Factors Affecting the Success Rate of Needle Extraction

As an important means of modern medical diagnosis, its success rate is directly related to the accurate determination of the disease and the subsequent development of a treatment plan. According to the data published by the Hong Kong Hospital Authority in 2022, more than 150,000 needle tests are performed in Hong Kong every year, of which thyroid biopsies, breast biopsies, and prostate biopsies account for 68% of the total. However, approximately 12-15% of cases require repeated surgeries due to inadequate sampling or misalignment, which not only increases healthcare costs but also creates unnecessary psychological and physical burden on patients. The main factors affecting the success rate include multiple aspects, including the acquisition of anatomical knowledge, the rationality of instrument selection, the standardization of operations, the accuracy of image guidance, and the cooperation between doctors and patients. In particular, the incidence of complications such as local bleeding, infection, and pain due to the side effects of needle extraction is significantly negatively correlated with the technical proficiency of the operator, with complication rates of less than 3% for skilled physicians and as much as 8% for novice physicians. This fully shows that improving surgical technology is not only a need to improve diagnostic efficiency, but also an important link to ensure patient safety.

Proficiency in Anatomical Knowledge: Precise Targeting of Target Tissues

Anatomical knowledge is the basis for needle extraction of deep tissues and lesions, especially those adjacent to vital organs. Taking thyroid acupuncture as an example, important structures such as the common carotid artery, vagus nerve, and trachea are distributed around the thyroid gland, and surgeons need to accurately determine the direction, thickness, and lesion boundaries of the thyroid lobe in three-dimensional space. According to research data from the Department of Radiology at the Prince of Wales Hospital in Hong Kong, the target accuracy rate of thyroid nodule puncture is 94.7% for physicians with more than three years of experience in ultrasound interventions, compared to 78.3% for junior doctors. This difference is mainly reflected in the ability to identify mutated anatomy, such as the ability to predict vascular variations in the neck (e.g., hypothyroidism inferior arteries), which can effectively avoid the formation of hematomas due to vascular damage. In addition, it is important to understand the texture of the tissue: breast fibroadenoma has a hard texture and requires increased puncture force, while liver cancer tissue is usually brittle and brittle, so negative pressure must be controlled. Beginners are advised to gradually establish a repositioning cognitive system through a three-step training method: anatomical specimen practice, image map control, and real-time verification of intraoperative ultrasound.

Choosing the right needle: needle selection, specifications

The choice of needle directly determines the quality of the specimen and the risk of complications. Currently, the commonly used types of clinical needles and applicable scenarios are as follows:

• Fine needle (22-25G): Suitable for cytological examinations such as thyroid nodule aspiration. The risk of bleeding from a 25G needle is only 1.2%, but the amount of tissue obtained is limited
• Core Pin (14-18G): Used for histopathological examinations such as breast mass biopsy. 18G needle can obtain 15-22mg tissue specimen
• Vacuum-assisted biopsy needle: Suitable for diffuse lesions such as prostate cancer screening, multiple tissue specimens can be collected at one time

A study by Queen Mary Hospital in Hong Kong has shown that differentiation needles should be used for tissues of different densities: a 16G Mengini needle is recommended for liver puncture (a specimen integrity rate of 91% is obtained), and a 19G coaxial needle with sheath technique is recommended for hilar lymph node biopsy to reduce the risk of pneumothorax. Pay special attention to the impact of needle tip design: True-cut needles are suitable for fibrotic tissue, while side-notch needles are suitable for parenchymal organs with uniform texture. According to the guidelines of the Hong Kong Medical Device Committee, in order to ensure puncture accuracy, all needles should be checked for elastic deformation before use, and the number of repeated uses should not exceed 70% of the manufacturer's specified value.

Standardized operating process: Every step must be done correctly and appropriately

Standardized operating procedures are a key factor in ensuring the success rate of needle extraction. The complete one should include 8 core links: preoperative assessment, positioning, disinfection and towels, local anesthesia, guidance and positioning, puncture sampling, specimen processing, and postoperative observation. According to the "Percutaneous Puncture Surgery Standards" formulated by Queen Elizabeth Hospital in Hong Kong, for ultrasound-guided thyroid puncture, the probe sterilization time should be more than 3 minutes, and the insertion point of the skin needle should be 1.5-2cm away from the edge of the probe. It should be noted that the injection volume of 1% lidocaine should not exceed 1 ml in the subcutaneous layer, and deep tissue infiltration should be performed under ultrasound monitoring so as not to mask the lesion with the drug. The timing of the puncture is especially important - studies have shown that inserting a needle when the patient pauses breathing at the end of a gentle exhalation can reduce organ movement by 3-7 mm. The specimen processing should follow the principle of "collect and fix", and the tissue strips should be placed in formalin solution within 10 seconds to avoid the illusion of natural drying. These detailed specifications have led to an increase in hospital specimen certification rates from 82% in 2019 to 95.6% in 2023.

Improving Piercing Techniques: Controlling Angle, Depth, and Force

The coordinated control of angle, depth, and force is at the core of the art of determining the success or failure of pulling the needle. The needle insertion angle should be dynamically adjusted according to the target position: superficial lymph nodes are recommended to insert the needle at an angle of 15-30° to avoid blood vessels, while liver puncture requires 0° vertical needle insertion to ensure sampling depth. Needle marking can be utilized for depth control, such as setting a virtual needle insertion trace line on the ultrasound probe during prostate puncture, and the error can be controlled within ±1.5mm. Puncture of breast fibroma requires an instantaneous explosive force of 200-300 g to break through the capsule, while aspiration of a thyroid cyst only needs to maintain a constant negative pressure of 50 g. According to research data from the Medical Simulation Training Center of the Chinese University of Hong Kong, doctors who conduct more than 30 training sessions through the force feedback simulator can reduce the puncture force error from ±42% to ±9% during initial training. Particularly noteworthy is the application of "high-speed reciprocating technology": during papillary thyroid carcinoma puncture, the needle tip can move back and forth 3-4 times in the lesion in the range of 5-7mm, which can improve the diagnostic accuracy to 97.8% (89.3% in the control group).

