Chison ECO 2 - Page 25

ECO 2 Ultrasound Diagnostic System
Page 16 / 189
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