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Wednesday, February 13, 2013

How to make your own ultrasound gel (which is also sterile and edible and environmentally friendly) **UPDATED--NEW RECIPE**

I have been doing lots of bedside ultrasound lately and realized how useful it would be in areas far off the beaten track like Haiti, for instance. With a bedside ultrasound (mine fits in my pocket) I could diagnose heart disease, kidney and gallbladder problems, various cancers as well as lung and intestinal diseases. Then I realized that I would have to take a whole bunch of ultrasound gel with me which would mean that I would have to check luggage, which is a real pain when traveling light to a place where luggage disappears. I heard that you can use water, or spit, in a pinch, or even lotion, though oil based coupling media apparently break down the surface of the transducer. Or, of course, you can just use ultrasound gel.

Ultrasound requires an aqueous interface between the transducer and the skin or else all you see is black. Ultrasound gel is a clear goo, looks like hair gel or aloe vera, and is made by several companies out of various combinations of propylene glycol, glycerine, perfume, dyes, phenoxyethanol or carbapol R 940 polymer along with lots of water. It is hard to find this information, but it is available in the material data safety sheets for the various companies that make it. The recipes are proprietary. Ultrasound gel is not super expensive, but it is not that easy to find in a store or in a developing country. It costs about $25 for 5 liters on Amazon, or $5 for a nice 8.7 oz squeeze bottle. It smells ever so slightly medicinal and leaves a sticky, then dry white residue as it dries.

There should really be some sort of powder that you mix up with water that makes ultrasound gel so we don't have to be shipping the water part of it, which is undoubtedly about 99% of the contents, long distances. But there isn't a powder. I have been looking. No instant ultrasound gel.

With a mixture of optimism and singularity of purpose I went to the kitchen and tried out 6 different recipes for an aqueous goo that would transmit sound waves. I thought that I could make ultrasound jam out of water and pectin, but that doesn't really work. Obviously there is something magic about fruit that makes pectin gel, maybe the acid or the sugar. Without fruit, even no-sugar pectin becomes about the consistency of spit. (I also tried spit, which does work, but has various obvious drawbacks.) I tried plain gelatin and water and got beautiful clear jello, which falls off the transducer, but kind of works, but is also messy. I tried corn starch and water, as if making extremely boring gravy. That was lovely and white, but the water wants to come out of it so it just slides off the transducer. I tried tapioca flour which I boiled with water, producing a nice clear, very mucoid gel which dries like glue on the skin and is very uncomfortable. I tried xanthan gum, a bacterial polysaccharide used to bind and thicken, boiled and cooled, and although it thickens the water it is slimy and falls off the transducer and makes a mess.

The recipe that worked (and worked great) is guar gum, salt and water. Guar gum has been used for a very long time in countries like India and Pakistan to thicken food and is now used often by people who can't eat gluten, to thicken gravies and make breads. Guar gum is the ground endosperm of the guar bean, which is very rich in a carbohydrate that avidly absorbs water. Guar beans are also eaten green and the pods are used as a vegetable ingredient after shelling out the beans. Guar gum is available in the flour section of many grocery stores and costs about $10 for a 220 gram bag. It is purported to be good for diarrhea, constipation, diabetes and lowering cholesterol. It has been added to infant tube feed formula in intensive care units to decrease stool frequency.

I messed with the recipe awhile and came up with a very nice slightly caramel tinged ultrasound gel this way:

1. Mix 2 teaspoons of guar gum with 1-2 teaspoons of salt. (The amount of salt isn't vitally important since it is just added to keep the guar gum from clumping. Using slightly less than a teaspoon of salt per 2 cups makes a gel with which is isotonic, which would be ideal for use near eyes or other mucus membranes or on open wounds).

