The Malaysian Journal of Analytical Sciences Vol 16 No 2 (2012): 142 – 147
STABILITY OF THE ABSORBED DOSE TO WATER CALIBRATION COEFFICIENT, ND,w FOR THERAPY LEVEL IONIZATION CHAMBERS BELONGING TO LOCAL RADIOTHERAPY CENTRES: ANALYSIS OF RESULTS OBTAINED DURING 2004 -2010
(Kestabilan Pekali Kalibrasi Dos Terserap Terhadap Air, ND,w Untuk Kebuk Pengionan Tahap Terapi Kepunyaan Pusat Radioterapi Tempatan: Analisis Keputusan Yang Diperoleh Sepanjang 2004-2010)
S. B. Samat1*, W. Priharti1, S. S. Chong1, T. Kadni2 and M.T. Dolah2
1School of Applied Physics,
Faculty of Science and Technology, Universiti Kebangsaan Malaysia
43600 UKM Bangi, Selangor
2Secondary Standard Dosimetry Laboratory (SSDL)
Malaysian Nuclear Agency (Nuclear Malaysia)
43000 Kajang, Selangor
*Corresponding author: sbsamat@ukm.my
Abstract
According to the IAEA, the calibration of therapy level ionization chambers in terms of absorbed dose to water calibration coefficient, ND,w must be within ± 1.5% acceptance limit. This is for the purpose of getting accurate absorbed dose for the patient undergoing radiotherapy treatment. The objective of this work is to evaluate the deviation of ND,w for 29 chambers belonging to 16 local radiotherapy centres. Eight types of chambers have been calibrated at the SSDL Laboratory of Malaysian Nuclear Agency for the period of seven years. The mean µ of the ND,w deviation together with its standard error (SE) and standard deviation σN-1 were calculated. It is found that out of 29 chambers, 26 chambers yielded µ ± SE within the permitted value of ± 1.5%. For the other three chambers, despite their values of µ ± SE lie slightly outside the range of ± 1.5%, they are still within the 95% confident interval of the ± 1.5%. It is concluded that the ND,w of the chambers belonging to the local radiotherapy chambers are stable in their performance the dose to the patients measurement.
Keywords: absorbed dose to water calibration coefficient ND,w, local radiotherapy centres, percentage deviation, SSDL Malaysia, stability of ND,w
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