Radiation Safety Considerations

The effective whole body dose from a cumulative standard application of 10 MBq 224RaCl is approximately 2.5 Sv (27). This dose is slightly above the value obtained by high-dose radioiodine treatment in thyroid cancer. However, owing to the different linear energy transfer (LET) factors of a and ¡3 particles and g radiation, the data are difficult to be compared with each other. a radiation from 224RaCl has a higher emission rate, a much higher energy, and leads to a more localized, intense radiation load compared with 3 or g radiation. The dose estimates for several organs are shown in Table 5. Owing to the mechanism and sites of incorporation, the bone surface and the red bone marrow have the highest dose coefficients with 88 and 8.5 Sv per 10 MBq 224RaCl, respectively. The dose-limiting organ is the bone surface with a cumulative absorbed dose of 4.4 Gy.

Considering the radiation load to other persons, such as medical personnel, family members or coworkers of a patient treated with 224RaCl, both the a and ¡

Table 5 Effective Organ Doses Owing to Cumulative Application of 10 MBq 224RaCl (Radium Chloride)

Effective organ dose

Organ

(Sv/10 MBq 224RaCl)

Bone surface

88.0

Red bone marrow

8.50

Liver

2.60

Colon

1.40

Kidneys

1.50

Lung

0.45

Ovaries

0.56

Uterus

0.45

Testes

0.55

Whole body

2.5

Source: From Ref. 27.

particles have a range too short to exert any significant effects. Only the additional g radiation should be taken into account. However, this radiation dose is very low. With the assumption of continuous residence after injection of 1 MBq 224RaCl at a distance of 1 m, 32 mSv would be the maximum total effective dose for a noninvolved person, for example, a total maximum of 320 mSv from 10 MBq 224RaCl [expertise from the Federal Office for Radiation Protection (BfS), Germany, concerning the radiation load for uninvolved persons during 224RaCl (data of patients with AS, 6/20/1997)]. This dose is comparable with one mammogram, and lower than the dose from a single conventional X-ray of the spine. Emission of activity from 224RaCl by exhalation is negligible. Oral incorporation of patient excretions by insufficient hygienics of others during patient care would be the only way to receive a significant radiation load.

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