[1] Univ Sains Malaysia, Sch Phys, Main Campus, Minden 11800, Penang, Malaysia
[2] Minist Hlth Malaysia, Perak State Dept, Jalan Panglima Bukit Gantang Wahab, Ipoh 30590, Perak, Malaysia
[3] Univ Putra Malaysia, Fac Sci, Dept Phys, Serdang 43400, Selangor, Malaysia
[4] Univ Diponegoro, Dept Phys, Jl Prof Soedarto, Sh Tembalang 50275, Semarang, Indonesia
[5] Minist Hlth Malaysia, Med Radiat Surveillance Div, Level 4,Blok E3,Kompleks E, Pusat Pentadbiran Keraja 62590, Wilayah Perseku, Malaysia