Guided by images: Improving positioning accuracy

Modern image-guided techniques have evolved from blind piercings to visual precision manipulation. Ultrasound-guided has become the first choice for superficial organs due to its powerful advantages without the use of radiation in real time, among which elastography techniques can identify breast cancer lesions through differences in tissue hardness, with a specificity of 92.3%. CT guidance is suitable for deep tissues (e.g., small nodules in the lung) and the use of low-dose CT protocols (120kV/20mA) in Hong Kong sanatoriums and hospitals can reduce the radiation dose to 30% of conventional scans. The newly developed fusion imaging technology superimposes real-time ultrasound images with pre-acquired MRI images to increase the detection of clinically significant cancers by 34% in prostate cancer targeted puncture. The application of the navigation system further improves the accuracy, and the electromagnetic navigation puncture system can display the three-dimensional position of the needle tip in real time with an error of less than 1.1mm through the sensor. It should be noted that the higher the resolution of the imaging equipment, the better - the ultrasound frequency during thyroid puncture should be 12-15 MHz, and if the frequency is too high (18 MHz), and the attenuation of sound waves obscures the deep structures.

Reducing Patient Anxiety and Tension: Good Communication and Comfort

Studies have shown that anxiety can increase muscle tone by 47% and lead to an increased rate of puncture deviation. With the introduction of the "5-step comfort method", the incidence of intraoperative transfer in patients is reduced from 18.7% to 5.3%, and 3D models are used to explain before surgery, and physical needles are displayed to solve riddles. Family members during surgery are allowed to accompany and provide stress balls to distract attention. Customized natural sound effects (rain and waves) played in the operating room reduce skin-to-electricity response levels by 22%. We will notify you immediately after surgery and build a relationship of trust. Pediatric patients are recommended to use medical gamification guidance (e.g., "drinking juice through a straw") as a metaphor for suctioning movements, while older patients should emphasize the time of the operation (clearly informing "only 3 minutes of silence"). It is worth noting that communication skills should be given the same attention as technical manipulations - the time the doctor takes his eyes off the monitoring screen and makes eye contact with the patient should account for 15-20% of the total operating time, which allows you to reduce the patient's pain score (VAS) by 1.8 points out of 10.

Problems that arise during processing: bleeding, pain, inability to suck, etc.

Real-time management of intraoperative complications is an important part of ensuring safety. Bleeding is the most common side effect of needle extraction, and slight bleeding can be controlled with 5-10 minutes of compression. Pain management requires hierarchical management: mild pain (VAS 3-4 points) avoids areas of high nerve density by adjusting the needle path. For moderate pain (5-6 points), you can add 0.5 ml of lidocaine. In case of severe pain (more than 7 points), the operation should be interrupted to assess the cause. Common solutions for not being able to suck:

For cystic lesions that are difficult to suction, you can try the "double needle method": insert a 19G guide needle into the cyst cavity, replace it with a 22G thin needle and suction, and increase the extraction rate of viscous liquid from 67% to 91%. To avoid secondary damage from blind manipulation, all therapeutic measures should be carried out under video surveillance.抽針過程

Coping strategies in different situations

Special cases require an individual strategy. In obese patients (BMI>30), the increased thickness of the subcutaneous fat layer attenuates the ultrasound by 40-60%. For patients with abnormal coagulation function (INR>1.5), it is recommended to administer 10 mg of vitamin K1 intravenously 4 hours before surgery and use the "coaxial" scissor method to reduce the risk of needle bleeding. Adjust the plan according to the characteristics of different organs: liver puncture should avoid the bile duct (3 cm in front of the right branch of the portal vein is a safe zone), pancreatic puncture should choose the anterior gastric route to avoid the intestinal tract. For multiple lesions, Princess Margaret Hong Kong established the principle of "priority sampling": priority sampling was given to lesions with SUVmax>4.0 on PET-CT, followed by MRI-enhanced scanning to enhance obvious lesions in the arterial stage and improve the detection rate of malignant lesions by 28.4%. Treatment of special site lesions: Pulmonary apical lesions use the "oblique needle insertion + deep inhalation and breath hold" technique, and the success rate of avoiding rib occlusion is 86.7%.

Continuous learning and practice to improve the success rate of needle removal

Refinement in needle pulling techniques is a continuous learning process. In Hong Kong vocational schools, radiologists are required to complete 200 simulated surgeries and 50 clinically supervised surgeries during the training period before practicing independently. It is recommended to create an individual technical profile: record the type of needle for each operation, the number of needle insertions, the length of the specimen, the choice of complications, and perform a quarterly retrospective analysis. For example, the Hong Kong Radiological Society's "Ultrasound-guided Puncture Quality Improvement Program" improved the diagnostic adherence rate of participating physicians from 83.6% to 91.8% within one year through a double-blind review of specimen quality. Techniques such as elastic imaging-guided ultrasound and contrast-enhanced ultrasound can improve the detection sensitivity of specific lesions by 15-22%. The most important thing is to maintain a strict attitude - regard each operation as the first operation, strictly check patient information, lesion location, and surgical plan, and only through systematic training, continuous reflection, and technological innovation can we improve the success rate of needle extraction to an ideal level, and ultimately provide patients with safe and accurate diagnostic services.

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