Discussion on the repair and methods of imaging equipment

The lack of advanced medical equipment constitutes a significant deficiency in the material foundation for medical institutions to conduct medical treatment, teaching, and research, and it also reflects their general strength; modern medicine is increasingly reliant on medical equipment, especially medical imaging equipment including X-ray machines, CT, MRI, DSA, ultrasound diagnostic instruments, and SPECT, which are key and core equipment.  

Medical imaging equipment involves substantial investment, complex systems, high technological content, and stringent work environment requirements; strict requirements apply to its installation, operation, and use; ensuring that the equipment is consistently in good working order and effectively utilized is crucial for improving the quality of medical services and achieving the expected benefits; therefore, proactive equipment maintenance is particularly important.

Based on the new concept of combining prevention and treatment, with prevention as the priority, maintenance should include two parts: maintenance and repair.

1. Maintenance

Maintenance belongs to proactive maintenance, also known as preventive maintenance; this is an effective measure to ensure the healthy operation of equipment, improve the availability rate, and extend its service life. Maintenance can be divided into daily maintenance and regular maintenance.

1.1 Daily Maintenance

Daily maintenance is generally carried out by the using department and operators. It is a daily task that should be institutionalized, and its content should be included in the operating procedures and precautions; the using department should assign a technician with a certain understanding of the equipment and a strong sense of responsibility to serve as a full-time or part-time equipment manager to assist and guide operators in this work. Daily maintenance generally includes:

(1) Cleaning of the equipment room and equipment; observing and adjusting the stable temperature and humidity of the equipment room.

(2) Checking the mechanical parts, rotating parts, pneumatic and hydraulic systems, screws, nuts, etc., to ensure they are functioning normally.

(3) Checking whether the switches, knobs, indicator lights, instruments, and displayed parameters on the instrument surface are normal.

(4) Before formal operation, use the instrument's self-test program to detect the status of various parts of the instrument.

(5) Pay attention to any unusual smells or sounds during the operation of the instrument, and whether the image quality is normal.

(6) Check whether the operators' operation of the instrument complies with the regulations and correct any deviations promptly.

1.2 Regular Maintenance

Regular maintenance is generally carried out by the equipment manager in cooperation with engineering and technical personnel. It is an organized and planned maintenance measure that is continuously cycled, which helps to understand the operation rules of the equipment and facilitates troubleshooting; the content and time of regular maintenance vary depending on the equipment. It can generally be divided into three levels:

(1) Level 1 Maintenance: This is generally carried out once a month to once a quarter. In addition to daily maintenance work, the main content includes disassembling the casing, removing dust, dirt, foreign objects, tightening screws, and adding lubricants; checking components and parts for wear, deformation, burning, breakdown, looseness, dampness, aging, poor grounding, etc.; testing the voltage and ripple of each group of power supplies, checking the operation and contact of high-voltage components, etc.

(2) Level 2 Maintenance: This is generally carried out once every six months to a year. In addition to Level 1 maintenance, the main content includes testing and calibrating the sensitivity and accuracy of various instruments and operating control systems on the main control console, replacing expired consumables such as high-voltage generator insulating oil, and systematically testing and performing bias tests on the voltage and waveform at various test points in the circuit.

(3) Level 3 Maintenance: This is generally carried out once every 2-4 years. In addition to Level 2 maintenance, if necessary, the entire machine can be completely disassembled for cleaning and repair. Components that have exceeded their service life should be replaced or repaired as much as possible. The instrument should undergo a more comprehensive and thorough debugging to restore its working accuracy and performance, and it is entirely possible to reach or exceed the level of a new machine.

2. Troubleshooting

Troubleshooting is also known as passive maintenance; medical imaging equipment, like other types of instruments, is bound to experience malfunctions during long-term use due to various reasons. Troubleshooting remains an important task for equipment management and engineering and technical personnel.

2.1 Troubleshooting Methods for Instruments and Equipment

(1) In terms of organizational management: such as dividing into specialized groups, with one person specializing in multiple areas; calculating the complexity coefficient of the instrument and reasonably allocating tasks; assigning responsibility for departments or instruments to individuals; organizing troubleshooting consultations; and implementing a chief engineer responsibility system, etc.

(2) In terms of talent cultivation: such as combining introduction and cultivation to gradually form a talent echelon, combining on-the-job improvement and external training, and combining in-depth basic theory with professional skills improvement, etc.

(3) In terms of repair procedures: first understand the cause of the instrument failure, be familiar with the working principle of the instrument, and then use the basic theoretical knowledge to analyze the possible location of the failure based on the instrument's circuit diagram, gradually detect and troubleshoot, find the real location of the failure, and finally repair or replace the faulty components and complete partial or whole machine debugging.

(4) Specific repair methods: should follow the principles of inquiry first, then diagnosis; visual inspection first, then testing; comprehensive first, then local; transmission first, then circuit; independent first, then whole machine; external first, then chip; control first, then data; qualitative first, then quantitative. The failure location is generally more common in mechanical parts than in circuit parts; high-voltage parts are more common than low-voltage parts; high-temperature parts are more common than low-temperature parts; power supply parts are more common than main body parts; transmission parts are more common than stationary parts; plug-in parts are more common than fixed parts; resistive components are more common than semiconductor components; analog circuits are more common than digital circuits, etc. Detection methods include tapping, visual inspection, measurement, comparison, replacement, temperature variation, signal tracing, signal input, forward and backward tracing, load separation, etc.

2.2 Repair Methods for Equipment Without Drawings

In recent years, manufacturers have provided less and less equipment drawings and data, which undoubtedly poses greater difficulties for equipment maintenance. Through the practice of a large number of engineering and technical personnel, many methods have been explored. For example:

(1) First rule out poor contact faults. When equipment malfunctions, as long as it is not obviously violent or smoky, it may be caused by poor contact. Especially when the malfunction is intermittent, poor contact should be suspected first. Methods such as light shaking, tapping, plugging and unplugging, slight twisting, and pressing can be used to reproduce the fault and trace the fault location.

(2) Make full use of every piece of information in the manual to find the fault; in the absence of an instrument circuit diagram, the instrument's basic principles, flowcharts, function selection, operating procedures, status display, debugging methods, and signals and waveforms at certain detection points of the instrument in the operating instructions can all, to a certain extent, provide clues for checking instrument faults. After repeated and detailed analysis, board-level repair may be achieved.

(3) Make full use of the instrument's self-test function: The instrument's self-test is a system in which the instrument's internal computer control system uses software procedures to detect the operating status of various parts of the instrument and prompts the cause of the fault in the form of a code; with the help of this system, we can more easily analyze the possible cause or location of the fault, generally achieving board-level repair.

Within this scope, further detailed analysis is carried out by integrating the basic theories of various disciplines. If necessary, the local circuit of the key suspected part can be mapped out to facilitate analysis, and component-level repair can be achieved as much as possible.

(4) Use a circuit maintenance tester to find faulty components. Using this instrument to find faults in instruments without drawings is an effective method: This instrument is a new testing tool that combines modern electronic technology and computers. It has online and offline testing functions; it can analyze large-scale ICs or measure VI characteristic curves; it can detect analog and digital circuits; it can use the data in the database for comparison, and can also learn and compare non-standard circuit components; it also uses post-drive technology to isolate the influence of surrounding components, and the test system automatically performs the corresponding tests. After analysis and comparison, the faulty components are found, realizing component-level repair - bringing convenience and hope to finding faults to a certain extent.

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