Fluke 18-216 User Manual

Nuclear Associates

18-216, 18-216-1000

Single-Exposure High Contrast Resolution Phantom

March 2005
Manual No. 18-216-1 Rev. 2
©2004, 2005 Fluke Corporation, All rights reserved.
All product names are trademarks of their respective companies

Operators Manual

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Table of Contents

Section 1: General Information................................................................................... 1-1

1.1 Objective...................................................................................................... 1-1

1.2 Description of Phantom................................................................................ 1-1

Section 2: Operation.................................................................................................... 2-1

2.1 Use of the Phantom ..................................................................................... 2-1

2.2 Data Interpretation and Analysis.................................................................. 2-1

2.3 Suggested Performance Criteria and Corrective Action .............................. 2-1

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General Information

Objective

Section 1

General Information

1.1 Objective

Focal spot performance may be evaluated by determining limiting resolution using a high-contrast
resolution pattern providing a test up to 16 lp/mm and preferably 20 Ip/mm (either a bar pattern, a star
pattern, or a wedge pattern marked to identify the number of Ip/mm in the image at the appropriate
points).

1.2 Description Of Phantom

The Single-Exposure High Contrast Resolution Phantom
incorporates two 17.5 micron thick gold-nickel alloy bar
patterns positioned at 90 degrees. This allows assessment
of resolution perpendicular and parallel to anode-cathode
axis in just one exposure. Each pattern has 17 segments
from 5 Ip to 20 Ip/mm and is equivalent to 25 microns of
lead or 2.6 mm of aluminum at 20 keV.

1

The bar patterns are permanently embedded in a thin
acrylic wafer to protect them from wear or damage.

The phantom body is available in BR12 (Model 18-216) or
BR50/50 (Model 18-216-1000). It enables consistent,
reproducible positioning of the bar pattern at 4.5 cm above
the breast support plate and 1 cm from the chest wall,
centered laterally (as recommended by the American
College of Radiology). The bar pattern can also be
positioned at a variety of heights for more thorough
evaluations. The Single-Exposure High Contrast Resolution
Phantom includes a 30X hand-held microscope.

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Nuclear Associates 18-216, 18-216-1000

Operators Manual

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Operation

Use of the Phantom

Section 2

Operation

2.1 Use Of The Phantom*

1. Place the pattern at the desired height above the breast support plate, either with no extraneous
materials between the bar pattern and the breast support, or with a homogeneous phantom
supporting the pattern. Position the pattern within 1 cm of the chest wall edge of the image
receptor, centered laterally. It is important that the test pattern be positioned in a reproducible
manner. A test stand or jig may be helpful.

2. Place the image receptor in the location where it would normally be used for mammography, (i.e., in
the cassette holder for contact mammography.) If a stationary grid is normally used with the
imaging system, remove it to avoid moire patterns.

3. Select the kVp, mA, and focal spot used for
imaging an average breast during normal
radiography and an exposure time that will
produce a background optical density from 1.2 to

1.6. This may be done either manually or in the
AEC mode.

4. Make an exposure and process the film.

5. Repeat steps 1 through 6 for other focal spots
and other geometries. In magnification mode, the
bar pattern should be positioned 4.5 cm above
the magnification breast support. Be sure to
record the magnification factor.

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

8 mm

20 Line Pair/mm Test Target

28 mm

2

2.2 Data Interpretation And Analysis*

1. Under masked conditions, view the high-contrast resolution pattern images with 10x to 30x
magnification.

2. Note the highest frequency pattern with lines that are distinctly visible throughout at least half of the

bar length (for a bar pattern) and record the highest frequency visible for each test image.

2.3 Suggested Performance Criteria And Corrective Action*

In the contact mode, measurements made with the bars parallel to the anode-cathode axis should be at
least

13 Ip/mm; measurements with the bars perpendicular to the anode-cathode axis should be at least

11 Ip/mm. In magnification mode, the limiting spatial resolution should be no lower than the above

specifications.

If the above specifications are not met, remove the compression paddle and the grid and retest (while
maintaining geometry consistent with that before). If the results are still below the above specifications, a
more detailed investigation of the reason should be made using a slit camera.

.

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Nuclear Associates 18-216, 18-216-1000

Operators Manual

For acceptance testing, it is recommended that both slit and high-contrast resolution pattern adjustments
be made and compared. Then, for routine QC, high-contrast resolution pattern images can be obtained
and compared with those images obtained during acceptance testing.

NOTE

*Excerpts taken from The American College of
Radiology Mammography Quality Control Manual,
1994 Revised Edition, pages 145-146.

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