Lesion area dividing device, medical image diagnostic system, lesion area dividing method, and non-transitory computer-readable medium storing program

1. A lesion area dividing device comprising:

hardware, including a processor and memory;

a rectangle creating unit implemented at least by the hardware and configured to create a rectangle circumscribing a lesion area in a medical image;

a division-number-ratio calculating unit implemented at least by the hardware and configured to calculate a ratio of an image aspect ratio of an input image to be input to a device configured to identify a lesion to a rectangle aspect ratio between a length in a vertical direction and a length in a horizontal direction of the rectangle, as a division-number ratio of a number of divisions in a vertical direction to a number of divisions in a horizontal direction when a rectangular image encircled by the rectangle and including the lesion area is divided;

a multiplying-factor calculating unit implemented at least by the hardware and configured to calculate, based on the division-number ratio, a resizing multiplying-factor for each of the vertical direction and the horizontal direction of the rectangular image;

a resizing unit implemented at least by the hardware and configured to resize the rectangular image with the resizing multiplying-factor; and

a dividing unit implemented at least by the hardware and configured to divide the resized rectangular image into one or more images in such a manner that a size in the vertical direction of each divided image matches a size in the vertical direction of the input image and a size in the horizontal direction of each divided image matches a size in the horizontal direction of the input image,

wherein the multiplying-factor calculating unit, by a calculation method which differs depending on a magnitude of the division-number ratio with respect to a threshold determined based on a predetermined upper limit value of a number of divisions,

calculates a number of divisions in the short-side direction based on the upper limit value and the division-number ratio,

calculates, based on the upper limit value and the number of divisions in the short-side direction, the division-number ratio of the rectangular image after resizing in such a manner that the number of divisions in the vertical direction and the number of divisions in the horizontal direction of the rectangular image after the resizing do not exceed the upper limit value, and

calculates, based on a comparison of the division-number ratio after resizing with 1, sizes in the vertical direction and in the horizontal direction of the rectangular image and sizes in the vertical direction and in the horizontal direction of the input image, the resizing multiplying-factor for resizing the rectangular image in the vertical direction and in the horizontal direction in such manner that the resized rectangular image does not include any residual portion other than a rectangle having the size of the input image.

2. The lesion area dividing device according to claim 1 , wherein the multiplying-factor calculating unit sets, when the division-number ratio calculated by the division-number-ratio calculating unit is less than a first threshold that is less than 1 and that is predetermined depending on the upper limit value, the number of divisions in the horizontal direction of the rectangular image after the resizing as the upper limit value to calculate, based on the upper limit value, the resizing multiplying-factor for the horizontal direction of the rectangular image after the resizing.

3. The lesion area dividing device according to claim 1 , wherein the multiplying-factor calculating unit sets, when the division-number ratio calculated by the division-number-ratio calculating unit is equal to or greater than a second threshold that is greater than 1 and that is predetermined depending on the upper limit value, the number of divisions in the vertical direction of the rectangular image after the resizing as the upper limit value to calculate, based on the upper limit value, the resizing multiplying-factor for the vertical direction of the rectangular image after the resizing.

4. The lesion area dividing device according to claim 1 , wherein the multiplying-factor calculating unit sets, when the division-number ratio calculated by the division-number-ratio calculating unit is equal to or greater than a first threshold that is less than 1 and that is predetermined depending on the upper limit value and is less than a second threshold that is greater than 1 and that is predetermined depending on the upper limit value, the number of divisions in the horizontal direction and the number of divisions in the vertical direction of the rectangular image after the resizing to be equal to each other.

5. A medical image diagnostic system comprising:

a lesion area dividing device configured to divide a lesion area in a medical image; and

a lesion identifying device configured to identify a lesion using the divided lesion area,

wherein the lesion area dividing device comprises:

hardware, including a processor and memory;

a rectangle creating unit implemented at least by the hardware and configured to create a rectangle circumscribing the lesion area;

a division-number-ratio calculating unit implemented at least by the hardware and configured to calculate a ratio of an image aspect ratio of an input image to be input to a device configured to identify a lesion to a rectangle aspect ratio between a length in a vertical direction and a length in a horizontal direction of the rectangle, as a division-number ratio of a number of divisions in a vertical direction to a number of divisions in a horizontal direction when a rectangular image encircled by the rectangle and including the lesion area is divided;

a multiplying-factor calculating unit implemented at least by the hardware and configured to calculate, based on the division-number ratio, a resizing multiplying-factor for each of the vertical direction and the horizontal direction of the rectangular image;

