The present invention relates to a nuclear medicine emission imaging system and an attenuation correction method using a single transmission image. The present invention obtains an original CT image and an original emission image in a first session among multi-sessions and obtains an emission image in the rest session except for the first session among the multi-sessions and calculates a realignment value based on a spatial position error between an emission image of a second session and the original emission image. The present invention makes the original CT image into the realignment original CT image of the second session using the realignment value and makes the realignment original CT image for the rest sessions with the same method and performs attenuation correction for an emission image of the corresponding session using the realignment original CT image by each session. [Reference numerals] (AA) Start；(BB,DD) No；(CC,EE) Yes；(FF) ENd；(S501) Photograph a first session emission image；(S502) Save the image；(S503) N session photographed ?；(S504) Photograph one original CT image；(S505) Reorganize the emission image of the next session；(S506) Calculate realignment values for the original emission image and the reorganized emission image；(S507) Distinguish the body parts and the background parts of the original CT image and separate them；(S508) Realign the body parts of the original CT image using the calculated realignment values；(S509) Bond the realigned body parts of the original CT image and the background parts of the original CT image；(S510) Save the realigned original CT image according to the emission image of the session；(S511) N session CT image created ?；(S512) Perform a attenuation correction progress본 발명은 핵의학 방출 영상 시스템 및 단일 투과 영상을 이용한 감쇠보정 방법에 관한 것으로, 멀티 세션 중 제1 세션에서 원본 CT 영상과 원본 방출 영상을 획득하고, 멀티 세션 중 상기 제1 세션을 제외한 나머지 세션에서 방출 영상을 획득하며, 멀티 세션 중 제2 세션의 방출 영상과 상기 원본 방출 영상간의 공간적 위치 오차를 기반으로 재정렬값을 산출하고, 상기 재정렬값을 이용하여 상기 원본 CT 영상을 상기 제2 세션의 재정렬된 원본 CT 영상으로 만
