Fluke Biomedical 07-645 - Manual (Page 6)

Nuclear Associates 07-645
Operators Manual
1-2
1.2.1 Example One
Image Readings
The copper sheets (a total of 2.0 mm of Cu) and Test Plate A are positioned as depicted in Figure 1-1.
The fluoroscopic tube potential stabilizes at 80 kVp. In the fluoroscopic image of Test Plate A two targets
are seen in Row 1, two targets are seen in Row 2 and three targets are seen in Row 3, Test Plate A is
removed and replaced with Test Plate B. In the fluoroscopic image of Test Plate B two targets are seen in
Row 1, two targets are seen in Row 2 and two targets are seen in Row 3.
Interpretation of Readings
If the fluoroscopic x-ray tube potential stabilizes at 80 kVp, the contrast of the targets are given by their
target or hole number (see Figure 1-2 and Table 1-1). The lowest contrast target that is visualized is
target 3 in Row 3 of Test Plate A and the low contrast resolution of the fluoroscopic unit is 3.0%.
1.2.2 Example Two
Image Readings
The copper sheets (a total of 2.0 mm of Cu) and Test Plate A are positioned as depicted in Figure 1-1.
The fluoroscopic tube potential stabilizes at 90 kVp. In the fluoroscopic image of Test Plate A two targets
are seen in Row 1, two targets are seen in Row 2 and two targets are seen in Row 3. Test Plate A is
removed and replaced with Test Plate B. In the fluoroscopic image of Test Plate B two targets are seen in
Row 1, two targets are seen in Row 2 and two targets are seen in Row 3.
Interpretation of Readings
When the number of targets seen on both plates are the same, the lowest contrast target seen is on Plate
B. In this example it is Target 3.5 in Row 1. The contrast of Target 3.5 at 90 kVp and 2.0 mm of copper
beam attenuator is given in Table 1 and is 3.2%.
1.2.3 Example Three
Image Readings
The copper sheets (a total of 2.0 mm of Cu) and Test Plate A are positioned as depicted in Figure 1-1.
The fluoroscopic tube potential stabilizes at 65 kVp. In the fluoroscopic image of Test Plate A two targets
are seen in Row 1, two targets are seen in Row 2 and three targets are seen in Row 3. Test Plate A is
removed and replaced with Test Plate B. In the fluoroscopic image of Test Plate B two targets are seen in
Row 1, two targets are seen in Row 2 and three targets are seen in Row 3.
Interpretation of Readings
The lowest contrast target seen is Target 2.5 in Row 3 of Plate B. The contrast of this target at 65 kVp
can be determined by interpolating between the 60 and 70 kVp target contrast values in Table 1. The
contrast of Target 2.5 at 60 kVp is 3.28%. At 70 kVp the target contrast is 2.79%. Interpolating between
the two values one obtains a contrast resolution of 3.0%.