Radiographic imaging system

A radiographic imaging system for reconstructing a tomographic image in a given cross section of a subject from projection images of a subject acquired in tomosynthesis imaging, the radiographic imaging system comprising:

• a frequency filtering processor for producing band limiting image signals having different frequency response characteristics from projection image signals corresponding to the projection images;
• a non-linear conversion processor for performing non-linear conversion of the band limiting image signals according to non-linear conversion characteristics in which conversion coefficients for a portion of the band limiting image signals exceeding a first given value is smaller than conversion coefficients for a portion of the band limiting image signals not exceeding the first given value;
• an integration processor for adding up the band limiting image signals having undergone non-linear conversion through the non-linear conversion processor to produce converted image signals;
• a back projection processor for reconstructing the tomographic image in the given cross section of the subject from the converted image signals corresponding to the projection images;
• wherein the back projection processor is adapted to reconstruct the tomographic image from the converted images,
• the radiographic imaging system further comprising:
• a similarity calculator for calculating a similarity between pixels of the converted images cumulatively added to a same position in the tomographic image;
• a weighting coefficient calculator for calculating weighting coefficients that increase with the similarity for each of the pixels of the tomographic image;
• and
• a multiplication processor for multiplying pixel values of the pixels of the tomographic image by corresponding weighting coefficients to produce a multiplication-processed image.

A radiographic imaging system for reconstructing a tomographic image in a given cross section of a subject comprising:

• a radiation detector for acquiring a plurality of projection images of the subject taken at discrete different angles of radiation in tomosynthesis imaging and for outputting a plurality of projection-image signals corresponding to the plurality of projection-images;
• a frequency filtering processor for producing a plurality of band-limited image signals having different frequency bands from each projection-image signal of the plurality of projection-image signals;
• a non-linear conversion processor for performing a first non-linear conversion of the band-limited image signals of each projection-image signal according to multiplying first non-linear conversion coefficients to each value of the band-limited image signals, wherein the first non-linear conversion coefficients for each value exceeding a first given value in each band-limited image signal of the plurality of band-limited image signals is smaller than each value not exceeding the first given value of the band-limited image signal;
• an integration processor to produce a converted image signal corresponding to each projection-image signal, by adding up each band-limited image signal transformed by the non-linear conversion processor;
• and
• a back projection processor for reconstructing the tomographic image in the given cross section of the subject from the plurality of converted image signals corresponding to the projection-images.

A radiographic imaging system for reconstructing a tomographic image in given cross section of a subject comprising:

• a radiation detector for acquiring a plurality of projection images of subject taken at discrete different angles of radiation in tomosynthesis imaging and outputting a plurality of projection-image signals corresponding to the plurality of projection-images;
• a filtering processor which converts each projection-image signal of the plurality of projection-image signals into each filtering-processed projection-image signal;
• a non-linear conversion processor for performing a third non-linear conversion of the filtering-processed projection-image signal to produce each converted-image signal of a plurality of converted-image signals;
• a back projection processor for reconstructing the tomographic image in the given cross section of the subject from the plurality of the converted-image signals;
• wherein the filtering processor converts through Fourier-transform each projection image signal, of the plurality of projection-image signals, into each frequency image signal composed of a plurality of frequency components, enhances high-frequency components in each frequency image signal, and converts through inverse-Fourier-transform the each high frequency enhanced image signal into each filtering-processed projection-image signal;
• and
• wherein the non-linear conversion processor multiplies third non-linear conversion coefficients to each value of filtering-processed projection-image signal, and the third conversion coefficients for each value exceeding a fourth given value in each filtering-processed projection-image signal of the plurality of filtering-processed projection-image signals, corresponding to each projection-image signal, is smaller than the each value not exceeding the fourth given value of the filtering-processed projection-image signals.