Minyoung Youn

Prompt gamma measurements for locating the dose falloff region in the proton therapy

The location of the distal falloff in the proton therapy is an important but often uncertain parameter as different tissue elements are traversed by the beam. A multilayered collimator system has been constructed as a practical means to locate the dose ends by measuring prompt gammas. The collimator is designed to moderate and capture fast neutrons and to prevent unwanted gammas from reaching the scintillation detector. The system has been studied using Monte Carlo technique and has been tested in the beam energy range of 100–200MeV. Measurements clearly indicated correlations between the gamma distributions and the distal falloff regions.

Histological analysis on the medieval mummy in Korea

Recently, there have been some reports on the mummies from the medieval tombs in Korea, which were not made on purpose. Although these mummies could be an invaluable source for the studies on the physical state of medieval Koreans, there were not any reports on this subject until now. In this study, we first tried to investigate the various tissues using light- and electron-microscopic techniques. In the organs we have examined, even though the collagen fibers were profusely found within all of them, some types of cells, such as red blood cells, chondrocytes, hepatocyte and muscle cells, were also visible in various tissues. The histological characteristics of the current case seemed to be well matched with the previous study in general even though there were also somewhat different findings from the previous reports on the mummies. Although the cause of the mummification in Korea was not completely explained, we think that the cause in this case could be correlated with cultural aspects--not with natural conditions--because the mummies were only found in cases where the lime-soil barrier was maintained until their discovery, and which separated the inner space of the coffins from the outer space. As similar cases are frequently reported nowadays, invaluable data on the physical status of the medieval Koreans could be attainable if systemic investigation could be performed on similar cases which are found in the future.

Radiological analysis on a mummy from a medieval tomb in Korea.

Although naturally mummified corpses have frequently been found in medieval tombs of Korea, there have been no scientific reports on the physical status of the mummies. In this study, we first tried to investigate the mummy using radiological methods. On physical examination, there were no findings suggestive of the cause of the death. From the radiological studies, we found that some internal organs were well preserved, while the bones showed similar appearances to those of living cases. From the stage of development of the teeth and carpal bones, the age of the mummy was estimated to be 4.5 to 6.6 years old. Although the exact cause of the mummification could not be clearly elucidated, it may be due to the lime-soil mixture outside the outer coffin, completely sealing the inner coffin from the outer spaces. In this study, as the mummy in the medieval tomb has proved to be well preserved over the last 400 years, similar cases could give invaluable clues to the physical status of medieval Koreans.

Energy measurement of 50 MeV proton beam with a NaI(Tl) scintillator

Abstract Energy measurement of 50 MeV proton beam produced on the AVF MC-50 Cyclotron was conducted using a detector telescope with a NaI(Tl) scintillator as an E counter. Protons of various energies, elastically and inelastically scattered from the 12 C target nucleus were measured at four different angles of 35°, 40°, 50° and 55°. We applied the chi-square method to determine the beam energy, which showed a well defined minimum chi-square corresponding to a beam energy of 49.6 ± 2.3 MeV at the 68% confidence level. Also the light output response of NaI(Tl) to proton energies between 31 and 44 MeV is linear within 0.5 MeV and is in good accord with the recent result of Romero et al. [Nucl. Instr. and Meth. A 301 (1991) 241].