[en] This proceedings contains articles of the Korean Association for Radiation Protection Spring Meeting, 2011. It was held on Apr.21-22, 2011 Ramada Hotel in Seoul, Korea and subject of the Korean Association for Radiation Protection Spring Meeting 2011. This proceedings is comprised of 8 sessions. The main topic titles of session are as follows: Radiation protection 1, Medical treatment and Biology 1, Radiation Measurement 1, Radiation environment and disasters prevention 1, Radiation protection 2, Medical treatment and Biology 2, Radiation Measurement 2, Radiation environment and disasters prevention 2

[en] Cryogenic detectors using heat generation below 1 K have become an attractive alternative because of their outstanding energy resolution. Significant improvement in gamma spectroscopy has been achieved with high resolution transition edge sensors (TESs) for nuclear material analysis. In alpha spectroscopy, superior resolution to that of conventional detectors has been also demonstrated. Since all the deposited energy can be converted into thermal energy by surrounding a radioactive source with metal foil, alpha energy can be measured without any correction for selfattenuation. Accompanying electrons, x-rays, and/or γ-rays are also converted into thermal energy. Thus measurement of alpha decay in 4π geometry returns the Q value, the total decay energy, independent of decay branches without loss of energy and count, enabling Q spectroscopy.

[en] The purpose of this study is planning comparison of helicaltomotherapy and Cyber knife in spine radiosurgery. Spine radiosurgery is an alternative to invasive spine surgery. The tomotherapy is megavoltage CT(MVCT) based image guided helical IMRT delivery system. The cyberknife using robotic arm and image guided based fiducial marker killo voltage X-ray image. The helical tomotherapy is modulated by a 64-multileaf collimator that has paired, pneumatically driven, 6.25-mm-wide leaves calculated to open or close at approximately every 7 .deg. of LINAC rotation, or 51 times per gantry rotation. But cyber knife use 100 or more than bean path. Although, cord maximum dose in CKP is lower than HTP, target homogeneity in HTP is better than CKP. Target coverage is 85% in CKP, 92% in HTP. It was benefit of helical radiation therapy. Tomotheapy and cyberknife are useful equipment to spine radiosurgery.

[en] Non-Hodgkin's lymphoma (NHL) of the gastro- intestinal tract accounts for 4% to 20% of all NHLs and is a common extranodal site of presentation There are just few historical data of whole abdominal irradiation (WAI) for intestinal lymphoma. However, there is no confirmed indication or radiation dose schedule of WAI for intestinal lymphoma. On the other hand, there are also many reports about the serious complication of WAI. So, it is necessary to obtain more effective and less toxic WAI tool with feasible indication. The aim of this study was to implement WAI applied by tomotherapy into the multimodal treatment concept of intestinal NHL. Helical tomotherapy is feasible and valuable for WAI. Simultaneous integrated boost technique can be incoporated. Tomotherapy enabled excellent coverage of the PTV and effective sparing of liver, kidneys and bone marrow. And we will have to analyze the comparison with simple AP-PA technique WAI and also local control or survival when chemotherapy alone for intestinal NHL. Meanwhile we think more follow-up period and patients are needed for analysis of local control, survival and late RT complications in the future.

[en] Use of intensity-modulated radiation therapy (IMRT) for head and neck cancer is gradually increasing, because it could facilitate more sophsticated treatment of target volumes and reduction of acute and late sequelae. However, theoretically, there is a potential risk of increased skin surface dose resulting from multiple obliquity effects caused by multiple tangential beams. Moreover, we sometimes confronted with more skin reactions in the patients treated with IMRT than conventional techniques. In this study, we evaluated skin surface dose adjacent to the target volumes to verify whether the use of IMRT would increase the skin dose more than we predicted. This study had shown that the use of IMRT did not increase the skin surface hot point dose. The measured skin surface dose was 20 to 40 percent of the adjacent target prescription dose, and was within acceptable dose range. Our study had some limitations with small number of experimental patients and methodological problems. Potential risk of increasing skin dose with bolus effect of aquaplaster should be examined in the future trials. In addition, the accurate set-up verification should be maintained because of steep dose gradient between skin surface and target volumes within a short distance in the head and neck cancer patients.

