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Objective: To evaluate the CT image reconstruction field of view (Field of View, FOV) and the size of the dose calculation and volume assessment of radiation treatment planning may exist. Methods: the original CT scan data of 16 patients with nasopharyngeal carcinoma patients to line 45cm routine the FOV and 65cm extended FOV (Extended Reconstructed FOV, EFOV) reconstruction and transfer to the radiation treatment planning system, all cases were in the regular FOV reconstruction of CT images outlined tumor volume (Gross Tumor Volume, GTV), clinical target volume (Clinical Target Volume, CTV) and the brain stem, crystal, parotid gland, spinal cord and other organs at risk, and to develop the wild isometric dynamic IMRT plans (GTV prescription dose 70Gy). Two reconstruction method of image after the fusion of the coordinate manner in accordance with the medical digital image communication 3.0 standard (DICOM 3.0), copies of the target area on the image of the conventional FOV and endanger the organ to EFOV image, and the treatment plan the image EFOV, treatment planning centers transplanted to two images of the same types of reconstruction methods DICOM coordinates, dose-volume histograms (Dose-Volume Histogram, DVH) tool to calculate the GTV, CTV and brain stem, crystal, parotid, the volume of the spinal cord, the maximum dose Dmax, the average dose in the image of the two reconstruction methods Dmean and minimum dose Dmin, paired t-test for statistical analysis of the two sets of data. Into the group of patients in each treatment plan 7 wild to import conventional 45cm the conventional reconstruction FOV and 65cm EFOV of two-dimensional the flux diagram validation equipment Mapchek 1175 motif from the agreement (Distance to the Agreement, DTA) analysis 5cm depth plane absolute The pass rate between the dose calculated and measured results, paired t-test analysis of the treatment program on the two sets of images 1 to 7 wild pass rate. The result: two reconstruction methods image GTV, CTV target and brainstem, crystal, parotid gland, spinal cord and other organs at risk volume difference was statistically significant, group of patients of all income target volume and organs at risk in conventional FOV image are greater than the volume of the EFOV image. Smaller crystal maximum dose Dmax differences between conventional the FOV and EFOV image was statistically significant (t = -3.14, P lt; 0.007) the rest of the target volume and organs at risk were no significant differences in the maximum dose Dmax . CTV, GTV average dose Dmean on in EFOV images larger than the FOV image, and the difference between the two was statistically significant (CTV: t = -6.45, P lt; 0.001; the GTV: t = -5.65, P lt; 0.001 ), endangering the average organ dose Dmean not statistically significant. Target volume and organs at risk minimum dose Dmin no statistical significance (P gt; 0.05). Two reconstruction methods image was no significant difference between the seven portal through rate of the treatment plan. Conclusion: Evaluation of image reconstruction FOV size for the target volume and organs at risk volume and dose calculation in radiotherapy CT simulation process results and treatment plan; observe and verify the two-dimensional the flux diagram by rate, both between the difference was not significant.
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