RECONSTRUCTION ACCUMULATED DOSES AND RETROSPECTIVE EPIDEMIOLOGICAL STUDY OF DIAGNOSTIC RADIOLOGY

Kalnitsky S.A., Ivanov E.V., Shubic V.M. Institute of Radiation Hygiene, St.-Petersburg, Russia E-mail: [email protected]; [email protected]

Abstract The article contains the information of the summary medical X-ray exposure of the population (1950- 2000) in some areas of Russia. There were fixed low and high X-ray doses during the long period of time. Disease and mortality were explored in these regions during the period of the last ten years (1992-2001). The causes of death contained leukemia and other types of . More significant levels of disease and mortality were fixed in the areas where were the high levels of medical irradiations. These facts show the influence of the medical irradiation on the level of mortality and diseases.

1. Introduction

The medical irradiation take leading place among all kinds of irradiation man. Its contribution to common dose makes in the different countries from 14 % up to 75 %. On nuclear power, professional irradiation and the accidents in total are less than 1 % collective dose (table1).

Table 1. The basic sources of population irradiation

Kinds and sources Effective dose, mSv Russia Health-care World level I* Natural 2,40 2,40 2,40 Medical 1,05 1,29 0,4 Man-made** 0,003 0,004 0,0007 Accidents 0,022 0,003 0,002 Total 3,5 3,7 2,8 * more 1 physician on 1000 man, ** including professional

2. Peculiarity of medical irradiation

Medical irradiation of the patients and population consist from prophylactic, diagnostic and therapy sources. Therapy is not used at estimation collective doses. The indisputable leader among diagnostic irradiation, both in scales of application and by way of dose, was and there is diagnostic radiology. It is necessary more than 99 % of medical and 95 % man-made dose [4]. Medical effective dose of population for Russia is more than 1,0 mSv, as for health-care level I countries. Actually medical irradiation is much more, as there are not taken into account repeated irradiations because of a technical marriage and the cases methodical overexposure of the patient because of non-observance of technological conditions of realization X-ray examinations are frequent. In separate regions of Russia the situation considerably differs from average, including increasing of a dose. Medical and, in particular, X-ray exposure is one of most important among all ionizing sources and is characterized by very high dose rate (table 2). It is necessary to note peculiarities only for X-ray exposure among other features irradiation: - Influence on ill or weakening organism; - repeated influence; - local influence, as a rule, on the same bodies, including radiosensitive, such as lung, thyroid and breast, bone marrow, stomach etc.; - dependence dose irradiation from qualification of the physician, diagnostic imaging equipment and protecting means.

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Table 2. The comparative characteristic of the basic sources of population irradiation

Kind of Annual The relation of Time of irradiation effective dose, X-ray dose rate to irradiation mSv natural dose rate for year, h

Natural 2,4 - 8,8 х 103

Diagnostic radiology 1,0 3,5 х 106 9,4 х 103

Thus, the X-ray exposure of the patients and so population acts as one of most important, but at the same time more risky among various sources irradiation. Even at short-time influence it is more dangerous by way of biological action, than other kinds of irradiations of the man. It is necessary to note the tendency of reduction of professional exposure at radiologists and increase X-ray exposure of the patients now in the world. Both parameters are determined by technical progress, in particular, by large doses of X-ray exposure of the patients at new kinds of examinations, such as CT, interventional radiology etc.

