Transducer facts and go figures.
Physics 101 for transducers:
Transducers work on the fact that piezo-electric substances create an electric current when struck. This was discovered when certain types of quartz rocks, when struck, generated current. It was then discovered that when an electric current was applied to these substances they "jumped" as if struck. They are actually warping slightly as current passes through them. According to the size and shape of the substance, a pulse of sound is emitted. If the substance is small then the sound is in the frequency range (>20,000 Hz) and considered "ultrasound" if the substance is large enough, then the sound will be in the hearing range of humans and we would call it a speaker! This is the basis of all ultrasound transducers. They are extremely high tech speaker/microphones and because of the small size of the crystals and the brittleness of the materials, they are very very fragile. Protect this wonder of nature that we have harnessed, buy an ultrasound transducer wall rack! A typical transducer has many crystals. There are many different ways to configure the crystal placement. The important thing to remember is that in each transducer cable there is one or two wires per crystal. The crystal count per transducer can be very high (as high as 512 in many instances) so you can imagine how small and fragile these connecting wires become. To give you some idea, if a wire were as small as a lead pencil refill (.7mm) and you only had 100 wires in a cable, your cable would be about 7 cm in diameter. These wires have to be extremely small and still have a coating of insulation. Back in "the day" a transducer with 128 crystals was about as thick as an average thumb and quite stiff, now transducers with 512 crystals routinely have cables as small as a 5th finger and are quiet flexible. The wonders of modern technology are certainly awesome even in something as mundane as a cable. Transducer crystals are sawn from a block of piezo-electric material with a saw blade so fine that it can cut a human hair end on (split ends) four to seven times! A person trains on a saw for months before they are actually allowed to make a cut with the saw. The electrical connections are generally hand soldered (up to over 1000 times in a transducer) and these are the reasons that transducers are somewhat expensive.
What is a channel...?
Each manufacturer defines the term channel count differently. Basically it has to do with the number of crystals your system is able to fire in a transducer. Some manufacturers just count the maximum number of crystals they are able to drive and call that their channel count. Some manufacturers count each crystal as one channel for transmit, one channel for receive, effectively doubling the number of channels they can claim. One manufacturers 512 channel may be effectively the same as another manufacturers claim of 1024 channels. Another trick seen is counting each send and recieve and multiplying that by the number of times a pulse is manipulated in a system on post processing and coming up with phenomenal (or ridiculous) claims of channel counts.
Why the wierd numbers? 64, 128, 512...
The strange numbers associated with ultrasound machines goes back to computing. Remember that each byte of information contains 8 pieces of information or bits. These are the famous 1s and 0s we see and hear so much of. A computer counts differently than you or I do. We have a base 10 counting system; meaning everything we count we tend to group in groups of 10s, 100s or 1000s. A computer on the other hand groups its counts into groups of 8s. Therefore you get groupings such as nintendo 64 (8x8=64), the Acuson 128xp (8x16=128) and so on.
Transducer Safety:
Transducers should be cared for according to your manufacturers instructions and should be checked daily for cracks in the transducer housing (can cause shocks or burns to patients) and cords should be checked for tears. Any cracks or tears in the housing or cord automatically takes that transducer out of service and under no circumstances should that transducer be used until checked and tested by authorized personnel.
Transducer Cleaning and Disinfection:
Transducers are also excellent vectors for the spread of infection and should be thoroughly cleaned between patients with an antiseptic/anti-viral solution approved by the manufacturer.
FAQs for transducer cleaning:
1. What are the differences between high level, mid level and low level disinfection?
High Level Disinfection destroys all microorganisms except bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers).
Mid Level Disinfection inactivates mycobacterium tuberculosis, vegetative bacteria, most viruses and most fungi but does not necessarily kill bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers).
Low level Disinfection can kill most bacteria, some viruses, and some fungi but can not be relied on to kill resistant microorganisms such as tubercule bacilli or bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers). (DISINFECTION is the selective removal of microbial life).
