Varieties of ultrasound probe stand-offs

The purpose of a stand-off is to move the surface of the probe a little further away from the skin. There are two benefits to be derived from this:

  1. If you are scanning around the ankle, where it is knobby and uneven, the stand-off gel pad makes it much easier to maintain contact during the exam.
  2. Whenever you are imaging something superficial, ultrasound has a tendency to introduce artifacts in the near-field, making it more difficult to pull in a sharp image. By “stepping off” the probe from the skin the thickness of a gel stand-off pad, you are effectively moving everything a little further away from the probe, and into a region of increased focus. (A useful metaphor: if you hold your hand very close to your eyes, it’s difficult to focus on it. But by moving your hand a little further away, it snaps into a better plane of focus, allowing you to see it clearly. The probe stand-off basically moves what you are imaging a little further way, into a better plane of focus.)

There are a number of different stand-offs available for ultrasound probes, ranging from the reusable variety that actually hook onto your probe and give you about a centimeter distance between the probe and the skin … to the disposable wound-dressing varieties used to provide a sterile barrier between the probe and the skin.

You can see the various stand-offs available below on this page.

We will eventually have separate pages on techniques for using each, but for right now we can lead off with the most common variety currently being provided to our clients, the newest and latest and greatest stand-off option …

 

The Big Block

Using a stand-off probe attachment like the one shown below is pretty straightforward, but there are a few tips I can share …

  1. Care: While your stand-off arrives dry, store it WET in the Tupperware container. Whenever you are finished using it, rinse it off thoroughly in the sink, get all of the gel out of and off of it, and with it dripping wet put it back in the container. If you have T-Spray (which you can see by clicking here) you can use that to disinfect it, but rinse with water before storing. You want to avoid storing it with alcohol on it, which could dry it out.
  2. Gel (inside and out): Use plenty of gel inside of the stand-off (to connect the surface of the probe to the inside of the stand-off), and plenty of gel on the outside as well (to connect the stand-off with the skin).
  3. Uses: Primarily use the stand-off when imaging tendons, anything around the ankle (where everything is not only shallow but also often along an uneven surface), and for things like foreign bodies, ganglions, etc.
  4. Settings: Remember that since everything on the screen has been shifted down by the thickness of the stand-off, your settings must correspond accordingly. For example, normally you would use 10 MHz for tendon imaging, but since the stand-off pushes the image down lower on the screen (about to where you normally would find plantar fascia without a stand-off), you can leave the frequency at 7.5 MHz. Be sure to adjust your focus pointers if necessary, and tweak the gain sliders corresponding to where you are now seeing the image on the screen. Have a look, for example, at the images below, featuring the Achilles tendon with and without the stand-off.

Stand-Off

 

Without StandOff

Notice that without the stand-off in place, the skin is at the very top of the image, and therefore we are using 10 MHz as our frequency and the focus pointers are rolled to the top of the screen.

 

With StandOff

Notice here, however, with the stand-off in place, we have an empty area at the top of the screen, and this gives the ultrasound waves time to get moving before encountering the skin and the Achilles beneath it, providing a sharper image. And since everything has been pushed down on the screen, we are at 7.5 MHz and the focus pointers have been rolled down a couple of notches to correspond with where the Achilles now appears in the image.

 

 

Assorted Stand-Off Solutions

There are three main types of "stand-off" for your ultrasound probe:

  1. The kind that actually attaches to your probe.
  2. The kind that looks like a clear gel hockey puck or gel pouch.
  3. The kind that is more like a disposable, individually-wrapped wound-dressing.

Unfortunately, I have not yet assembled a library of sample images showing each of these in use. I am in the process of collecting additional images, particularly of wound ultrasounds. If you come up with a good one, I would love to be able to include it in our collection. Just email me with the image or images, and even better, if you could email me the images along with a short write-up concerning the procedure [you can write me at my usual address: shawn [at] fisherbiomedical.com].

 

 

The Stand-Off Probe Attachment with Gel Inserts

The stand-off attachment comes in two varieties. One is a gel block that you fit on the end of the probe, the other a small, oval-shaped plastic attachment (usually stored in a little baggie inside of a small Tupperware container), equipped initially with three small disposable gel inserts, each in its own little plastic container.

If you have the gel block variety, you simply stick it on the end of your probe (with gel on the probe first, to make sure the probe surface and the gel block are connected). And that’s it. I cover that one first on this page, because it’s our preferred stand-off.

If you have the attachment-with-gel-insert variety, it’s a little more complicated, but not much (see the image below).

