Prenatal Radiation Exposure: Dose Calculation

Abstract

The unborn child requires special protection. In this context, the indication for an X-ray examination is to be checked critically. If thereupon radiation of the lower abdomen including the uterus cannot be avoided, the examination should be postponed until the end of pregnancy or alternative examination techniques should be considered. Under certain circumstances, either accidental or in unavoidable cases after a thorough risk assessment, radiation exposure of the unborn may take place. In some of these cases an expert radiation hygiene consultation may be required. This consultation should comprise the expected risks for the unborn while not perturbing the mother or the involved medical staff.

For the risk assessment in case of an in-utero x-ray exposition deterministic damages with a defined threshold dose are distinguished from stochastic damages without a definable threshold dose. The occurrence of deterministic damages depends on the dose and the developmental stage of the unborn at the time of radiation.

To calculate the risks of an in-utero radiation exposure a three-stage concept is commonly applied. Depending on the amount of radiation, the radiation dose is either estimated, roughly calculated using standard tables or, in critical cases, accurately calculated based on the individual event. The complexity of the calculation thereby increases from stage to stage. An estimation based on stage one is easily feasible whereas calculations based on stages two and especially three are more complex and often necessitate execution by specialists.

This article demonstrates in detail the risks for the unborn child pertaining to its developmental phase and explains the three-stage concept as an evaluation scheme. It should be noted, that all risk estimations are subject to considerable uncertainties.

• Radiation exposure of the unborn child can result in both deterministic as well as stochastic damage und hitherto should be avoided or reduced to a minimum.

• In case of radiation a suitable hygiene consultation may be necessary.

• For risk assessment a three-stage concept is applied, which, depending on the radiation exposure, estimates or calculates the dose for the unborn child.

• The radiologist plays a crucial role as a competent advisor and provider of reliable expert information.

Citation Format:

• Scharwächter C, Röser A, Schwartz CA et al. Prenatal Radiation Exposure: Dose Calculation. Fortschr Röntgenstr 2015; 187: 338 – 346

Zusammenfassung

Embryo und Fetus bedürfen eines besonderen Schutzes. In diesem Kontext ist die Notwendigkeit einer Röntgenuntersuchung besonders kritisch zu prüfen. Bei einer nicht vermeidbaren Mitbestrahlung des Unterbauches und damit des Uterus, sollte die Untersuchung bis zum Ende der Schwangerschaft verschoben oder die Möglichkeit alternativer Verfahren erwogen werden. Unter speziellen Umständen kann es jedoch, entweder inzidentell oder nach reiflicher Risikoabwägung gezielt, zu einer Röntgenuntersuchung und konsekutiv zu einer Strahlenbelastung des Ungeborenen kommen. In diesem Fall kann eine strahlenhygienische Beratung erforderlich werden. Diese enthält die zu erwartenden Risiken für das Ungeborene, ohne unnötige Ängste und Sorgen sowohl bei der Schwangeren, als auch bei behandelnden Kollegen zu induzieren.

Für die Risikobewertung werden im Falle einer Exposition in utero deterministische Strahlenschäden mit einer definierbaren Schwellendosis und stochastische ohne Schwellendosis differenziert. Das Auftreten von deterministischen Schäden ist zusätzlich zur Dosis vom Entwicklungsstadium des Ungeborenen zum Zeitpunkt der Strahlenexposition abhängig.

Als Bewertungsschema hat sich im Falle einer Strahlenexposition in utero ein dreistufiges Konzept bewährt. In Abhängigkeit der Expositionsausprägung wird entweder eine Abschätzung der Dosis bzw. eine grobe Berechnung anhand von Rechenmodellen vorgenommen oder es erfolgt im ausgeprägtesten Fall eine auf den Einzelfall bezogene Berechnung so exakt wie möglich. Die Komplexität der Bestimmung nimmt dabei mit jeder einzelnen Stufe zu. Während eine Abschätzung nach Stufe eins normalerweise problemlos machbar ist, ist eine Berechnung nach Stufe zwei und insbesondere drei komplex und oft nur von Spezialisten durchführbar.

Im folgenden Artikel werden die Risiken für das Ungeborene in Abhängigkeit von den verschiedenen Entwicklungsphasen differenziert dargestellt und das Drei-Stufen-Konzept als Bewertungsschema näher erläutert. Hierbei ist zu berücksichtigen, dass die entsprechenden Risikoschätzungen mit nicht unerheblichen Unsicherheiten behaftet sind.

