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_ A 0.495-MeV g-ray interacts with a K-shell electron by the photo- electric process.If the binding energy of the K-shell electron is 28keV, what happens to the rest of the photon energy?

_ If 1mCi of a radionuclide is adequately shielded by 5 HVLs of a shield- ing material, how many HVLs are needed to provide equal shielding for (a) 5mCi and (b) 8mCi?

_ A 1-mm lead apron will afford approximately twice as much protection as a 0.5-mm apron, or does this shielding depend on the energy of the radiation?

_ How many HVLs are approximately equivalent to three tenth-value layers?

_ Suppose 5% of the 364-keV photons of 131I are transmitted after passing through a lead brick of 10-cm thickness.Calculate the HVL of lead for 131I.

_ There is a 75% chance that a monoenergetic photon beam will be atten- uated by 4mm of lead.What is the HVL of lead for the photon?

_ Which of the following radiations has the highest LET? (a) 120-keV x-ray (b) 100-keV electron (c) 5-MeV a-particle (d) 10-MeV proton (e) 14-MeV neutron

_What is the difference between the effective dose equivalent and effective dose?

- Calculate the absorbed dose to the thyroid gland of a hyperthyroid patient from a dosage of 30mCi 131I, assuming 60% uptake, a biologi- cal half-life of 4 days for thyroid clearance of 131I, and S equal to 2.2 × 10−2rad/mCi•hr.

_ Calculate the dose in rems and sieverts to a tumor that received 35rads (0.35Gy) from neutron therapy (radiation weighting factor = 10 for neutrons).

_Calculate the cumulated activity in a 55-g source organ containing 3 mCi (111MBq) of 99mTc (t1/2 = 6hr) with a biological t1/2 = 14hr.

_ A target organ has a mass of 35g and contains 1mCi (37MBq) of a radionuclide emitting a b−-particle with D1 = 0.3g•rad/mCi•hr and f1 = 1.0, and a g-radiation with D2 = 0.2g•rad/mCi•hr and f2 = 0.35. Calculate the mean absorbed dose per cumulated activity.

_ An external beam deposits 360ergs of energy in 3g of tissue.What is the radiation dose in rad and cGy?

_The absorbed doses are 10rad (10cGy) to organ A, 5rad (5cGy) to organ B, and 6rad (6cGy) to organ C from each radiation from a 20mCi (370MBq) source containing two radiations having radiation weighting factors, Wr, as 1 and 10. The tissue weighting factors of organs A, B, and C are 0.30, 0.22, and 0.46, respectively. Considering the contribution from other organs negligible, calculate the effective dose.