CT scanning techniques and systems thereof are disclosed. In various embodiments, a body surface measuring point of a subject on a scanning bed can be identified according to a frontal image captured by a first image capturing device. A measuring projection angle can be acquired using the body surface measuring point. A lateral image of the subject can be captured using a second image capturing device. Based on the lateral image, a vertical distance between the body surface measuring point and the scanning bed, a current height and the initial height of the scanning bed, a horizontal position of the body surface measuring point under the initial height can be acquired. A horizontal position of the body surface measuring point under the current height can be determined based on above acquired parameters.