Fat mass derivation device, fat mass derivation method, and fat mass derivation program

A fat mass derivation method comprising:

• deriving a fat mass distribution of a subject from a first radiation image and a second radiation image acquired by imaging the subject with radiation having different energy distributions;
• deriving a visceral fat mass distribution of the subject based on a shape of the fat mass distribution in a cross section orthogonal to a body axis of the subject;
• deriving the fat mass distribution of the subject from the first radiation image and the second radiation image acquired by imaging the subject from a front surface or a rear surface;
• deriving the visceral fat mass distribution by separating the fat mass distribution into a subcutaneous fat mass distribution and the visceral fat mass distribution based on minimum points of the fat mass distribution and symmetry of the fat mass distribution;
• detects both end points of the fat mass distribution;
• detects maximum points that first appear in a case in which the fat mass distribution is traced inward from the end points;
• sets a center line which bisects the end points or the maximum points;
• sets correspondence points corresponding to the minimum points at a position symmetrical with respect to the center line;
• connects the end points, the maximum points, the minimum points, and the correspondence points with line segments;
• in a case in which the two line segments intersect with the minimum point and the correspondence point at an upwardly convex angle, excludes the minimum point and the correspondence point and connects the minimum point and the correspondence point with the line segment again;
• repeats connecting processing until there are no intersecting line segments at the upwardly convex angle;
• approximates remaining minimum points and correspondence points between the maximum points with a curve;
• and
• derives the fat mass distribution above the curve in the fat mass distribution as the visceral fat mass distribution.

A non-transitory computer-readable storage medium that stores a fat mass derivation program causing a computer to execute:

• a procedure of deriving a fat mass distribution of a subject from a first radiation image and a second radiation image acquired by imaging the subject with radiation having different energy distributions;
• a procedure of deriving a visceral fat mass distribution of the subject based on a shape of the fat mass distribution in a cross section orthogonal to a body axis of the subject;
• a procedure of deriving the fat mass distribution of the subject from the first radiation image and the second radiation image acquired by imaging the subject from a front surface or a rear surface;
• a procedure of deriving the visceral fat mass distribution by separating the fat mass distribution into a subcutaneous fat mass distribution and the visceral fat mass distribution based on minimum points of the fat mass distribution and symmetry of the fat mass distribution;
• a procedure of detecting both end points of the fat mass distribution;
• a procedure of detecting maximum points that first appear in a case in which the fat mass distribution is traced inward from the end points;
• a procedure of setting a center line which bisects the end points or the maximum points;
• a procedure of setting correspondence points corresponding to the minimum points at a position symmetrical with respect to the center line;
• a procedure of connecting the end points, the maximum points, the minimum points, and the correspondence points with line segments;
• in a case in which the two line segments intersect with the minimum point and the correspondence point at an upwardly convex angle, a procedure of excluding the minimum point and the correspondence point and connecting the minimum point and the correspondence point with the line segment again;
• a procedure of repeating connecting processing until there are no intersecting line segments at the upwardly convex angle;
• a procedure of approximating remaining minimum points and correspondence points between the maximum points with a curve;
• and
• a procedure of deriving the fat mass distribution above the curve in the fat mass distribution as the visceral fat mass distribution.