Fluke Biomedical 07-611 - Manual (Page 10)

Nuclear Associates Radiographic and Mammographic Focal Spot Measurement Products
Operators Manual
2-4
2.1.5 Procedure for Under-Table X-Ray Tube Focal Spot Test Stand Alignment
1. Level the tabletop using a spirit level and place the test stand on x-ray tabletop (Figure 2-7). Assure
that the leveling screws are flush with the bottom of the stand.
2. Level the bottom of the stand using a spirit level, by adjusting the leveling screws.
3. Place the large adaptor ring and test stand alignment device on the base of the stand.
4. Rotate the test stand alignment device array of four beads so they are parallel to the anode-
cathode axis.
5. Repeat steps 4 and 7 from the Procedure for Over-Table X-Ray Tube Focal Spot Alignment,
Section 2.1.4.
6. Place the image intensifier tower over the stand and verify that the tower and x-ray tube are
aligned, i.e., the interlocks allow fluoro.
7. Center the image of the test stand alignment device, using the fluoroscopic image on the TV
monitor as a guide, by moving the stand. It may be necessary to adjust the mA and kVp manually to
provide a good image.
Figure 2-7. Focal Spot Test Stand on Table (Under-Table X-Ray Tube)
2.1.6 Procedure for Slit Measurement For Mammographic X-Ray Tube Focal Spot
Measurements
1. Replace the magnification insert with the slit assembly, parallel to the anode-cathode axis.
2. Place the mammographic cassette in the focal spot test stand tunnel.
3. Select a technique of about 28 kVp and 30 mAs for Kodak Min R Fast screens with TMM II film.
4. Align the slit assembly parallel to the anode-cathode axis to make the focal width measurement.
5. Expose the cassette at the selected technique factors. Film density should be between 0.8 and 1.2
above the base-plus-fog of the film.
6. Rotate the slit assembly 90° to measure the focal length.
7. Expose the cassette or film at the selected technique factor.
8. Process and view the slit images (Figure 2-8).