Objective To dosimetrically compare three delivery techniques of VMAT,IMRT and 3D-CRT in the treatment of accelerated partial breast irradiation (APBI).Methods Twenty patients with T1/2N0M0breast cancer were treated with VMAT.These cases were subsequently re-planned using static gantry IMRT and 3D-CRT technology to evaluate dosimetric differences.Dosimetric parameters including dose conformity index (CI),dose volume histogram (DVH) analysis of normal tissue coverage,dose parameters of PTV and normal tissues were evaluated,the delivery parameters including MU and delivery time were also analyzed.Results The IMRT and VMAT plans provided lower maximum dose,better mean dose and more conformal target dose distributions than the 3D-CRT plans (F =14.86,8.57,18.23,P ＜0.05).The volume of ipsilateral breast receiving 5 Gy for VMAT technique was significantly less than that of3D-CRTor IMRT(F=5.83,P＜0.05).The ipsilateral lung volume receiving 20 Gy (V20),5 Gy(V5) and the 5％ volume dose (D5) of IMRT were superior to those of 3D-CRT and VMAT(F =16.39,3.62,4.81,P ＜ 0.05).The low volume dose distributions of D5 in contralateral lung for IMRT was better than that of VMAT and 3D-CRT(F =3.99,3.43,P ＜ 0.05).The total mean MUs for VMAT,3D-CRT and IMRT were 621.0 ± 111.9,707.3 ± 130.9 and 1161.4 ± 315.6,respectively (F =31.30,P ＜ 0.05).The average machine delivery time was(1.5 ± 0.2)min for the VMAT plans,(7.0 ± 1.6)min for the 3D-CRT plans and (11.5 ± 1.9)min for the IMRT plans.Conclusions VMAT and IMRT techniques offer improved dose conformity as compared with 3D-CRT techniques without increasing dose to the ipsilateral lung.In terms of MU and delivery time,VMAT is more efficient for APBI than conventional 3D-CRT and static beam IMRT.

Objective To evaluate the effect of pretreatment with calcipotriol on protoporphyrin Ⅸ (PpIX) content in the normal epithelium of nude mice after topical application of aminolevulinic acid (ALA).Methods A total of 36 BALB/C nude mice were randomly and equally divided into 2 groups:calcipotriol + ALA group topically pretreated with calcipotriol ointment for 3 days followed by topical application of ALA,and ALA group topically treated with ALA alone.At 2,3,4,5,6 and 7 hours after ALA application,3 mice in each group were sacrificed separately,and skin tissues were obtained from the experimental region in the back of mice.A fluorospectrophotometer was used to detect the PpIX content in the normal epithelial tissue of the nude mice,and an inverted fluorescence phase-contrast microscope to observe the fluorescence intensity and distribution of PpIX in the frozen sections of epithelial tissues.Results During 2-8 hours after topical application of ALA,the content of PpIX in the skin tissues of nude mice in the two groups gradually increased over time.Correlation analysis revealed no correlations between the PpIX content in the ALA group and the treatment duration (r =0.451,P =0.369),while the PpIX content in the calcipotriol + ALA group was strongly correlated with the treatment duration (r =0.913,P =0.011).The PpIX content in the ALA group reached a peak at 5 hours [(461.24 ± 43.45) ng/g tissues],while the PpIX content in the calcipotriol + ALA group peaked at 6 hours [(668.88 ± 42.46) ng/g tissues].At 2,3,4,5,6 and 7 hours after ALA application,the PpIX content was significantly higher in the calcipotriol + ALA group than in the ALA group (P ＜ 0.05 or 0.01).Frozen-section examination showed that PpIX was diffusely distributed in the epidermis and dermis of the nude mice,and the fluorescence intensity of PpIX was higher in the calcipotriol + ALA group than in the ALA group at 5,6 and 7 hours after ALA application.Conclusion Pretreatment with calcipotriol can increase the content of PpIX in the normal epidermis and dermis of nude mice after topical application of ALA,which provides a theoretical basis for the clinical application of calcipotriol as a local synergist of ALA-PDT.