• The Journal of Korean Society for Radiation Therapy
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• v.18 no.1
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• pp.1-5
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• 2006

Purpose: IMRT quality assurance(Q.A) is consist of the absolute dosimetry using ionization chamber and relative dosimetry using the film. We have in general used 0.015 cc ionization chamber, because small size and measure the point dose. But this ionization chamber is too small to give an accurate measurement value. In this study, we have examined the degree of calculated to measured dose difference in intensity modulated radiotherapy(IMRT) based on the observed/expected ratio using various kinds of ion chambers, which were used for absolute dosimetry. Materials and Methods: we peformed the 6 cases of IMRT sliding-window method for head and neck cases. Radiation was delivered by using a Clinac 21EX unit(Varian, USA) generating a 6 MV x-ray beam, which is equipped with an integrated multileaf collimator. The dose rate for IMRT treatment is set to 300 MU/min. The ion chamber was located 5cm below the surface of phantom giving 100cm as a source-axis distance(SAD). The various types of ion chambers were used including 0.015cc(pin point type 31014, PTW. Germany), 0.125 cc(micro type 31002, PTW, Germany) and 0.6 cc(famer type 30002, PTW, Germany). The measurement point was carefully chosen to be located at low-gradient area. Results: The experimental results show that the average differences between plan value and measured value are ${\pm}0.91%$ for 0.015 cc pin point chamber, ${\pm}0.52%$ for 0.125 cc micro type chamber and ${\pm}0.76%$ for farmer type 0.6cc chamber. The 0.125 cc micro type chamber is appropriate size for dose measure in IMRT. Conclusion: IMRT Q.A is the important procedure. Based on the various types of ion chamber measurements, we have demonstrated that the dose discrepancy between calculated dose distribution and measured dose distribution for IMRT plans is dependent on the size of ion chambers. The reason is small size ionization chamber have the high signal-to-noise ratio and big size ionization chamber is not located accurate measurement point. Therefore our results suggest the 0.125 cc farmer type chamber is appropriate size for dose measure in IMRT.

• Radiation Oncology Journal
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• v.23 no.3
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• pp.176-185
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• 2005

Purpose: Film dosimetry as a part of patient specific intensity modulated radiation therapy quality assurance (IMRT QA) was peformed to develop a new optimization method of film isocenter offset and to then suggest new quantitative criteria for film dosimetry. Materials and Methods: Film dosimetry was peformed on 14 IMRT patients with head and neck cancers. An optimization method for obtaining the local minimum was developed to adjust for the error in the film isocenter offset, which is the largest part of the systemic errors. Results: The adjust value of the film isocenter offset under optimization was 1 mm in 12 patients, while only two patients showed 2 mm translation. The means of absolute average dose difference before and after optimization were 2.36 and $1.56\%$, respectively, and the mean ratios over a $5\%$ tolerance were 9.67 and $2.88\%$. After optimization, the differences in the dose decreased dramatically. A low dose range cutoff (L-Cutoff) has been suggested for clinical application. New quantitative criteria of a ratio of over a $5\%$, but less than $10\%$ tolerance, and for an absolute average dose difference less than $3\%$ have been suggested for the verification of film dosimetry. Conclusion: The new optimization method was effective in adjusting for the film dosimetry error, and the newly quantitative criteria suggested in this research are believed to be sufficiently accurate and clinically useful.

• Korean Journal of Food Science and Technology
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• v.34 no.1
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• pp.96-102
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• 2002

The levels of biologically active compounds, such as isoflavone, total saponin, dietary fiber, soy oligosaccharides, and lecithin from each serving size of commercial soy products, were quantitatively determined from the raw soybean, soymilk, tofu, isolated soy protein (ISP), soybean paste(toenjang), natto, and tempeh from local and foreign market. Soy flour, natto, and soymilk contained 489.1 mg, 308.3 mg, and 138.1 mg of isoflavone in each 100 g of dry matter, respectively. The ratios of aglycone to glucoside of soybean paste and tempeh showed relatively high level compared with other tested soy products. Commercial soymilk showed the highest ratio of soluble fiber to total dietary(59%). The higher levels of dietary fiber (20.1 g) and lecithin (1.13 g) were also found in tofu. The lecithin and saponin content of isolated soy protein(ISP) were highest (0.63 g and 0.65 g/ 100 g of dry matter) among the tested samples. In conclusion, soy flour showed the highest level of biologically active compounds, such as saponin, isoflavone, dietary fiber, and soy oligosaccharides. But when the evaluation was based on the serving size, soymilk containing 31.5 mg of isoflavone, 2.59 g of dietary fiber, 0.57 g of oligosaccharides, 0.10 g of lecithin, and 0.11 g of saponin showed similarity to those of the tested soybeans(20 g).