Medical Image Process_ Medical Imaging coordinate system

One difficulty in processing medical images is the inconsistency of coordinate systems.

1. World coordinate system; 2. Anatomical coordinate system (patient coordinate system); 3. The coordinate systems of the image coordinate system present their data in different ways;

2. Anatomical coordinate system (patient coordinate system)

(1) Cross section (The axial plane): the side that is parallel to the ground. Divide a person into upper body (superior) and lower (inferior) two parts;

(2) coronal surface (the coronal plane): perpendicular to the ground, the human body is divided before and after (anterior and posterior) two parts;

(3) sagittal plane (the sagittal plane): perpendicular to the ground, dividing the human body into two parts of left and right;

In this space, the image is sampled;

These six directions, that is the positive direction, which is the negative direction???

#1: LPs is positive (for DICOM images with ITK toolkit;)

#2: RAS is positive (just opposite LPs, for 3D Slice software)

There is no fundamental difference between the two coordinates, in the processing time, you need to know what kind of coordinate system the image refers to;

3. Image coordinate system

The medical scanner creates a regular point and matrix array of meshes whose origin is in the upper- left corner , and in addition to the strength values of each voxel, the Origin and spacing of the image in the anatomical coordinate system was also saved down;

This origin represents the position of the first voxel voxel (0,0,0) in the anatomical coordinate system , such as (100mm, 50mm, -25mm);

This spacing specifies the actual distance between the sample points of the voxel in the anatomical coordinate system, for example (1.5mm (spacing[0]), 0.5mm (spacing[1]), 0.5mm ( SPACING[2]))

If we know the origin and spacing, we can calculate the corresponding position of each voxel in the anatomical coordinate system . (by affine transformation )

The origin of the coordinates of the image corresponds to the anatomical coordinates ((), the image on LS, and the spacing is (50mm,50mm)

Why add a 1 on the last side, this is because the original point of the image coordinates from (0,0), without the end of the 1, the origin of the corresponding coordinates, will get 0;

Medical Image Process_ Medical Imaging coordinate system