python Medical image segmentation for liver preprocessing

** Recently encountered a problem in the pre-processing stage of the realization of liver segmentation. I don't know how to return the first non-0 pixel coordinate after projection. **

The preconditioning process is described in the original paper as follows: according to an anatomical priori, the liver is usually located in the right part of the human abdominal cavity. In CT tomography, the liver region mainly appears on the left side of the abdominal cavity in the transverse view image, as shown in Figure 1(a). In order to obtain the region of interest containing the complete liver and remove the interference of unrelated tissues and organs, CT images need to be cropped. Firstly, threshold and mathematical morphology methods [17] were used to segment the ribs and spine in CT images, and the results were obtained as shown in Figure 1(b). Then, the segmentation results were projected in rows and columns, and the rows and columns where the first and last non-0 pixels were located were respectively taken to construct a rectangular box with length Lw and width Lh, and the abdominal cavity area was located, as shown in Figure 1(c). Considering that the liver region is usually located on the left side of the abdominal cavity of CT section, the center point O of the rectangle box was shifted Lw/4 to the left to obtain point P, and a square area with a size of 320×320 was taken as the final clipping result. Finally, the window position and window width of the clipped area image are adjusted. According to the prior knowledge of radiological medicine, the range of CT values of human tissues that can be displayed is generally -1 000~1 000 Hu, while the range of CT values of liver, spleen, kidney, muscle and other organ soft tissues is usually 40 ~70 Hu. In order to enhance the contrast between liver and adjacent tissues, the window level and window width of CT images were set to 60 and 170 Hu respectively in this paper, and the pre-processed images were obtained, as shown in Figure 1(d).

Figure(b) has been implemented, but figure(c) does not know what function or method to implement it. Need your help, give some ideas or suggestions. Thank you.