All about the doses and harm of X-ray irradiation in medicine
Mar 25, 2018
X-ray types of examination in medicine still have a leading role.Sometimes without an X-ray, it is impossible to confirm or to diagnose correctly.Every year, techniques and X-ray technology are being improved, becoming more complex, becoming more safe, but, nevertheless, the damage from radiation remains.Minimizing the negative effect of diagnostic radiation is a priority task of roentgenology.
Our task is to understand at the level accessible to any person the existing radiation dose numbers, units of their measurement and accuracy.Also, let us touch upon the reality of possible health problems, which can cause this type of medical diagnosis.Table of contents: What is X-ray radiation? What are the dosages of the radiation received on the human body? In what units are the doses of the radiation received? Natural radiation background? Forced diagnostic doses of X-ray irradiation? . Recommended reading:
What is X-rays?
X-rayRadiation is a stream of electromagnetic waves with a length in the range between ultraviolet and gamma radiation.Each type of waves has its own specific effect on the human body.
X-rays are inherently ionizing radiation.It has a high penetrating ability.Its energy is a danger to man.The radiation is the more harmful the greater the dose obtained.
On the Harmful Effects of X-Ray Radiation on the Human Body
Passing through the tissues of a human body, X-rays ionize them, changing the structure of molecules, atoms, in simple language - "charging" them.The consequences of the received irradiation can appear in the form of diseases in the person himself( somatic complications), or in his offspring( genetic diseases).
Each organ and tissue is differently influenced by radiation.Therefore, the coefficients of radiation risk have been created, which you can see in the picture.The higher the value of the coefficient, the higher the susceptibility of the tissue to the action of radiation, and hence the danger of getting a complication.
Hematopoietic organs - red bone marrow - are most susceptible to radiation.
The most common complication that appears in response to radiation is the pathology of the blood.
- has reversible blood composition changes after minor irradiation values;
- Leukemia - a decrease in the number of leukocytes and a change in their structure, leading to malfunctions of the body, its vulnerability, decreased immunity;
- Thrombocytopenia is a decrease in the content of platelets, blood cells responsible for clotting.This pathological process can cause bleeding.The condition is aggravated by damage to the walls of the vessels;
- hemolytic irreversible changes in blood composition( decomposition of erythrocytes and hemoglobin), as a result of exposure to powerful radiation doses;
- erythrocytopenia - Reduction of red blood cells( red blood cells), causing the process of hypoxia( oxygen starvation) in tissues.
Other ASE51ASD pathologists and :
- development of malignant diseases;
- premature aging;
- damage the lens of the eye with the development of cataracts.
Important : Dangerous X-rays become in the case of intensity and duration of exposure.Medical equipment uses low-energy irradiation of short duration, therefore when applied, it is considered relatively harmless, even if the examination has to be repeated many times.
Single exposure, which the patient receives in routine radiography, increases the risk of developing a malignant process in the future by approximately 0.001%.
Note : unlike the effects of radioactive substances, the harmful effect of rays stops immediately, after turning off the device.
Rays can not accumulate and form radioactive substances, which then will be independent sources of radiation.Therefore, after X-rays, no measures should be taken to "remove" radiation from the body.
In what units are measured the doses of the radiation received
It is difficult for a person far from medicine and roentgenology to understand the abundance of specific terminology, the dose numbers and the units in which they are measured.Let's try to bring information to an understandable minimum.
So, what is the dose of X-rays measured?There are a lot of radiation units.We will not disassemble everything in detail.Becquerel, curie, rad, gray, rem - that's the list of the basic quantities of radiation.They are used in different measurement systems and fields of radiology.Let us dwell only on practically significant in X-ray diagnostics.
We will be more interested in X-ray and Sievert.
The level of penetrating radiation emitted by an X-ray unit is measured in a unit called "X-ray"( P).
To evaluate the effect of radiation on humans, the concept of equivalent absorbed dose( EPD) was introduced. In addition to EPD, there are other types of doses - they are all presented in the table.
The equivalent absorbed dose( in the picture - the Effective equivalent dose) is the quantitative value of the energy absorbed by the body, but the biological response of body tissues to radiation is taken into account.It is measured in sievert( Sv).
Sievert is approximately comparable to a value of 100 X-rays.
The natural background of irradiation and the doses given by the medical X-ray equipment are much lower than these values, so the values of a thousandths( million) or one millionth( micro) Sievert and Roentgen are used for their measurement.
