The dependence ofNKRvs KR: the initial, thermal, volumetric recombination and screening effect on the efficiency of collected charges on the calibration of si hdr 1000 plus well chambers with192ir hdr sources

Biomed Phys Eng Express. 2022 Jan 17. doi: 10.1088/2057-1976/ac4c2a. Online ahead of print.

ABSTRACT

By using the statistical techniques of ANOVA: mean test and regression, it was found that the N_KRcalibration factor of Standard Imaging (SI) model HDR 1000 plus chambers presents a quadratic dependence with the reference air kerma rateK_R(from 6.9 mGy h^-1to 43.9 mGy h^-1). In order to understand and correct this dependency one model is presented for total recombination:k_s=I₃₀₀/I₁₅₀=1+k_ini+ k_d+k_volI₃₀₀+k_screenI₃₀₀², wherek_iniis the initial recombination,k_dthe thermal diffusion recombination,k_volthe volumetric recombination andk_screenthe screening for the currents/charges collected at the potential differences of 300 and 150 V. In conclusion, the total recombinationk_sis composed by onek_iniwith a constant contribution of 0.019%, onek_dcontribution of 0.017%, onek_volI₃₀₀contribution from 0.022% to 0.138%, and thek_screenI₃₀₀²effects from 0.002% to 0.09% in the range ofK_Rrate above. However, when this model fork_sis applied to try to correct the quadratic dependence of theN_KRvs K_R, explicitly there is no improvement in the variation range of 0.5% of theN_KRvs K_R.Nonetheless, it allows to obtainN_KRvalues consistent with a u_c≤ 0.7 %, which is less than 1.25% reported in the literature by ADCL or SSDL.

PMID:35039465 | DOI:10.1088/2057-1976/ac4c2a