[en] McGregor et al. showed thermal neutron detection efficiency with respect to the thickness of neutron converter films. And for thermal neutron flux measurements, a thin film of "6LiF was used up to 25 μm thickness. In this study, two PIN-type SiC semiconductor neutron detectors, which are for thermal neutron detection by charged particle emissions of 6"LiF reaction and for fast neutron detection by elastic and inelastic scattering SiC atoms, were designed and fabricated for comparison of two neutron detector's responses. Neutron responses were measured at ENF (Ex-core Neutron irradiation facility) in HANARO research reactor. McGregor et al. showed thermal neutron detection efficiency with respect to the thickness of neutron converter films. And for thermal neutron flux measurements, a thin film of "6LiF was used up to 25 μm thickness. In this study, two PIN-type SiC semiconductor neutron detectors, which are for thermal neutron detection by charged particle emissions of "6LiF reaction and for fast neutron detection by elastic and inelastic scattering SiC atoms, were designed and fabricated for comparison of two neutron detector's responses. Neutron responses were measured at ENF (Ex-core Neutron irradiation facility) in HANARO research reactor.

[en] As a dosimeter for ESR dosimetry, alanine has many useful features including relatively long endurance time of radicals and almost no difference with the radiation dose rate and radiation quality. Alanine dosimeters have been accepted as transfer dosimeters for their good precision at high radiation range. For alanine/ESR spectra, it was reported that the peaks of the spectra are due to the three kinds of radicals induced by radiation. The ratio of the weak 'satellite line' and the central peak of the three man in alanine specta(in this study "x/y ratio") are changed on the LET value of radiation. In case of lithium formate monohydrate was recently identified as a promising dosimetric material. in addition, it was reported the the peak height in the signal spectra is not easily saturated when power is irradiated with relatively high LET radiation such as neutron rays. The difference in the peak height ratio was reported to be caused by increased local radical density following the radiation of high LET. The spectrum shape of some alanine dosimeter installed in the containment buildings of NPPs showed differences in comparison with dosimeters exposed only to gamma rays. There was apparent change of spectra, expressed as the 'x/y ratio'. As noted in other papers, high LET radiation such as neutron rays causes shape changes of the spectrum of alanine dosimeters. Thus, the unanticipated high dose level and low 'x/y ratio' of some alanine dosimeters from the containment building could be explained b exposure to mixed radiation with high LET. Generally, the locations evaluated in this study are regarded as being exposed only to gamma rays, because the positions are blocked from direct neutron rays, because the positions are blocked from direct neutron rays from reactor by thick cement barriers and heavy instruments.

[en] As one of the stereotactic body radiation therapy (SBRT) techniques, dynamic conformal arc therapy (DCAT) is commonly adopted to efficiently deliver conformal doses. However, as the DCAT uses numerous beams at individual control points, the dosimetric errors generated from each beam can be accumulated and manifested. In SBRT, therefore, due to the high fractional dose within a few fractions to moving target, the determination of the applied plan parameters can be critical and the evaluation of dosimetric impact of planning parameters would play an important role in DCAT planning process. In this study, we systematically evaluated the dosimetric influence caused by the variable grid size and the angular increment in DCAT for lung SBRT. Dose variations with different parameters were estimated for spherical and elongated tumors on an anthropomorphic phantom. The systematic analysis of the generated dose variation would guide to determine appropriate plan parameters and to estimate the dose errors in planning process in a clinical perspective of DCAT. It was found that two plan parameters, grid size and angular increment, in DCAT could cause non-negligible dose uncertainty. Coarse grid size led patients to get unnecessary overdose. Coarse angular increment could make significantly inaccurate prediction of OAR dose, resulting in either over- or under- estimation depending on the location of OAR relative to the isocenter.