These three medical sources are all strong inspection and measurement instruments. First, from the nature of medical three sources, the definition of measuring instruments is clearly put forward in the detailed rules for the implementation of the measurement law. Measuring instruments refer to devices, instruments, measuring tools and reference materials that can directly or indirectly measure the numerical value of the measured object. Medical X-ray machine, B-ultrasound machine and laser therapy machine respectively measure human physiology and pathology through medical radiation source, ultrasonic source and laser source contained in these devices, determine their output energy, and control the numerical value through control equipment to achieve the purpose of diagnosis and treatment. According to the definition of measuring instruments, medical three sources contained in medical diagnosis and treatment equipment should belong to measuring instruments.
Secondly, from the legal point of view, the "Administrative Measures for Verification of Measuring Instruments in People's Republic of China (PRC)" (issued by the State Council, the effectiveness of administrative regulations is higher than departmental regulations) has included the medical three sources in the catalogue of measuring instruments subject to compulsory verification.