아크릴 팬톰에서 GafChromic 필름을 이용한 고선량률 근접치료용 Ir-192 선원의 근접 거리에서 비등방성 측정 = Anisotropy in a Few mm Regions from an Ir192 High Dose Rate Source Measured with a GafChromic Film in Acrylic Phantom

국문 초록 (Abstract)

GafChromic 필름은 높은 분해능과 낮은 민감도 그리고 조직 등가 물질에 유사하게 구성되어 있다. 본 연구의 목적은 GafChromic 필름을 이용하여 고선량률 근접치료에 사용하는 Ir-192선원 근접 거리에서의 비등방성을 측정하는 것이다. GafChromic 필름은 0 Gy 105 Gy까지 4 MV 선형가속기를 이용하여 흑화도를 구하였다. 비등방성 값은 아크릴 팬톰에서 GafChromic 필름을 이용하여 측정하였고, 측정된 값은 J. F. Williamson이 몬테칼로 계산한 값과 비교하였다. 비교 결과 거리(r) 2.5 mm, 각도 50～130도까지 영역에서 4.4% 이내로 일치하였고 반면 140도 부근에서 17.6% 차이가 나는 것을 알 수 있었고, 한편 거리(r) 5 mm, 각도 35～160도까지 3.7% 이내로 일치하였고, 30도 부근에서는 7.6% 정도 차이가 나는 것을 알 수 있었다. GafChromic 필름은 고선량률 근접치료 Ir-192선원의 근접 거리에서 비등방성 측정 시 기존에 사용되고 있는 측정 장비보다 매우 유용한 것으로 생각된다.

다국어 초록 (Multilingual Abstract)

Radiochromic film has several advantages; high spatial resolution, relatively low spectral sensitivity, near tissue equivalence and requires no special development procedure. The object of this study was to measure the anisotropy of an Ir-192 source (microSelectron manufactured by Nucletron) in a few mm regions from the source, using the GafChromic film. The GafChromic film was calibrated in the range of 0～105 Gy, using a 4 MV photon beam, and the anisotropy function measured in an acrylic phantom using the GafChroimic film. The data obtained gave agreement to within 4.4% of the Monte Calro calculation, by J. F. Williamson, at a radial distance of 2.5 mm with polar angles of 50 to 130o, while a maximum deviation of 17.6% was observed at angles near 140o and agreement within 3.7% at a radial distance of 5 mm at polar angles between 35 to 160o and a maximum deviation of 7.6% was observed at angles near 30o. A GafChromic film can be used as a more efficient detector for measuring the anisotropy of an HDR 192Ir source at close distances than any other detector.

참고문헌 (Reference)

1 "diode and Monte Carlo dosimetry of an Ir-192 source for high-dose rate brachytherapy" 40 : 2015-2036, 1995

2 "The anisotropic dose distribution of an HDR iridium-192 source" 1 : 286-289, 1992

3 "Monte Carlo aided dosimetry of the microSelectron pulsed and high dose-rate Ir-192 source" 22 : 809-819, 1995

4 "Investigated as a precision dosimeter" 24 : 1997

5 "Anisotropy of of a microSelectron- HDR Ir-192 source" 7 : 39-42, 1995

6 "Anisotropy of an 192Iridium high dose rate source measured with a miniature ionization chamber" 24 : 751-755, 1997

7 "Anisotropy measurement of a high dose rate Ir-192 source in air and polystyrene" 21 : 1131-1134, 1994