Thyroid nodule FNA biopsy should be done under ultrasound guidance. This improves diagnostic accuracy by confirming needle placement within the nodule of interest. It also helps to reduce the frequency of non-diagnostic results. When setting up for ultrasound guided thyroid FNA, it's important to make sure that the patient is appropriately positioned. Lay the exam table flat and place a pillow under the patient's neck and shoulders to extend the neck. This allows for thyroid nodules in the lower poles to be visualized. Now let's talk about what equipment you'll need. You'll need to clean the neck, either with alcohol prep pads or iodine solution. You should also use a sterile probe cover. First, place gel over the ultrasound probe itself before placing the sterile probe cover on top. You'll also want to use sterile gel on top of this when performing the FNA procedure, as this will allow for a clear image. Thyroid FNA biopsy should be performed using a 25 or 27 gauge needle. The needle is often attached to a 6 to 10 cc lower lock syringe that is filled with 1 to 2 ccs of air, allowing for some negative pressure within the system. Also a free needle approach can be used. Many patients prefer to have the FNA procedure performed under local anesthetic. We usually use lidocaine. Lidocaine should be injected into the skin and soft tissues along the same needle track that you would take for the FNA biopsy procedure. Lidocaine should not be injected into the thyroid itself. Now that you have all your equipment set up, it's time to get started with the FNA procedure. Let's take a few moments to discuss the different approaches that can be used. There are two probe options for thyroid FNA, the linear probe and also curvilinear or microconvex probe. There are two common approaches utilized in thyroid FNA, the parallel approach and perpendicular approach. The parallel approach is the most common approach used. The perpendicular approach may allow for FNA of deep nodules. Let's review both in a little more detail. With the parallel approach, the needle is oriented and introduced at either end of the mid portion of the transducer in parallel to the long axis or sagittal plane. Using this approach, the needle can be tracked from its point of insertion along its entire path and ultimately in the nodule. In the perpendicular approach, the nodule is imaged and positioned in the mid portion of the screen and the needle is inserted at the midpoint of the transducer's long axis. Utilizing this approach, the needle cannot be visualized along its entire path and instead is seen as a pinpoint within the nodule. The curvilinear probe has a small curve footprint. This probe can be rotated in plane, allowing for a more vertical needle orientation to be utilized. This allows for the FNA of deep nodules while allowing for the entire needle path to be visualized during the biopsy procedure. The needle is inserted under ultrasound guidance with the bevel up to improve visualization and then advanced into the thyroid nodule of interest. Once there, the needle is moved in a back and forth motion at a rate of three cycles per second for a total of three to six seconds before being removed. The whole procedure should then be repeated. When rapid on-site evaluation of FNA smears is available, generally two to three passes into the thyroid nodule in different areas is recommended. The smears are then stained and evaluated under the microscope for adequacy. Adequacy is defined as at least six groups of 10 or more follicular cells. You now know the basics of how to perform thyroid nodule FNA. Let's go practice!

thyroid nodule

fine-needle aspiration

ultrasound guidance

diagnostic accuracy

non-diagnostic results