Image reconstruction, projection data evaluating method and X ray CT device

The method implemented even in the completely opposite situation data may be reconstructed from the projection data of good quality image of the portion of the scan, and X-ray CT image reconstruction may be performed such. In the image channel spacing measured projection data collection portion scanned on measured projection data does not exist in the data point A, with its mirror point A 'in the measured projection data to supplement form projection data of full scanning according full scan projection reconstructed image data, the point when the mirror a 'is not measured projection data, which by using a plurality of data near points B, C are measured projection data are interpolated data.