User's Manual

Table Of Contents
104
combinationhasitsownuniquecharacteristicacousticoutput,andwillnotmatchthenominal
outputonwhichthedisplayestimatesarebased.Thisvariabilitybetweensystemsand
transducersintroducesanerrorintodisplayedvalue.Bydoingacousticoutputsampling
testingduringproduction,theamountoferrorintroducedbythevariabilityis
bounded.The
samplingtestingensuresthattheacousticoutputoftransducersandsystemsbeing
manufacturedstayswithinaspecifiedrangeofthenominalacousticoutput.
Anothersourceoferrorarisesfromtheassumptionsandapproximationsthataremadewhen
derivingtheestimatesforthedisplayindices.Chiefamongtheseassumptionsis
thatthe
acousticoutput,andthusthederiveddisplayindices,arelinearlycorrelatedwiththetransmit
drivevoltageofthetransducer.Generally,thisassumptionisverygood,butitisnotexact,and
thussomeerrorinthedisplaycanbeattributedtotheassumptionofvoltagelinearity.
Related guidance documents
InformationforManufacturersSeekingMarketingClearanceofDiagnosticUltrasound
SystemsandTransducers,FDA,1997.
MedicalUltrasoundSafety, AmericanInstituteofUltrasoundinMedicine(AIUM),1994.(A
copyisincludedwitheachsystem.)
AcousticOutputMeasurementStandardforDiagnosticUltrasoundEquipment,NEMA
UD22004.
AcousticOutputMeasurementandLabelingStandardforDiagnosticUltrasound
Equipment,
AmericanInstituteofUltrasoundinMedicine,1993.
StandardforRealTimeDisplayofThermalandMechanicalAcousticOutputIndiceson
DiagnosticUltrasoundEquipment,NEMAUD32004.
GuidanceontheinterpretationofTIandMItobeusedtoinformtheoperator,AnnexHH,BS
EN60601237reprintedatP05699.
Transducer surface temperature rise
Table 6andTable 7listthemeasuredsurfacetemperaturerisefromambient(23°C±3°C)of
transducersusedontheultrasoundsystem.Thetemperaturesweremeasuredinaccordance
withEN60601237section42withcontrolsandsettingspositionedtogivemaximum
temperatures
Table 6: Transducer Surface Temperature Rise, External Use (°C)
Test C11x C60x D2 HFL38x L25x L38x P10x P21x
Still air 17.6 16.2 8.3 15.5 16.1 16.3 15.6 16.8
Simulated
Use
9.1 8.8 1.9 7.9 8.5 9.6 9.8 9.0