Method of compressing a dynamic range for a radiation image

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg in accordance with an absolute value of a signal difference between a central pixel and a peripheral pixel, both said central pixel and said peripheral pixel being positioned within a mask region;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation
• Sproc=Sorg+f(Sus)

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg in accordance with a positional relation between a central pixel and a peripheral pixel, both said central pixel and said peripheral pixel being positioned within a mask region;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation;
• Sproc=Sorg+f(Sus)

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• displaying said original image corresponding to said original image signal Sorg on a display device;
• determining a compression rate and a compression region based on said original image;
• determining a function based on said compression rate and said compression region based on an equation:
• Dproc=Dorg+f(Dus)
• wherein:
• Dproc represents a density of the processed image signal
• Dorg represents a density of said original image displayed on said display device;
• and
• f(Dus) is a correction value which is a function that decreases as Dus increases
• transforming said density of the processed image signal Dproc, said density of said original image Dorg, and said correction value f(Dus) by use of a gradation conversion table which was determined by said original image signal Sorg;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg;
• obtaining a function based on an equation;
• Sproc=Sorg+f(Sus)
• wherein f(Sus) is a correction value that decreases as said unsharp mask signal Sus increases;
• and f(Sus) is obtained by transforming said correction value f(Dus) based on said gradation conversion table;
• and
• performing a processing operation based on said equation.

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation:
• Sproc=Sorg+f(Sus)
• wherein:
• said correction value f(Sus) has a positive maximum value at a point where said unsharp mask signal Sus has a predetermined value;
• and
• said correction value f(Sus) monotonically decreases as said unsharp mask signal Sus increases in a region where said unsharp mask signal Sus is greater than said predetermined value;
• and
• said correction value f(Sus) has a value that is monotonically decreasing as said unsharp mask signal Sus is one of decreasing and fixed to said positive maximum value in a region where said unsharp mask signal Sus is less than said predetermined value.

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation:
• Sproc=Sorg+f(Sus)
• wherein:
• said correction value f(Sus) has a negative maximum value at a point where said unsharp mask signal Sus has a predetermined value;
• said correction value f(Sus) monotonically decreases as said unsharp mask signal Sus increases in a region where said unsharp mask signal Sus is less than said predetermined value;
• and
• said correction value f(Sus) has a value that monotonically increases when said unsharp mask signal Sus is one of increasing and fixed to said negative maximum value in a region where said unsharp mask signal Sus is greater than said predetermined value.

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation:
• Sproc-Sorg+f(Sus)
• wherein:
• said correction value f(Sus) has a positive maximum value at a point where said unsharp mask signal Sus has a first predetermined value and has a negative maximum value at a point where said unsharp mask signal Sus has a second predetermined value greater than said first predetermined value;
• said correction value f(Sus) monotonically decreasing as said unsharp mask signal Sus increases in a region where said unsharp mask signal Sus is greater than said first predetermined value and is less than said second predetermined value;
• and wherein:
• said correction value f(Sus) has a value that monotonically decreases as said unsharp mask signal Sus is one of decreasing and fixed to the position maximum value in a region where said unsharp mask signal Sus is less than said first predetermined value;
• and
• said correction value f(Sus) has a value that monotonically increases as said unsharp mask signal Sus is one of fixed to said negative maximum value and is increasing in a region where said unsharp mask signal Sus is greater than said second predetermined value.

The dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• selecting a region of said object to be processed;
• determining a correction function F among a plurality of correction functions in accordance with said selected region to be processed;
• and
• conducting an operation based on an equation:
• Sproc=Sorg+F

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of:

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg by using a median value among a plurality of signal values in a mask region;
• obtaining a correction value f(Sus) which is a function that decreasing as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation:
• Sproc=Sorg+f(Sus)

A dynamic range compression method for a radiographic image, for obtaining a processed image signal Sproc having a dynamic range which is narrower than a dynamic range of an original image signal Sorg, the method comprising the steps of

• obtaining the original image signal Sorg representing the original image based on a radiation transmitted through an object;
• detecting an information of said object;
• obtaining an unsharp mask signal Sus corresponding to said original image signal Sorg, wherein at least one of a type of said unsharp mask signal Sus and a mask size of said unsharp mask signal Sus which are provided for obtaining said unsharp mask signal Sus, is determined in accordance with said information of said object;
• obtaining a correction value f(Sus) which is a function that decreases as said unsharp mask signal Sus increases;
• and
• conducting an operation based on an equation:
• Sproc=Sorg+f(Sus)