Sonoscape S2 User Manual

S2/S2BW
Digital Color Doppler Ultrasound System
2.5.1.1 Temperature Display for Transducers Intended for Internal Use
For transducers intended for internal applications, e.g. the intracavitary transducers, the transducer tip
temperature is displayed on the screen.To protect the patient against the harm of excessive temperature, the
system automatically turns off the transducer when the temperature of the transducer reaches a threshold
temperature.
2.5.2 Understanding the MI/TI Display
Track-3 follows the Output Display Standard for systems which include fetal Doppler applications. The acoustic
output will not be evaluated on an application-specific basis, but the global maximum de-rated Ispta must
be ≤ 720 mW/cm2 and either the global maximum MI must be ≤ 1.9 or the global maximum de-rated Isppa
must be ≤ 190 W/cm2. An exception is for ophthalmic use, in which case the TI=max (TIS_as, TIC) is not to
exceed 1.0; Ispta.3 ≤ 50mW/cm2, and MI ≤ 0.23. Track-3 gives the user the freedom to increase the output
acoustic power for a specific exam, and still limit output acoustic power within the global maximum de-rated
Ispta ≤ 720 mW/cm2 under an Output Display Standard.
For any diagnostic ultrasonic systems, Track-3 provides an Output Indices Display Standard. The diagnostic
ultrasound systems and its operator’s manual contain the information regarding an ALARA (As Low As
Reasonably Achievable) education program for the clinical end-user and the acoustic output indices, MI and
TI.
The MI describes the likelihood of cavitation, and the TI offers the predicted maximum temperature rise in
tissue as a result of the diagnostic examination.
In general, a temperature increase of 2.5oC must be present consistently at one spot for 2 hours to cause
fetal abnormalities. Avoiding a local temperature rise above 1oC should ensure that no thermally induced
biologic effect occurs.
When referring to the TI for potential thermal effect, a TI equal to 1 does not mean the temperature will rise
1 degree C. It only means an increased potential for thermal effects can be expected as the TI increases.
A high index does not mean that bioeffects are occurring, but only that the potential exists and there is no
consideration in the TI for the scan duration, so minimizing the overall scan time will reduce the potential for
effects. These operator control and display features shift the safety responsibility from the manufacturer to the
user. So it is very important to have the Ultrasound systems display the acoustic output indices correctly and
the education of the user to interpret the value appropriately.
R
F
: De-rating factor
In Situ intensity and pressure cannot currently be measured. Therefore, the acoustic power measurement is
normally done in the water tank, and when soft tissue replaces water along the ultrasound path, a decrease in
intensity is expected. The fractional reduction in intensity caused by attenuation is DENOTED by the de-rating
factor R
F
,
R
F
= 
(−.a· f ·z)
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).
P/N: 4710.00149A01
2-5

Sonoscape S2 Specifications

General

Brand	Sonoscape
Model	S2
Category	Medical Equipment
Language	English