Sains Malaysiana 38(2): 203-207(2009)

Variation Of Beam Quality Correction Factor With Time: Cases For Ne2571 And Ne2581 Chambers In The 6 And 10 Mv X-Rays Beams

 (Perubahan Faktor Pembetulan Kualiti Dengan Masa: Kes Untuk Kebuk

Ne 2571 Dan Ne 2581 Dalam Alur Sinar-X 6 Dan 10 Mv)

S. B. Samat and S. X. Too

School of Applied Physics, Universiti Kebangsaan Malaysia (UKM)

43600 UKM Bangi, Selangor, Malaysia

T. Kadni and M.T. Dolah

Secondary Standard Dosimetry Laboratory (SSDL)

Malaysian Nuclear Agency (Nuclear Malaysia), 43000 Kajang, Selangor

Malaysia

Received:    4 June 2008 / Accepted:   30 July 2008

ABSTRACT

The values of beam quality correction factor k_Q that were experimentally determined from year 2002 to 2008 were analysed. As k_Q is the function of ionization chamber and beam quality, the analysis were based on three cases namely (a)  k_Q(NE2571, 6 MV x-rays) that were determined from 17 measurements in the duration of 69 months at 6 radiotherapy centres, (b) k_Q(NE2571, 10 MV x-rays) from 7 measurements in the duration of 12 months at one radiotherapy centre,  and (c) k_Q(NE2581, 6 MV x-rays) from 5 measurements in the duration of 5 months also at one radiotherapy centre.   The purpose is to examine, in each case,  the variation k_Q for all the measurements. In other words, to see variation k_Q with time. Results obtained are 0.993(NE2571, 6 MV),  0.986(NE2571, 10 MV) and 0.986(NE2581, 6 MV).   This shows that in each case, despite the difference in the experimental data in getting k_Q for all measurement, k_Q remains constant with time. Reasons for this are explained. 

Keywords: variation of k_Q; ionization chamber; NE2571;  NE2581; 6 MV x-rays; 10 MV x-rays

ABSTRAK

Nilai faktor pembetulan kualiti k_Q yang ditentukan secara eksperimen dari tahun 2002 hingga 2008 dianalisis. Disebabkan k_Q adalah fungsi kepada kebuk pengionan dan kualiti alur, analisis dijalankan berdasarkan tiga kes berikut: (a)  k_Q(NE2571, sinar-x 6 MV) yang ditentukan dari 17 pengukuran dalam tempoh 69 bulan di 6 pusat radioterapi, (b) k_Q(NE2571, sinar-x 10 MV) dari 7 pengukuran dalam tempoh 12 bulan di satu pusat radioterapi, dan (c) k_Q(NE2581, sinar-x 6 MV) dari 5 pengukuran dalam tempoh 5 bulan juga di satu pusat radioterapi. Tujuan adalah untuk memeriksa, dalam setiap kes, perubahan bagi k_Q untuk semua pengukuran. Dengan perkatan lain, untuk melihat perubahan k_Q dengan masa. Keputusan yang diperoleh ialah 0.993(NE2571, 6 MV),  0.986(NE2571, 10 MV) dan 0.986(NE2581, 6 MV).   Ini menunjukkan dalam setiap kes, walaupun perbezaan dalam data eksperimen k_Q bagi semua pengukuran, k_Q tetap mempunyai nilai malar dengan masa. Sebab untuk ini dijelaskan. 

Kata kunci: perubahan; k_Q; kebuk pengionan; NE 2571; NE 2581; sinar-x 6 MV; sinar-x 10MV

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