In figures it looks like this:
- 1 Sieverte( Sv) = 1000 millisievert( mSv) = 1000000 microsiever( μSv)
- 1 X-ray( P) = 1000 milli-transforment( mR) = 1000000 milli-radentgen( microR)
To estimate the quantitative part of the radiation received per unit time( hour, minute, second) use the notion - dose rate, measured in Sv / h( sievert-hour), μSv / h( microsievert-hour), R / h(Roentgen-hour), md / h( micro-roentgen-hour).Similarly - in minutes and seconds.
It can be even simpler:
- total radiation is measured in X-rays;
- dose received by a person - in sieverts.
Doses received in sieverts accumulate throughout life.Now let's try to find out how many people receive these same sievert.
Natural radiation background
The level of natural radiation is everywhere different, it depends on the following factors:
- altitude above sea level( the higher the stiffer the background);
- geological structure of the terrain( soil, water, rocks);
- external causes - the material of the building, the presence of a number of enterprises that provide additional radiation load.
Note: is considered the most acceptable background when the radiation level does not exceed 0.2 μSv / h( microsievert-hour), or 20 μR / h( micro-roentgen hour)
The upper limit of the norm is the value up to 0, 5 μSv / h = 50 μR / h.
Within a few hours of irradiation, a dose of up to 10 μSv / h = 1 mR / h is allowed.
All types of X-ray studies fit into safe standards of radiation loads, measured in mSv( millisievert).
Permissible radiation doses for a person accumulated for life should not exceed 100-700 mSv.The actual values of irradiation of people living in the highlands can be higher.
On average, a person receives a dose of 2-3 mSv per year.
It is summarized from the following components:
- solar radiation and cosmic radiation: 0.3 mSv - 0.9 mSv;
- soil and landscape background: 0,25 - 0,6 mSv;
- radiation of housing materials and structures: 0.3 mSv and higher;
- air: 0.2 - 2 mSv;
- food: from 0.02 mSv;
- water: from 0,01 - 0,1 mSv:
In addition to the external radiation dose received, the human body accumulates its own radionuclide compounds.They also represent a source of ionizing radiation.For example, in bones this level can reach values from 0.1 to 0.5 mSv.
In addition, there is irradiation with potassium-40, accumulating in the body.And this value reaches 0.1 - 0.2 mSv.
Please note : for radiation background measurement you can use a conventional dosimeter, for example RADEKS RD1706, which gives an indication in sievert.
Forced diagnostic dose of X-ray exposure
The value of the equivalent absorbed dose for each X-ray examination may vary significantly depending on the type of examination.The dose of irradiation also depends on the year of release of the medical equipment, the workload on it.
Important : modern X-ray equipment emits radiation tens of times lower than the previous one.We can say this: the newest digital radiotechnics is safe for humans.
But still, try to give the average number of doses that a patient can receive. We draw attention to the difference in the data provided by digital and conventional X-ray equipment:
- digital fluorography: 0.03-0.06 mSv,( the most modern digital devices give radiation at a dose of 0.002 mSv, which is 10 times lower than their predecessors);
- film fluorography: 0,15-0,25 mSv,( old fluorographs: 0,6-0,8 mSv);
- radiography of thoracic cavity organs: 0,15-0,4 mSv;
- dental( dental) digital radiography: 0,015-0,03 mSv., Usual: 0,1-0,3 mVV.
In all these cases, we are talking about one image.Studies in additional projections increase the dose proportionally to the frequency of their conduct.
X-ray method( not for photographing the area of the body, but visual examination by a radiologist on the monitor screen) gives significantly less radiation per unit of time, but the total dose may be higher due to the duration of the procedure.So, for 15 minutes of fluoroscopy of chest organs, the total dose of the received irradiation can be from 2 to 3.5 mSv.
Diagnosis of the gastrointestinal tract - from 2 to 6 mSv.
Computed tomography uses doses ranging from 1-2 mSv to 6-11 mSv, depending on the organs being examined.The more modern the X-ray apparatus is, the lower it gives the dose.
Separately note radionuclide diagnostic methods.One procedure, based on the radiopharmaceutical, yields a total dose of 2 to 5 mSv.
A comparison of the effective radiation doses received during the most frequently used diagnostic tests in medicine and the daily doses received by a person from the environment is presented in the table.