“Overview of X-Ray Tube Technology”
X-ray is being used widely in medical and in other fields of science, engineering, and technology since its invention in the year 1895. Globally, the growing number of general population and the high prevalence of various critical diseases are augmenting the need for X-ray imaging equipment for an accurate diagnosis. Although X-ray tube technology (Coolidge tube) is about 106 years old, it has been still used widely today for medical diagnostic imaging. Various types of X-ray tubes are classified. The indicative list for the standards pertaining to performance and safety of medical electrical equipment and diagnostic X-ray tube assembly includes the following: IEC 60601-1-2/IS 13450-1-2, IEC 60601-1-3/IS 13450-1-3, IEC 60601-1-6, IEC 60601-1-8, IEC 60601-1-9, IEC 60601-2-28, IEC 60601-2-54, IEC 60522, IEC 60806, IEC 60336, IEC 61267, IEC 61674, IEC 61676, IEC 60613, IEC 60526, IEC 62304, IEC 62366, ISO 13485, ISO 14000, ISO 14971, and ISO 10993-1. The manufacturing processes of the X-ray tube assembly are listed as follows: (step 1) X-ray tube insert parts processing and cleaning; (step 2) X-ray tube insert parts (anode and cathode) assembly processing; (step 3) glass or metal-ceramic envelope processing; (step 4) degassing of X-ray tube insert; (step 5) seasoning of X-ray tube insert; (step 6) X-ray tube assembly processing; (step 7) final testing of X-ray tube assembly; and (step 8) quality control of X-ray tube assembly. As per the recommendations of Atomic Energy Regulatory Board (AERB), Government of India, the accuracy of the applied X-ray tube potential of the general radiography and fluoroscopy, computed tomography, mammography, and dental X-ray machine should be within ±5, ±2, ±1, and ±5, respectively, of the corresponding measured values. Linearity of the X-ray tube current (mA or mAs) loading stations (coefficient of linearity (CoL)) of the general radiography and fluoroscopy, computed tomography, mammography, and dental X-ray machine should be within <0.1, ±0.1, ±0.1, and <0.1, respectively. The most common causes for the X-ray tube failures include the following: (i) cathode filament burnout, (ii) target micro-cracking, (iii) tube arcing, (iv) slow leaks in the tube, and (v) bearings of rotating anode. Globally, more than 20,000 patents have been filed so far on the innovations of X-ray tube technology.
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