In DICOM, it is to describe the current image and the relative position of the body coordinate system and by Image Position Image Orientation.
DCM when you open the file, you will find two tag below the
(0020,0032) DS ImagePosition(Patient) "-20.000000\-150.000000\150.000000 "
(0020,0037) DS ImageOrientation(Patient) "0.000000\1.000000\0.000000\0.000000\0.000000\-1.000000"
It is this two tag to describe the current position and orientation of an image, which is used to calculate the amount of two bit lines, the space VR, MPR is calculated.
To understand these two quantities, first we want to understand the coordinate transformation in the three-dimensional space, the transformation includes transforming the position and posture conversion, often referred to as a kinematic i.e. pose transformation. First, there is an original coordinate o,
Wherein, O₁ O coordinate system is a system based on the order of a rotation angle θ about the z-axis, we can record this matrix is
, So and so, through a series of such transformation, we can get the final transformation matrix 
Here, we have referred to as T
But we know that we image is an amount of a 2-dimensional, because the z-direction of the current image pixel coordinates of the point relative to the current value of the image coordinate system are 0, the current coordinate point of the image can be (x, y, 0) vector is represented, in homogeneous coordinates represented manner it is (x, y, 0,1). Then, when you want to calculate a point on the original image with respect to the coordinate system of the coordinate, and directly by multiplying the transformation matrix T, referred to as
So, six on the amount of Image Orientation is obvious
. Image Position in the amount of three to
Original coordinate system, the left side of the body is a predetermined X-axis direction, a direction from the back face pointing direction of the y-axis represents. Coordinate system is regulated by the coordinate system in Dicom absolute coordinate system. However, the position coordinates of points, each vendor has their own opinion.
