How much is the lifespan of an ultrasound transducer?

My Stanley Cox US machine was the first piece of kit that I bought when I went into private practice in 1980! The only thing I have had to replace on it has been the jack plugs where staff might catch their foot in the cable, but as my husband's degree was electronics, he kindly replaces it when I need!! Transducer heads - no problem and not shiny!!!

Hi...in my case i have not seen any data to show this is the case. IF it is true and IF polishing the treatment applicator face surface reduces the beam inequality, I can see that there would be an advantage but that is supposition rather than fact.

I have been servicing and repairing Ultrasound devices in Physiotherapy for over 29 years now, over that time i have seen many makes & models. Some units (30+ years old) have very good outputs even today, (as long as they are serviced / calibrated each year) . The bond (glue) used to stick the crystal to the metal head plays a very large part in the quality of ultrasound transmission from the crystal to the head, if this is looked after, i.e not dropped or knocked then along with regular calibration they will work well and last for many years. However I have seen some very poor quality manufactured heads that certainly would not last more than a few years, luckily these are not in wide spread circulation.

The Ultrasound heads are matched to the base unit (driver) and when set up correctly, operate effectively. Out of calibration devices can cause the crystal to be driven at an unmatched frequency and therefore deliver a lower output. The most common cause for a crystal to fail is damage (a small blow to the head can cause damage even if it is not visible on the external surface of the head). We generally replace 1 or 2 crystal / heads a week, based on us servicing over 1500 per year in the UK.

So to conclude, I would estimate the average life of a crystal / head that is looked after (serviced yearly and not physically damaged) would be over 10 years. Please also note that crystals can be replaced, so the life of the Ultrasound can be extend (I still see machines that are 40+ years old working ) with the cost of parts being between £80 and £300 dependent on Manufacturer and availability.

As I understand it from ultrasound engineers, the more 'scratched' the ultrasound applicator face, the more 'disturbed' the ultrasound beam will be. The beam inequality (BNR) will be worse. That having been said, I have not seen any data to show this is the case. IF it is true and IF polishing the treatment applicator face surface reduces the beam inequality, I can see that there would be an advantage but that is supposition rather than fact. I will see if I can get an engineer to come up with some factual information. Tim

justine.waloch305 said:

Hello, Does anyone know if having an ultrasound head buffed to remove a scratch left by a service can effect its output? I have a chattanooga and the original finish on the soundhead was a bit textured and now it shines like a mirror. Thank you anyone that knows.

Good question... I THINK that the head is not shining in the market because is more expensive, nothing more. And so, the head rude or shining, the power and effectiveness, is the same. THEORETICALLY shined, the shape of emission...should be less dispersive. DIFFERENT if is shined like a mirror but become convex or concave ...

Hello, Does anyone know if having an ultrasound head buffed to remove a scratch left by a service can effect its output? I have a chattanooga and the original finish on the soundhead was a bit textured and now it shines like a mirror. Thank you anyone that knows.

Just a few days ago I saw a VIDEO of a US device never updated or controlled in 15 YEARS... well, at maximum power it evaporated all the water on the transducer in 1 sec °_° But ok, it is a "steampunk" device, really old style and maybe more durable and reliable. Mine devices, every 2 years do check up and calibration.

Just to clarify my prior post and Professor Watson's reply, I make a well at least 3/4 of an inch deep, or greater depending on the width of the tape I use to make the well. This allows me to pour a one to two ounces of water into the well and over the transducer head. I agree with Prof. Watson that just a few droplets of water can damage a transducer but with more water as I have described, we have never seen a decline in transducer function verified by calibration procedures.

Prof James. Many thanks for that suggestion. The drops of water on the transducer face - a commonly employed 'trick' looks great but potentially causes transducer damage. I like your idea - will go try it as it is not one that I have employed - and I can see the benefits as a demo and quick test without the risk of transducer damage. Thank you. I can feel a YouTube video coming on . . . . .!!!!!

Similar to Professor Watson's suggestion for a simple visual assessment of sound output, you can take some kind of tape, preferably 1" wide or more and apply it around the US head creating a well into which you can pour water. After you turn on the US device, I suggest initially testing with a 100% duty cycle and 1 W/cm2. If the transducer head is functioning, you will see a disturbance of the water surface in what appears to be concentric rings. As you decrease the duty cycle you will see the magnitude or severity of the water disturbance decrease with the decreasing duty cycle. In this manner you can at least determine if the transducer is still providing differing duty cycles. Another neat feature of this methods of assessing an US transducer is that you can get an idea of the effective radiating area (ERA) when looking down into the water well and seeing the diameter of the area where the water ripples originate in comparison to the size or diameter of the transducer head. Not a technical or specifications check, but a quick functional assessment and wonderful teaching lesson.

The first piece of equipment I bought when I went into private practice was an ultrasound machine. That was in 1980 and it is still going strong. I have a calibrated water balance and it still works to the original specs. We are also very careful with the heads and take care they are not knocked or dropped!

Thank you Tim for your contribution

KR Patrick

there used to be a very low cost water balance available (about 50 pounds GB) but I could not find it when I looked the other day. If I find anyone who still supplies it, I will post here.

I tried the thing with the water and it worked and was kinda fun to show it to a patient. Thanks for that and for the links. 225 pounds is not cheap price in Bulgaria though.

we use some equipment to test devices in the lab which is fairly expensive so would not be in routine use. There are some small and low cost ways to do a basic test using a 'water balance' indicator (I will paste example link below) but these will only give you and indication of approximate output - you will know if your device is working and in the right general power level but I would not count as accurate. Simplest way to test output - at zero cost - is to immerse ultrasound transducer in bowl of water, turn applicator face up towards the surface, put machine on continuous output, turn up to say 1.0 W cm^2 and if it is giving an output you will see water surface ripple/disturbed. Gives no indication of accuracy, but at least you will know whether something is happening and therefore whether some output. Examples of high cost water balance test kit: http://www.acoustics.co.uk/product/radiation-force-balance/ http://www.emsphysio.co.uk/product/precision-ultrasound-balance/

Low cost units such as: http://www.emsphysio.co.uk/product/budget-ultrasound-output-indicator/

Not sure which country you are based in - might make a difference

Well, I am not shure where I can test the machine in my country. Is there any easy way to do that without special equipment?

So long as they are looked after and (calibration) tested to be sure that they are functioning properly, they can last a lot longer. I was using a device manufactured in 1990 the other day and the transducer was delivering perfectly good ultrasound and was spot on when I checked the calibration. One of the things that seriously reduces life span is 'knocking' the transducer - so being careful does pay off. I am sure that some of the manufacturers might have a technical view - let's see if anybody comes up with anything