Application of region-of-interest (ROI) method to industrial X-ray computed tomography

Summary form only given, as follows. Numerical simulations and experiments have confirmed that the shape of an object´s cross section is correctly reflected on the reconstructed image obtained by ROI mode computed tomography (CT). The shape information can be described as the second derivative of the projection data. It can be mathematically proved that any contribution from outside the ROI to this derivative is very small, and shape information is not affected by it. Experiments were carried out using a prototype industrial X-ray CT system. An iron test phantom of 200-mm diameter was used to compare the CT images of the ROI mode and entire mode. The ROI area was 1/64 of the entire area of the phantom, and the measuring time of the ROI mode was 1/8 of the entire mode. The reconstructed images binarized to intensify contours of the holes on the phantom show that the ROI mode CT can correctly reproduce the object´s shape in the ROI, and ROI mode CT can be applied to industrial CT without correction or interpolation of projection data