S2/S2BW
Digital Color Doppler Ultrasound System
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 Mod-
els
Composition Mode Specification Typ. app
1TIS Soft tissue Unscanned Large aperture (>1cm
) Liver PW
2TIS Soft tissue Unscanned Small aperture (<1cm
) Pencil probe
3TIS Soft tissue Scanned Evaluated at surface Breast color
4TIB
Soft tissue and bone
Scanned Soft tissue at surface Muscle color
5TIB
Soft tissue and bone
Unscanned Bone at focus Fetus head PW
6TIC
Soft tissue and bone
Unscanned / Scanned Bone at surface Trans cranial
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, CW and M mode.
TI
TI is defined as the ratio of the In Situ acoustic power (W.3) to the acoustic power required to raise tissue
temperature by 1oC (Wdeg),
T I = W./W deg
Three TIs corresponding to soft tissue (TIS) for abdominal; bone (TIB) for fetal and neonatal cephalic; and
cranial bone (TIC) for pediatric and adult cephalic, have been developed for applications in different exams.
An estimate of the acoustic power in milliwatts necessary to produce a 1
°C
temperature elevation in soft tissue
is:
W deg = / f c
for model 1 to 4, where fc is the center frequency in MHz.
W deg = · K · D
for model 5 and 6, where K (beam shape factor) is 1.0, D is the aperture diameter in cm at the depth of
interest
MI
Cavitation is more likely to occur at high pressures and low frequencies in pulse ultrasound wave in the tissue,
which contains the bubble or air pocket (for instance, the lung, intestine, or scan with gas contrast agents).
P/N: 4710.00149A01
2-6
To Next Page
Loading...
Need help?
General
