A Brief Discussion on the Repair of Faulty Color Doppler Ultrasound Probes

Ultrasonic diagnostic equipment primarily uses ultrasound to extract various types of information from human tissue (such as tissue interface information and blood flow information). To achieve the purpose of transmitting information, it must have special-function devices—ultrasonic transducers (i.e., ultrasound probes). The ultrasonic transducer is an indispensable key part of ultrasonic diagnosis, known as the "eyes" of the ultrasonic instrument. Its value often accounts for one-fourth to one-third of the total value of an ultrasonic instrument. Moreover, it comes into contact with the patient's body through the hands of the operating physician every day, making it the component most prone to malfunction in ultrasonic equipment. Therefore, it is essential to use and maintain it properly.

In general, there are several types of ultrasound probe malfunctions: cracks or bubbles on the probe's working surface or exterior, decreased sensitivity; local image defects; cable cracks or broken electrode leads; poor probe contact, etc.

1. Cracks or bubbles on the probe's working surface or exterior, decreased sensitivity

(1) Although the manufacturers of ultrasound probes vary, their basic structures are largely similar:

The transducer is placed in the probe cavity, which is encased in plastic. We know that sufficient coupling agent must be applied to the examination site during an ultrasound examination. This coupling agent is the biggest threat to the outer packaging material of the probe. In many cases, cracks on the probe's working surface or exterior are due to the failure to completely wipe off the coupling agent from the probe's surface after the operation. Over time, the coupling agent corrosively penetrates the bonding area between the probe's plastic and rubber, causing substantial damage to the probe. Therefore, it is particularly important to completely wipe off the coupling agent from its surface after completing the work. It is best to use a clean, damp, soft cloth to wipe it. Another cause of cracks on the working surface or exterior is that the probe is often exposed to sunlight and large temperature differences. Sunlight can cause premature aging and deformation of the plastic material, leading to cracks. Under repeated large temperature differences, the probe's plastic material undergoes thermal expansion and contraction, making the bonding surface prone to cracking. Therefore, ultrasonic equipment should be placed in a temperature-controlled room and should be shielded from light. For example, if the probe experiences frequency instability, it is considered that the probe is damp. After moisture absorption treatment with anhydrous copper sulfate fails to resolve the issue, special tools are used to open the probe housing, and the small circuit board is gently removed. It is found that the circuit board has excessive oil stains. After soaking in 99.5% pure alcohol for ten minutes, the oil stains and dust are cleaned with a fine brush. After drying the circuit board with a hair dryer, it is put back, the housing is reinstalled, and the machine is turned on to test the probe. The frequency hopping fault is eliminated.

If cracks are found on the probe, and it is still under warranty, contact the dealer as soon as possible. Except for man-made damage, replacement is usually provided. If the warranty has expired, as long as the probe image is normal, a 703 single-component room-temperature vulcanizing silicone rubber coupling agent can be used to apply and fill the cleaned cracks. Because it is non-corrosive and waterproof, it bonds well with rubber materials and can prevent the coupling agent from entering the probe.

(2) Internal bubbles.

Generally speaking, the fault of decreased sensitivity is caused by defects in the probe's manufacturing process and only appears after a period of use. Especially after adjusting the host parameters, if the penetration ability is found to be poor, attention should be paid to whether it is related to this fault.

2. Local image defects

This is often caused by problems with certain chips in the probe. For example, a white bright band appears from top to bottom in the color ultrasound image, and there is no image information in the bright band. Later, the manufacturer confirmed that it was due to damage to some chips inside the probe.

3. Cable cracks or broken electrode leads

This is because the probe is constantly moved back and forth during use, which unconsciously pulls the cable, especially during the rotation of the probe, often causing the probe and cable to become entangled. Therefore, this type of fault is often related to poor operating habits or improper cable placement. For this type of fault, the repair method is to open the housing from one-third of the probe's length, reorganize all the leads, and then solder them (never damage the sound-absorbing material and acoustic insulation layer), and then firmly glue the housing with strong adhesive.

4. Poor plug contact

This situation often occurs in older machines, and the machines lack regular maintenance. The connectors often have a lot of dust. Under power-off conditions, a strong hair dryer can be used to clean the connectors, which usually restores functionality.

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