3. Investigative summary population medicine exposure

Taking into account a high modern level of a X-ray exposure and its not clear prospects, it was represented urgent to investigate this level for the last years. In this connection it was represented to make the following: - to reconstruct doses of X-ray exposure during several decades to determine a level of an irradiation of the population at past; - on the basis of the received data to investigate cancer of the population in view of the latent period and accumulated doses; - to compare the received results to reveal laws. Reconstruction of X-ray exposure of the patients and population also will be: - to promote optimization of a level of a diagnostic radiology; - brings in the contribution to study of influence of small doses. The level of X-ray exposure of the population depends on the following factors: - frequencies (number) of X-ray examinations; - structures of examinations; - kind of source of irradiation (X-generators) and of receiver irradiation (intensify screen, X-ray or photofluorography film etc.); - qualification of the personnel; - parameters and conditions of examinations; - radiating control. The realization of this problem consist the following decision of the following tasks: - definition of number and structure X-ray examinations, effective doses X-ray exposure of the patients and population, and also level and condition of the x-ray equipment now; - revealed regions with most differences in frequency and structure of X-ray examinations; - analysis common diseases in investigating regions; - analysis ecological and demography situation in investigating regions; - analysis X-ray equipment in diagnostic radiology in investigating regions; - reconstruction of frequency and structure X-ray examinations by available data; - definition of the radiating characteristics of the X-ray equipment, including X-ray generators, fluorescent and intensify screens, and also X-ray and photofluorography film in dynamics for long time;

2 - appreciation of effective doses in diagnostic radiology in investigating regions; - reconstruction effective doses of X-ray exposure of patients past years; - appreciation of collective effective doses X-ray exposure of patients past years; - research of changes of the average effective individual, collective and accumulated doses of X-ray exposure of the population for the long-time period. For realization of researches the following information was used: - the statistical archives medical data; - examinations and experiments; - the references.

3.1. Dynamics of number and structure X-ray examinations

The statistical data allow to determine frequency and structure X-ray examinations in any region of Russia and for any period of supervision down to 60-70 years of the XX century (table 3).

Table 3. Characteristic frequency and structure of X-ray examinations in Russia

Parameter Years 1950 1960 1970 1980 1990 2000

Value Frequency 650 960 1050 1310* 1260 1180 procedures, ‰ Structure 55,0 53,6 44,7 13,3 5,1 3,2 procedures, % 23,0 22,4 23,8 40,1 49,7 54,1

Photofluoro- 22,0 24,0 32,5 45,4 38,7 42,8 graphy *1985 - 1560 ‰

More difficultly was business with definition of parameters for 50, as the statistical information, as well as the literature for this time practically were absent. It is connected that the interest to a medical irradiation has appeared per 70 years in connection with development of scientific representations on the given direction [2,8]. Nevertheless, such data were received with the help of mathematical methods, including analysis of disease, with which, as was shown, the researched parameters have proportional dependence. As it is visible, in middle of the last century the frequency X-ray examinations (‰) in Russia was of a below modern level. The maximal meanings of frequency were observed later - in middle 80 years and make up 1500 ‰ and above. The structure of examinations those years essentially differed from a modern level. More half of all examinations had fluoroscopy. It is accompanied by very high doses of irradiation.

3.2. Dynamics X-ray generators

At the same time for a so long time were qualitative changes in x-ray generators. The spent investigations have shown, that the radiating output for modern 3-phase generators and before used low-power 1-phase X-ray generators considerably differs (table 4).

3 Table 4. Average radiating output in various types of X-ray generators

Type of X-ray generators U, kV 60 80 100 Radiating output, mR/mAc Modern (3-phase) 4,7± 2,5 8,3± 4,3 12,5± 5,1

Obsolete (1-phase) 2,1± 1,6 4,5± 2,9 8,1± 4,5

The 1-phase X-ray generators, maintained down to 90 years, had on the average twice lower radiating output in comparison with modern apparatus. It speaks that for reception of a qualitative film on the given generators it was necessary to increase exposition (mAs). And it is proportionally connected to increase dose irradiation of the patient. Taking into account, that in the past of 1-phase generators was more and in 50-80 they made the overwhelming majority of them, the doses of irradiation of the patients were by higher earlier (table 5). X-ray generators were improved in process of development X-ray equipment and include essentially new kinds. They promoted reduction of procedural doses. It is especially concerned fluoroscopy. The intensify of X-ray imaging, appeared in 80, in some times reduced a dose irradiation of fluoroscopy.

