Here, we will use B-Type ultrasound diagnostic systems as an example to provide a detailed analysis of their structural principles and maintenance techniques.
1. Structural Principles of B-Type Ultrasound Diagnostic Systems
B-Type ultrasound diagnostic systems are primarily composed of several components: the probe, transmitting and receiving circuits, analog signal processing circuits, keyboard control circuits, digital scan converters, image display circuits, and power supply circuits.
Based on their scanning methods, probes can be divided into two types: linear array scanning probes and phased array scanning (sector scanning) probes. The basic principle of linear array scanning is that a linear array transducer is composed of several oscillators arranged in a linear array. These oscillators are controlled by electronic switches, which work in a time-sharing manner, rotating from one side of the probe to the other, generating a composite beam for transmission and reception. The basic principle of phased array scanning is to excite the transducers in a linear array at different times, with equal time delays between the excitation pulses. This results in a phase difference between the direction of the composite beam and the normal to the plane in which the transducers are arranged. By uniformly varying the time delay, the phase difference also uniformly varies. Through time control, phased array scanning of the ultrasonic beam, also known as sector scanning, is achieved.
B-mode ultrasound diagnostic equipment uses brightness modulation to display reflected echoes from all interfaces in the depth direction. By rapidly scanning horizontally, ultrasound echoes are transmitted and received sequentially to produce two-dimensional ultrasonic tomographic images in the vertical plane, known as line scan images. Rapid scanning by varying the angle of the ultrasound beam produces two-dimensional ultrasonic tomographic images in the vertical sector, known as sector scan images. The transmitting circuit provides excitation voltage to the probe. By controlling the different arrangements of transducers and delaying the excitation, the ultrasonic system's beam is scanned and focused. The receiving circuit performs phase shift synthesis on the ultrasonic echo signals. The analog signal processing circuitry includes a preamplifier, a time-controlled gradient descent (TGC) circuit, a dynamic filter, and a logarithmic amplifier. The ultrasonic echo signals generated by the image detection circuit and the Doppler detection circuit are further processed by the scan converter. A digital scan converter is essentially a digital image processing system with image storage. Its primary function is to digitize the ultrasonic signal, process it, and ultimately display it on a monitor. The image processing circuit includes circuits for grayscale processing, histogram processing, and data interpolation. Its primary purpose is to improve image quality.
2. Troubleshooting Techniques for B-Type Ultrasound Diagnostic Systems
First, B-Type ultrasound diagnostic system failures are primarily caused by the heavy workload and poor environmental conditions. Factors such as temperature, dust, power supply fluctuations, and interference can increase the instrument's failure rate. Therefore, strengthening daily maintenance is an essential step in properly maintaining B-Type ultrasound diagnostic systems.
During hands-on troubleshooting, swapping the color and black-and-white ultrasound circuit boards is generally a method for troubleshooting. The following are key maintenance techniques and methods to consider:
First, before performing specific maintenance work, as a professional engineer specializing in B-mode ultrasound repair, you should first be familiar with the instrument's operating principles and specific circuit structure. This will help you understand the various symptoms of the problem from the fundamental perspective and improve the quality of the repair.
Second, before performing specific repairs, you should also first be familiar with the instrument's main functions and the various functions and operations related to the repair. This will help narrow the scope of the problem, identify the faulty part of the instrument, and shorten the repair time by understanding the various functions and their interrelationships.
Third, before performing repairs, you should carefully observe and investigate the various phenomena before and after the failure occurs, especially asking the operator for detailed information about the process and background of the failure. B-mode ultrasound is a large and valuable instrument, and maintenance is a complex task. Do not attempt repairs without fully understanding the fault and accurately determining its nature.
Fourth, the power supply is a common fault area in B-mode ultrasound diagnostic systems. Due to its high power consumption and high temperature, it has a high failure rate. Power supply failures can manifest in various ways, often manifesting as a malfunction of the entire system or a specific part of it. This type of fault also applies to equipment malfunction caused by interference introduced by the power supply. In most cases, the power supply should be checked first to ensure proper operation.
Fifth, peripherals in ultrasound systems are also a common area for failure. However, these peripherals are relatively straightforward, their structure is simple, and each component is relatively independent, making fault diagnosis and location relatively easy. For example, in the display, trackball, printer, etc., I have found that troubleshooting these types of faults is relatively simple.
Sixth, other components of the ultrasound system, such as the various system circuit boards, are highly integrated and mostly specialized devices, so they can usually only be repaired at the board level. During troubleshooting, a comprehensive assessment should be made based on circuit principles, the operator's description of the fault background and symptoms, the fault code displayed by the instrument, your own understanding and investigation of the instrument's fault symptoms, and other factors to determine the fault location. If an ultrasound system of the same or similar model is available, identical circuit boards can be swapped to facilitate fault location.
B-mode ultrasound diagnostic systems are highly sophisticated medical imaging devices. Maintenance requires not only technical experience but also a deep understanding of the device's structure and functionality. By mastering the six maintenance techniques described above, maintenance personnel can more quickly and accurately locate faults, improve maintenance efficiency, extend the lifespan of the equipment, and ensure the continuity and safety of medical services.
In addition, medical institutions are advised to regularly conduct comprehensive inspections and maintenance of their equipment to reduce the risk of failures at the source and provide more reliable imaging support for clinical practice.
