Brachytherapy, especially permanent seed implantation and intracavitary treatment, is classified as a high-risk Class III interventional procedure. Surgical instruments must meet the most stringent sterility standards. Any foreign contaminants, either biological (bacteria, endotoxins) or non-biological (metal particles, machining oil residues) introduced into the human body, may trigger infections at the implantation site, aggravated inflammation, treatment failure or even systemic complications. For this reason, the manufacturing environment and procedures for brachytherapy needles have far exceeded the scope of conventional mechanical processing, complying with strict cleanliness control criteria for minimally invasive implantable devices. Regulatory-compliant manufacturers adopt a three-in-one closed-loop system consisting of Class 10,000 clean environment, integrated precision intelligent manufacturing and multiple validated terminal sterilization, to ensure every finished brachytherapy needle reaches the ready-to-use sterility and safety standards for operating rooms.

1. Class 10,000 / Class 100,000 Cleanrooms: A Sterile Production Environment

Post-machining core processes including precision grinding, cleaning, assembly and primary packaging must be conducted in Class 100,000 cleanrooms, with critical zones maintained at Class 10,000. Such facilities impose strict limits on the count of airborne particles ≥ 0.5μm and settling bacteria.

Air circulates continuously through High-Efficiency Particulate Air (HEPA) filters and maintains positive pressure to prevent backflow of air from areas with lower cleanliness.

Constant temperature and humidity are regulated to reduce particle adsorption caused by static electricity.

Personnel are required to complete strict gowning and air shower procedures, and wear sterile suits, masks, gloves and shoe covers before entry.

All tooling, fixtures and containers are regularly cleaned and disinfected.

2. Integrated Precision Machining and Automated Assembly: Minimizing Human Intervention and Enhancing Consistency

To mitigate contamination risks and guarantee reliable performance, premium brachytherapy needles are processed integrally on Computer Numerical Control (CNC) machine tools. Starting from standard medical-grade metal bars, the needle tip, cannula and connecting section are fabricated in one go via continuous precision turning, drilling and grinding. This approach avoids potential contamination and structural weaknesses caused by secondary processes such as welding and adhesive bonding.

Automated or semi-automated assembly lines reduce the frequency and duration of direct human contact with products, lowering the risk of anthropogenic contamination.

Critical procedures including final assembly and primary packaging are completed inside clean benches.

3. Rigorous Multi-stage Cleaning and Terminal Sterilization: Final Purification and Safety Verification

All machining residues must be thoroughly removed from finished needle bodies.

• Multi-tank ultrasonic cleaning: Medical-grade detergents and purified water are applied to eliminate cutting oil and metal particles thoroughly via ultrasonic cavitation.
• Electrolytic polishing (optional yet recommended): It delivers a mirror-smooth surface to reduce tissue friction and seed delivery resistance. Meanwhile, the process features additional cleaning and passivation effects to further improve corrosion resistance.
• Multiple rinsing and drying: Final rinsing is performed with Water for Injection (WFI) to completely remove detergent residues, followed by thorough drying.

After cleaning, products are sealed in primary packaging pouches permeable to sterilants, such as medical-grade paper-plastic composite pouches, before terminal sterilization. Ethylene Oxide (EO) sterilization is the most widely adopted method due to its excellent penetration and zero damage to metal devices.

All parameters throughout the full sterilization cycle, including pre-vacuum, humidification, gas injection and aeration, undergo rigorous validation. This ensures a Sterility Assurance Level (SAL) of 10⁻⁶ for products at all positions inside the sterilizer. Post sterilization, products go through sufficient aeration to bring EO residues below safety limits.

4. Final Inspection Prior to Release: Data-driven Quality Gate

Samples are taken from each sterilized batch for sterility testing complying with pharmacopoeia standards and bacterial endotoxin testing. Package integrity is also verified. A batch can only be approved for delivery after all test items meet requirements and a quality release report is issued.

This manufacturing system integrating cleanroom technology, validated sterilization and strict final inspection ensures the sterility of brachytherapy needles is scientifically verified and fully reliable upon arrival at operating rooms, providing ultimate protection for patient safety.