Sains Malaysiana 38(2): 197-202(2009)

Absorbed Dose to Water Intercomparison Programme

for Radiotherapy Centres

(Program Antarabandingan Dos Terserap Kepada Air

Untuk Pusat Radioterapi)

S. B. Samat & S. X. Too

School of Applied Physics, Universiti Kebangsaan Malaysia (UKM)

43600 UKM Bangi, Selangor

T. Kadni & M.T. Dolah

Secondary Standard Dosimetry Laboratory (SSDL)

Malaysian Nuclear Agency (Nuclear Malaysia)

43000 Kajang, Selangor

Received:   8 May 2008 / Accepted:  20 June 2008

ABSTRACT

The importance of intercomparison programme for radiation therapy dose delivery at radiotherapy centres (RC) has widely been reported. We at Nuclear Malaysia Agency (NM) intend to develop a national level intercomparison programme in terms of absorbed dose to water D_w. We started with one RC which has voluntered to participate in the programme in the dose delivery of 6 MV x-ray beam. Two types of comparison were made to get the accuracy. Type I is based on the measured value of the D_w at reference depth, D_w(z_ref)_mea : RC results was compared with NM, in which NM results was taken as a standard. Type II is based on calculated value the D_w(z_ref), D_w(z_ref)_cal : both NM and RC results were compared with D_w(z_ref)_cal, in which D_w(z_ref)_cal was taken as a standard. Two on-site measurements were made at this centre to check for results consistency and to get the average accuracy. Results obtained were consistent for the two measurements and the average values in the accuracy are within the acceptable accuracy limit  of  ± 3%, namely Type I: 1.10 ± 0.58 % for the RC, and Type II: 0.99 ± 0.60 % and −0.11 ± 0.26% respectively for the RC and NM.

Keywords: Absorbed dose to water;  intercomparison programme;  radiotherapy centres

ABSTRAK

Kepentingan program antarabandingan untuk pemberian dos sinaran terapi di pusat radioterapi (RC) telah banyak dilaporkan.  Kami di Agensi Nuklear Malaysia (NM) berhasrat untuk membangunkan program antarabandingan peringkat kebangsaan dalam sebutan dos terserap kepada air D_w. Kami bermula dengan satu RC yang secara sukarela hendak menyertai program ini dalam pemberian dos alur sinar-x 6 MV. Dua jenis perbandingan dibuat untuk mendapatkan ketepatan. Jenis I berdasarkan nilai pengukuran D_w pada kedalaman rujukan, D_w(z_ref)_mea: keputusan RC dibandingkan dengan NM, dengan keputusan NM diambil sebagai standard. Jenis II berdasarkan nilai kiraan D_w(z_ref), D_w(z_ref)_cal : kedua-dua keputusan NM dan RC dibandingkan dengan D_w(z_ref)_cal, dengan mengambil D_w(z_ref)_cal sebagai standard. Dua pengukuran di tempat kajian dilakukan dipusat ini bagi tujuan penyemakan kekonsistenan dan mendapatkan purata ketepatan. Keputusan didapati adalah konsisten bagi dua pengukuran itu dan purata ketepatan berada di dalam had ketepatan yang diterima ± 3%, iaitu Jenis I: 1.10 ± 0.58 % untuk RC, dan Jenis II: 0.99 ± 0.60 % dan −0.11 ± 0.26% masing-masing untuk RC dan NM.

Kata kunci: Dos terserap kepada air;  program antarabandingan; pusat radioterapi

REFERENCES

Amat, A. 2006. Perbandingan Ketepatan dan Kepersisan Nilai Dos Terserap Kepada Air Ditentukan Dengan Protokol IAEA TRS-398 Dab AAPM TG-51 Pada Alur Sinar-X 6 MV. Tesis Sarjana Sains, Pusat Pengajian Fizik Gunaan, Universiti Kebangsaan Malaysia.

BJR. 1983. Central Axis Depth Dose Data For Use In Radiotherapy: A Survey Depth Dose And Related Data Measured In Water Or Equivalent Media, Supplement No: 17. London: The British Institute Of Radiology.

IAEA. 1997a. Absorbed Dose Determination In Photons And Electron Beams: An International Code Of Practice, TRS-277. Ed. 2. Vienna: International Atomic Energy Agency.

IAEA. 1997b. IAEA Certificate For Secondary Standard Ionization Chamber, Ref. No. MAL/INTER/97. Vienna: International Atomic Energy Agency.

IAEA. 2000. Absorbed Dose Determination In External Beam Radiotherapy: An International Code Of Practice For Dosimetry Based On Standards Of Absorbed Dose To Water, TRS-398. Vienna: International Atomic Energy Agency.

Izewska, J., Svensson, H. & Ibbott, G. 2002. Worldwide QA Networks For Radiotherapy Dosimetry. Proceedings Of An International Symposium On Standards And Codes Of Practice In Medical Radiation Dosimetry. Vol. 2: 139-155.

Samat, S.B., Too, S.X., Kadni, T. & Dolah, M.T. 2007. The Performance Stability Of  N_D,W Calibration Factor For Chambers Belonging To Local Radiotherapy Centres, Proceedings Of Malaysian Science And Technology Congress 2007 (MSTC 2007):172-177.

Too, S.X., Samat, S.B., Kadni, T. & Dolah, M.T. 2007. Procedures For D_w TRS-398 Intercomparison Programme Between Malaysian Radiotherapy Centres And SSDL Malaysia, Presented At Persidangan Fizik Kebangsaan 2007 (PERFIK 2007), Kuala Terengganu.

Wikipedia. 2008. Monitor Unit. Http://En.Wikipedia.Org/Wiki/Monitor_Unit. [28 April 2008].