A. Dosimetry Questions Al-A3 refer to the following table, which shows four possible treatments (A- D) involving ionizing radiation. Treatment Radiation Dose (Gy) A alpha particles 0.01 B X-rays 0.01 C protons 0.06 D beta particles 0.07 1. Rank the treatments (A-D) based on the amount of energy that would be absorbed by a patient, from largest to smallest. Explain your reasoning. 2. Rank the treatments (A-D) based on the amount of biological damage their corresponding doses would do to a patient, from largest to smallest. Explain your reasoning. 3. Imagine the dose for each treatment (A-D) became 0.10 Gy. Rank the treatments based on the amount of biological damage their corresponding doses would do to a patient, from largest to smallest. Explain your reasoning. When "I is ingested, it is taken up almost entirely by the thyroid gland. 4. "I has 53 protons and 78 neutrons. It decays into "Xe, which has 54 protons and 77 neutrons. What type of ionizing radiation does "I emit when it decays into 13 Xe? Explain. 5. If a patient receives "I with an activity of 1.85 x 10 Bq, then how many decays will the "I experience in one hour? Explain/show your reasoning.6. Each individual "I decay releases ionizing radiation with 1.55 x 10"*J of energy. If half of that energy is absorbed by the thyroid gland, then what is the radiation dose received by the 0.15 kg thyroid gland in one hour? Explain/ show your reasoning. 7. What is the dose equivalent that the thyroid gland receives in the first hour after ingesting the "I? Explain/show your reasoning. 8. Each person is exposed to approximately 3 mSv per year from the background radiation in the environment, although this number varies with both location and time. How does the dose equivalent you calculated in question A7 compare to the dose equivalent a person receives each year from background radiation?Many medical imaging techniques, such as X-rays and CT scans, expose patients to ionizing radiation. 1. If a chest X-ray delivers 0.25 mSv to 5.0 kg of tissue in the chest, how much total energy (in joules) does the tissue receive? Show your work. 2. How many joules of energy does a 75-kg person receive from environmental background radiation each year? Assume this radiation has an RBE of 1. Show your work. 3. How many chest X-rays would it take for a 75-kg person to receive the same total amount of energy from natural sources of radiation in one year? Show your work. 4. A single CT scan delivers 12 mSy to the entire body. How many chest X-rays would it take for a 75-kg person to receive the same total amount of energy as from a single CT scan? Assume the radiation from a CT scan has an RBE of 1. Show your work. 5. How does the amount of energy a person receives from a CT scan compare to the amount from natural sources of radiation?Introduction R adioactive substances are used in many medical situations, from cancer treatments to medical imaging. Since ionizing radiation can have damaging effects on biological molecules and tissues, many medical professionals are experts in dosimetry, which involves calculating the amount of radiation absorbed by the body and assessing its health effects. A dose is defined as the amount of energy from ionizing Table 1. RBEs radiation that is absorbed by 1 kg of tissue. However, Radiation RBE simply knowing the amount of absorbed energy is not X-rays 1 enough information to assess health effects, since gamma rays different forms of ionizing radiation can cause different beta particles 1 amounts of biological damage, even when they deliver protons 5 the same amount of energy to the body. The relative alpha particles 20 biological effectiveness (RBE) of a given type of ionizing radiation quantifies how much damage that radiation does relative to the damage done by the same amount of energy from X-rays. Table 1, at right, gives the RBEs of a few types of ionizing radiation. The dose equivalent for a given type of Table 2. Units for dosimetry quantities ionizing radiation is the RBE Quantity Unit multiplied by the dose. Two types lose gray (1 Gy = 1]/kg of absorbed energy) of ionizing radiation will produce lose rad (1 rad = 0.01 Gy) the same amount of damage if they RBE unitless have the same dose equivalent. dose equivalent sievert (1 Sv = RBE x dose in Gy) Table 2, at right, lists some dose equivalent rem (1 rem = 0.01 Sv) commonly used units for dosimetry quantities