Abnormal Development - Radiation

Embryology - 6 May 2024        Expand to Translate
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Introduction

Radiation warning Symbol

This page introduces the possible effects of radiation on development. The two main sources of exposure are environmental and those used for medical diagnostic or therapeutic purposes.

Studies have shown that in maternal X-ray diagnostic examination, where the beam does not irradiate the embryo/fetus directly (maternal skull and chest X-ray), the absorbed dose for the embryo or fetus is extremely low (less than 0.01 mGy).

Treatment of hyperthyroidism with 131 Iodine in a pregnant woman is strictly contraindicated due to the effects on the developing embryonic thyroid gland.

Some Recent Findings

Malformations in a chornobyl-impacted region "The overall rate of neural tube defects in Rivne is among the highest in Europe (22.2 per 10,000 live births). The rates of conjoined twins and teratomas also seem to be elevated. In Polissia, the overall rates of neural tube defects are even higher (27.0 vs 18.3, respectively; odds ratio: 1.46 [95% confidence interval: 1.13-1.93]), and the rates of microcephaly and microphthalmia may also be elevated." Recently revised diagnostic reference levels in nuclear medicine in Bulgaria and in Finland. "An EU twinning project entitled 'Strengthening of administrative structures for radiation protection and safe use of ionising radiation in diagnostics and therapy' was established between Bulgaria and Finland, lasting from June 2008 to May 2009."

Diagnostic Radiography

A recent Australian review study has shown minimal effects of standard diagnostic radiography underspecific conditions.

"The only adverse effect statistically proven at the dose levels associated with diagnostic radiation procedures is a very small increase in childhood malignancy, with an estimated increase of one additional cancer death per 1700 10 mGy exposures. The important exception was the risk to the fetal thyroid from radioiodine exposure after 12 weeks' gestation."

Dual X-ray Absorptiometry

These types of radiological studies can be carried out in osteoporosis examinations.

"The aim of the current study was to estimate the embryo/fetus radiation doses and risks associated with spinal and hip dual X-ray absorptiometry (DXA) scans performed on the pregnant mother."

"In conclusion, the embryo/fetus dose in bone density measurements of spine and femur using pencil beam DXA is lower than the average daily natural background in the United States of 8 mGy. The health provider can decide whether a DXA scanning is beneficial to a pregnant woman, taking into account the potential radiation risks to the embryo/fetus presented in the current study."

Damilakis J, Perisinakis K, Vrahoriti H, Kontakis G, Varveris H, Gourtsoyiannis N. Embryo/fetus radiation dose and risk from dual X-ray absorptiometry examinations. Osteoporos Int. 2002 Sep;13(9):716-22.

Computed Tomography

Computed Tomography or computed axial tomography (CAT or CT scan) began in 1970's using x-ray and a computer to produce images either as individual slices or reconstructed to give three dimensional (3D) views of specific anatomical regions or structures. While some standard x-ray examinations of the abdomen may not pose a serious risk, some abdominal and pelvic CT studies deliver greater amounts of radiation to a developing pregnancy.

Links: Computed Tomography

International Commission on Radiological Protection

"Almost always, if a diagnostic radiology examination is medically indicated, the risk to the mother of not doing the procedure is greater than is the risk of potential harm to the fetus. Most nuclear medicine procedures do not cause large fetal doses. However, some radiopharmaceuticals that are used in nuclear medicine can pose significant fetal risks. It is important to ascertain whether a female patient is pregnant prior to radiotherapy."

"...Fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy."

International Commission on Radiological Protection Pregnancy and medical radiation. Ann ICRP. 2000;30(1):iii-viii, 1-43.

"It should be also remembered that irradiation of the fetus in all trimesters of the pregnancy carries an increased risk of cancer in the newborn in the first or second decade of life and at therapeutic doses - or their significant fraction - this risk can be substantial. Therefore, in view of all mentioned factors termination of pregnancy may be considered. The decision should be based on careful estimation of the entailed risk to the fetus, which in turn requires calculation of the dose to conceptus by a qualified expert. The decision itself should be made by the women to be treated in consultation with their physician, partner and counsellor. Particularly difficult problems arise when radiotherapy is performed in a woman with early, undiagnosed pregnancy. The result is sometimes a massive irradiation of the conceptus in a period when malformations are easily induced (at or after 3 weeks post conception).

To avoid such unintentional irradiation it seems necessary to perform pregnancy tests to diagnose, or exclude the pregnancy before undertaking radiotherapy.

Therapy of hyperthyroidism with 131 Iodine in a pregnant woman is strictly contraindicated due to possibility of external irradiation of the foetus but mostly due to radioactive iodide crossing the placenta into the foetal circulation with subsequent uptake by its thyroid. The gland may well be destroyed by beta radiation from the nuclide taken up (131I). Therefore, other methods of treatment should be employed, if possible, until delivery." (Text extract from: ICRP Radiation and your Patient: A Guide for Medical Practitioners PDF document (17 pages, 142 kB)

Links: International Commission on Radiological Protection | Pregnancy and Pedical Radiation Powerpoint Slide set(1.3 Mb) | Radiation and your Patient: A Guide for Medical Practitioners PDF document (17 pages, 142 kB) |

Australia

Australia has a National Standard for Limiting Occupational Exposure to Ionising Radiation (1995, Republished March 2002). Published by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) to promote practices which protect human health and the environment from the possible harmful effects of radiation. ARPANSA is assisted in this task by its Radiation Health and Safety Advisory Council, which reviews the publication program for the Series and endorses documents for publication, and by its Radiation Health Committee, which oversees the preparation of draft documents and recommends publication.

Links: Standard - NOHSC:3022 PDF | [Safework Australia]

References

Books

• National Research Council (US); National Academy of Sciences (US); Neel JV, Schull WJ, editors. The Children of Atomic Bomb Survivors: A Genetic Study. Washington (DC): National Academies Press (US); 1991. Available from: http://www.ncbi.nlm.nih.gov/books/NBK234260/

Search Pubmed

June 2010 "Abnormal Development Radiation"

Search Pubmed: Abnormal Development Radiation

Glossary Links

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Cite this page: Hill, M.A. (2024, May 6) Embryology Abnormal Development - Radiation. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Radiation

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G