ObjectiveTo investigate the positioning error of esophageal carcinoma using the fan-beam online high energy X-ray computed tomography(MVCT), and analyze its influencing factors to provide a reference for clinical workers in CTV-PTV external spacing.
MethodsThe clinical data of the esophageal cancer patients treated with tomotherapy(TOMO) were investigated.The images obtained from the MVCT scan before treatment were registered with those from the simulated CT, and the errors in X(left and right), Y(head and foot), Z(abdomen and back) and ROLL(rotation along the cross section) were recorded and analyzed.
ResultsThe positioning errors of X, Z and ROLL directions in patients ≥ 70 years old were greater than those in patients < 70 years old(P < 0.01), and the difference of the positioning error of Y direction between two groups was not statistically significant(P>0.05).The results of positioning error in different directions showed that the positioning errors in the X-axis and Y-axis were mainly concentrated in 0-3 mm, while which in the Z-axis was mainly concentrated in 3.1-6 mm.The cross-sectional rotation error distributing in the interval 0°-, 1.1°-and 2.1°-were 537(88.2%), 62(10.2%) and 10(1.6%), respectively.The differences of the positioning errors in the X-axis and Z-axis were not statistically significant between body membrane fixation and cervical pleural fixation patients(P>0.05), and the positioning errors in the Y-axis and ROLL-axis in patients with body membrane fixation were greater than those in patients with cervical pleural fixation(P < 0.01).In the Y-axis direction, the positioning error of women was greater than that of men(P < 0.05), and there was no statistical significannce in the positioning errors of X, Z and ROLL directions between male and female(P>0.05).
ConclusionsDifferent fixation methods have advantages and disadvantages in treating esophagus.In delineating the distance outside the target area, clinicians should consider various factors of patients, such as age and gender.
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