Key words

health policy and practice - radiation effects - radiation safety - pregnancy

• References

• 1 Wakeford R. Childhood leukaemia following medical diagnostic exposure to ionizing radiation in utero or after birth. Radiat Prot Dosimetry 2008; 132: 166-174
• 2 DRG, DGMP. Pränatale Strahlenexposition aus medizinischer Indikation. DGMP Bericht Nr. 7 2002;
• 3 Preston DL, Cullings H, Suyama A et al. Solid cancer incidence in atomic bomb survivors exposed in utero or as young children. J Natl Cancer Inst 2008; 100: 428-436
• 4 Wertelecki W. Malformations in a chornobyl-impacted region. Pediatrics 2010; 125: 836-843
• 5 Schull WJ. The children of atomic bomb survivors: a synopsis. J Radiol Prot 2003; 23: 369-384
• 6 Little MP. Cancer and non-cancer effects in Japanese atomic bomb survivors. J Radiol Prot 2009; 29: A43-A59
• 7 Fujimori K, Kyozuka H, Yasuda S et al. Pregnancy and birth survey after the Great East Japan Earthquake and Fukushima Daiichi Nuclear Power Plant accident in Fukushima prefecture. Fukushima J Med Sci 2014; 60: 75-81
• 8 Mousseau TA, Møller AP. Genetic and ecological studies of animals in Chernobyl and Fukushima. J Hered 2014; 105: 704-709
• 9 Taira W, Nohara C, Hiyama A et al. Fukushima's biological impacts: the case of the pale grass blue butterfly. J Hered 2014; 105: 710-722
• 10 Fushiki S. Radiation hazards in children - lessons from Chernobyl, Three Mile Island and Fukushima. Brain Dev 2013; 35: 220-227
• 11 Takamura N, Yamashita S. Lessons from Chernobyl. Fukushima J Med Sci 2011; 57: 81-85
• 12 Yoshii H, Saito H, Kikuchi S et al. Report on maternal anxiety 16 months after the great East Japan earthquake disaster: anxiety over radioactivity. Glob J Health Sci 2014; DOI: 10.5539/gjhs.v6n6p1..
• 13 Macklon NS, Geraedts JP, Fauser BC. Conception to ongoing pregnancy: the ‘black box’ of early pregnancy loss. Hum Reprod Update 2002; 8: 333-343
• 14 Larsen EC, Christiansen OB, Kolte AM et al. New insights into mechanisms behind miscarriage. BMC Med 2013; 11: 154
• 15 Queißer-Luft A, Spranger J. Fehlbildungen bei Neugeborenen. Dtsch Arztebl 2006; 103: A2464-A2471
• 16 RKI. Krebs in Deutschland 2007/2008. 8. Ausgabe. Berlin: Robert Koch-Institut (Hrsg) und die Gesellschaft der epidemiologischen Krebsregister in Deutschland e.V. (Hrsg); 2012
• 17 RKI. Krebs in Deutschland 2007/2008. Berlin: Robert Koch-Institut (Hrsg) und die Gesellschaft der epidemiologischen Krebsregister in Deutschland e.V. (Hrsg); 2012 8. Ausgabe.
• 18 Brent RL, Bolden BT. Indirect effect of x-irradiation on embryonic development. V. Utilization of high doses of maternal irradiation on the first day of gestation. Rad Res 1968; 36: 563-570
• 19 Russell LB. X-ray induced developmental abnormalities in the mouse and their use in analysis of embryological patterns. I. External and gross visceral changes. J Exp Zool 1950; 114: 345-602
• 20 Russell LB. X-ray-induced developmental abnormalities in the mouse and their use in analysis of embryological patterns. II. Abnormalities of the vertebral column and thorax. J Exp Zool 1956; 131: 329-395
• 21 Rugh R, Grupp E. Exencephalia following x-irradiation of the pre-implantation mammalian embryo. J Neuropathol Exp Neurol 1959; 18: 468-481
• 22 Müller WU, Streffer C. Lethal and teratogenic effects after exposure to X-rays at various times of early murine gestation. Teratology 1990; 42: 643-650
• 23 Jacquet P, de Saint-Georges L, Vankerkom J et al. Embryonic death, dwarfism and fetal malformations after irradiation of embryos at the zygote stage: studies on two mouse strains. Mutat Res 1995; 332: 73-87
• 24 Gu Y, Kai M, Kusama T. The embryonic and fetal effects in ICR mice irradiated in the various stages of the preimplantation period. Radiat Res 1997; 147: 735-740
