and should receive clinical breast exam and mammography at 1~2-year intervals after age 40.