SonoSite S-Cath - MI and TI Output Display Accuracy; Factors that Contribute to Display Uncertainty

84
EvenwhenMIislessthan1.0,thesystemprovidesacontinuousreal‐timedisplayofMIinall
imagingmodes,inincrementsof0.1.
ThesystemmeetstheoutputdisplaystandardforTIandprovidesacontinuousreal‐time
displayofTIinallimagingmodes,inincrementsof0.1.
The
TIconsistsofthreeuser‐selectableindices,andonlyoneoftheseisdisplayedatanyone
time.InordertodisplayTIproperlyandmeettheALARAprinciple,theuserselectsan
appropriateTIbasedonthespecificexambeingperformed.SonoSiteprovidesacopyofAIUM
MedicalUltrasound
Safety,whichcontainsguidanceondeterminingwhichTIisappropriate(See
“Relatedguidancedocuments”onpage 85).
MI and TI output display accuracy
TheaccuracyresultfortheMIisstatedstatistically.With95%confidence,95%ofthemeasured
MIvalueswillbewithin+18%to–25%ofthedisplayedMIvalue,or+0.2ofthedisplayedvalue,
whichevervalueislarger.
TheaccuracyresultfortheTIisstated statistically.With95%confidence,
95%ofthemeasured
TIvalueswillbewithin+21%to–40%ofthedisplayedTIvalue,or+0.2ofthedisplayedvalue,
whichevervalueislarger.Thevaluesequateto+1dBto–3dB.
Adisplayedvalueof0.0forMIorTImeansthatthecalculatedestimatefortheindex
islessthan
0.05.
Factors that contribute to display uncertainty
Thenetuncertaintyofthedisplayedindicesisderivedby combiningthequantifieduncertainty
fromthreesources:measurementuncertainty,systemandtransducervariability,and
engineeringassumptionsandapproximationsmadewhencalculatingthedisplayvalues.
Measurementerrorsoftheacousticparameterswhentakingthereferencedataarethemajor
sourceoferror
thatcontributestothedisplayuncertainty.Themeasurementerrorisdescribed
in“A co us t ic measurementprecisionanduncertainty”onpage 121.
ThedisplayedMIandTIvaluesarebasedoncalculationsthatuseasetofacousticoutput
measurementsthatweremadeusingasinglereferenceultrasoundsystemwithasingle
referencetransducer
thatisrepresentativeofthepopulationoftransducersofthattype.The
referencesystemandtransducerarechosenfromasamplepopulationofsystemsand
transducerstakenfromearlyproductionunits,andtheyareselectedbasedonhavingan
acousticoutputthatisrepresentativeofthenominalexpectedacousticoutputfor
all
transducer/systemcombinationsthatmightoccur.Ofcourseeverytransducer/system
TEEx/8-3 MI
No No No No
TIC, TIB, or TIS
No No Yes Yes
Table 5: TI or MI is ≥ 1.0 (Continued)
Transducer Model Index
2D
MMode
CPD/
Color
PW
Doppler
CW
Doppler