Fluke Biomedical 84-350 - Manual (Page 5)

Introduction
Introduction
1
1-1
Section 1
Introduction
1.1 Introduction
This phantom is constructed from a patented solid elastic material called Zerdine™. Zerdine, unlike other
phantom materials on the market, is not affected by changes in temperature. It can be subjected to boiling
or freezing conditions without sustaining significant damage. Zerdine is also more elastic than other
materials and allows more pressure to be applied to the scanning surface without subsequent damage to
the material. At normal or room temperatures, the Zerdine material found in the Near Field Phantom will
accurately simulate the ultrasound characteristics found in human breast tissue. The 84-350 contains low
scatter masses in a range of sizes and depths, a calibrated volumetric test object and an assortment of
nylon monofilament target groups. The phantom is protected by an acrylic case and plastic membrane to
facilitate scanning and minimize desiccation. The 84-350 was designed to allow for assessment of
linearity, axial and lateral resolution, depth calibration, dead-zone measurement, volumetric calibration
and registration.
The Nuclear Associates series of ultrasound phantoms, unlike human subjects or random scannable
materials, offers a reliable medium that contains specific, known test objects for repeatable qualitative
assessment of ultrasound scanners over time.
1.2 Description
Background Material
The manufacturer maintains specific proprietary fabrication procedures that enable close control over the
homogeneity of Zerdine and the reliability of its acoustic characteristics from batch to batch. The speed of
sound in Zerdine can be adjusted between 1430 and 1650 meters per second. The acoustic attenuation
can be adjusted between .05dB/cm/MHz and 1.50 dB/cm/MHz. The relation between the acoustic
attenuation A and the acoustic frequency F is of the form A = A°F
n with values of the power coefficient n
in the range of .8 to 1.10, indicating the proportional increase of the acoustic attenuation with frequency.
Backscatter characteristics can be adjusted through the addition of predetermined amounts of calibrated
scatter material. Zerdine can be molded into very intricate shapes and the material can be cured in layers,
allowing the production of "multi-tissue" phantoms. Zerdine, like most other phantom materials will
desiccate if unprotected, but Zerdine has a sponge-like property. Any moisture lost to evaporation will be
reabsorbed when the material is immersed in water. Barring any damage to the case or scanning
membrane, the phantom should lose only minimal amounts of moisture over time.
Near Field Resolution Target
The target consists of parallel 0.1 mm nylon wires horizontally spaced 6 mm apart from center to center.
Vertical distance from the center of each wire to the top edge of the scanning surface ranges from 9 mm
down to 1 mm in 1 mm increments (see Figures 1-1 and 1-5). This target is designed to measure a
transducer's dead zone, otherwise referred to as the "ring-down distance.”