Is fluoroscopy dangerous?

 Question:
How dangerous is radiation exposure during an X-ray or nuclear medicine examination?


Short answer

In conventional X-ray and nuclear medicine examinations, the risks associated with radiation exposure are generally considered to be small. The hypothetical number of damages is purely statistical because the occurrence of such cases cannot be proven, as they disappear underground (spontaneous rate). Especially with long-term fluoroscopy and also with CT examinations (computer tomographies), damage cannot be excluded from a purely arithmetical point of view if the lethal and non-lethal risk of the radiation effect is taken as 0.7% per 100 mSv effective dose. In the case of very long fluoroscopic examinations, as are possible with intervention, deterministic effects can occur, such as hair loss, reddening of the skin, etc.

illustration


Effective doses in comparison: for selected X-ray and nuclear medicine examinations, the range of annual natural radiation exposure (for around 90% of the population) and annual limit values ​​for occupationally and non-occupationally exposed persons.

Explanation

The radiation risk in a medical examination with ionizing radiation can be specified with the effective dose. The effective dose due to natural radiation sources is, for example, an average of 3 mSv per year. When comparing with natural radiation exposure, it must be taken into account that the dose is applied within a fraction of a second when taking an X-ray. This can play a role in the repair effects. In the case of medical radiation exposure, it can always be assumed that a direct benefit results for the patient, namely a diagnosis which will determine the further treatment of a disease.

In an X-ray examination, the effective dose is usually below 20 mSv. High effective doses are achieved in: complex or long fluoroscopic examinations (up to 100 mSv), CT examinations of the thorax, abdomen and pelvis (10 - 15 mSv), angiographies (10 - 20 mSv), interventional examinations (5 - 20 mSv) mSv). Individual organ doses can reach up to 100 mSv in an examination, e.g. the eye dose around 50 mSv in a CT skull examination

In a nuclear medicine examination, the effective dose can be up to 35 mSv. High effective doses are achieved with: thyroid examination with I-131 (34 mSv), tumor examination with Ga-67 (22 mSv), adrenal examination with Se-75 (20 mSv), myocardial examination with Tl-201 (18 mSv) . Individual organ doses in nuclear medicine examinations can reach high values, e.g. 100 mSv in the thyroid gland with a thyroid scintigraphy with I-131 or 300 mSv in the adrenal gland with an adrenal scintigraphy with I-131.

The radiation risk is given as 5% per Sv for deaths due to radiation-induced cancer and 7.5% per Sv, even if non-fatal radiation inductions including genetic defects are included. If the risk of dying from cancer within 70 years due to natural radiation exposure is calculated from this, then it would be 1% (i.e. every hundredth person who can live to be 70 years would theoretically die from natural radiation exposure). In the case of medical examinations with ionizing radiation, the maximum risk would be 0.5% for lethal and 0.7% for lethal and non-lethal effects. These risks are small; but one in 2,000 CT examinations of the thorax must be calculated with a somatic effect of the radiation exposure.

In long fluoroscopic examinations of more than an hour, radiation effects on the body surface can occur under certain conditions (e.g. non-optimal filtering, short focus-surface distance). In rare cases, hair loss, erythema (reddened skin) and necrosis (tissue death) are observed. These deterministic effects could occur within a few days and are mostly reversible.

During pregnancy, the uterine dose is decisive for the risk assessment of an embryo or fetus. According to current radiobiological findings, a dose of up to 50 mSv is generally judged to be small or acceptable compared to other risks during pregnancy, and an interruption is only considered at doses of 100 mSv or more for the sole reasons of possible radiobiological damage. According to the current level of knowledge in radiation biology: In blastogenesis (pre-implantation), radiation damage usually manifests itself in germ death, which is hardly recognized. Serious malformations or fetal death can occur in organogenesis. However, the prerequisite for this are doses in the range of around 100 mSv and more. The period between the 8th and 15th week of pregnancy has proven to be a particularly radiation-sensitive phase for intellectual development (4% at 100 mSv or a decrease in IQ by 3 points per 100 mSv). In the fetal period, severe visible damage becomes less likely after doses of around 100 mSv as the development phase progresses.

It is difficult to determine the dose in nuclear medicine examinations during pregnancy, as the fetus or embryo dose is determined not only by the gamma radiation from the surrounding organs, but also by the absorption and storage capacity of the radiopharmaceutical used in the uterus, placenta and in the fetus itself. The beta radiation of the radionuclide must also be taken into account.

Jakob Roth, Basel, October 2005