Specifications

4. Center the source assembly over the test stand using the means
provided, e.g. bucky light.
5. Bring the source assembly down into firm contact with the spacer.
6. Center the cassette tray with the source assembly using the means
provided, e.g. bucky light.
7. Insert the plastic cassette into the slide assembly. Then insert the slide
assembly into slot 5 (see Figure 5-2).
8. Center the film cassette in the cassette tray and insert into position. If the
positive beam limitation will not operate at this SID, raise the source
assembly and lock in position at the first operable SID.
9. Make an exposure. Develop the image. Measure and record and length
and with dimensions of the image.
10. Calculate the field size correction factor as the SID/A where:
a. SID is the indicated source-to-image receptor distance, and
b. A is the indicated source-to-tabletop distance less 19.5 cm.
Multiply each of the measured dimensions by the correction
factor.
X-Ray field length at
undertable image receptor = SID x (X-Ray field length at slot 5)
A
X-Ray field width at
undertable image receptor = SID x (X-Ray field width at slot 5)
A
November 2005 ( 5 - 19) Linear MC150-C Collimator
Determine the difference without regard to sign between the corrected length and
width dimensions and the corresponding cassette film size dimensions (20 by 25,
13 by 18, etc.). Each of these differences must be less than 3 percent of the SID,
and the sum of these differences must be less than 4 percent of the SID.
NEMA Standards 5-15-79
.02 METHOD II - ALTERNATE TEST STAND METHOD
A. GENERAL