Chison ECO 6, Руководство по эксплуатации

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ECO 6 Digital Color Doppler Ultrasound System
12
Where a is the attenuation coefficient in dB cm-1 MHz-1, f is the transducer center frequency, and z is the
distance along the beam axis between the source and the point of interest.
De-rating factor RF for the various distances and frequencies with attenuation coefficient 0.3dB cm-1 MHz-1
in homogeneous soft tissue is listed in the following table. An example is if the user uses 7.5MHz frequency,
the power will be attenuated by .0750 at 5cm, or 0.3x7.5x5=-11.25dB. The De- rated Intensity is also referred
to as ‘.3’ at the end (e.g. Ispta.3).
Distance Frequency (MHz)
(cm) 1 3 5 7.5
1 0.9332 0.8128 0.7080 0.5957
2 0.8710 0.6607 0.5012 0.3548
3 0.8128 0.5370 0.3548 0.2113
4 0.7586 0.4365 0.2512 0.1259
5 0.7080 0.3548 0.1778 0.0750
6 0.6607 0.2884 0.1259 0.0447
7 0.6166 0.2344 0.0891 0.0266
8 0.5754 0.1903 0.0631 0.0158
I’=I*RF Where I’ is the intensity in soft tissue, I is the time-averaged intensity measured in water.
Tissue Model:
Tissue temperature elevation depends on power, tissue type, beam width, and scanning mode. Six models are
developed to mimic possible clinical situations.
Thermal Models Composition Mode Specification Application
1
TIS Soft tissue Unscanned
Large aperture
(>1cm
2
)
Liver PW
2
TIS Soft tissue Unscanned
Small aperture
(<1cm
2
)
Pencil Probe
3
TIS Soft tissue Scanned
Evaluated at
surface
Breast color
4
TIB Soft tissue and bone Scanned
Soft tissue at
surface
Muscle color
5 TIB Soft tissue and bone Unscanned Bone at focus Fetus head PW
6 TIC Soft tissue and bone Unscanned/scanned Bone at surface Transcranial
Soft tissue:
Describes low fat content tissue that does not contain calcifications or large gas-filled spaces.
Scanned: (auto-scan)
Refers to the steering of successive burst through the field of view, e.g. B and color mode.
Unscanned:
Emission of ultrasonic pulses occurs along a single line of sight and is unchanged until the transducer is moved
to a new position. For instance, the PW and M mode.
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