Table 5. Changes of various types of the X-ray equipment

Equipment Parameter Years 1950 1960 1970 1980 1990 2000 Volume equipment, % X-ray generator 1-phase 100 100 77,5 73,6 57,7 0 3-phase 0 0 22,5 26,4 42,3 100 X-ray film Sensibility 30< 30- 40 50 60 100 40

Photofluoro- The size of 32 45 45 64 82 100 graphy film film

Sensibility 50 58 67 75 83 100

3.3. Dynamics X-ray film

Other various means, influencing on level of an irradiation of the patients, are intensify screens and film. During evolution they also have undergone essential modernization, that also decrease of level of irradiation of the patients (table 5). Use of optimum modes of X-ray examinations (limitation field, filtration radiation ect.) also decreases irradiation. They depend on qualification of the personnel. Unfortunately, the experience shows, that till now in most cases optimization will not be carried out or will be carried out unsatisfactorily. It is basically because of absence of appropriate education or low qualification of the personnel. As such picture takes place now, it especially was in the past at earlier stages of use of diagnostic radiology (second half of last century and especially its middle), when neither knowledge, nor the sufficient experience of optimization of an irradiation was not. It leaded to essential increasing

4 of dose irradiation. In result the dose of irradiation for examination and on the patient and, therefore, population, as a rule, was higher.

3.4. Dynamics exposure patients

About opportunity of such course of development dose in diagnostic radiology speaks negative experience of use of medical diagnostic irradiation of the patient and, in particular, application in the past of unreasonable kinds of examinations, such as prophylactic fluoroscopy, photofluorography and xerography. They accompanied with extremely high levels irradiation of the patients. From modern positions the given fact is simply inadmissible. They took root just in 70-80 of past century and resulted to the increase of a medical diagnostic irradiation of the patients and population. In process of development of engineering and technology of photochemical processes the X-ray film also was improved. Having on early terms by low sensitivity, the X-ray film in due course became more effective. As it is visible from table 5. Now sensitivity of a X-ray film considerably increased in comparison with used earlier. A X-ray film, as a rule, are used with intensify screens. They with time also underwent essential change from less to more sensitive. The most area diagnostic radiology, traditionally connected in Russia with significant levels of irradiation of the population is photofluorography. It spent as with diagnostic, so, especially, with the prophylactic purposes. All speaking concerns and to photofluorography film. It is especially important, as the contribution of photofluorography in diagnostic radiology on second half of last century, first, was rather significant and, secondly, constantly grew because of a high level of tuberculosis disease. Besides reduction of sensitivity of photofluorography film the important moment in the increasing dose is the size of film. In process of reduction of the size of the film the dose can considerably grow in comparison with using now. It also testifies to increase of level irradiation of the patients at past time. The summary received data testify, that 50 years back average effective dose was approximately in 10 times above modern (table 6) and the accumulated effective dose could make this time at the old man on the average 150-200 mSv. The real size of this dose can be in some times greater because of use before the not optimized conditions of examinations and poor meanings protection of patients.

Table 6. Reconstruction of average effective dose of X-ray exposure of population

Parameter Years 1950 1960 1970 1980 1990 2000

Value Effective dose, mSv 10,3 7,30 5,80 3,26 1,80 1,00

By our estimations for this reason the accumulated effective dose at the patients (now old) could make 500 mSv and more. All speaking concerns to irradiation of average man, when each inhabitant receives for one year about one X-ray examination. Investigations of distribution X-ray examinations among the population shown, that it is non-uniformly: the fifth part of the population (about 20 %) receives in 3 times the large examinations in comparison with an average level, 10 % - in 6 times higher, and about 2-3 % - in 10 times large. Therefore for last group the accumulated dose of irradiation can be much times more average and make the maximal meanings in several Sv on the man. It is a real situation, because the patients, especially chronic, as a rule, receive some examinations for year. In result they have the high level of irradiation, which can cause high radiation risk.

5 4. Medical influence X-ray exposure

The submitted concept was checked in one of administrative territory of Russia - Tumen province (Siberian). Regions with various accumulated doses of diagnostic radiology were revealed here. Dose caused first of all by different frequency and structure X-ray examinations. The accumulated effective doses of the population were designed for these regions (table 7). The accumulated dose in regions with high and low level of irradiation makes for 50 years accordingly 235±50 and 93±6 mSv. On size of the accumulated dose the regions with low and high level of irradiation differ in 2,5 times. The differences are statistically reliable (р < 0,01).

