How should Patient Orientation (0020,0020) values be interpreted?

David Clunie

2008-04-01 09:38:08 UTC

Hi Wayne

Rows first, then columns, and the directions of the vectors.

So a "normal" looking frontal chest x-ray (AP or PA) with the
head at the top and the patient's left side on the right side
of the pixel data would be "L\F":

H

_o_
R | L* ----> L
/ \ |
|
F* \ /
F

An orientation of "H\R", which would be really bizarre, would
be such an image rotated 90 degrees clockwise and then flipped
top to bottom, such that the head was on the right side of the
pixel data and the patient's right side on the bottom of the
pixel data:

L

\ |
F - o H* ----> H
/ | |
|
R* \ /
R

PS 3.17 - 2007 Page 18 "fourth image down" is supposed to show
a Patient Orientation (0020,0020) of L\F (at the ends of the
vectors), not H\R (which you are perhaps confusing with the
labels on the sides of the image).

David

Post by e***@hotmail.com
How should Patient Orientation (0020,0020) values be interpreted?
-----------------------------------------------------------------------------------------
DICOM Standard 2007 part 3 defines Patient Orientation (0020,0020) as
C.7.6.1.1.1 Patient Orientation
The Patient Orientation (0020,0020) relative to the image plane shall
be specified by two values
that designate the anatomical direction of the positive row axis (left
to right) and the positive
column axis (top to bottom). The first entry is the direction of the
rows, given by the direction of
the last pixel in the first row from the first pixel in that row. The
second entry is the direction of the
columns, given by the direction of the last pixel in the first column
from the first pixel in that
column.
Anatomical direction shall be designated by the capital letters: A
(anterior), P (posterior), R
(right), L (left), H (head), F (foot). Each value of the orientation
attribute shall contain at least one
of these characters. If refinements in the orientation descriptions
are to be specified, then they
shall be designated by one or two additional letters in each value.
Within each value, the letters
shall be ordered with the principal orientation designated in the
first character.
How do I interpret the what is defined in C.7.6.1.1.1 Patient
Orientation?
For instance, if CR modality sends a CR AP CHEST with the head of the
anatomy at the top of the image (e.g looks like the bottom most
coronal image in PS 3.17 - 2007 Page 18 fourth image down) with a
Patient Orientation (0020,0020) of H/R, is that correct?
My understanding is that the Patient orientation (0020,0020) values
should match up with the pixel data orientation. So the Patient
Orientation (0020,0020) labels for the above image should be L/F.
That is if the modality sends "H/R" in tag (0020,0020), the pixel data
orientation should reflect that. So the rows of the pixel data going
from Left to right of the image should be towards the patient's head
and rows of the pixel data going from the top to bottom should be
towards the patient's right anatomy.
Please comments.
Thanks in Advance.
Wayne