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Ch.21 - Nuclear Chemistry
Chapter 21, Problem 56

Why is it important that radioisotopes used as diagnostic tools in nuclear medicine produce gamma radiation when they decay? Why are alpha emitters not used as diagnostic tools?

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1
Understand the nature of gamma radiation: Gamma rays are high-energy electromagnetic waves that can penetrate the body and be detected by external sensors, making them ideal for imaging purposes in nuclear medicine.
Recognize the role of gamma radiation in diagnostics: Gamma radiation allows for the creation of images of the inside of the body, helping doctors to diagnose conditions without invasive procedures.
Consider the properties of alpha particles: Alpha particles are heavy and have a very short range, meaning they cannot penetrate the skin and are not suitable for imaging purposes.
Evaluate the safety concerns: Alpha particles can cause significant damage to tissues if ingested or inhaled, making them unsuitable for diagnostic use where minimal exposure is desired.
Conclude the suitability of gamma emitters: Gamma emitters are preferred in diagnostics because they provide clear imaging capabilities with minimal risk to the patient, unlike alpha emitters.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gamma Radiation

Gamma radiation is a form of high-energy electromagnetic radiation emitted during radioactive decay. It is highly penetrating, allowing it to pass through body tissues and be detected by imaging equipment. This property makes gamma emitters ideal for diagnostic purposes in nuclear medicine, as they provide clear images of internal structures without causing significant harm to the patient.
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Alpha Radiation

Alpha radiation consists of helium nuclei and is relatively heavy and positively charged. Due to its low penetration power, alpha particles can be stopped by a sheet of paper or even human skin, making them unsuitable for diagnostic imaging. Their inability to penetrate tissues means they cannot provide useful information about internal organs or structures in a medical context.
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Nuclear Medicine

Nuclear medicine is a medical specialty that uses radioactive substances for diagnosis and treatment. It involves the administration of radioisotopes, which emit radiation that can be detected by imaging devices. The choice of radioisotope is crucial; those that emit gamma radiation are preferred for diagnostics due to their ability to provide detailed images while minimizing patient exposure to harmful radiation.
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Related Practice
Textbook Question

Based on the following atomic mass values: 1H, 1.00782 amu; 2H, 2.01410 amu; 3H, 3.01605 amu; 3He, 3.01603 amu; 4He, 4.00260 amu—and the mass of the neutron given in the text, calculate the energy released per mole in each of the following nuclear reactions, all of which are possibilities for a controlled fusion process:

(a) 21H + 31H → 42He + 10n

(b) 21H + 21H → 32He + 10n

(c) 21H + 32He → 42He + 11H

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Open Question
The isotope 6228Ni has the largest binding energy per nucleon of any isotope. Calculate this value from the atomic mass of nickel-62 (61.928345 amu) and compare it with the value given for iron-56 in Table 21.7.
Textbook Question

Iodine-131 is a convenient radioisotope to monitor thyroid activity in humans. It is a beta emitter with a half-life of 8.02 days. The thyroid is the only gland in the body that uses iodine. A person undergoing a test of thyroid activity drinks a solution of NaI, in which only a small fraction of the iodide is radioactive. (c) A normal thyroid will take up about 12% of the ingested iodide in a few hours. How long will it take for the radioactive iodide taken up and held by the thyroid to decay to 0.01% of the original amount?

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Open Question
(a) Which of the following are required characteristics of an isotope to be used as a fuel in a nuclear power reactor? (i) It must emit gamma radiation. (ii) On decay, it must release two or more neutrons. (iii) It must have a half-life of less than one hour. (iv) It must undergo fission upon the absorption of a neutron. (b) What is the most common fissionable isotope in a commercial nuclear power reactor?
Open Question
Which of the following statements about the uranium used in nuclear reactors is or are true? (i) Natural uranium has too little 235U to be used as a fuel. (ii) 238U cannot be used as a fuel because it forms a supercritical mass too easily. (iii) To be used as fuel, uranium must be enriched so that it is more than 50% 235U in composition. (iv) The neutron-induced fission of 235U releases more neutrons per nucleus than the fission of 238U.
Open Question
What is the function of the control rods in a nuclear reactor? What substances are used to construct the control rods? Why are these substances chosen?