Comparision Of Dosimetry In Four Different External Irradiation Techniques For The Radical Radiotherapy Of Cervical Cancer

Objective:to evaluate the differences and merits of dosimetry in patients treated with Conventional radiotherapy(CR)、3D-CRT、IMRT and IMAT for radical radiotherapy of cervical cancer and to provide a reasonable approach to clinical treatment.Meterials and Method:A total of14patients with cervical cancer receiving radiotherapy (RT) were evaluated. All patients were training strictly to adapt to bladder control. Planning CT and MRI were performed in a state of filling the bladder and emptying the rectum. And sent to the TPS station to do digital image reconstruction. The target and the organs at risk were delineated and the treatment planning of four different irradiation techniques were accomplished by the same medical team. PTV was delieved46Gy/23f. The plans were compared in terms of dose distribution、dose volume histograms (Dose Volume Histogram, DVH)、 the maximum dose (Dmax), the minimum dose (Dmin), the mean dose (Dmean), conformal index (Comformal Index, CI), homogeneity index (Homogeneity Index, HI) of PTV、the volume and dose of organs at risk (rectum, bladder, intestines, bilateral femoral head),and the isodose distribution required. Results:1. The comparison of dose distribution of four different external irradiation in cross-section, sagittal-section and coronal-section showed that IMRT and IMAT is better than the CR and3D-CRT when PTV reached to46Gy. IMRT and IMAT have reduced the volume of irradiated rectum and bladder, while the conventional radiotherapy and3D-CRT were not; the bilateral femoral head were irradiated by46Gy partly, while the other techniques were not.2. For the conventional radiotherapy, the Dmax (4877.34±69.2cGy), Dmin (2030.54±492.11cGy), Dmean (4595.25±115.74cGy) were different respectively (P<0.0001), when compared to the other three irradiation techniques:3D-CRT (5036.21±31.55cGy,3816.52±192.04cGy,4809.47±20.82cGy), IMRT (5065.02±53.84cGy,3817.43±356.17cGy,4769.66±29.14cGy), IMAT (4971.65±117.63cGy,4415.29±213.15cGy,4754.07±72.37cGy); IMAT were different respectively compared to3D-CRT and IMRT (P<0.0001);3D-CRT and IMRT showed no difference respectively (P>0.05).3. The CI of IMRT and IMAT were0.64±0.1and0.65±0.17, better than conventional radiotherapy (0.1±0.06) and3D-CRT (0.32±0.06), respectively (P<0.0001).4. The HI of four different irradiation techniques showed no difference respectively (P=0.233).5. The irradiation of OARs by conventional radiotherapy was significantly higher than the other three techniques, respectively (P <0.05), Especially the V46, V4o, V35. And IMRT and IMAT were significantly better than3D-CRT respectively (P<0.05). IMRT and IMAT showed no difference in OARs respectively, except for V25(P>0.05).6. IMRT and IMAT showed significantly difference in machine hops respectively (1488.86mu vs625.64mu, P<0.001).Conclusion:1. IMRT and IMAT showed superior in dosimetry, target conformality and OARs when compared to conventional radiotherapy and3D-CRT. It is saying that IMRT and IMAT applied to clinical treatment is a reasonable approach.2. IMAT showed no superior in the target conformality, uniformity and OARs when compared to IMRT, but its hops is less than IMRT, this made treatment time shorter.