Lesion determination apparatus, similar case searching apparatus, lesion determination method, similar case searching method, and non-transitory computer-readable storage medium

A lesion determination apparatus comprising:

• an image set acquiring unit configured to acquire a tomography image set containing a plurality of tomography images of an object part;
• an operation instruction receiving unit configured to receive a first operation instruction to view tomography images included in the plurality of tomography images in a first order in which a tomography image position number for identifying each of the tomography images increases, and a second operation instruction to view tomography images included in the plurality of tomography images in a second order in which the tomography image position number decreases;
• a number-of-images acquiring unit configured to acquire and record, on occurrence of a direction change that is either a first state in which the second operation instruction is received immediately after receipt of the first operation instruction or a second state in which the first operation instruction is received immediately after receipt of the second operation instruction, a number of one-directionally viewed images that is either a number of tomography images continuously viewed in response to continuous first operation instructions including the first operation instruction contained in the first state or a number of tomography images continuously viewed in response to continuous second operation instructions including the second operation instruction contained in the second state;
• and
• a locality determining unit configured to determine whether the object part is a focal lesion or a diffuse lesion based on a change in the number of one-directionally viewed images,
• wherein the tomography image position number is assigned such that a tomography image of a tomographic slice plane closer to a particular portion of the object part has a smaller tomography image position number.