EBME Forums Forums Maintenance Technical Assistance Ultrasound probe repair

Hello Phil

No, I had never heard about that one; but, there again, why should I (even though it took place six years ago)?


All for the want of a dated sticker! It makes me wonder if the hospital even has (had) a biomed on the staff.

"Blaming the kit" (again); who would have thought it?

No mention of a faulty probe, though. But at least they apparently had a manual.

But having spent a whole chunk (note the American "terminology" there) of my life banging on (preaching?) about PM, I can only imagine that the message has yet to reach Philadelphia, USA.

Placental abruption

Hello Geoff,

You wrote:

No mention of a faulty probe, though.

That's true, ..but surely where a probe has been repaired, without a certificate verifying the probe performance, the probe is in the same boat as the scanner with no service record?

Phil

That would depend upon the nature and extent of the repair, I should imagine. Anything done by a Third Party would always carry a piece of paper for the files, I would have thought.

Geoff,

The problem starts where the acoustic lens or underlying layers are repaired. There are test devices which will check the elements for Element Sensitivity, Capacitance, Pulse Width, Pulse Shape, Center Frequency (MHz) and Fractional Bandwidth (%).

Can I draw your attention to the BMUS publication below:

"Recognising small image quality differences for ultrasound probes and the potential of misdiagnosis due to undetected side lobes"

Georg Doblhoff, Jaroslav Satrapa, Philip Coulthard

First Published January 23, 2017

Taken from the abstract

"Ultrasonic imaging is an integral and routine procedure in many medical applications. An increased awareness of the need for quality assurance in this field has led to numerous tests being proposed. Due to the complexity of the problem, the tests directly measuring the important parameters of resolution and contrast of low-echoic structures are not unified, often more qualitative than quantitative, and are performed at large periodic intervals. Uniform sensitivity of an array transducer is a necessary but insufficient requirement for imaging quality of an ultrasound probe. Good probe uniformity should in no way be confused with meaning the ultrasound probe is working as it should."

IEC TS 61390 now incorporates test methods which from our tests are capable of measuring subtle changes in probe performance which your community may wish to consider.

Regards

Phil C

I may be wrong Geoff but I suspect that over the years US has been dumped in the EBME lap. US has always been the Cinderella service provided by radiation protection and there are few active US expert physics people around today. I am not sure that in the transfer all relevant background information came your way. For example who knows about this little gem available in Google books?

https://books.google.co.uk/books?id...%20ivan%20zuna%20propagation&f=false

There is a meeting coming up in Manchester. We have submitted an abstract which we hope will be accepted I hope that anyone involved in US can make this meeting and take that finance officer twisting your arm to save money.

Ultrasound QA 2018

Date: 31 Jul 2018

Location: Manchester

This meeting provides an update for physicists, scientists and technologists working with Ultrasound equipment and involved in ultrasound QA and is an excellent opportunity to exchange knowledge and experiences and ideas and is an excellent networking opportunity.

Yes Phil, I'm afraid you are wrong ... in my experience, ultrasound has always been "dumped in the EBME lap" (and quite rightly so).

In the UK, "Medical Physics" may have been involved; but I've never worked in one of those places myself.

What are you selling, by the way?

Perhaps you can enlighten me then Geoff:

I appreciate that the management of equipment lies with EBME but the equipment QA is or was carried out by Radiation Protection, in the UK at least. Going back further physicists were US clinicians as well. Most contracts for Radiation protection listed on tenders have a component of Ultrasound QA, where this is implemented. This has been my experience and focus over the last 10 years in a physics coop but the message I am trying to get across is not the right or wrong of who carries out the QA.

You are right to ask "what is Phil selling" and you could have also asked "why now"? To be honest I had just about abandoned any hope or interest in US QA test methods using Satrapa's void phantoms and put it down to just bad luck. I was like King Canute holding back the tide when everyone else was out there boating and enjoying the waves. I had settled into a routine of contract management, physics QA and best of all pushing grandkids around Hexham in the pram.

One day I was assessing a breast US scanner and came across a anomaly which I could not ignore. It was decided by the members that we should inform the MHRA and that started an avalanche which ended up with us loosing the contract for radiation protection services through no fault of our own. The anomaly is on the web and if your members are interested I can provide the password for a limited period:

https://medicalphysicscoop.co.uk/2017/03/17/anomaly/

Its password protected to stop general viewing and there is some remaining issues that we need to address with the manufacturer as well as the data being a source for a potential publication.

