Principle 

The principle of image-guided RF access is simple: see the target, place the tip, deliver the energy. The operator uses imaging to visualize the needle tip in relation to the target, adjusts the position as needed, and then activates the RF generator. The imaging modality depends on the clinical application and the availability of equipment.

Ultrasound is the most common imaging modality for RF ablation. It provides real-time visualization of the needle and the target, without the use of ionizing radiation. The operator can see the needle tip as it advances through the tissue, and can adjust the position based on the ultrasound image. Ultrasound is particularly useful for superficial targets, such as thyroid nodules, and for targets that are visible on the ultrasound image, such as liver tumors.

CT provides high-resolution images of the anatomy and the needle. CT is used for procedures where the target is not visible under ultrasound, such as lung tumors or bone lesions. The operator performs a CT scan to identify the target, plans the approach, and then advances the needle under CT guidance. CT provides excellent spatial resolution but involves ionizing radiation and is not real-time.

Fluoroscopy provides real-time X-ray imaging. Fluoroscopy is used for cardiac electrophysiology procedures, where the target is visible under X-ray. The operator advances the needle under fluoroscopic guidance, using the X-ray image to confirm the position of the tip. Fluoroscopy involves ionizing radiation but provides real-time visualization.

The choice of imaging modality depends on the clinical application, the availability of equipment, and the operator's preference. In many cases, a combination of imaging modalities is used. For example, ultrasound is used for the initial placement, and fluoroscopy is used to confirm the final position.

Device Types (Continued)

CT-Compatible Non-Ferromagnetic Tips​ are designed for procedures performed under CT guidance. The tip is made from a non-ferromagnetic material, such as titanium or a non-magnetic stainless steel alloy, to avoid artifacts on the CT image. This allows the operator to see the tip clearly without distortion.

Angled-Bevel Disposable RF Stylets​ have a beveled tip that is angled to facilitate insertion and to improve the visibility of the tip under ultrasound. The bevel creates a bright echo on the ultrasound image, making it easier to track the needle as it advances.

3D-Mapping EP RF Needles​ are designed for cardiac electrophysiology procedures. These needles are compatible with 3D electroanatomic mapping systems, which create a 3D model of the heart and track the position of the needle in real time. The operator can see the needle tip on the 3D map, without the use of fluoroscopy.

Hybrid Ablation+Biopsy Disposable Cannulas​ combine the ability to ablate tissue with the ability to obtain a biopsy sample. These devices have a channel that allows the operator to obtain a tissue sample before or after the ablation. This is useful in cases where the diagnosis is uncertain and a biopsy is needed.

Hands-on Guide (Continued)

The following steps represent best practice for image-guided RF access.

Step 1: Ultrasound: Short-Axis Needle Visualization.​ When using ultrasound, the needle should be visualized in the short axis, meaning that the needle is perpendicular to the ultrasound beam. This provides the clearest image of the needle tip. The operator should adjust the transducer angle to achieve a short-axis view.

Step 2: CT: Confirm Tip in Lesion Center, Not Capsule.​ When using CT, the operator should confirm that the tip is in the center of the lesion, not at the edge. A tip at the edge will create an incomplete ablation zone. The operator should review the CT images in multiple planes to confirm the tip position.

Step 3: Fluoroscopy: EP/Ablation Path Only.​ Fluoroscopy should be used only for procedures where the target is visible under X-ray, such as cardiac electrophysiology. The operator should minimize the use of fluoroscopy to reduce radiation exposure.

Step 4: Never Deliver Energy if Tip Position Is Unclear.​ This is the most important rule. If the operator is not certain that the tip is in the correct position, the energy should not be delivered. The operator should reposition the needle and confirm the position before activating the RF generator.

Step 5: Ablate in Overlapping Cones for Irregular Lesions.​ For irregular lesions, the operator should create overlapping ablation zones. The first ablation is performed in the center of the lesion, and subsequent ablations are performed at the margins, creating a "halo" of ablated tissue around the lesion.

Field Experience (Continued)

Centers using ultrasound-first report fewer pneumothorax, fewer repeat sticks, and better cosmesis in thyroid cases. The ultrasound image provides real-time feedback, allowing the operator to adjust the needle position as it advances. This reduces the number of attempts and the risk of complications.

One important lesson from the field: the ultrasound image is not always clear. The needle may be difficult to see in some patients, particularly those with dense tissue or scarring. The operator should use a needle with an echo-enhancing tip and should adjust the transducer angle to improve the image.

Another lesson: the imaging guidance is only as good as the operator's ability to interpret the image. The operator must be trained to read the ultrasound or CT image and to correlate the image with the anatomy. This training is essential for safe and effective image-guided RF access.

Summary (Continued)

The disposable RF needle combined with image guidance provides prescribed thermal geometry. The operator can see the target, place the tip accurately, and deliver the energy precisely. This reduces the risk of complications and improves the outcome of the procedure.

The result is a procedure that is safer, faster, and more reproducible. The operator is not guessing; they are seeing. The patient is not exposed to unnecessary radiation; the imaging is targeted and minimal.

Outlook and Recommendations (Continued)

The future of image-guided RF access will be shaped by advances in imaging technology.

Augmented Reality Overlay.​ Augmented reality will be used to overlay the 3D model of the target onto the patient's body, allowing the operator to see the target through the skin. This will improve the accuracy of the needle placement and reduce the need for repeated imaging.

Robotic Insertion.​ Robotic systems will be used to insert the needle automatically, based on the pre-operative imaging. The robot will place the needle with sub-millimeter accuracy, reducing the risk of human error.

Automatic Tip-to-Vessel Safety Lock.​ The RF generator will be able to detect when the needle tip is too close to a vessel and automatically reduce the power or stop the energy delivery. This will prevent the heat-sink effect and reduce the risk of incomplete ablation.

For procurement, the recommendation is to invest in imaging equipment and training. The disposable RF needle is only as good as the imaging guidance used to place it. The cost of imaging equipment and training is small compared to the cost of a complication.