Specifications

C. VERIFICATION OF COMPLIANCE
For determination of misalignment, compare the edges of the X-Ray field to the
edges of the light-field as defined by the outer edges of the metal strips. On
each side of the rectangular fields, measure the separation between the X-Ray
field and the outside edge on the image of the respective metal strip. Sum these
measured separations for opposite sides of the X-Ray field to yield a total
misalignment in the length and width dimensions. Record the length
misalignment and width misalignment, both without regard to sign (see
Paragraph D and Figure 5.3).
D. CALCULATIONS
Calculate the source to image distance (SID) per the following formula (to slot 6)
as the indicated source-to-table top distance minus 4.7 centimeters (1.85 in) and
record. Calculate 2 percent of this SID and record. Both the length and width
misalignment must be less than 2 percent of SID (to slot 6).
2.5 = X
S X + 13.95
2.5X + (2.5) 13.95 = XS
(2.5) 13.95 = XS - 2.5X
34.875 = X (S - 2.5)
X = 34.875
S - 2.5
The misalignments are calculated as follows:
Length misalignment = L
1
+ L
2
≤ 2% SID
Width misalignment = W
1
+ W2 ≤ 2% SID
Calculate 2% of the measured SID. Each of the misalignments, length or width,
must be less than or equal to 2% of the measured SID for compliance.
NEMA Standards 5-15-79
.02 METHOD II - METAL MARKER METHOD
A. GENERAL
The actual versus indicated source-to-image receptor distance (SID) test must
be performed prior to attempting this test.
November 2005 ( 5 - 10 ) Linear MC150-C Collimator