Product Manual

Safety
7-16 Vscan – User Manual
GM092207 02
Acoustic output
Definition of the acoustic output parameters
Thermal Index
TI is an estimate of the temperature increase of soft tissue or
bone. There are three thermal index categories:
• TIS: Soft tissue thermal index. The main TI category. Used
for applications that do not image bone.
• TIB: Bone thermal index (bone located in a focal region).
Used for fetal application.
• TIC: Cranial bone thermal index (bone located close to the
surface). Used for transcranial application.
Reference to calculation of TI can be found in:
• NEMA Standards Publication UD 3: “Standard for Real-Time
Display of Thermal and Mechanical Acoustic Output Indices
on Diagnostic Ultrasound Equipment”, Revision 2
• IEC 60601-2-37. Medical electrical equipment. Part 2-37:
Particular requirements for the safety of ultrasonic medical
diagnostic and monitoring equipment
Mechanical Index
MI is the estimated likelihood of tissue damage due to cavitation.
The absolute maximum limits of the MI is 1.9 as set by the FDA
510(k) guidance of September 9, 2008.
Ispta
The Ispta is the Spatial Peak Temporal Average Intensity. The
absolute maximum limit of Ispta is 720 mW/cm
2
as set by the
FDA 510(k) guidance of September 9, 2008.
Acoustic output and display on the Vscan
MI and TI values are displayed on the scanning screen. For all
imaging modes of Vscan, TIS equals TIB and is displayed as TI.
The Vscan chooses the correct category based on mode of
operation and chosen application, and presents only one TI to
the operator. It is therefore important that the operator chooses
the right application.
The maximum possible MI and Ispta on the Vscan is within the
limits set in Track 3 in the FDA 510(k) guide of September 9,
2008, MI <1.9 and Ispta <720 mW/cm
2
.