KHAO S A T C A C D I E U KIEN ANH H l T d N G LEN SU* ON DINH M A U CUA LIEU KE R A D I O C H R O M I C DANG P H I M SAU CHIEU XA NGUYEN NGUYET DIEU, DOAN BINH, PHAM THI THU HONG, CAO VAN CHUNG, NGUYEN THANH DUOC Trung tdm Nghien ciru vd Trien khai Cdng ngh? Buc xg 202A Dudng 11, P Linh xudn Q Thu DOc, Tp Ho Chi Minh Email: ngnguyetdieu@gmaH.com Abstract: B3 dosimeter is a thin film with average thickness of 0.0194 mm, which is supplied by the Gex Company from the United States This dosimeter was influenced by many factors: light, temperature, humidity during and after irradiation process In fact, B3 film dosimeters will be stable under certain conditions such as tightly sealed packs, controlled irradiation and stored temperature after irradiated Therefore, investigation of the stability effect of postirradiated B3 film dosimeters on the heating temperature, heating time and storing time is carried out before the absorbed dose is read and followed standard reading procedures When exposed to ionizing radiation, the dosimeters change from colorless to colour The absorbed doses are read on a Genesys 20 Spectrophotometer at a wavelength of 544 nm Absorbed dose range is investigated from 0.55 to 80 kGy Experimental results were indicated that colour stability of the postirradiated dosimeters at a temperature of 65± 3°C for 30 minutes and keeping them in desiccator for minutes before read out Under these conditions, colour stability of B3 film dosimeter has maintained for months Tdrklwa: chieu xg dn dinh, gamma, lieu ke dgng phim I Gl6l THIEU Lieu ke dang phim B3 dupe san xuit boi Cong ty Gex - Hoa Ky Cdng ty Gex cung cap lieu ke phim B3 va h$ lieu hoan chinh, sau da thuc bien nhieu cai tien chdt lugng qua trinh san xuat va dong goi sdn phdm, nhihig cdi tien lien tuc mang lal ket qua cao va giam sai so qua trinh chieu xg ciing nhu dgc lieu Lieu ke dupe dtuig de xac djnh lieu hap thu buc xa nguon gamma va tia dien tu dua tren dp chuyen mau tiep xiic voi biic xg ion hoa Lieu ke phim B3 c6 kich thuoc nho ggn, \k dgng mang mong eo dg day trung binh 0,0194 mm, phdn cau tao la hon 90% PVB, lgi la chdt mau, chat mau lieu ke co cdu tnic ben la hexa (hydroxyethyl) amino triphenyl acetonitril Lieu ke co tinh on dinh truoc va sau chieu xa, co dp hap thu gdn giong voi nuoc Lieu ke dang phim B3 chiu tac dgng cua nhieu yeu to nhu nhiet do, dp am va thoi gian luu sau chieu xa Sau chieu xa, lieu ke dugc sdy va li dieu ki6n nhiet dp va thoi gian thich hop nham 6n dinh mdu cho lieu ke Vi vay, ngi dung cua bai bao la: khdo sat tuong quan giiia lieu hap thu, th6i gian sdy, nhiet dp sdy va thoi gian lim anh huong din 6n dinh mau cua lieu ke II THUC NGHIEM Chuan bj lieu ke Lilu kl phim B_3 nhay vdi dnh sdng va dp dm, do tnr6c chieu xa lilu kl cdn dugc bao bi kin Tai moi lieu chilu tuong iing voi moi khodng nhi?t va thoi gian sdy khdo 372 Hdi nghi Khoa hgc vd Cdng nghi hgt nhdn todn qudc idn thir IX Ninh Thudn 