Fluke Biomedical 84-340 - 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 effected by changes in temperature. It can be subjected to boiling
or freezing conditions without sustaining significant damage. Zerdine is also more effective 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 General Purpose Phantom
will accurately simulate the ultrasound characteristics found in human liver tissue. The 84-340 contains
dense and cystic masses in a range of sizes, one high-density target 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 84-340 was designed to allow for assessment of
linearity, axial and lateral resolution, depth calibration, dead-zone measurement, and registration within
two different backgrounds of .5 and .7 dB/cm/MHz. This series of ultrasound phantoms, unlike human
subjects or random scannable materials, offers a reliable medium that contains specific, known test
objects 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 .05 dB/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 such as the 84-340. 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. Baring any damage to the case or
scanning membrane the phantom should lose only minimal amounts or moisture over time.
Near Field Resolution Target
The target consists of parallel .30 mm nylon wires horizontally spaced 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 1-4). This target is designed to measure a transducer's
dead-zone otherwise referred to as the “ring-down distance.”