2. Boil two cups of water.

3. Slowly sprinkle the guar gum/salt mixture into the boiling water while stirring vigorously with a fork or whisk.

4. Boil for about 1-2 minutes until thick and well mixed.

5. Cool before using. Save lives.

This is wonderful ultrasound gel (see photo above). I tried it and it works at least as well as the proprietary stuff, and probably doesn't dry out quite as fast. It wipes off easily and doesn't leave a sticky film. Even though it is not entirely transparent, there is no reduction in the quality of the ultrasound image compared with the standard clear ultrasound gel. It costs about 25 cents for a half pint, is sterile when you have finished making it and is completely non-toxic. The ingredients are available in many developing countries, not to mention the US. It is edible. It is not particularly bacteriostatic, though it could be made bacteriostatic with a little EDTA (but then it wouldn't be edible). It is probably best made and used for a couple or 3 days, then discarded if unused, though I kept some in a clean bottle at room temperature and it was stable and smelled fresh for over a week.

It is quite thick, like regular ultrasound gel, so it is a bit of a trick to get it into a squeeze bottle. A large bore funnel works, or the cooled gel can be squeezed into the bottle out of the cut end of a plastic bag. It can also be kept in a jar and used with a spoon.

This is kind of exciting. Now I will no longer be dependent on ultrasound gel manufacturers. If I was in Haiti, either I or someone at the house where I was staying could make up a batch of this the night before clinic and I would have fresh clean ultrasound gel with which I could be generous in my scans.  The water wouldn't even have to be sterile since the stuff is boiled when it is made. Let there now be ultrasound in places that Amazon.com does not reach!

Here's a YouTube video of how to do it.

**This article has been very popular and readers have left all sorts of new good ideas as comments. In order to make good ultrasound gel it is really only necessary to have some kind of a powder that, when mixed with water, creates a mostly transparent gel which clings to the ultrasound transducer. Polysaccharides are good for this, and guar gum is one of the least expensive that is available worldwide. A reader, however, just told me that he used glucomannan powder in a proportion of 1/2 teaspoon to a cup of water. I just tried it and it is EVEN BETTER THAN GUAR GUM. It, like guar gum, is a thickener and emulsifier, it is used by dieters to decrease appetite and is safe both topically and internally. It is available online and probably in health food sections of grocery stores as a dietary supplement. Glucommanan is a cell wall component of many plants, including the roots of the Konjac plant. Unlike guar gum it does not clump and can be mixed in cold water then allowed to thicken over a few minutes. If it is mixed into boiling water its texture is smoother than when it is made with cold water, and of course it is also sterile, which is very useful. It is almost completely clear, has no flavor or smell and leaves very little residue. Thank you commenter who goes by the name "addedupon"!

19 comments:

Anonymous said...

Dear Janice,
I work in East Timor as an obstetrician with very limited resources. I have been using water instead of ultrasound gel for my obstetric scans , with very poor results. Today I managed to source some guar gum from Australia and make my own gel and it was fantastic! Thank you so much for the advice

Janice Boughton said...

Thanks for letting me know! Please post how and where you got it here in the comments

Janice Boughton said...

It is a trick to find guar gum in developing countries, even though it is produced in both Africa and India. It is an ingredient in various industrial products including hydrofracking fluid and so is available in huge lots, 2+ metric tons, at a cost of $1-2 per kg. Some producers will sell smaller lots or 1kg at a time. Alibaba.com, an amazon-like online warehouse out of China, has food and cosmetic grade guar gum and does deliver to Africa and all over Asia. It is possible to get it in the US online as well and in bags or bulk.

Anonymous said...

Janice
THANK YOU! I am a researcher, but not an expert in US gel, trying to develop a new simple hybrid optical-ultrasound method to detect and monitor TBI. Your article was very very helpful.

Andrew T said...

Hi,
I really appreciate the work you did and the post here to serve as a starting place for people like me. Can you tell me if you have any experience with how long a batch of guar gum gel might last at room temperature before things start growing in it or it becomes a microbial hazard?

Janice Boughton said...

