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Jcusiter
12-04-2010, 03:28 PM
I am working on a project with the Medical Physics department of NHS Lothian. The team have developed a calibration device for portable ultrasound equipment.

What is the current practice for calibrating equipment within other NHS trusts/healthcare organisations?

Any info much appreciated.

physiobob
13-04-2010, 01:53 PM
I tend to get the various sales teams from the companies to come and service and check the equipment. Not sure how they calibrate it. I remember that if the ultrasound is on continuous and you turn it on and up then you can visually see the gel move. Suppose that means it's working but doesn't tell me much more than that. I device that is cheap and that we all could use would be rather useful :)

emeservices
08-02-2011, 03:37 PM
Resurrecting an older thread here... but to give you an insight into how we calibrate ultrasound machines.

First things first, knowledge... each ultrasound is different, some use bespoke calibration modules which we plug in to enable various test routines, where we can monitor/adjust drive levels, other machines use software based service modes, many older machines require a good old fashioned tweak of the oscillator and voltage drive levels. We attend training courses put on by the manufacturers, in order to keep up to date with their equipment and calibration routines.

However, it isn't that straight forward, you have to take into account the condition of the transducer and machine too, if the transducer has lost efficiency, you find yourself having to turn the drive levels up to produce the correct output, too much of this puts a lot of stress on the output circuits of the machine and can cause components to fail, even burning of the board/components.

To calibrate, our main measuring instrument is a digital UPM ultrasound power meter, made in the USA, we use the same unit many of the manufacturers, such as Chattanooga, use for the initial calibration of the machine before it leaves the factory. We also have several calibration jars made by Enraf Nonius for field world. It is also important to use degassed water as the little air bubbles in normal water don't allow for ultrasonic transmission and can affect the readings.

You can use the gel/tap water on the transducer for a quick indication that there is output, but as physiobob says, how much output? Last year we came across an old Therasonic in an NHS clinic during routine service work - as far as the therapist was concerned, it was producing output as the gel was moving. When we put it on our ultrasonic power meter, we discovered a fault where the machine indicated it was producing 0.2W/cm2 however it was actually producing 20 acoustic Watts of power at all power settings. This is a rare find however, as most of the time, when we find the calibration to be out, we find the power output has dropped lower than what the therapist expects.

Physio-Med tried to address this problem a while ago by selling some small, reasonably cheap (compared to the professional equipment) water jars with a small power level balance. While not very accurate and not suitable for calibration purposes, they do provide the therapist with more of an indication of the dosage they are treating the patient with.

joesmith407
26-06-2011, 05:22 AM
from my understanding, there's no new for calibration on the new digital equipment. they just do a PM once a year


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physiobob
27-08-2011, 09:34 PM
Physio-Med tried to address this problem a while ago by selling some small, reasonably cheap (compared to the professional equipment) water jars with a small power level balance. While not very accurate and not suitable for calibration purposes, they do provide the therapist with more of an indication of the dosage they are treating the patient with.Actually the guys who came to test my unit this year used that simple bit of kit in the water jar and it worked a treat.