Part 2 of a 5-part series on the advantages of a freehand technique over a needle-guide system for ultrasound-guided biopsies. If you haven't read the rest of this post, please start at part 1.
Planning and scanning
When using the needle guide, many users identify only one spot to scan and then insert the needle through the guide portal to the side of the transducer. Therefore, they may not have adequately examined the actual route through which the needle will pass to see if it will encounter any structures unsafe to puncture. The needle is fixed at a fairly shallow angle to the transducer and may be harder to see. I will discuss this more in Part 3.
To optimize the freehand technique, you should look for TWO spots. One should be over the direct route of the needle (somewhere outside where the transducer will be while you are guiding the needle) and this should be marked before prepping the skin. The other point will be the position you will be using to view while inserting the needle. You don’t need to mark this because it might change, but you at least need to know that there is at least one good viewing point.
For freehand biopsies, unlike using the needle guide, there is no limitation to where you view, other than you need to be able to be within the plane of the needle. Of course, the closer your transducer is to perpendicular to your needle, the more easily visible it should be because of basic principles of ultrasound reflection. So, a position farther away from the needle may actually give you a better chance of finding it quickly and seeing more of it.
While we like to think that our procedures are “sterile,” they are better termed “clean.” I don’t want anyone to suggest that I am being capricious about spreading nosocomial infections, because I religiously follow hand washing protocols. However, I believe the perception that we need true sterility suggests a glorification that what we are doing is just short of a surgical procedure. Actually, we use a needle not really much larger than one used to draw blood, for which a lab tech may only use a quick alcohol swab swipe. I use a needle that does not even require a scalpel nick. If you prep your transducer and skin thoroughly with betadine and use sterile gloves, you should not induce an infection. I am not aware that I have ever done that.
Adequate local anesthesia is one of the most important aspects to optimizing the patient’s experience. So, I focus strongly on this part of the procedure. I am fascinated by the consistency (incorrectly, I believe) with which residents perform local anesthesia for ultrasound-guided biopsies whether the guide is used or not. This even includes thyroid FNAs. If someone else has instructed them before I observe their first procedure, they typically inject the lidocaine by taking the transducer in their left hand and placing it on the skin. They then take the lidocaine syringe in their right hand and insert it vertically into the skin as though they were placing the needle through an invisible guide portal! It is always awkward to use the syringe at that angle with one hand and then reliably achieve anesthesia at the skin. Clearly, this is a technique “learned” from doing deep biopsies with the guide. So, when using the guide many also attempt to achieve local anesthesia (often less effectively) through the needle portal rather than doing it as I describe below.
Instead, I inject in two stages. At the first stage, I hold the syringe in both hands (with no transducer) and insert the needle subcutaneously tangential to the skin. I then inject and raise a wheal. With the vertical (needle-guide-like technique), it is difficult to verify that you are truly numbing the skin and superficial tissues. I have observed a number of instances where the needle-guide approach to local anesthesia has led to unnecessary pain while doing the biopsy to the point where patients have asked to terminate the procedure. I instruct the resident that the first step should be to numb the skin, because it will be less painful when you inject the deeper tissues, I also point out that you don’t need a transducer to see the skin, which is often a liberating concept for them. They can then fully control the needle, the location of and the volume of lidocaine injected. Note that I believe that you should do it this way even if you DO use the needle guide.
Then, after a moment to allow anesthesia to take effect while I continue setting up the tray, I begin a second stage. I use the transducer to locate the proposed needle track and achieve deeper local anesthesia. Since I am trying to get deep to the skin, I take the transducer in my left hand and pick up the syringe with my right hand with my thumb on the plunger, insert and watch with ultrasound. As soon as I get to the depth I want, I can inject to cover the entire tract I will be traversing.
In part 3 of this series, I will discuss more about planning the procedure to design the best approach and about the added flexibility you have with a freehand approach.
In this series:
Lincoln L. Berland, MD is Professor Emeritus of the Abdominal Imaging Section of University of Alabama at Birmingham.
NB: Opinions expressed are those of the author alone, and are not those of his employer nor of Radiopaedia.org.