Chapter 7
Page no. 684
JC-ELE-A-028.fm
GE Healthcare
Senographe DS
Revision 1
Service Information and Procedures Class A 2385072-16-8EN
Job Card ELE A028 - Collimation Checks
7-2
Measurements
7-2-1
X-ray Field Passing All Four Edges
From the RAW digital image on the AWS determine, whether each of the four edges of the X-ray field
are outside of the edge of the image receptor. That is, you should not be able to see any of the four
edges of the X-ray field in the digital image.
•
If you can see any of the four edges of the X-ray field in the digital image, there is a problem with the
Collimator blade alignment. In this case, you must re-calibrate the Collimator. Once you have re-cali-
brated the Collimator you must take new exposures before you continue with the measurements
described in
•
If you cannot see any of the four edges of the X-ray field in the digital image, the Collimator blades
are aligned correctly. You can continue with the measurements described in
7-2-2
XR-M Film Measurements
From the film and AWS (Acquisition Workstation) RAW digital image, you must make various measure-
ments as described below. Use the
Segment
tool on the AWS for measurements on the image receptor.
Measurements both from the film and the AWS must be scaled to the image receptor plane.
You must follow the measurements and calculations described below for each edge of the field (each
XR-M film strip A, B, C and D), and complete the following tables.
In the tables below, items in
bold italics
are measured/determined and items in
bold
are calculated.
Mo/Mo
Rh/Rh
Step 1
Step 2
Step 3
Step 4
Y
f
D
Z
f
=
D -
Y
f
Global Scaling Factor (S) =
1.063 x
d
(in mm) / 10
Z
i
(S x Z
f
)
Left edge (Film A)
Anterior edge (Film B)
CW edge (Film C)
Right edge (Film D)
Step 1
Step 2
Step 3
Step 4
Y
f
D
Z
f
=
D -
Y
f
Global Scaling Factor (S) =
1.063 x
d
(in mm) / 10
Z
i
(S x Z
f
)
Left edge (Film A)
Anterior edge (Film B)
CW edge (Film C)
Right edge (Film D)
