PROBLEM TO BE SOLVED: To provide a medical image alignment device, method, and program that are capable of accurately performing alignment of two medical images without increasing a processing time.SOLUTION: A medical image alignment device comprises: a frequency distribution acquisition unit 11 for acquiring a frequency distribution of density values of at least one medical image of a first medical image 5 and a second medical image 6 that are obtained by photographing the same subject； a gradation processing unit 12 for applying gradation processing, which enlarges the frequency distribution's part in a density range having the relatively large number of pixels included in a unit density width and reduces the frequency distribution's part in a density range having the relatively small number of pixels included in a unit density width, to the at least one medical image； and an alignment processing unit 13 for applying alignment processing, which associates the subject's anatomical position in the first medical image 5 with that in the second medical image 6, to the first medical image 5 and the second medical image 6, at least one of which has received the gradation processing.SELECTED DRAWING: Figure 1【課題】処理時間を増大させることなく、高精度に２つの医用画像の位置合わせを行うことができる医用画像位置合わせ装置および方法並びにプログラムを提供する。【解決手段】同一の被検体を撮影した第１の医用画像５および第２の医用画像６のうちの少なくとも一方の医用画像の濃度値の頻度分布を取得する頻度分布取得部１１と、頻度分布のうち単位濃度幅に含まれる画素数が相対的に多い濃度範囲の頻度分布を拡大し、かつ単位濃度幅に含まれる画素数が相対的に少ない濃度範囲の頻度分布を縮小する階調処理を上記少なくとも一方の医用画像に施す階調処理部１２と、少なくとも一方に階調処理が施された第１の医用画像５および第２の医用画像６に対して、第１の医用画像５および第２の医用画像６に含まれる被検体の解剖学的位置を対応づける位置合わせ処理を施す位置合わせ処理部１３とを備える。【選択図】図１