18-19 sat cdn chuan bi lieu ke, cac lieu ke dupe dat cimg mgt vj tri chilu xa tren nguQn gamma Co-60 Sii dung lieu ke bac dicromat chieu kem vd so sanh voi lieu kl phim ChiSu xa Trong suot qua trinh chieu xa lieu ke phim B3 bi anh hudng bed cdc yeu nhu: d6 Sm anh sang va nhiet Do dm 30-70% khong ^ih budng den hap thu lilu ciia lilu kl; nhiSt dp se tac dpng gay sai so 2% tai khoang Heu tir 20 kGy trd len doi vdi chieu xa gamma va vdi chieu xa tia dien tii la tii 40 kGy Sau chieu xa, lieu ke phim B3 ciing chiu nhieu yeu to tac dgng: anh sang, nhiSt d5, dp dm, thdi gian luu lieu ke va thiet bi De xac dinh su on dinh mau ciia lilu kl sau chilu xa tai cac lilu 3,8, 10,2, 15,6, 19,1 kGy tren ngu6n gamma Co-60, sudt lilu 1,2 kGy/gio; da tien hanh khao sat moi tucmg quan giiia lieu hap thu, thoi gian say va nhiet dp sdy; moi tuong quan giiVa nhiet dp say vd thdi gian luu III KET QUA VA BAN LUAN \ Anh huorng cua nhiet say va thoi gian say lieu ke sau chieu xa den ket qua lieu Lieu ke dugc chieu xa tren nguon gamma Co-60 tai 3,8, 10,2, vd 15,6 kGy Sau chieu xa, lieu ke dupe say d cac nhiet dp khac nhau: 60, 65, 70, 75°C nhiing khoang thdi gian: 5, 10, 15, 20, 25, 30, 35 phut Sau say lieu ke dugc cho vao binh but dm phiit trude tren mdy quang ke Genesys 20 tai buoc song 544 nm (hinh 1) Hinh 2, va cho thdy moi tuong quan giiia ket qua lieu hap thu vdi thdi gian say lieu ke tai cac nhiet dp khac nhau, co the nhan thay tai nhiet dp say 65''C gia tri dugc ve lieu hap thu ciia Heu ke dat cao nhdt Nhu vay khoang nhiet dp 65±3°C va thdi gian sdy 30 phiit la thich hgp de xii ly lieu ke sau ehiSu xa nham dam bdo dp on djnh mau cho Heu ke 10 15 Hinh May quang phd ke Genesys 20 20 25 Thdi gian say, phut Hinh Mdi tuang quan giira kit qud liiu hdp thu vd thdi gian sdy liiu ki sau chiiu xg 3,8 kGy tgi nhiet khdc Hgi nghj Khoa hgc vd Cdng ngh? hgt nhdn todn qudc lan thir IX, Ninh Thudn 18-19/8/2011 373 Thdi gian sdy, phiit Hinh Mdi tuong quan giUa kit qud lieu hdp thM va thdi gian sdy liiu ki sau chieu xg 10,2 kGy tgi nhiet dg khdc Thdi gian say, phut Hinh Moi tuang quan giiia kit qud liiu hdp thu vd thai gian sdy liiu ki sau chiiu xg 15.6 kGy tgi nhiet dg khdc D9 on djnh cua lilu ke sau say Lilu ke dupe chilu xa tai 3,8, 10,2, 19,1 kGy tren nguon gamma Co-60, sudt lilu 1,2 kOy/gid Sau chilu xa, lilu k l dugc sdy tai 60 °C 30 phiit, dupe bao kin va luu d nhiet dp phong 28-30'^C khodng thdi gian tuong iing nhiet dp nay, k i t qua lilu cho thdy lieu kl phim B3 van tri dp 6n dinh ciia gia tn sau thang luu (bang 3,4, 5) 374 Hdi nghi Khoa hgc vd Cdng nghe hgt nhdn toan qudc lin thi IX, Ninh Thudn 18-19 Bdng Kit qud lieu hdp thu theo thai gian luu cita liiu ki duac chiiu xa 3,8 kGv Thcri gian uu, thang N^^ Ket qua dgc Nji^u, kGy Ma so \, 406B 3,7 ±0,010 3,7 ±0,010 3,7 ±0,010 3,7±0,010 397A 3,8 ±0,000 3,8 ± 0,000 3,8 ± 0,000 3,8 ± 0,000 397B 3,7 ± 0,020 3,7 ± 0,020 3,8 ± 0,022 3,7 ± 0,020 406A 4,0 ± 0,005 4,0 ± 0,005 3,9 ±0,010 4,0 ± 0,005 404A 3,8 ± 0,000 3,8 ±0,005 3,8 ± 0,005 3,8 ±0,005 lieu ke \, Bdng Ket qud lieu hdp thu theo thai gian luu cua lieu ke duac chieu xg 10,2 kGy \ ^ K6t qua dpc Thai gian !iru, thang Njieu, kGy Ma so \^ lieu ke \ 039B 9,9 ±0,010 9,9 ±0,010 9,9 ±0,010 9,9±0,0i0 004B 10,1 ±0,010 10,1 ±0,010 10,1 ±0,010 10,1 ±0,010 426A 9,5 ± 0,020 9,5 ± 0,020 9,5 ± 0,020 9,5 ± 0,020 039A 10,3±0,015 10,2 ±0,020 10,3 ±0,015 10,3 ±0,015 427A 10,2 ±0,020 10,2 ±0,020 10,2 ±0,020 10,2 ±0,020 Bdng Ket qud liiu hdp thu theo thai gian luu cua lieu ke duac chieu xg 19,1 kGy \, Thcri gian luu, thang Ket qua doc \ l i e u , kGy 409A 19,3 ±0,010 19,3 ±0,010 19,3 ±0,010 19,3 ±0,010 409B 18,8±0,016 18,9 ±0,018 18,8 ±0,016 18,8 ±0,016 400A 18,8±0,016 18,8 ±0,016 18,8 ±0,016 18,8 ±0,016 400B 18,8 ±0,016 18,8 ±0,016 18,9 ±0,016 18,8±0,016 398A 19,2 ±0,005 19,0 ±0.005 19,0 ±0.005 19,2 ±0,005 Ma so \, lieu k6 N Hgi nghi Khoa hgc vd Cdng ngh? hgt nhdn todn qudc Idn thir IX Ninh Thudn 18-19/8/2011 375 Lilu kl phim B3 tilp xiic vdi biic xa ion hoa se chuyen tir khong co mau sang mau hong, lieu hap thu cang cao d6 mdu cua lilu ke cang dam (hinh 5) IV KET LUAN Lilu ke phim B3 co day lieu chiSu rong, dugc diing de lieu hap thu cua biic xa gamma va tia dien tii De dam bao dp ben mau sau chieu xa, lieu ke phim dugc sdy (3 65±3''C vong 30 phiit va cho vao binh OkGy 3,8 kGy 10 kGy 15 6kGv 19 kGy hill dm phiit trude lieu hap thu tren Hinh Dg thay ddi mdu ciia lieuce mdy quang ke Genesys 20 chieu xg Lieu ke phim B3 tri dp on djnh mau sau thang dieu kifn bdo quan tai 28-30°C TAI LIEU THAM KHAO [1] Martin J Butso, Peter K.N Yu, Tsang Cheung, Peter Metcalfe, "Radiochromic film for medical radiation dosimetry", Mater Sci Eng, R41, 61-120,2003 [2] A Miller, W Batsberg, W Karman, "A new radiochromic thin-film dosimeter system" Radiation Physics and Chemistry, Volu Radiat Phys Chem 31,491-496, 1988 [3] Atef A Abdel-Fattah, Ame Miller, "Temperature, humidity and time Combined effects on radiochromic film dosimeters", Radiat Phys Chem 47, 611-621, 1996 [4] Chappas W J., "Temperature and humidity effects on the response of radiochromic dye films", Radiat Phys Chem 18, 1017-1021, 1981 [51 Janovsky and Mehta K., "The effects of humidity on the response of radiochromic film dosimeters FWT-60-00 and GafChromic-DM-1260" Radiat Phys Chem 43, 407-409, 1994 ... la tii 40 kGy Sau chieu xa, lieu ke phim B3 ciing chiu nhieu yeu to tac dgng: anh sang, nhiSt d5, dp dm, thdi gian luu lieu ke va thiet bi De xac dinh su on dinh mau ciia lilu kl sau chilu xa... 20 chieu xg Lieu ke phim B3 tri dp on djnh mau sau thang dieu kifn bdo quan tai 28-30°C TAI LIEU THAM KHAO [1] Martin J Butso, Peter K.N Yu, Tsang Cheung, Peter Metcalfe, "Radiochromic film for... huorng cua nhiet say va thoi gian say lieu ke sau chieu xa den ket qua lieu Lieu ke dugc chieu xa tren nguon gamma Co-60 tai 3,8, 10,2, vd 15,6 kGy Sau chieu xa, lieu ke dupe say d cac nhiet dp