https://radiopaedia.org/articles/chiba-needle

For interventional physicians, the 18G Chiba needle is not just a tool but an extension of the hand. Mastering its operation skills and cultivating precise "touch" is the key to safely and efficiently completing surgeries. This article will, from the perspective of the operator, deeply explore the practical application points of the 18G Chiba needle, the strategies for dealing with common challenges, and the advanced methods for improving operational proficiency.

I. Core Operating Skills and Hand Feel Training

Insertion: Steady, Precise, Firm

Holding the needle and advancing: It is recommended to adopt the "pistol-style" or "pen-holding-style" grip, using fingers for stable support and utilizing the slight movements of the wrist and forearm to advance. During the advancement, it should be smooth and uniform, avoiding rough puncturing. The rigidity of the 18G needle provides good force feedback. When the needle tip passes through different tissue layers (such as skin, subcutaneous fat, fascia, and organ capsule), the operator can feel the subtle changes in resistance characteristics - the "breakthrough sensation," which is an important tactile information for determining the needle tip position.

Path planning and angle correction: Plan the insertion point, angle, and depth using preoperative imaging. Since the 18G needle is not prone to bending, the initial angle setting is particularly crucial. During the advancement process, if a slight adjustment of direction is needed, the "lifting-pulling-rotating" method can be used: retract the needle tip slightly, slightly change the needle tip orientation, and then advance. The needle tip's inclined surface direction can also be used for guidance. The needle tip tends to move towards the side where the inclined surface is pointing.

Aspiration and Biopsy: Skill and Rhythm

Diagnostic aspiration: When the needle tip reaches the target, connect the syringe. During aspiration, maintain a moderate and stable negative pressure. Excessive negative pressure may cause normal tissues or blood to be sucked into the syringe, contaminating the sample; too little negative pressure may not allow for effective cell collection. Combining short, small-amplitude needle tip movements (within approximately 3-5mm range) can cut and collect cells.

Histological biopsy (with biopsy gun): This is the core application of the 18G needle. The key lies in confirming the needle tip position. It must be confirmed that the needle tip is located within the predetermined sampling area of the lesion through imaging (such as ultrasound, CT) before activating the biopsy gun. When activating, the assistant should firmly hold the needle sheath to prevent it from shifting. For automatic biopsy guns, it is necessary to be familiar with their "range" (such as forward ejection of 22mm, backward retraction of 20mm), ensuring that the entire sampling slot is within the lesion range and avoiding injury to important structures behind.

"Bloodless" Puncture and Safety Assurance: In CT-guided puncture, an important safety technique is "negative pressure insertion." That is, pre-inject a small amount of normal saline into the syringe before inserting the needle. During the insertion process, maintain a slightly retracted state of the syringe. If the needle tip accidentally enters a blood vessel, blood will immediately be sucked into the syringe, providing an immediate warning. At this time, the insertion should be stopped immediately and the direction adjusted.

II. Common Challenges and Countermeasures

• Movement of lesions: Especially for organs such as the lungs and liver that move with breathing. The response strategy is to train patients to perform calm and consistent breathing coordination. Usually, patients are required to hold their breath at the end of inhalation or exhalation. The operator needs to be familiar with the movement trajectory of the lesion and conduct "pre-emptive" puncture.
• Dense tissues or tough capsules: At this time, the rigidity advantage of the 18G needle is manifested. If there is a large resistance, a rapid and gentle "woodpecker" style advancement can be adopted, that is, using wrist strength to give a series of short and gentle pushes instead of continuous forceful pushing. This helps the needle tip gradually "bite through" the tough tissue and avoids the needle body suddenly losing control and rushing forward.
• Unsatisfactory specimen acquisition: This may be due to the needle tip being located in the necrotic area or fibrous septum. Under the confirmation of the image, adjust the needle tip to the solid and enhanced area of the lesion for re-collection of samples. For larger lesions, the "fan-shaped" or "multiple multi-directional" puncture method can be used, obtaining samples from different areas.

III. Advanced Points: The Essence of Coaxial Technology

Mastering the coaxial technique using 18G Chiba needles as the working channel is a sign of advancing one's proficiency in interventional operations.

• Technical process: First, use a finer needle (such as 22G) to puncture to the edge of the target area, and confirm that the position is safe and ideal. Then, push the 18G Kashima needle along the fine needle puncture path until its tip reaches or slightly exceeds the tip of the fine needle. After that, withdraw the fine needle. At this point, the 18G needle becomes a stable working sheath. Subsequently, this sheath can be used to repeatedly and multi-angledly insert the biopsy gun to collect samples, without the need to repeatedly puncture the organ membranes and important tissues.
• Core advantages: Significantly increases the amount and diversity of sample collection, while minimizing the risk of multiple punctures (only one puncture is required). Particularly suitable for cases where multiple samples are needed or where the risk of sample collection is high.

Conclusion

Operating with 18G Chiba needles is a highly coordinated and precise art involving the collaboration of hands, eyes, and brain. The "feel" of the operation stems from an understanding of the mechanical properties of the needle, the interpretation of tissue feedback, and the muscle memory formed through extensive practice. From the basic smooth needle insertion to the advanced application of coaxial techniques, every step involves considerations for patient safety and surgical quality. Continuously reflecting on the details of the operation and accumulating experience in dealing with complex situations are the necessary steps for every interventional physician to maximize the effectiveness of this "golden median" tool.