An excellent close-range radiotherapy needle is not only valuable for its design concept, but also because of the material science and precise manufacturing process behind it. The 18th-sized fine needle of the E type is precisely the embodiment of the top-level technology in this field.

I. The Strict Requirements for the Materials

The materials used to manufacture the 18-gauge fine needle type E must meet multiple stringent requirements:

• High strength and toughness: The needle body must be able to withstand the axial pressure and lateral bending force during puncture, especially when passing through calcified or fibrotic tumor tissues, and must ensure that the needle body does not break or deform. Medical-grade 304 stainless steel or titanium alloy are the mainstream choices, as they have excellent tensile strength and fatigue life.
• Biocompatibility: The material must be non-toxic, non-allergenic, and non-carcinogenic, and must not corrode or release harmful ions in the body fluid environment. Special surface treatment of steel can effectively resist electrochemical corrosion.
• Radiographic permeability and compatibility: The absorption coefficient of the needle material for X-rays should be moderate, so that it can clearly show on CT/MRI images without generating excessive artifacts that interfere with imaging. At the same time, the material must not undergo nuclear reactions with radioactive isotopes or affect their decay characteristics.

II. Micro-nano Processing of E-Type Needle Tips

The manufacturing of "E-type" needle tips is a technical challenge. Usually, a precise numerical control grinding process is employed, where the needle tip is ground into a specific multi-sided geometric shape under a microscope. For instance, a common E-type design includes a main inclined surface and a secondary inclined surface, forming a structure similar to a "pen tip." This design enables the needle tip to smoothly separate tissue fibers along the intersection line of the two inclined surfaces when penetrating the tissue, rather than causing a "plug effect" like ordinary needles. Advanced laser welding technology is used to connect the needle base and the needle tube, ensuring a smooth and burr-free connection and reducing tissue dragging.

III. Coating Technology and Lubrication Performance

To further reduce the puncture resistance, many high-end 18-gauge E-type needles employ surface coating technology.

• Silicone oil coating: The most common method involves applying a very thin layer of medical-grade silicone oil on the surface of the needle, significantly reducing the friction coefficient and enabling the needle to glide smoothly into the tissue.
• Hydrophilic coating: A more advanced technique. The coating becomes extremely lubricated upon contact with water (such as tissue fluid), minimizing friction to the lowest level. This is particularly beneficial for operations that require multiple insertions and withdrawals (such as changing the catheter or particles) at the same puncture site.

IV. Quality Control and Sterility Assurance

Each batch of the 18th fine needle type E must undergo strict factory inspection, including: appearance inspection (no rust spots, burrs), size measurement (outer diameter, length, bevel angle), sharpness test (simulating puncturing standard membranes), and air tightness test (to ensure no leakage). Finally, the products are packaged in a clean room and sterilized with ethylene oxide to ensure they meet the industry's highest standard of SAL (sterility assurance level) 10⁻⁶. It is precisely these seemingly insignificant details that together have created the reliable quality of this "needle of life."