PD IEC TS 63070:2019 pdf free.Ultrasonics – Field characterization – Infraredimaging techniques for determining temperature elevation in tissue-mimicking material and at the radiation surface of a transducer in still air.
Measurement of the temperature inside a phantom is one goal for observations by the lR-camera. So one of the most important requirements of the phantom is its ability to be split intotwo pieces of TMM with flat (or slightly convex) cross-sectional surfaces that can be exposedto the lR-camera. TMM is vulnerable to dehydration and mechanical damage. A practicalphantom may be kept in a rigid housing in order to avoid dehydration and malfunction causedby cracking the TMM during the operation of combination and separation during themeasurement procedure. See Annex A.
The TMM should have acoustic and thermal properties that mimic the appropriate tissue ofthe human body.The emissivity of the split surface should be known.One of the applicablematerials equivalenttosofttissue is specified in IEC 60601-2-37:2007 andIEC 60601-2-37:2007/AMD1:2015; its emissivity was determined in [7] to be 0,94 bycomparison with black body tape.
Minimizing multiple reflections of ultrasound between the transducer and the bottom surfaceof the phantom should be taken into consideration. Lining material,which is used in othercircumstances to absorb ultrasound propagating in a water tank and has a high attenuationproperty,may be appropriately placed at the bottom of the phantom to be effective for thispurpose.Bone-mimicking material or sterilized bone fragments [8] [9] [10] should be used asnecessary with soft-tissue mimicking material.
lf high temperature rise is expected in the TMM, such as when heating with a HITU system,then the properties of the TMM should be known and stable,over the range of expectedtemperature rises during the measurement.
7.2 Periodic validation
Periodic validation should be performed from the viewpoint of both acoustic and thermalproperties. The specified values of attenuation coefficient,thermal conductivity and heatcapacity in lEC 60601-2-37:2007 and lEC 60601-2-37:2007/AMD1:2015 should be maintainedwithin the specified tolerances.The period between validations should be one year.
The replacement with new split TMM phantom should be considered when the structuralabnormality like cracks and/or the degradation like change of colour are found by visualinspection.
The properties of the selected tissue-mimicking phantom should be appropriate to the tissuebeing simulated and the purpose of the measurement.
8Measurement procedure
8.1 Split TMM setup
PD IEC TS 63070 ln an infrared measurement there are two phases: first,the ultrasound transducer coupled tothe TMM (see recommendation in the last paragraph of 8.1.1) is driven and it generates anacoustic field in the TMM.Heat is generated inside the TMM.Secondly, after a given time ofinsonation, the configuration of the phantom is changed to allow the lR-camera to observe thetwo-dimensional temperature distribution over a cross-sectional plane that was inside theTMM during the first phase.
switching off the electrical drive to the transducer, so that the temperature distribution overthe separated surface can be measured by the lR-camera. To pull the blocks firmly togetherand subsequently to separate them quickly, a mechanism has to be built on which the blocksare stable, secure and movable. The IR-camera looks at the front surface (split surface) of theTMM after opening.The infrared picture has to be saved in a format (two-dimensional, colour-coded) that can be processed off-line to calculate,for example,the one-dimensionaltemperature profiles in lateral and axial directions.
The thermal cooling rate, in air on the exposed surface,after opening the TMM-blocks, hasbeen measured to be about 0,3 C/s in the first 20 s after switching off the ultrasoundradiation.Corrections are to be made by extrapolation back to the moment of opening the splitTMM-blocks and switching off the ultrasound (lt is assumed that these occur at the sametime.).
Care should be taken that the pressure to keep the two parts of TMM together is not changingthe properties of the TMM. Appropriate pressure is required to realize the firm combination ofTMM blocks while also avoiding destruction.Refer to A.3 c).
The appropriate emissivity value for the split TMM should be applied either at the time ofmeasurement or during later analysis.See [7]for example.
Annex A gives an example of lR-measurement procedures from setups to obtained results.The sequential steps in the procedure are as follows.
a) Initial temperature equilibrium of TMM: In order to obtain initial stability and uniformity of the temperature distribution on the cross-sectional surface,the wrapped TMM is kept formore than one hour on the laboratory table.
b) Focus adjustment of lR-camera: The focus adjustment of the lR-camera is performed according to manufacturer’s recommendations for obtaining maximum temperature withthe sharpest edge.
The location and angle of TMM to the IR-camera should be adjusted and be recorded tominimize the reflection of unexpected lR-signals,which are mainly generated by theIR-camera itself.
c) Coupling of TMM: A set of two split TMM-blocks [(A) and (B)] is made by coupling their cross-sectional surfaces under water that is in thermal equilibrium with the ambienttemperature. This process is for making tight acoustic and thermal coupling between apair of TMM-blocks before the measurement.
d) Alignment of transducer: The alignment of the transducer is performed for coincidence between the scan plane of the transducer and the cross-sectional plane of the split TMM.e) Shielding from stray lR-radiation and air currents: A cardboard box surrounding the phantom is closed.
f) Driving the transducer: The transducer is driven for a certain period, for example, three minutes.This drive period is an example for presenting the measurement procedure.The insonation time should be specified depending on the purpose of measurement.PD IEC TS 63070 pdf download.