Waterjetting 17c - Discriminate cutting of tissue

In the last two posts I have noted that, by tailoring the pressure at which a waterjet is aimed at a surface, it is possible to discretely remove different layers that cover that surface, while leaving the underlying layers undamaged. The examples extend from removing individual layers of paint to the rubber left on a runway after planes have landed. But this idea also works in the removal of damaged concrete from bridge decks and garage floors. Here it is the ability of the jet to grow the longer cracks in the damaged concrete that makes it able to discriminate between the good and bad parts of the deck.

The idea can be extended into other areas that are not quite as obvious. And it began with a conversation with my dermatologist – Dr. Van Stoecker. We were discussing the change in state of different tumors when I brought up the discriminatory ability of waterjets. And so I went home and tried a simple experiment. I took an apple and bruised it – and left it for a couple of days. (The pictures come from a repeat of the experiment that I carried out today).

Figure 1. Bruised apple, showing the darkened damaged flesh under the skin

Then I removed the skin over the bruise and using a water pick washed away the soft damaged tissue, while leaving the healthy tissue undamaged, since the jet did not have enough power to remove it.

Figure 2. Showing the peeled region around the damaged part of the apple, and the old model WaterPik used for the demonstration.

The process was a little slow, and since the tip was hand-held and not rotating (the better way to ensure total areal coverage) took longer than it would with a spinning jet.

Figure 3. Partially cleaned apple.

The pulsating jet is manually oscillated over the apple surface, and cuts down through the softer flesh, but is not powerful enough to remove the healthy apple tissue beneath it.

Figure 4. The apple after the damaged flesh had been removed. Because of the simple manual manipulation the cleaning of the final surface was not quite as thorough as is achieved with a spinning head. The procedure takes varying amonts of time depending on the pulsation setting and the type of apple being used – this was a Granny Smith.

A water pick operates at a relatively low pressure, but the demonstration was sufficient that Dr Stoecker obtained an excised human skin tumor and we carefully cleaned the tumor surface, aspirating the spent water and debris using a small version of the vacuum system that we used to collect radioactive waste from underground storage tanks. When the tissue was then sent away for analysis it turned out that the water had effectively removed all the diseased tissue – which is softer – while leaving the healthy tissue in place.

Testing progressed through testing on dogs, and the concept was ultimately patented and was licensed.

One of the advantages of the tool, and the approach is that the jet will penetrate and remove the small tendrils of cancer that can spread out from the main tumor since the jet will follow these paths and remove the soft tissue content, while leaving the stronger healthy flesh. This has the benefit of reducing the scarring of the flesh in the vicinity of the tumor, and thus the amount of subsequent cosmetic treatment.

The argument for reduced excision of healthy tissue is equally or perhaps of more concern where the tumor lies in the brain, and colleagues in Germany have carried out operations on individuals to evaluate how effective waterjet removal (hydro-surgery) (Waterjet dissection of the brain: experimental and first clinical results. Technical note. Piek J, Wille C, Warzok R, Gaab MR.) No complications were found with the first nine patients who received this treatment.

The use of pulsating jets, of the WaterPick variety and at higher pressures has found increasing use for other purposes. Before the recent popularity of chemical washes it was, for example, shown that the use of a pulsating jet to flush wounds helped both remove any foreign matter still in the wound (particularly with “gravel rash” type injuries) and to lower the bacterial count.

Figure 5. Change in relative bacterial counts after conventional and pressure washed wound treatment (From PTJournal)

For this to be effective jet pressures had to be higher than 25 psi. Specialized equipment has now been developed for these uses, which have been shown to provide the benefits of: - shortening of the wound healing process, - reduction of the scar tissue, - low stress effects for the patients because the treatment is relatively painless.

Two different tools, the Debritom and the Versajet have been marketed for use in cleaning skin injuries (and while photos exist – for example here, I will recognize that some readers may be sensitive and will forego showing them.

The Versajet is a slightly different concept in which a very small high-pressured jet cuts across the face of the instrument and back into a collection chamber, so that it can peel off thin layers of necrotic and other undesired tissue and clean up wounds, particularly with burn injuries, more positively. The vacuum created by the jet passage into the chamber helps collect the debris.

Figure 6. Schematic showing the operation of the Versajet system.(Smith and Nephew )

Precision cutting and discriminatory cutting of flesh and other parts of the body have grown in application as the ability to manufacture smaller and more precise component,s that can operate at higher pressure, have been developed.

I will conclude this short section on some of these developments in the next post.