When I was in Tanzania we used exclusively guar gum gel for teaching and a research project on malaria. We found that the gel can last as little as 2 days at room temperature before becoming a much thinner liquid. I think that was due to some bacterial growth. It did not smell bad, though. It lasted longer when I cleaned the bottles well and rinsed them with boiling water. It also lasted better if refrigerated, which is not often an option. We also found that it worked great for ocular ultrasound. We were looking at optic nerve diameter and it was completely non-irritating when used on the eyelid directly, even if a little got in the eye. We also found that the tiny sieves that they had in the market in Tanzania, I think they were for making tea, worked great as a way to sprinkle the powder into the boiling water. We sometimes used a little more than a teaspoon of guar gum for a cup of water, just depending on what consistency we were looking for. I would suggest re-making the gel every 2-3 days and cleaning the bottle or jar well with boiling water between batches. I also found that I could pour very hot water or gel into the standard gel containers and they held up fine, didn't melt, which was good for sterility. Also the just boiled gel pours much more easily than after it cools when it thickens considerably.

Carrie said...

Janice,

You.Are.Awesome.

Anonymous said...

Thanks for the feedback. I am a resident and will be traveling abroad in a couple months and saw that this might be helpful. I bought some guar gum and tried some experimenting and also noticed some growth after about two days. One thing that also seemed to be a potential challenge was having to boil water in order to make the gel. I tried stirring in some powder into room temperature water but as you mentioned this was likely thicker than the same ingredient ratios at a higher temperature, and I was stuck with all of these bubbles in the gel after mixing which would have ruined any images. It seems the water boiling part is not easily sidestepped. However perhaps there is still potential applicability. Thanks again for your informative post and response!

Anonymous said...

Hi,
Mix the guar gum with vegetable glycerin (just enough to wet it) before adding to the water (which can be room temperature which takes care of the issue of boiled water). This will prevent the gum from forming into balls and you don't need to blend it as much. If you do get air bubbles in your gel, just smack the container on your open palm and the bubbles will work themselves up to the surface. Glycerin is also a preservative to a limited degree, but should make the gel last a bit longer. I've never made ultra sound gel, just lots of other natural product, fyi.

Anonymous said...

Might it be possible to use a Dakin's base if you needed a batch to last longer? - Phil

Anonymous said...

I can supply fine guar gum powder in 1 kg and 5 kg bags from Pakistan. Looking for a distributor who can deliver to customers. 1 kg bag will cost USD 10 and will be able to produce about 25 kgs of ultrasound gel by mixing tab water. regards ABDUL WAHID e-mail: gazianieng@hotmail.com

fenn said...

I've never seen guar gum in any grocery store.

why not use commonly available hand sanitizer gel? it's definitely not going to go sour, although you wouldn't want to get it in your eye. the active gelling ingredient is carbomer, a common cosmetic ingredient also used in aloe vera gel and hair gel. it also contains 50% alcohol and glycerin.

Janice Boughton said...

Hand sanitizer gel is fine in a pinch, but evaporates so fast that you have to keep on applying it. Also high alcohol containing products will break down the transducer's glue. The main arguments for guar gum are that it is lightweight, so you can transport the equivalent of a lot of gel in a small package, and don't have to deal with airline restrictions on transporting fluids, that it is nontoxic and non-irritating (no problem using it on eyes or mucus membranes) and that its consistency is very like commercial ultrasound gel.

Janice Boughton said...

Re: availability. That can be a problem. I buy it online or at the local coop. Much cheaper online (Amazon has it.)

addedupon said...

i just tried making the gel but used glucomanon in the raitio of 1 teaspoon to 2 cups of water with salt. It looks very good. We'll see how that works. My glucomanon is white powder fiber and absorbs more water.

Thank you very much for this fabulous idea!

Janice Boughton said...

I just tried using xanthan gum again. It works fine. Even though it is supposed to thicken more than guar gum, it's pretty much the same ratio: 1 teaspoon to a cup of water. It doesn't get quite as thick, but basically it's the same, and sometimes it's available when guar gum isn't.

Janice Boughton said...

I'm going to try the glucomannan. Great idea! 8 oz cost me $12, and if the ratio is better that is competitive with guar gum. Xanthan gum is a little more expensive.

Amy said...

Has anyone tried...just squeezing some natural aloe vera gel from the slit open aloe leaf?

Lucas said...

Thanks! I tried the guar gum recipe and it works very well with my abdominal toning belt. I find it a little bit cheaper than the glucomanon option, at least in the UK.