a resizing unit implemented at least by the hardware and configured to resize the rectangular image with the resizing multiplying-factor; and

a dividing unit implemented at least by the hardware and configured to divide the resized rectangular image into one or more images in such a manner that a size in the vertical direction of each divided image matches a size in the vertical direction of the input image and a size in the horizontal direction of each divided image matches a size in the horizontal direction of the input image,

wherein the multiplying-factor calculating unit, by a calculation method which differs depending on a magnitude of the division-number ratio with respect to a threshold determined based on a predetermined upper limit value of a number of divisions,

calculates a number of divisions in the short-side direction based on the upper limit value and the division-number ratio,

calculates, based on the upper limit value and the number of divisions in the short-side direction, the division-number ratio of the rectangular image after resizing in such a manner that the number of divisions in the vertical direction and the number of divisions in the horizontal direction of the rectangular image after the resizing do not exceed the upper limit value, and

calculates, based on a comparison of the division-number ratio after resizing with 1, sizes in the vertical direction and in the horizontal direction of the rectangular image and sizes in the vertical direction and in the horizontal direction of the input image, the resizing multiplying-factor for resizing the rectangular image in the vertical direction and in the horizontal direction in such manner that the resized rectangular image does not include any residual portion other than a rectangle having the size of the input image, and

wherein the lesion identifying device is configured to identify a lesion using each divided image.

6. A lesion area dividing method performed by a computer and comprising:

creating a rectangle circumscribing a lesion area in a medical image;

calculating a ratio of an image aspect ratio of an input image to be input to a device configured to identify a lesion to a rectangle aspect ratio between a length in a vertical direction and a length in a horizontal direction of the rectangle, as a division-number ratio of a number of divisions in a vertical direction to a number of divisions in a horizontal direction when a rectangular image encircled by the rectangle and including the lesion area is divided;

calculating, based on the division-number ratio, a resizing multiplying-factor for each of the vertical direction and the horizontal direction of the rectangular image;

resizing the rectangular image with the resizing multiplying-factor; and

dividing the resized rectangular image into one or more images in such a manner that a size in the vertical direction of each divided image matches a size in the vertical direction of the input image and a size in the horizontal direction of each divided image matches a size in the horizontal direction of the input image,

wherein calculating the resizing multiplying-factor of the rectangular image the multiplying-factor comprises, by a calculation method which differs depending on a magnitude of the division-number ratio with respect to a threshold determined based on a predetermined upper limit value of a number of divisions,

calculating a number of divisions in the short-side direction based on the upper limit value and the division-number ratio,

calculating, based on the upper limit value and the number of divisions in the short-side direction, the division-number ratio of the rectangular image after resizing in such a manner that the number of divisions in the vertical direction and the number of divisions in the horizontal direction of the rectangular image after the resizing do not exceed the upper limit value, and

calculating, based on a comparison of the division-number ratio after resizing with 1, sizes in the vertical direction and in the horizontal direction of the rectangular image and sizes in the vertical direction and in the horizontal direction of the input image, the resizing multiplying-factor for resizing the rectangular image in the vertical direction and in the horizontal direction in such manner that the resized rectangular image does not include any residual portion other than a rectangle having the size of the input image.

7. The lesion area dividing method according to claim 6 , further comprising setting, when the calculated division-number ratio is less than a first threshold that is less than 1 and that is predetermined depending on the upper limit value, the number of divisions in the horizontal direction of the rectangular image after the resizing as the upper limit value to calculate, based on the upper limit value, the resizing multiplying-factor for the horizontal direction of the rectangular image after the resizing.

8. The lesion area dividing method according to claim 6 , further comprising setting, when the calculated division-number ratio is equal to or greater than a second threshold that is greater than 1 and that is predetermined depending on the upper limit value, the number of divisions in the vertical direction of the rectangular image after the resizing as the upper limit value to calculate, based on the upper limit value, the resizing multiplying-factor for the vertical direction of the rectangular image after the resizing.

9. The lesion area dividing method according to claim 6 , further comprising setting, when the calculated division-number ratio is equal to or greater than a first threshold that is less than 1 and that is predetermined depending on the upper limit value and is less than a second threshold that is greater than 1 and that is predetermined depending on the upper limit value, the number of divisions in the horizontal direction and the number of divisions in the vertical direction of the rectangular image after the resizing to be equal to each other.