Fluke Biomedical 07-661-7662 - Manual (Page 7)

Introduction
Interpretation of Results
1
1-3
1.3.2 Alignment of X-Ray Field and Image Receptor
In addition to the alignment of the light field with the x-ray field, NCDRH also specifies that the center of
the x-ray field must be within 2% of the SID of the center of the image receptor in the plane of the image.
To determine the center of the image receptor, draw diagonal lines from opposite corners of the x-ray film.
The two lines will cross in the center of the image receptor (film). Draw diagonal lines from the corners of
the imaged x-ray field. If the centers of the x-ray field and image receptor (film) are the same, the
diagonals of both sets of lines should cross at the same point (Figure 1-3).
At 40”, the error between the
image receptor and the x-ray field center should not be greater than 2% of the SID--approximately 2 cm
(0.8"),
for a 40” source-table distance (Figure 1-4).
Figure 1-3. Picture of X-ray Film Showing Interpretation of X-ray Field and Image Receptor
Figure 1-4.
Field Alignment Error Greater than 3 cm and Unacceptable at 1m (40”) SID