APPLICATION OF X-RAY CT FOR DETECTION OF PHYSICAL FOREIGN MATERIALS IN FOODS

A medical X-ray CT scanner was used as a non-destructive inspection me thod for the detection of selected non-metallic materials embedded in various fluids and food materials. The X-ray absorption characteristic s of tested materials were expressed as X-ray CT numbers. It was found that the CT number of a foreign object was affected by a systemic err or (a point spread function), even if its size was greater than I pixe l in the video image provided by the scanner. Within the interface reg ion between the foreign object and its surrounding matrix, CT numbers were found to vary smoothly between characteristic values for the obje ct and the matrix thus pointing to important effects to consider when developing X-ray CT techniques for the detection and identification of foreign materials in foods. Specific threshold values for CT numbers of selected foodstuffs were defined for successful detection of foreig n materials. This study also pointed out the limitation of using X-ray linear absorption coefficients from typical CT systems to detect cert ain combination of foreign materials and foodstuffs.