X-ray imaging

An X-ray scanning apparatus for locating a contaminant in a product, the apparatus comprising:

• means for generating an X-ray image of the product;
• means for assigning a grey scale value to a plurality of pixels;
• means for identifying a plurality of suspect pixels, wherein a pixel of the plurality of pixels is identified as a suspect pixel if the pixel has a grey value that exceeds a predetermined grey value;
• means, which for each suspect pixel:
• selects two neighbouring pixels in a first direction lying on opposed sides of the suspect pixel and determines which of the first direction pixels has the lowest grey value;
• selects two neighbouring pixels in a second direction lying on opposed sides of the suspect pixel and determines which of the second direction pixels has the lowest grey value;
• determines a first direction difference value by taking the grey value difference between the lowest grey value first direction pixel and the grey value of the suspect pixel;
• determines a second direction difference value by taking the grey value difference between the lowest grey value second direction pixel and the grey value of the suspect pixel;
• determines a first direction score from the first direction difference value, wherein the first direction score is weighted based at least in part on the first direction difference value and a first ratio between the predetermined grey value and the lowest grey value of the first direction pixels;
• determines a second direction score from the second direction difference value, wherein the second direction score is weighted based at least in part on the second direction difference value and a second ratio between the predetermined grey value and the lowest grey value of the second direction pixels;
• compares said scores with a threshold value;
• and
• identifies the suspect pixel as representing a contaminant if said threshold value is exceeded.