SonoSite S-Cath - Related Guidance Documents; Transducer Surface Temperature Rise

Chapter 6: Safety 85
Safety
combinationhasitsownuniquecharact eristicacousticoutput,andwillnotmatchthenominal
outputonwhichthedisplayestimatesarebased.Thisvariabilitybetweensystemsand
transducersintroducesanerrorintodisplayedvalue.Bydoingacousticoutputsampling
testingduringproduction,theamountoferrorintroducedbythevariabilityis
bounded.The
samplingtestingensuresthattheacousticoutputoftransducersandsystemsbeing
manufacturedstayswithinaspecifiedrangeofthenominalacousticoutput.
Anothersourceoferrorarisesfromtheassumptionsandapproximationsthataremadewhen
derivingtheestimatesforthedisplayindices.Chiefamongtheseassumptionsis
thatthe
acousticoutput,andthusthederiveddisplayindices,arelinearlycorrelatedwiththetransmit
drivevoltageofthetransducer.Generally,thisassumptionisverygood,butitisnotexact,and 
thussomeerrorinthedisplaycanbeattributedtotheassumptionofvoltagelinearity.
Related guidance documents
• InformationforManufacturersSeekingMarketingClearanceofDiagnosticUltrasound
SystemsandTransducers,FDA,1997.
•MedicalUltrasoundSafety,AmericanInstitute ofUltrasoundinMedicine(AIUM),1994.(A
copyisincludedwitheachsystem.)
•AcousticOutputMeasurementStandardforDiagnosticUltrasoundEquipment,NEMA
UD2‐2004.
•AcousticOutputMeasurementandLabelingStandardforDiagnosticUltrasound
Equipment,AmericanInstituteofUltrasoundinMedicine,1993.
• StandardforReal‐TimeDisplayofThermalandMechanicalAcousticOutputIndiceson
DiagnosticUltrasoundEquipment,NEMAUD3‐2004.
•GuidanceontheinterpretationofTIandMItobeusedtoinformtheoperator,AnnexHH,
BSEN60601‐2‐37reprintedatP05699.
Transducer surface temperature rise
Table 6liststhemeasuredsurfacetemperaturerisefromambient(23°C±3°C)oftransducers
usedontheultrasoundsystem.ThetemperaturesweremeasuredinaccordancewithEN
60601‐2‐37section42withcontrols andsettingspositionedtogivemaximumtemperatures.