The Dosimetry Comparison Between Intensity Modulated Arc Radiation(IMRT) And Intensity Modulated Radiation Therapy (IMRT) In Limited And Mid-high Risk Prostate Cancer

Objective:To investigate the advantages and disadvantages from the aspect of dosimetry and treatment efficiency in limited and mid-high risk prostate cancer using Intensity modulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT)respectively.Methods:Choose clinical data of11patients in limited and mid-high risk prostate cancer from April2011and December2013in our hospital. Under the same planning system,each patient was drawn out two radiotherapy plans of intensity-modulated arc and fixed field intensity-modulated radiation therapy (IMRT) plans respectively. We use the isodose curve and dose volume histogram (DVH) to evaluate and compare the two kinds of plans. Comparison was done with respect to dosimetry parameters,it included related parameters of target,organs at risk and normal tissue. In addition,the total monitor units (MU) and total treatment time (T) are all taken into account in the comparison of this two radiotherapy technologyResults:In this study, comparison of the target dose parameters: PTV1PTV2, conformal index (CI) IMAT plan is better than that of IMRT plan, differences were statistically significant (P<0.05), and Homogeneity index (HI) has no statistically significant difference (P>0.05). PTV1, PTV2on Dmax, Dmin,Dmean all had no statistical significance (P>0.05). Comparison of the organs at risk dose parameters:for rectum Dmax, rectum V70, IMRT is superior to the IMAT, the difference has statistical significance (P<0.05). The others,such as rectum V50, small intestine Dmax, bladder Dmax, bladder V50, L-femoral head Dmax, L-femoral head V50, results are similar in two kinds of plan, and have no statistical significant difference. Dose difference has statistical significance of rectum V40,R-femoral head Dmax, R-femoral head V50, and IMAT is better than that plan of IMRT(P<0.05). Comparison of the normal tissue dose parameters:V5, V10, V15differences had no statistical significance (P>0.05), and for V20, V25, V30, V35, V40, V45, V50differences had statistical significance (P<0.05). Comparison of the monitor units for phasel (S1), MUIMRT=1706.57+/-260.97, MUIMRT=749.00+/-154.94, the IMAT than IMRT plans an average of957fewer (56%), difference has statistical significance (P<0.05). For phase2(S2), MUIMRT=1105+/-197.77, MUIMRT=836.29+/-166.31, the IMAT than IMRT plans an average of269fewer (24%), difference has statistical significance (P<0.05). Comparison of the total treatment time:in a general way, one-arc plan needs about70-90seconds, two-arc plan needs about3minutes, however, a IMRT plan needs about15minutes.Conclusion:Compared with IMRT plan, the conformal index of target in IMAT plan is improved, the rest parameters of the target appeared no obvious difference,the dose of organs at risk are similar and the dose of normal tissue are significantly reduced. In addition, the IMAT program can significantly reduce the total monitor units and the total treatment time.