2. What is sterilization? What are the compatible sterilization methods?
Currently, extended soaking in liquid sterilants is the approved method for sterilization of Acuson transducers. Some products, such as sterililization units using a chemical plasma are not currently compatible with some transducer materials. Contact your applications specialist for specific compatibility information. (STERILIZATION is the complete elimination or destruction of all forms of microbial life).
3. Why do I need a precleaner?
It is desirable to use precleaners to remove mucous or bioburden prior to disinfection. Often times the only method used between patients for transthoracic exams. Not a sufficient disinfection method for endocavity or TEE exams. Allows for reduced soak time for high level disinfection. Typically very easy to use (soak times are short).
4. How long should I soak the transducer?
Soak time depends on the level of disinfection or sterilization specified by the type of disinfectant used. Varies from solution to solution and brand to brand. For high level disinfection, glutaraldehydes generally require 20 minutes with a precleaner or 45 minutes without a precleaner. For example: Cidex OPA needs only 12 minutes for high level disinfection. Cidex requires 20 minutes if a precleaner is used or 45 minutes without a precleaning step for high level disinfection. Cidex requires 10 hours for complete sterilization. Gigasept ff requires only 4 hours for complete sterilization (European) Milton requires just 1 hour for complete sterilization (Australia and New Zealand)
5. When and how should I use glutaraldehydes?
It is still the only option for older TEE probes (built before 2000). There are health hazards associated with glutaraldehydes. Glutaraldehydes require special ventilation to reduce the risk of worker exposure.
What are my nonglutaraldehyde alternatives?
Cidex OPA is a new high level disinfectant cleared by the FDA in January 2000. The active ingredient is 0.55% ortho-Phthalaldehyde and this solution can disinfect devices in 12 minutes. This solution is compatible with all Acuson transducers including the new TEE products. Please contact your Acuson representative for more details. Staining may occur on selected endocavity probes. Acoustic performance and image quality will not be affected. When using Cidex OPA, transducers must be thoroughly rinsed according to the manufacturer's recommendations. Advanced Sterilization Products recommends three 1-minute rinses in water using two gallons of fresh water each time. This will ensure that no Cidex OPA residue remaining on the transducer. Cidex OPA residue was found to react with protein which will result in transducer staining.
Nonglutaraldehyde Alternatives for Low Level Disinfection
Quaternary Ammonium solutions (Quats) such as Ascend, Engarde, Hi-Tor Plus, and Medallion. Quats are not High Level Disinfectants and are generally not tuberculocidal or effective against Hepatitis B. Quats are generally considered low level disinfectants and are acceptable to use on external probes. Quats generally are sold as concentrates. A gallon goes a long way!
6. Can I use bleach to disinfect?
Probes should not be soaked in bleach, even in dilute solutions Soaking a probe in bleach will cause lens delamination as well as material degradation Wiping a probe with a 10% bleach solution is an acceptable low level disinfection method and will not harm probe.
7. Is isopropyl alcohol safe to use?
Probes should not be soaked in IPA. Soaking a probe in IPA will lead to lens delamination. Wiping a probe with IPA or solutions containing IPA will not harm probe. Using IPA as a wipe may provide low level disinfection.
8. What types of gel should I use?
Should not contain mineral oil or perfumes. High viscosity or low viscosity does not affect compatibility. Check with your particular manufacturer for recommendations.
To summarize care of transducers:
1. Use the appropriate cleansers recommended by the manufacturers of your equipment. (using trhe wrong solutions may void the transducer warranty.
2. Treat your transducers as fragile pieces of equipment. Try never to drop them and don't put them where they may be brushed onto the floor. (Your Ultrasound Transducer Wall Rack is an important tool in protecting your investment).
