Part 4 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

Geometry

When planning the procedure, you need to visualize the geometry of the transducer and needle in your head and take care to view the true plane of the transducer. You must make sure that when you insert the needle, that it is in the plane of the transducer and that as you manipulate both the transducer and needle that you coordination the planes. The human eye is also remarkably good at estimating angles and you will be surprised how close you are to the proper angle when you start doing these. Yes, these are skills you may need to hone, but ones that help for other procedures and ones that virtually anyone who does procedures using needle guides can master…. really. 

Positioning

First, positioning the patient and yourself is crucial, although many do not adequately account for their own positioning as well as they do the patient’s positioning. You need to be able to brace your scanning arm and sometimes the arm with which you are doing the biopsy, so you may need to elevate the table or move the patient. So, once the patient and you are properly positioned, you should brace yourself with your hand, arm and/or elbow resting on something immobile. I bring the lesion into optimal view, but before I actually insert the needle, I try to place my eyes directly within the plane of biopsy itself. If you are looking AT the plane rather than WITHIN the plane, you may not appreciate a subtle deflection of the needle from the viewing plane.

Finally — insert the needle

Once you see the lesion and you are properly braced, nothing is going to move (at least very much). If you are seeing the lesion and you know that you are inserting the needle in the plane of viewing, then you know that when you insert the needle, that it will be in the plane of viewing or very close. Here is the key that is nearly impossible for novices to accomplish psychologically: You should be looking at the needle and transducer as you insert, NOT the screen. Once you take your eyes off the needle and plane and turn your head (or even just your eyes) to look at the screen, you lose your eye-hand coordination and are likely to inadvertently incorrectly angle the needle or transducer. I have even sometimes stood in front of the screen or held my hand over it so the resident cannot see it as she/he inserts the needle. 

If you are looking at the needle while you insert it, it will be close to the right place. So, upon initial insertion, I don’t usually go all the way down to the lesion unless it is large and the orientation wouldn’t be a problem. I want to get it through the surface of the organ and within range of being able to see it. One other point, though, particularly for novices, is that you shouldn’t incrementally edge the needle into the patient millimeter by millimeter because you are scared to hurt something. If you have planned properly, you know that your route is safe and you will cause the patient considerably less discomfort if you insert swiftly through the sensitive peritoneum, liver capsule or other tissue plane rather than stretch and tent those surfaces as you insert slowly.

Readjust

Once the needle is inserted, you can find it with subtle readjustments of the transducer and quickly figure out how to reposition, if necessary. You just need to appreciate that the screen and real geometry are nearly the same so that you intuitively know which way you need to re-angle the needle. So, yes, you may need to withdraw the tip to a more superficial position and reinsert. There are many different types of needles that you may use, so I won’t discuss actually acquiring or saving the specimens. Using the freehand technique is independent of these factors.

In the final 5th part of this series, I will discuss why the freehand technique is often less traumatic than using the needle guide and is cheaper and faster.

In this series: 

Lincoln L. Berland, MD is Professor Emeritus of the Abdominal Imaging Section of University of Alabama at Birmingham. 

Twitter: @linkberland

NB: Opinions expressed are those of the author alone, and are not those of his employer nor of Radiopaedia.org. 

 

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Publication date: 15th Oct 2016 05:42 UTC

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