The way you will use these inserts is like this: Put gel on the probe itself, then put the gel insert into the probe stand-off attachment, and put the attachment onto the end of the probe — usually you want to push it on far enough to where the little gel insert protrudes a bit from the attachment — and then add more gel to the surface. (Basically you are making a gel sandwich: probe surface – ultrasound gel – gel insert – attachment to hold insert in place – then more ultrasound gel.)

As long as you rinse these little inserts off in warm soapy water and store them WET in the Tupperware container and keep that somewhere they won’t dry out or be exposed to the sun, you should get 3 to 4 weeks of use from each gel insert before having to toss it or before it rips. Then just pull out the next one.

For the first week or so the attachment may want to pop off the probe unless you hold it there. If this happens with yours, rest assured, after a while it will conform to the probe and stay on much better. But initially it may prove a rather slippery affair, and if so, I recommend holding the probe like a big fat marker, where your first finger is on the end with the bump and your thumb and middle finger hold the attachment in place on the probe. This gets easier after about a week. It can just take a little bit for the stand-off attachment to adapt to the probe. Stay with it.

(And don’t lose the stand-off attachment. Believe it or not, that little piece of custom plastic recently went up in price and costs $185 to replace, even at dealer cost.)

Definitely practice with this and try it across various applications. Remember, though: the stand-off moves your image down a little on the screen, so you may need to tweak your focus pointers and lower your frequency to compensate.

If you need more gel inserts you can either print out the PDF order form available here, or just have someone at your office give us a call and we can get some more out to you. The little gel inserts are $20 for a pack of three (each should last you about a month of solid use, with good care).

standoff attachment

 

 

The Disposable "Hockey-Puck" and Reusable "Gel Bag" Varieties

The larger 1.5cm hockey-puck-style pads do not attach to your probe, and therefore can sometimes require two hands to manipulate; but they are definitely more sturdy and you should get a lot more use out of them (assuming you store them wet). They can certainly be much easier to use on some procedures, particularly around the ankle or over a wound.

"Wound-mapping" is a fancy name given to simply using your ultrasound to take an image of a wound, either when you first see the patient (and again, later, when you check on them during a follow-up), or immediately pre- and/or post- surgery.

Putting the probe head directly onto an open wound probably isn’t the best idea. So using a sterile gel pad as a buffer makes sense. It also moves the image down on the screen by about one and a half to two centimeters, which will improve the image you are able to capture — the idea being to capture an image of the wound and measure ("map") its depth and width at various points, and possibly even its perimeter and area (using your "Area" measurement mode). Note: I will be compiling a great deal more material on this application over the coming weeks. Stay tuned!

We can get you these gel hockey pucks at $10 apiece with free shipping. Simply download and fax in the order form available here.

stand-off puck

A variation of this type of gel stand-off would be the "gel bag" variety. Where the "hockey-puck" variety will eventually need to be replaced, the "bag" variety should last forever — which accounts for its $75 price tag. These acoustic stand-offs come in two thicknesses and are definitely larger than the hockey-puck. Civco has 4" x 6" gel bag acoustic stand-offs in both .4" and .8" thicknesses. You can try these out if you like by downloading our PDF order form here.

gel bag

 

 

The Ultrasound-Transparent Sterile Disposable Wound Dressing

The absolute best solution for ultrasounding wounds is surely the Sterile HydroScan Couplant Sheet: a sterile, disposable wound-dressing, transparent to ultrasound waves. You don’t really get the "step-off" you would with a reusable gel pad, but the couplant sheets are certainly going to be the most sterile during and after surgeries — which is something your patients will doubtless appreciate.

Civco has 4" x 6" sterile couplant sheets, five sheets to a pack. We can get you packs of these if you simply fill out and send in our order sheet available here.

couplant sheet

And particularly where it comes to these disposable sheets, I would love to see some of your results. If you send me a few really nice images of wounds you have imaged using these sheets, maybe with a few lines of commentary, I will happily send you some more of the sheets for free.

We have the exciting situation of having dozens and dozens of podiatrists around the country all using the CTS-5500+ and CTS-7700+ (and becoming increasingly effective at using them). It makes sense to bring the group of you together to share the things you particularly are getting great results at. You might be great at plantar fascia injections, but not so comfortable yet with neuromas — but someone else might be great at neuromas while having a challenge with the Achilles tendon. My hope is to help everyone get better, across the board, in a dozen different applications. This series (and the website coming soon) should help make that possible, and all the more so if everyone contributes an image or two (and/or some short commentary on the images).