Table 7. Distribution of regions of the Tumen area on accumulated effective dose of X-ray exposure

Level of №№ regions Time of observation, years* medicine 10 25 50 irradiation Accumulated dose, mSv High 1. 20,0 80,0 330 3. 8,0 44,7 180 5. 11,0 53,0 220 7. 19,5 50,8 203 9. 19,9 71,2 285 11. 11,6 47,6 190 On average 15,0 57,8 235 Low 2. 5,0 21,8 87 4. 5,7 24,9 99 6. 6,1 24,9 99 8. 6,2 24,1 96 10. 5,0 21,5 86 12. 4,2 22,3 89 On average 5,7 23,3 93 * from 1950

The high meanings of the accumulated effective doses of a medical irradiation and significant differences of them in regions could be reflected on a level cancer disease and mortality the in next decades. For check given assumption we carried out comparison cancer for last 10 years (1990-2000) in several regions of Tumen area with high and low doses of medical irradiation, comparable on the ecological factors (fig.1).

Fig. 1. Cancer on 100 thousand population in regions with high (1) and low (2) dose of X-ray exposure

6 As it is visible, during all period of supervision cancer disease and mortality in regions with a high level of accumulated doses was clearly higher, than in regions with a low level of an irradiation. By the certain confirmation of the given influence were revealed features in display of various kinds cancer. The greatest growth of cancer was revealed for a skin, thyroid, breast, and also lung – organs, exposed to the greatest irradiation at the most X-ray examinations. The similar situation was observed for lymph and blood. They are significant part of leukemia, being the recognized factor of radiation. Influence of others unfavorable factors, including ecological, during research was reduce to minimum by a choice of regions with identical conditions etc. Correlation between the accumulated doses and has appeared high (r = 0,7). This testifies to influence of medical irradiation on cancer in investigation regions (fig. 2).

Dose Cancer

500

Dose, 400 mSv., 300 Cancer on 100 200 thous. 100 0 15342 Regions

Fig. 2. Accumulated live-time dose of X-ray exposure and cancer of population in investigation regions

5. Conclusion

In the present message the part of the received data is submitted only. They testify to the important role of possible influence of a diagnostic radiology on health population. The submitted information is, first, preliminary and, secondly, is received at regional level. To make complete impression about examined problem, it is necessary the realization of the further researches in the given direction. They should give the answer to the put questions.

References

1. Vorobjov Е.I., Stavitsky R.V., Knizcnikov V.А. ect. Irradiation of population USSR in 1981- 1982 in application of sources ionizing radiation in medicine. Atominform. Мoscow (1984) (in Russian).

7 2. Golikov V.Y., Korenkov I.P. Radiation protection in application ionizing radiation. Medicine. Мoscow (1975) (in Russian). 3. Kishkovsky А.N., Тjutin L.А. Medical X-ray engineering. Medicine. Leningrad (1983) (in Russian). 4. Medical irradiation population in Russia (1980-1997). Hand-book. Ivanov S.I. etc. Мoscow (2000) (in Russian). 5. Nikitin V.V., Ermakov I.А., Zherbin Е.А. ect. The assessment of population doses from X-ray examination in USSR (1970-1980). Atominform. Moscow (1986) (in Russian). 6. Stavitsky R.V., Vakturina V.P. Principles of radiation protection in diagnostic radiology. Мoscow. (1969) (in Russian). 7. Technical means of diagnostic radiology. By I.А.Pereslegin. Medicine. Мoscow (1981) (in Russian). 8. Feigin М.I. Photofluorography. Medicine. Leningrad. (1984) (in Russian). 9. Photofluorography lung. By L.I.Ykelis. Medicine. Leningrad. (1988) (in Russian). 10. Equivalent doses in organs and tissues of man in diagnostic radiology. Hand-book. Energoatomizdat. Мoscow. (1989) (in Russian).

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