| Objective:To provide some references for the radiotherapy plan design of the postoperative recurrence of rectal cancer patients by analyzing the dose characteristics of three dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT)Methods:From the first affiliated hospital of DaLian medical university, we were choosing fifteen cases recurrenced of colorectal cancer resection (Dixon) and giving pelvic radiation therap.In order to filling of bladder and imaging the intestine clearly, the fifteen patients were asked to urinate one hour before imaging, drunk1000ml water (including14ml contrast agent).After then kept the patients in prostration,arms crossed on the forehead, filt the American MED-TEC fixed plate under the body, fixed the chest with the hot forming body membrane on the positioning plate, marked in body surface and body and the membrane.Depicting the gross target volumes, clinical target volumes and risky organs on the images.3F3D-CRT,5F3D-CRT and5F IMRT plans were performed for every target area of patients.all the plans in our study have not been given the additional dose for sequential or simultaneous irradiation.the prescribed dose for every plan was2Gy/time of irradiation,5time/week,25times, the total dose of50Gy.Prescription dose was set95%of PTV acceptable dose and the limited dose of risky organs were V50of bladder <50%, V50of small intestines<10%and V50of bilateral femoral head<5%.We evaluated these plans with the dose-volume histograms and dose curve.The main parameters were CI (Conformity Index) and HI (homogeneity index), Dmax, Dmean of PTV, Dmax, V50of small intestines, Dmax, V50of bladder, Dmean and V50of bilateral femoral head.Results:1.The target dose distribution:all the plans in our study have not been given the additional dose for sequential or simultaneous irradiation. Among them,5F IMRT plan contains50Gy covered the least normal tissue while the3F3D-CRT plan covered the most.2. PTV main parameters:three kinds of programs, five field IMRT,5and3wild3D-CRT plans CI values were0.83±0.021,0.72±0.053and0.69±0.046.5target of IMRT conformal field better than3D-CRT program, the differences were statistically significant (P<0.05).5field IMRT,5and3wild wild3D-CR T3D-CRT plans HI values were1.05±0.017,1.12±0.032and1.15±0.056,5f ield IMRT plan target dose uniformity better than3D-CRT plans, the differences were statistically significant (P<0.05).3Wild3D-CRT meter and5wild3D-C RT plans than five wild3D-CRT plans target dose uniformity better than3wild scheme, the difference was statistically significant (P=0.045); while three wild3D-CRT meter and5wild3D-CRT plans to target conformal there was no sig nificant difference (P=0.603).3.Organs at risk parameters:three group plans organs at risk by volume in line with normal tissue radiation tolerance dose limits.5field IMRT plan small intestine, bladder, bilateral femoral head V50were lower than three wild3D-CR T plans and five wild3D-CRT, differences were statistically significant (P<0.05).3Wild3D-CRT plans and five wild3D-CRT pelvic organs at risk there wer e no significant dosimetric advantage.Conclusions:1.5field IMRT plan, and two3D-CRT plans than five wild IMRT plans C I and HI values closer to1, the target dose conformal degrees and better unifor mity.2.3Wild3D-CRT and five3D-CRT compared to five wild3D-CRT’s target dose uniformity better than3wild plan and target conformal did not differ sign ificantly.3.IMRT and3D-CRT plans compared to the pelvic organs at risk can signi ficantly reduce the volume of high-dose irradiation. The three wild wild3D-CRT and five3D-CRT compared with no significant differences in dosimetry.4.This study is limited to theoretical dosimetry studies in actual clinical radiation therapy, the choice of treatment plans for each patient should also re fer to other clinical factors, the results of this study need to be further confir med by a large number of clinical studies. |
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