Fortunately we had published the paper as mentioned in the last post, which gave us some credibility when in discussions with the US physics community and the MHRA but turning the IPEM boat around to a different way of thinking, takes a long long time. Meanwhile a couple of very recent posts on the physics JISCMAIL from technologists with concerns over probe repair came to light and I suspect that this is the tip of the iceberg and these were the good guys. It has been clear for some time that IPEM currently have no answer to a test method capable of showing subtle probe defects albeit they have made it clear that without guidance from a US MPE, probe repair should not be considered.

Acceptance by the IEC committee TS 61390 by such esteemed professors as Dr Paul Carson and Dr Peter Edmonds means we really do not have to sit like mushrooms in the dark any longer. Sure, we need evidence to back up the IEC approval if we are to get revised IPEM guidance but that can only come through use. We have the anomaly mentioned above but there needs to be many more people pushing the US agenda for change. It is my hope that this community can help me identify just how big a problem this probe repair issue is and what QA if any is implemented. So that's what I am selling Geoff, change in thinking, change in our capability to say no to bad probes, change in the perceived merit of US QA, change in the relevance of QA to clinical diagnosis and perhaps a few less sleepless nights wondering if we made the right decision. Who knows, if enough people engage this time, with your help, perhaps we can take what is in essence a ageing inventor and a sales / enthusiast guy in a garden shed to innovate a new way of product delivery also.

PS for some people out there this is bad news. They will have invested heavily in probe repair in their hospital. Having a test method capable of detection of subtle defects raises the question of patient recall and potential litigation. Perhaps there is a window for reconciliation, "we never knew" but that window is closing fast.

Regards
PC

OK; but what (which) test or QA method are we talking about?

Do you mean this?

What test kit is involved; and who supplies it?

Can (or should) this stuff be done in-house ... or is it only of use when probe repairs have been carried out (eg, by a manufacturer, or third party)?

PS: I'm interested in the scene shown at the banner of your website. Where is that? Not Hexham, surely?

Geoff,

OK; but what (which) test or QA method are we talking about?

The BMUS publication you linked to shows a cross filament phantom which provides a 3D qualitative presentation of the beam shape throughout depth as described in the text. This test object is a useful tool to give a more in depth understanding of the physics behind what we see clinically but it cannot provide quantitative data. The set up time is longer due to alignment of the threads. This test object could be used to establish a baseline to be referred to over time and for educational purposes but it would not be the first choice of tool to use for routine QA.

On the other hand a random void phantom (RVP) can provide quantitative data in terms of "Sonic Contrast" ( SC) which is defined in IEC TS 61390. SC has clinical significance and can be used to determine whether or not a probe should be used for a given clinical application taking into account the amount of overlying fat of a given patient. Further research into the clinical uses of SC is needed. The RVP also provides a way of viewing image data in 3D which makes subtle defects evident to the eye. The RVP in essence is a recticulated foam sponge of known attenuation, immersed in salt water, again described in the TS 61390. Image capture is quick and alignment issues are overcome.

The tests can be carried out in house as part of a routine QA program. Once you are up to speed little additional test time is required. Analysis can be done back at the office. The stored information would then be used as a reference should a probe be repaired or the image quality is suspect.

It would not be too much of a stretch of the imagination to envisage manufacturers building a propriety version of the software into their scanner and request a daily test scan by the sonographer for the probe selected with a on screen message appearing should a probe go out of tolerance. It is important to retain an independent version of the test method to ensure transparency of evaluation of the manufacturers results. It would be unlikely "anomalies" in their images would be flagged up as out of tolerance. Nor are propriety versions likely to provide comparative image quality information.

Having reread what I have written I don't want to mislead anyone into thinking Sonic Contrast (SC) is in all cases quantifiable, it is not. Ultrasound imaging, especially with the introduction of median filters is non linear and it is not possible at this time to make comparative assessments between scanners or get a true SC for any given machine for any system settings.

For a true Rayleigh distribution of the grey levels we can have more confidence in the SC derived but on modern scanners this is increasingly rare. Even so, SC points the way towards a quantifiable and comparative test method which is very sensitive to subtle changes in image quality as potentially any repaired probe with have. One should not expect manufacturers to leap in to provide access to raw or unprocessed data. It was once suggested to me the purpose of a good phantom from a manufactures perspective was to show the merit of "our scanners" not the competitions. Comparative phantoms could be a manufactures night mare.

One way to put pressure on the manufactures to open the way for change and greater quantification would be for this community to engage on SC measurement and start asking the questions.