Fluke Biomedical 07-649 - Manual (Page 12)

Nuclear Associates 07-649
Operators Manual
2-6
remainder of the aluminum between the probe and the ABC. Make an exposure, and record in
mR/min the reading for 4.5 mm of aluminum.
10. Move an additional 2 mm of aluminum from the top of the phantom to the tabletop beneath the
probe. This will place 6.5 mm of aluminum between the tube head and the probe, leaving the
remainder of the aluminum between the probe and the ABC. Make a 15-second exposure, and
record in mR/min the reading for 6.5 mm of aluminum.
2.12 Estimated HVL
Using a graph, plot the exposure rate versus the aluminum thicknesses used. Determine the HVL to the
nearest tenth of a millimeter of aluminum by drawing the best straight line fit to all but the first.
Low and Low Contrast Fluoroscopy Imaging Data
With the phantom properly positioned in the beam, remove the probe and all aluminum filters. Have the
operator set up the unit with the standard patient techniques. Center the Fluoroscopic Test Tool on the
tabletop beneath the phantom. Set the system to the one-on-one format. Observe the fluoroscopic image
and determine the number of holes you can see on the inner ring, and the number of screen meshes you
can see on the outer ring. Repeat this process three times and record the average for the three
observations.
2.13 Target To Tabletop Distance
Place the Fluoroscopic Test Tool on the tabletop beneath the phantom. The engraved side of the test tool
must be toward the phantom; the large aluminum disc rests on the tabletop. Place a loaded cassette in
the spot film device, set the format to one-on-one and make a spot film exposure. Measure (in
centimeters) and record the distance from the center of the spot film cassette to the tabletop.
On the processed spot film, measure (in centimeters) and record the diameter of the image of the inner
aluminum disc (innermost circle).
Use the following equation to calculate the target-to-tabletop distance in centimeters and record the
values.
4.4 x SD
Target-to-Tabletop
Distance =
Diam = 4.4
cm
where
SD = Distance, in centimeters, from the center of the spot film cassette to the tabletop
Diam = Diameter, in centimeters, of the image of the inner aluminum disk (innermost circle)