• 25 Wood J, Johnson KG, Omori Y. Mental retardation in children exposed in utero to the atomic bombs in Hiroshima and Nagasaki. Am J Public Health 1967; 57: 1381-1390
• 26 Wood J, Keehn R, Kawamoto S. The growth and development of children exposed in utero to the atomic bombs in Hiroshima and Nagasaki. Am J Public Health 1967; 57: 1374-1380
• 27 Schull WJ, Otake M. Cognitive function and prenatal exposure to ionizing radiation. Teratology 1999; 59: 222-226
• 28 Verheyde J, Benotmane MA. Unraveling the fundamental molecular mechanisms of morphological and cognitive defects in the irradiated brain. Brain Res Rev 2007; 53: 312-320
• 29 Otake M, Schull WJ. In utero exposure to A-bomb radiation and mental retardation; a reassessment. Br J Radiol 1984; 57: 409-414
• 30 Yamazaki JN, Schull WJ. Perinatal loss and neurological abnormalities among children of the atomic bomb. Nagasaki and Hiroshima revisited, 1949 to 1989. JAMA 1990; 264: 605-609
• 31 Otake M, Schull WJ, Lee S. Threshold for radiation-related severe mental retardation in prenatally exposed A-bomb survivors: a re-analysis. Int J Radiat Biol 1996; 70: 755-763
• 32 Wakeford R, Little MP. Risk coefficients for childhood cancer after intrauterine irradiation: a review. Int J Radiat Biol 2003; 79: 293-309
• 33 Little MP. Cancer and non-cancer effects in Japanese atomic bomb survivors. J Radiol Prot 2009; 29: A43-A59
• 34 Doss M. Evidence supporting radiation hormesis in atomic bomb survivor cancer mortality data. Dose Response 2012; 4: 584-592
• 35 Fornalski KW, Dobrzyński L. The cancer mortality in high natural radiation areas in poland. Dose Response 2012; 10: 541-561
• 36 Scott BR, Bruce VR, Gott KM et al. Small γ-Ray Doses Prevent Rather than Increase Lung Tumors in Mice. Dose Response 2012; 10: 527-540
• 37 Ray JG, Schull MJ, Urquia ML et al. Major radiodiagnostic imaging in pregnancy and the risk of childhood malignancy: a population-based cohort study in Ontario. PloS Med 2010; 7: 1-8
• 38 Brent RL. Carcinogenic risks of prenatal ionizing radiation. Semin Fetal Neonatal Med 2014; 19: 203-213
• 39 Benjamin SA, Lee AC, Angleton GM et al. Mortality in beagles irradiated during prenatal and postnatal development. I. Contribution of non-neoplasia diseases. Radiat Res 1998; 150: 330-348
• 40 Nakano M, Kodama Y, Ohtaki K et al. Chromosome aberrations do not persist in the lymphocytes or bone marrow cells of mice irradiated in utero or soon after birth. Radiat Res 2007; 167: 693-702
• 41 Brent RL, Bushberg JT, Linet M et al. NCRP Report No. 174. Preconception and prenatal radiation exposure: health effects and protective guidance. 2013: 351
• 42 Minkov V, Nekolla EA, Nosske D et al. Nuclear-medical irradiation during pregnancy. Risk assessment for the offspring. Nuklearmedizin 2009; 48: 10-16
• 43 Wachsmann F, Drexler G. Kurven und Tabellen für die Radiologie. 2. Aufl. Berlin-Heidelberg-New York: J. Springer; 1976
• 44 Thomasz E, Eckerl H, Drexler G. Experimental determination of conversion factors between organ doses and measured quantities for external photon irradiation. Health Phys 1985; 49: 897-905
• 45 Drexler G, Panzer W, Stieve FE et al. Die Bestimmung von Organdosen in der Röntgendiagnostik. 2. Aufl. Berlin: H.Hoffmann; 1993
• 46 Harrison J, Day P. Radiation doses and risks from internal emitters. J Radiol Prot 2008; 28: 137-159
• 47 Nishizawa K, Maruyama T, Takayama M et al. Determinations of organ doses and effective dose equivalents from computed tomographic examination. Br J Radiol 1991; 64: 20-28
• 48 Nagel HD. Strahlenexposition in der Computertomographie. ZVEI Fachverband. Frankfurt: Elektromedizinische Technik; 1999
• 49 Bailey TM, Vealé BL. Advanced computed tomography technology and patient dose: a literature review. Radiol Manage 2011; 33: 43-46