Calibration of 125I seeds at Mexico City altitude
Introduction.Several publications had indicated the fail of conventional correction for air density kTP to x rays 1,2,for low energy 3,4 and 60Co photons 5 in dosimetry measurements with ionization chamber;therefore,it is necessary employ an additional correction factor for air density corrections kPT.Objectives.(1).-To calibrate 125I seeds in terms Sk - for interstitial brachytherapy to treatment of prostate cancer- with and without this additional factor kPT.(2).- To show that Sk values of a sample seeds are statistically equal within the relative expanded uncertainty ±7% (k=2) specify by the manufacturer.Method.(1) Nine 125I seeds,Amersham model 6711 are calibrated on Sk with an ionization well chamber traceable to Wisconsin University,following AAPM recommendations 6.(2) The Tukeys ANOVA mean and ANOM test 7 are used to demonstrate the hypothesis H0: That Sk mean values –without the additional correction– are statistically equal.Also is used the capability sixpack test (between/within) to verify the uncertainty claimed for the manufacturer,8,9.Results.The kPT=1.3287±0.0047 and kPT= 0.8966±0.0022,both for air density condition of 23.9 oC and 76.76 kPa;therefore (kPT)total=1.1913±0.0052 which is less 10.8% than the conventional kPT.For α=0.05 is rejected the H0,the mean test shows that the manufacturers Sk value is inaccuracy 4% above the Sk great mean value with the kPT conventional correction-,nevertheless that uncertainty is consistent with the uc=3.5% established.Conclusions.The application of conventional kPT overestimates the Sk values for the environment conditions of the Mexican upland.The ANOVA mean test is a quality tool to accomplish the recommendations of the report 59 10 to verify the manufacturers Sk value.
LDR brachytherapy air density correction 125I seed Tukey test uncertainty analysis
J.T. álvarez Romero O. Hernández-Oviedo Víctor M. Tovar-Mu(n)oz
ININ, Ionizing Radiation Metrology Department, SSDL, La Marqueza, México 52750 ABC Medical Center, Cancer Center, Mexico City, México 01120
国际会议
World Congress on Medical Physics and Biomedical Engineering (2012年医学物理及生物医学工程国际会议(IFMBE))
北京
英文
1758-1760
2012-05-26（万方平台首次上网日期，不代表论文的发表时间）