metrology in medicine

From Big Medical Encyclopedia

METROLOGY (grech, metron a measure + logos the doctrine) — the field of knowledge and practical activities devoted to methods of measurement, ensuring unity of measurements and required accuracy. The m can be divided into theoretical (scientific), applied and legislative M. K of theoretical M. carry the general theory of measurements, including methods of assessment of accuracy, development of units of physical quantities and their systems, a research of interrelation between them. The main objectives of applied M. consist in development of methods and means of reproduction of units of physical quantities (standards), methods and means of model and working measurements, and also methods of transfer of the sizes of units from standards to model means and from them to working measuring instruments. Legislative M. includes a complex of the interconnected rules, requirements and norms aimed at providing unity of measurements and uniformity of measuring instruments and subjects to control (supervision) from state and departmental metrological services (see. Metrological health service ).

Historically M. arose from any description of measures for their names, divisions, a mutual ratio. The measures which were in the course (linear, volume, weight, time), and also monetary units differed in an extreme variety and diversity (at various times in the certain countries and even in the different cities and areas measures of various names and sizes were used).

The quantum leap in M. happened in connection with development and deployment in practice of metric system of measures. It led to elimination in a number of the countries of isolation and a complexity of national and local measures and need of carrying out the corresponding researches for creation of metric system. In 1875 with the assistance of the Russian scientists B. S. Jacobi, G. I. Vilda and G. V. Struva the Metric convention was drafted, to-ruyu representatives of 17 countries signed (including Russia). At the same time on the general means of the states which signed the Convention the International bureau of measures and scales which created new standards of metric measures for all countries — participants of the Convention was founded. Acceptance by the majority of the countries of uniform system of measures and scales led to the fact that descriptive M. turned into the industry of modern physics leaning on physical experiments of high precision.

The basic concepts of M. are concepts of physical quantity and measurement. Physical quantity call property, in a qualitative sense the general to many physical objects, their states or the processes proceeding in them, but in a quantitative sense individual for each object. An example of physical quantities are the weight, pressure, length, temperature etc. For expression and comparison of values of physical quantities their units serve, i.e. such number of physical quantities, the Crimea are conditionally appropriated the numerical values equal to unit. The kilogram (kg), pascal (Pa), meter (m), degree etc. can be an example of units of measurements.

The main and derivative units of physical quantities combine in systems of units, in to-rykh they are optimum connected. In the majority of the countries including in the USSR, it is accepted and the International System of Units of physical quantities — the SI is implemented (see. Units ).

Measurement call pilot finding of value of physical quantity by means of special technical means. Distinguish direct and indirect measurements depending on that, find required value of size directly from the experimental data or on the basis of the known dependence between the required size and sizes received directly from experience. An example of direct measurements is measurement of weight on lever scales. An example of indirect measurements is measurement of concentration of substance in solution on the optical density of test of this solution. As a rule, in indirect measurements use steady statistical dependences between physical quantities or the dependences caused by physical laws.

Any measurements are characterized by the accuracy, i.e. degree of approximation of results of measurements to a true value of the measured size. The deviation of results of measurements from a true value of the measured size is called an error of measurements and quantitatively expressed in absolute or relative units. At the same time distinguish two components of an error of measurements: error of a method of measurements and tool error. So, at measurements of body temperature there can be its inexact assessment at the expense of the wrong arrangement of the thermometer (an error of a method of measurements) and inexact indications of the thermometer (a tool error).

In medical science and practice use measurements of almost all known physical quantities characterizing properties or states biol, an object, taken from it samples, tests of the environment, measurement of parameters of the different types of radiation (light, thermal, x-ray, ultrasonic) used in the physiotherapeutic and surgical purposes and also measurement at the dosed administration of medicines and biol, drugs.

Along with constants or slowly changing sizes (anthropometrical parameters, a galvanic current, etc.) measure dynamic sizes in medicine (pressure and an expense biol, gases and liquids, electric biopotentials), and in the field of sizes of the electromagnetic nature of measurement cover all range of electromagnetic oscillations — from low-frequency, radio-frequency and optical ranges before hard ionizing radiation.

Modern methods of medical researches demand use of achievements of all natural sciences, all-physical laws and the principles, to-rye are implemented in the applied measuring instruments of physical quantities. Proceeding from it, the medical science and practice widely use all original positions of theoretical, applied and legislative M., and ensuring unity of measurements in medicine is reached by use of reference base of the country, nation-wide park of model measuring instruments, testing schemes, shots of verificators by the known types of measurements, and also use of the general for all spheres of the national economy of rules of metrological supervision.

R. I. Utyamyshev, A. N. Grishin.