Cardia Three-dimensional Conformal Intensity-modulated Radiotherapy Dosimetry

Objectives: To assess the dose distribution by three dimensional conformal treatment planning system (TPS) for intensity modulated radiation therapy (IMRT) and three dimensional conformal radiation therapy (3D-CRT) and conventional radiation therapy (RT) for cardia cancer.Methods: CT images of ten patients were studied. IMRT, 3D-CRT and RT treatment plannings were done with TPS. The prescription dose was 4500cGy. The differences of target dose and organs at risk dose were compared with DVH.Results: The mean dose received by planning target volume (PTV ) of RT,3D-CRT and IMRT were 4338.48±115.17,4475.77±113.50,4558.22±21.02cGy (P=0.015,0.000,0.174)respectively; the mean dose received by gross tumor volume (GTV ) were 4349.75±114.67,4540.86±95.71,4658.92±52.51cGy(P=0.001,0.000,0.037);The average dose of PTV in the three dimensional conformal plan and in the intensity modulated plan is significantly increased , compared with the conventional plan. The average dose of GTV in the intensity modulated plan increases more significantly than in the three dimensional conformal plan. The mean dose received by liver were 559.47±223.29,1130.14±221.02,751.72±297.51 cGy(P=0.000,0.154,0.003).Compared with the conventional plan, the percentage of irradiated volume in high dose of liver is decreased in the three dimensional conformal pan and the percentage of irradiated vloume in low dose and the mean dose of liver are increased at the same time. But the percentage of irradiated volume in high dose of liver is decreased in the intensity modulated plan and the average dose of live isn't increased,compared with the conventional plan. The largest dose of spinal cord were 4478±176.828,1668.41±701.28,1087.93±557.88cGy(P=0.000,0.000,0.027);and the largest dose of heart were 4544.72±343.218,3733.147±139.121,3049.908±1775.403 cGy(P=0.170,0.07,0.247). The largest dose of spinal cord and heart are both significantly reduced in the three dimensional conformal plan and in the intensity modulated plan, but the maximum dose of the spinal cord is more reduced in the latter than the former.Conclusion :The IMRT is better than 3D-CRT and RT in dose distribution.