**7. Radiation protection: ionizing radiation and radiobiology. Objective, pillars and radiological protection measures**

#### **7.1. Ionizing radiation and radiobiology**

Nuclear medicine is the medical speciality that uses non-encapsulated sources of artificial ionizing radiation with diagnostic-therapeutic use and research. In these cases, the patient is the source of radiation. For these reasons, there is a risk of external radiation to health personnel, patients' relatives and the general public. In addition, special attention is paid to the possibility of contamination because these tracers are excreted physiologically by tear secretions, saliva, sweat, urine, feces, genital fluids or breastfeeding.

When a patient is treated with 131I and released, it is important that members of the public, including the family, are not exposed to significant radiation. The regulations vary between countries, but there are certain general conditions under which outpatient therapy can be arranged. Between them, no adult can be exposed to 5 mSv (500 mrem), patients can be released when the administered dose is <1.22 GBq (33 mCi) [1221 MBq] and the emitted radia-

Nuclear Medicine in the Assessment of Thyrotoxicosis Associated with Increased Thyroid…

http://dx.doi.org/10.5772/intechopen.77161

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Several studies have measured radiation rates to family members and have confirmed that simple measures, such as sleeping in a separate bedroom and remaining more than 2 m from family members for a few days, ensure that the regulations are fulfilled [16]. In our nuclear medicine department of the *Regional University Hospital of Málaga*, we have prepared an informative document with the recommendations and precautions that patients should follow in treatment with radioiodine, which is explained and delivered to each of these patients

*"In nuclear medicine, a woman of childbearing age is considered pregnant until proven otherwise".* In the nuclear medicine services, there are visible information leaflets to the public, especially for women of childbearing age who may be pregnant and whose duty it is to inform the center's

In addition, it is mandatory to ask the date of last menstruation and about the possibility of pregnancy in the clinical history. Also, all women in this age group who are to be treated with radionuclides of iodine must have a negative pregnancy test, prior to the administration of the radiopharmaceutical as therapy [16]. The result of the pregnancy test will be recorded in

Pregnant women with untreated overt hyperthyroidism are at increased risk for spontaneous miscarriage, congestive heart failure, thyroid storm, preterm birth, pre-eclampsia, fetal

Regarding the use of radioiodine, fertility could be reduced and abnormalities offspring will be increased. Several studies are related to larger doses of 131I that are used to treat thyroid cancer [16]. Medical personnel should warn patients to avoid becoming pregnant during the time following the procedure with radionuclides. The time required depends on the type of radiopharmaceutical used; in the case of 131I (either used for the treatment of hyperthyroidism or as ablative therapy of possible thyroid remnants in differentiated thyroid carcinoma) the consensus is that the conception should be deferred for 12 weeks (minimum 6 months) and

By avoiding pregnancy during this period, the objective is achieved to reduce the probability that the dose received to an embryo or fetus is greater than 1 mSv (dose limit to the public). Keep in mind that these compounds cross the placental barrier and there is a risk of an exposure of the fetus that can reduce the intelligence quotient by 30 points per gray (100 rads), and

growth restriction, and increased perinatal morbidity and mortality [9].

that maternal thyroid function should be normal [16].

**8. Special situations in nuclear medicine and radiation protection**

tion must be <7 mrem/h at 1 m [16].

**8.1. Pregnancy and breastfeeding**

(Appendix 1).

health personnel.

the patient's health history.

Radiobiology studies the effects of ionizing radiation on cells. These effects are diverse and are classified into three large groups:


### **7.2. Objective, pillars and radiological protection measures**

The main objective of radiation protection is to prevent the appearance of deterministic effects and limit the possibility of stochastic effects. The pillars of radiological protection are based on:


The general measures in radiological protection are:


When a patient is treated with 131I and released, it is important that members of the public, including the family, are not exposed to significant radiation. The regulations vary between countries, but there are certain general conditions under which outpatient therapy can be arranged. Between them, no adult can be exposed to 5 mSv (500 mrem), patients can be released when the administered dose is <1.22 GBq (33 mCi) [1221 MBq] and the emitted radiation must be <7 mrem/h at 1 m [16].

Several studies have measured radiation rates to family members and have confirmed that simple measures, such as sleeping in a separate bedroom and remaining more than 2 m from family members for a few days, ensure that the regulations are fulfilled [16]. In our nuclear medicine department of the *Regional University Hospital of Málaga*, we have prepared an informative document with the recommendations and precautions that patients should follow in treatment with radioiodine, which is explained and delivered to each of these patients (Appendix 1).
