How many 131 I atoms are administered in a typical thyroid cancer treatment? (a) 4.2 10

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How many 131I atoms are administered in a typical thyroid cancer treatment?

(a) 4.2 × 1010;

(b) 1.0 × 1012;

(c) 2.5 × 1014;

(d) 3.7 × 1015.


Iodine in the body is preferentially taken up by the thyroid gland. Therefore, radioactive iodine in small doses is used to image the thyroid and in large doses is used to kill thyroid cells to treat some types of cancer or thyroid disease. The iodine isotopes used have relatively short half-lives, so they must be produced in a nuclear reactor or accelerator. One isotope frequently used for imaging is 123I; it has a half-life of 13.2 h and emits a 0.16-MeV gamma-ray photon. One method of producing 123I is in the nuclear reaction 123Te + p → 123I + n. The atomic masses relevant to this reaction are 123Te, 122.904270 u; 123I, 122.905589 u; n, 1.008665 u; and 1H, 1.007825 u.

The iodine isotope commonly used for treatment of disease is 131I, which is produced by irradiating 130Te in a nuclear reactor to form 131Te. The 131Te then decays to 131I. 131I undergoes b- decay with a half-life of 8.04 d, emitting electrons with energies up to 0.61 MeV and gamma ray photons of energy 0.36 MeV. A typical thyroid cancer treatment might involve administration of 3.7 GBq of 131I.

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University Physics with Modern Physics

ISBN: 978-0133977981

14th edition

Authors: Hugh D. Young, Roger A. Freedman

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