Pulmonary nodule detection in a chest radiograph

A method of detecting pulmonary nodules from a chest radiograph, the method comprising the steps of:

• producing a map of a clear lung field;
• correcting for non-uniform X-ray illumination and body thickness variation by removing low frequency variation from the clear lung field to generate a level image;
• setting a region outside of the clear lung field in the level image to code values that are low relative to the code values in the clear lung field;
• performing at least one grayscale morphological operation on the level image using a grayscale morphological filter to generate a nodule-bone image comprising a bone image subtracted from a nodule image, comprising:
• performing a first grayscale morphologic operation on the level image using a nodule template to generate a nodule image;
• performing a second grayscale morphologic operation on the level image using a bone template to generate a bone image;
• and
• subtracting the bone image from the nodule image to generate the
• nodule-bone image;
• identifying candidate nodule locations in the nodule-bone image;
• segmenting a region around each candidate nodule location in the nodule-bone image;
• and
• using features of the segmented region to determine if a candidate is a nodule.

A method of generating a pulmonary nodule image from a chest radiograph, the method comprising the steps of:

• producing an image of a clear lung field using a mask;
• correcting for non-uniform X-ray illumination and body thickness variation by removing low frequency variation from the clear lung field to generate a level image;
• performing at least one grayscale morphological operation on the level image using a grayscale morphological filter to generate a nodule image;
• performing at least one grayscale morphological operation on the level image to generate a bone image;
• and
• generating a nodule-bone image.