3. Be gentle with connections and cables, a broken wire will have the same effect as a broken crystal.
Transducers work on the fact that piezo-electric substances create an electric current when struck. This was discovered when certain types of quartz rocks, when struck, generated current. It was then discovered that when an electric current was applied to these substances they "jumped" as if struck. They are actually warping slightly as current passes through them. According to the size and shape of the substance, a pulse of sound is emitted. If the substance is small then the sound is in the frequency range (>20,000 Hz) and considered "ultrasound" if the substance is large enough, then the sound will be in the hearing range of humans and we would call it a speaker! This is the basis of all ultrasound transducers. They are extremely high tech speaker/microphones and because of the small size of the crystals and the brittleness of the materials, they are very very fragile. Protect this wonder of nature that we have harnessed, buy an ultrasound transducer wall rack! A typical transducer has many crystals. There are many different ways to configure the crystal placement. The important thing to remember is that in each transducer cable there is one or two wires per crystal. The crystal count per transducer can be very high (as high as 512 in many instances) so you can imagine how small and fragile these connecting wires become. To give you some idea, if a wire were as small as a lead pencil refill (.7mm) and you only had 100 wires in a cable, your cable would be about 7 cm in diameter. These wires have to be extremely small and still have a coating of insulation. Back in "the day" a transducer with 128 crystals was about as thick as an average thumb and quite stiff, now transducers with 512 crystals routinely have cables as small as a 5th finger and are quiet flexible. The wonders of modern technology are certainly awesome even in something as mundane as a cable. Transducer crystals are sawn from a block of piezo-electric material with a saw blade so fine that it can cut a human hair end on (split ends) four to seven times! A person trains on a saw for months before they are actually allowed to make a cut with the saw. The electrical connections are generally hand soldered (up to over 1000 times in a transducer) and these are the reasons that transducers are somewhat expensive.
What is a channel...?
Each manufacturer defines the term channel count differently. Basically it has to do with the number of crystals your system is able to fire in a transducer. Some manufacturers just count the maximum number of crystals they are able to drive and call that their channel count. Some manufacturers count each crystal as one channel for transmit, one channel for receive, effectively doubling the number of channels they can claim. One manufacturers 512 channel may be effectively the same as another manufacturers claim of 1024 channels. Another trick seen is counting each send and recieve and multiplying that by the number of times a pulse is manipulated in a system on post processing and coming up with phenomenal (or ridiculous) claims of channel counts.
Why the wierd numbers? 64, 128, 512...
The strange numbers associated with ultrasound machines goes back to computing. Remember that each byte of information contains 8 pieces of information or bits. These are the famous 1s and 0s we see and hear so much of. A computer counts differently than you or I do. We have a base 10 counting system; meaning everything we count we tend to group in groups of 10s, 100s or 1000s. A computer on the other hand groups its counts into groups of 8s. Therefore you get groupings such as nintendo 64 (8x8=64), the Acuson 128xp (8x16=128) and so on.
Transducer Safety:
Transducers should be cared for according to your manufacturers instructions and should be checked daily for cracks in the transducer housing (can cause shocks or burns to patients) and cords should be checked for tears. Any cracks or tears in the housing or cord automatically takes that transducer out of service and under no circumstances should that transducer be used until checked and tested by authorized personnel.
Transducer Cleaning and Disinfection:
Transducers are also excellent vectors for the spread of infection and should be thoroughly cleaned between patients with an antiseptic/anti-viral solution approved by the manufacturer.
FAQs for transducer cleaning:
1. What are the differences between high level, mid level and low level disinfection?
High Level Disinfection destroys all microorganisms except bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers).
Mid Level Disinfection inactivates mycobacterium tuberculosis, vegetative bacteria, most viruses and most fungi but does not necessarily kill bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers).
Low level Disinfection can kill most bacteria, some viruses, and some fungi but can not be relied on to kill resistant microorganisms such as tubercule bacilli or bacterial spores (See Clinical Recommendations for applicability to specific uses of ultrasound transducers). (DISINFECTION is the selective removal of microbial life).
