Energy subtraction processing method and apparatus

Claim 2

An energy subtraction processing method, comprising the steps of: i) obtaining frequency signals, each of which is of one of a plurality of different frequency bands and which have been obtained by transforming each of a plurality of image signals into a multi-resolution space, each of the plurality of the image signals representing one of a plurality of radiation images of a single object and being made up of a series of image signal components, the plurality of the radiation images of the single object having been formed respectively with a plurality of kinds of radiation having different energy distributions, different images of at least part of the object being embedded in the plurality of the radiation images, ii) weighting the signal components of the frequency signals, which are of an identical frequency band and correspond to different image signals among the plurality of the image signals, with weight factors, which are set in accordance with the frequency band, said signal components of said frequency signals representing corresponding picture elements in frequency images represented by said frequency signals, iii) subtracting the weighted signal components of said frequency signals from one another, which signal components represent corresponding picture elements in said frequency images represented by said frequency signals, a difference signal being thereby obtained for said identical frequency band, iv) carrying out said weighting and subtracting operations for each of the plurality of the different frequency bands, a plurality of difference signals being thereby obtained, and v) carrying out an inverse transform on said difference signals having been obtained for the plurality of the different frequency bands, an energy subtraction signal being thereby obtained.

Claim 3

A method as defined in claim 1 wherein said transform of each of the plurality of the image signals into the multi-resolution space is carried out with a technique selected from the group consisting of a Laplacian pyramid technique, a wavelet transform, and a sub-band transform.

Claim 4

A method as defined in claim 1 wherein each of the plurality of the radiation images has been stored on a stimulable phosphor sheet.

Claim 5

A method as defined in claim 3 wherein each of the plurality of the image signals representing the plurality of the radiation images is obtained by exposing each stimulable phosphor sheet to stimulating rays, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation, and photoelectrically detecting the emitted light.

Claim 6

A method as defined in claim 1 wherein each of the plurality of the radiation images has been recorded on photographic film.

Claim 7

An energy subtraction processing apparatus, comprising: i) a storage means for storing frequency signals, each of which is of one of a plurality of different frequency bands and which have been obtained by transforming each of a plurality of image signals into a multi-resolution space, each of the plurality of the image signals representing one of a plurality of radiation images of a single object and being made up of a series of image signal components, the plurality of the radiation images of the single object having been formed respectively with a plurality of kinds of radiation having different energy distributions, different images of at least part of the object being embedded in the plurality of the radiation images, ii) a subtraction processing means for weighting the signal components of the frequency signals, which are of an identical frequency band and correspond to different image signals among the plurality of the image signals, with weight factors, which are set in accordance with the frequency band, said signal components of said frequency signals representing corresponding picture elements in frequency images represented by said frequency signals, said subtraction processing means subtracting the weighted signal components of said frequency signals from one another, which signal components represent corresponding picture elements in said frequency images represented by said frequency signals, a difference signal being thereby obtained for said identical frequency band, said subtraction processing means carrying out said weighting and subtracting operations for each of the plurality of the different frequency bands, a plurality of difference signals being thereby obtained, and iii) an inverse transform means for carrying out an inverse transform on said difference signals having been obtained for the plurality of the different frequency bands, an energy subtraction signal being thereby obtained.

Claim 8

An energy subtraction processing apparatus, comprising: i) a storage means for storing frequency signals, each of which is of one of a plurality of different frequency bands and which have been obtained by transforming each of a plurality of image signals into a multi-resolution space, each of the plurality of the image signals representing one of a plurality of radiation images of a single object and being made up of a series of image signal components, the plurality of the radiation images of the single object having been formed respectively with a plurality of kinds of radiation having different energy distributions, different images of at least part of the object being embedded in the plurality of the radiation images, ii) a subtraction processing means for weighting the signal components of the frequency signals, which are of an identical frequency band and correspond to different image signals among the plurality of the image signals, with weight factors, which are set in accordance with the frequency band, said signal components of said frequency signals representing corresponding picture elements in frequency images represented by said frequency signals, said subtraction processing means subtracting the weighted signal components of said frequency signals from one another, which signal components represent corresponding picture elements in said frequency images represented by said frequency signals, a difference signal being thereby obtained for said identical frequency band, said subtraction processing means carrying out said weighting and subtracting operations for each of the plurality of the different frequency bands, a plurality of difference signals being thereby obtained, and iii) an inverse transform means for carrying out an inverse transform on said difference signals having been obtained for the plurality of the different frequency bands, an energy subtraction signal being thereby obtained.

Claim 9

An apparatus as defined in claim 6 wherein said transform of each of the plurality of the image signals into the multi-resolution space is carried out with a technique selected from the group consisting of a Laplacian pyramid technique, a wavelet transform, and a sub-band transform.

Claim 10

An apparatus as defined in claim 6 wherein each of the plurality of the radiation images has been stored on a stimulable phosphor sheet.

Claim 11

An apparatus as defined in claim 8 wherein each of the plurality of the image signals representing the plurality of the radiation images is obtained by exposing each stimulable phosphor sheet to stimulating rays, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation, and photoelectrically detecting the emitted light.

Claim 12

An apparatus as defined in claim 6 wherein each of the plurality of the radiation images has been recorded on photographic film.