A New Series - Waterjetting 1a

In October of 1965 I started work on a doctoral dissertation that would look at whether streams of high-pressure water could be used to mine minerals, rather than using the mechanical tools that my ancestors had been using for many generations to mine coal. Until the time of my great-grandfather the main tool had been a hand-swung pick, but he had made the transition to become a compressed-air-powered, coal-cutter operator, and worked with my grandfather on running that machine until the first World War, when his son joined the Northumberland Fusiliers and went off to Belgium.

When I started my work, after my mining engineer father had approved, I found that there was little information on hydraulic mining available in the technical literature. The Internet did not exist, and the few books and articles that I could obtain came through the Brotherton Library at Leeds University, where Inter-Library Loans would find a source, and even, on occasion, a translation, but in weeks not days.

Those conditions no longer hold true, and yet, while a computer now makes it easier to get instant access to all the world’s knowledge, filtering through that vast stack to find that needed bit of information still takes time. And there are other factors that have come into play, so that much of the knowledge that has been gained may soon be lost, forgotten or spread into so many distant places as to be effectively gone. And so I am going to put together a new series of posts about this technology. Since this is the first it is more of an explanation of the background, and as the posts continue so the structure and location may change, trying to better serve those who follow me in what has been the truly fascinating development of a new very broad-based industry.

Over the past decades high-pressure waterjets have found a wide variety of different uses around the world. From the small pumps that can be bought at the local hardware store and allow you to clean houses, furniture and cars through the thousands of horsepower used in pumps for the excavation and mining/petroleum industry a quiet revolution has occurred in many industries, beyond the sight of the general public. I was fortunate enough to be a part of the relatively small group of scientists/engineers/technicians who helped bring these changes about. Around the world there were perhaps 50 or so of us, and much of our interaction took place at conferences, where we learned more from each other in bars and restaurants than we did from the formal papers that we all gave. Some changes were fairly dramatic, the use of cleaning jets on oil platforms comes to mind, and were instantly adopted, others were a longer struggle, and yet these tools have yet to find more than 90% of their ultimate market, which will likely be in fields that most of us have not even thought of yet. And the tools that have already been developed are used in many more industries than the general public understands.

I retired a couple of years ago, and followed many of that original group in moving on to other interests. Before I left, however, I had written a book, and taught a class to senior undergraduates dealing with manufacturing use, as well as the earlier mining applications. The class is not taught now, and interest in the topic has also shrunk at the other major universities, as faculty have changed, and other topics bring the “research rain” that is needed to sustain the graduate classes of today.

This does not mean that waterjetting is less valuable, but instead is recognizes that the first flush of development is over, and that the really low-hanging fruit of application has been picked by folks such as myself. The range of applications remains immense, but the rewards are not now as easily obvious, and the research results now are not so dramatic.

The current plan is to begin the series with posts that come from my lecture set. But instead of being of the usual length they will be broken down into a set of sub-topics, so that there may be three or four posts that will cover the material of a single class. This will make each post of around a thousand words, and then the four sub-topics will be combined into a “class” version which will be posted as a pdf, and this will be down-loadable, and could be printed and put into what will, over time, become a somewhat updated version of that earlier book, but in a different format.

Since none of the anticipated readership is yet aware that this is happening, I expect that it will take some time for comments and questions to develop, but as these do they will be added into the mix.

Once the original posts have become established I hope to be joined by some of the folk that are still working in the field – as I said earlier it is one that is still continuing to grow at a fairly steady pace (one of the companies that makes equipment was on the national news recently because it could not get enough trained folk to help it meet demand). New ideas will turn up, and I look forward to giving my opinions. Sadly these may appear a bit negative at first, but there were many things we tried that looked good, but did not pan out. And those were usually not, therefore, the things that we wrote papers about. But knowing something won’t work, and more particularly why not, is also useful.

The early posts will also deal more with the history and general background, since these are likely to have a more general interest, and the more technical parts of the discussion will come later, though I will try and keep that at a relatively simple level for explanation.

I got my last patent this week, it dealt with drilling oilwells – the one before that dealt with treating skin cancer. I have worked on intercontinental ballistic missiles, at nuclear facilities, on land-mine clearance and in blocked caves. So perhaps I could claim to be a surgeon, rocket scientist, nuclear scientist, fire-fighting expert, and hazardous material specialist – and that neglects all the work on manufacturing and the evolution of tools that can cut through an inch of material within an accuracy of a thousandth of in inch.

All because of the power that comes when you push a pint of water through a tiny hole. Who’d a thunkit!!