2. What is sterilization? What are the compatible sterilization methods?
Currently, extended soaking in liquid sterilants is the approved method for sterilization of Acuson transducers. Some products, such as sterililization units using a chemical plasma are not currently compatible with some transducer materials. Contact your applications specialist for specific compatibility information. (STERILIZATION is the complete elimination or destruction of all forms of microbial life).
3. Why do I need a precleaner?
It is desirable to use precleaners to remove mucous or bioburden prior to disinfection. Often times the only method used between patients for transthoracic exams. Not a sufficient disinfection method for endocavity or TEE exams. Allows for reduced soak time for high level disinfection. Typically very easy to use (soak times are short).
4. How long should I soak the transducer?
Soak time depends on the level of disinfection or sterilization specified by the type of disinfectant used. Varies from solution to solution and brand to brand. For high level disinfection, glutaraldehydes generally require 20 minutes with a precleaner or 45 minutes without a precleaner. For example: Cidex OPA needs only 12 minutes for high level disinfection. Cidex requires 20 minutes if a precleaner is used or 45 minutes without a precleaning step for high level disinfection. Cidex requires 10 hours for complete sterilization. Gigasept ff requires only 4 hours for complete sterilization (European) Milton requires just 1 hour for complete sterilization (Australia and New Zealand)
5. When and how should I use glutaraldehydes?
It is still the only option for older TEE probes (built before 2000). There are health hazards associated with glutaraldehydes. Glutaraldehydes require special ventilation to reduce the risk of worker exposure.
What are my nonglutaraldehyde alternatives?
Cidex OPA is a new high level disinfectant cleared by the FDA in January 2000. The active ingredient is 0.55% ortho-Phthalaldehyde and this solution can disinfect devices in 12 minutes. This solution is compatible with all Acuson transducers including the new TEE products. Please contact your Acuson representative for more details. Staining may occur on selected endocavity probes. Acoustic performance and image quality will not be affected. When using Cidex OPA, transducers must be thoroughly rinsed according to the manufacturer's recommendations. Advanced Sterilization Products recommends three 1-minute rinses in water using two gallons of fresh water each time. This will ensure that no Cidex OPA residue remaining on the transducer. Cidex OPA residue was found to react with protein which will result in transducer staining.
Nonglutaraldehyde Alternatives for Low Level Disinfection
Quaternary Ammonium solutions (Quats) such as Ascend, Engarde, Hi-Tor Plus, and Medallion. Quats are not High Level Disinfectants and are generally not tuberculocidal or effective against Hepatitis B. Quats are generally considered low level disinfectants and are acceptable to use on external probes. Quats generally are sold as concentrates. A gallon goes a long way!
6. Can I use bleach to disinfect?
Probes should not be soaked in bleach, even in dilute solutions Soaking a probe in bleach will cause lens delamination as well as material degradation Wiping a probe with a 10% bleach solution is an acceptable low level disinfection method and will not harm probe.
7. Is isopropyl alcohol safe to use?
Probes should not be soaked in IPA. Soaking a probe in IPA will lead to lens delamination. Wiping a probe with IPA or solutions containing IPA will not harm probe. Using IPA as a wipe may provide low level disinfection.
8. What types of gel should I use?
Should not contain mineral oil or perfumes. High viscosity or low viscosity does not affect compatibility. Check with your particular manufacturer for recommendations.
To summarize care of transducers:
1. Use the appropriate cleansers recommended by the manufacturers of your equipment. (using trhe wrong solutions may void the transducer warranty.
2. Treat your transducers as fragile pieces of equipment. Try never to drop them and don't put them where they may be brushed onto the floor. (Your Ultrasound Transducer Wall Rack is an important tool in protecting your investment).
3. Be gentle with connections and cables, a broken wire will have the same effect as a broken crystal.
