Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-08-28
2001-07-31
Powell, Mark R. (Department: 2779)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S182000, C358S452000
Reexamination Certificate
active
06268870
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image display method, image display apparatus and image-based diagnostic apparatus. More particularly, the invention relates to an image display method, image display apparatus and image-based diagnostic apparatus capable of making the image display swiftly responsive to the operator's action of altering the window level and/or window width.
FIG. 7
is a block diagram showing the principal portion of a conventional image-based diagnostic apparatus. The image-based diagnostic apparatus
500
consists of an X-ray TV
20
which produces an X-ray transparency image of a subject body and evaluates pixels of the image, and an image display apparatus
50
which displays an image based on the values of pixels.
The image display apparatus
50
includes an operation panel
51
used by the operator, with window level alteration keys
1
a
for altering the window level WL and window width alteration keys
1
b
for altering the window width WW being laid out, a window setting circuit
52
which initializes a lookup table (LUT)
3
based on the default window level WL
0
and default window width WW0 and also revises the entire contents of LUT
3
in accordance with an immediate window level WL and window width WW inresponse to the operation of a window level alteration key la and/or window width alteration key
1
b
, the LUT
3
which converts pixel values of an X-ray transparency image into values for display, and a display device
4
such as a CRT display device.
FIG. 8A
shows window C
1
having window level WL1 and window width WW1, and
FIG. 8B
shows the contents of LUT
3
for the window C
1
.
This LUT
3
converts pixel values ranging from “−32768” to “32768” into display values ranging from “0 (black)” to “255 (white)”.
In
FIG. 8A
, the window level WL1 indicates the center pixel value of the range of pixel values to be converted into display values of “1” to “254” between the minimum display value “0” and the maximum display value “255”. The window width WW1 indicates the width of the conversion range.
In
FIG. 9A
, when the operator operates a window level alteration key
1
a
and window width alteration key
1
b
to alter the window level from WL1 to WL2 and alter the window width from WW1 to WW2, the window setting circuit
52
revises the entire contents of LUT
3
in accordance with the new window level WL2 and window width WW2.
FIG. 9B
show the contents of LUT
3
for window C
2
.
The foregoing conventional technique is disclosed in Japanese Patent Laid-open Publication No. Hei-8-7074, for example.
As described above, the conventional image display apparatus
50
or image-based diagnostic apparatus
500
is designed to revise the entire contents of LUT
3
in response to the operator's action of altering the window level and/or window width.
However, it takes a long time for the LUT
3
to revise 65536 pieces of data, and therefore the image display cannot respond swiftly to the alteration of the window level and/or window width.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image display method, image display apparatus and image-based diagnostic apparatus capable of making the image display swiftly responsive to the operator's action of altering the window level and/or window width.
In the first viewpoint, the invention resides in an image display method for displaying an image on a screen by converting values of pixels into values for display based on a conversion table, wherein in revising the contents of conversion table in response to the operator's action of altering at least one of the window level which indicates the center pixel value of the range of pixel values to be converted into display values between the minimum display value and the maximum display value and the window width which indicates the width of the conversion range, the conversion table is revised only in the range from a start point &agr; to an end point &bgr; calculated as follows, instead of the revision of the entire contents of conversion table:
&agr;=max{Rmin, min(WL1−WW1/2, WL2−WW2/2)} (1)
&bgr;=min{Rmax, max(WL1+WW1/2, WL2+WW2/2)} (2)
where max{ } is the function of selecting the maximum value, min{ } is the function of selecting the minimum value, Rmin is the lower limit of the revision range, Rmax is the upper limit of the revision range, WL1 is an original window level, WW1 is an original window width, WL2 is a new window level, and WW2 is a new window width.
In the image display method of the first viewpoint, the conversion table is revised only in its revision range from the start point &agr; to the end point &bgr;, instead of the entirety. Generally, the smallest pixel value appearing in an image is larger than the minimum pixel value in the LUT and the largest pixel value of the image is smaller than the maximum pixel value of the LUT, and therefore there arises no problem practically when the smallest pixel value of the image is set to the lower limit Rmin of revision range and the largest pixel value of the image is set to the upper limit Rmax of revision range. Consequently, the revision range of LUT is narrowed significantly to the range from the lower limit Rmin to the upper limit Rmax at most. (It will be narrowed much more depending on the values of WL1, WW1, WL2 and WW2.) Accordingly, the time expended for revising the LUT can be reduced significantly, and it becomes possible to make the image display swiftly responsive to the alteration of window level and/or window width.
In the second viewpoint, the invention resides in an image display apparatus for displaying an image on a screen by converting values of pixels into values for display based on a conversion table, wherein the apparatus includes an operation means which is used by the operator for altering at least one of the window level which indicates the center pixel value of the range of pixel values to be converted into display values between the minimum display value and maximum display value and the window width which indicates the width of the conversion range, and a window setting means which revises the contents of conversion table only in its range from a start point &agr; to an end point &bgr; calculated as follows, instead of the revision of the entire contents of conversion table, in response to the operator's action of altering the window-level and/or window width:
&agr;=max{Rmin, min(WL1−WW1/2, WL2−WW2/2)}
&bgr;=min{Rmax, max(WL1+WW1/2, WL2+WW2/2)}
where max{ } is the function of selecting the maximum value, min{ } is the function of selecting the minimum value, Rmin is the lower limit of the revision range, Rmax is the upper limit of the revision range, WL1 is an original window level, WW1 is an original window width, WL2 is a new window level, and WW2 is a new window width.
The image display apparatus of the second viewpoint can carry out the image display method of the first viewpoint properly.
In the third viewpoint, the invention resides in an image-based diagnostic apparatus which produces an image of a subject body and converts values of pixels of the image into values for display based on a conversion table and displays the image on a screen, wherein the apparatus includes an operation means which is used by the operator for altering at least one of the window level which indicates the center pixel value of the range of pixel values to be converted into display values between the minimum display value and maximum display value and the window width which indicates the width of the conversion range, and a window setting means which revises the contents of conversion table only in its range from a start point &agr; to an end point &bgr; calculated as follows, instead of the revision of the entire contents of conversion table, in response to the operator's action of altering the window level and/or win
GE Yokogawa Medical Systems Limited
Harrison Chante E.
Kojima Moonray
Powell Mark R.
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