Read the following passage. In two (2) paragraphs write about the uses of radioactive isotopes possible damage to other macromolecules, such as cellular DNA, and weigh that risk against the potential therapeutic benefits of radiation therapy.
Protons, neutrons, and electrons are responsible for the chemical properties of atoms. They also have other properties that can be useful in a clinical setting. For example, they have been used to develop methods for examining the inside of the body. Health professionals and researchers commonly use radioactive isotopes because sensitive measuring devices can detect their radioactivity, even when they are present in very small amounts.
Radioactive isotopes have unstable nuclei, which spontaneously change to form more stable nuclei. As a result, either new isotopes or new elements are produced. In this process of nuclear change, the nuclei of radioactive isotopes emit alpha particles, beta particles, and gamma rays. Alpha (α) particles are positively charged helium ions (He2+), which consist of 2 protons and 2 neutrons. Beta (β) particles are electrons formed as neutrons change into protons. An electron is ejected from the neutron, and the proton that is produced remains in the nucleus. Gamma (γ) rays are a form of electromagnetic radiation (high-energy photons) released from nuclei as they lose energy.
All isotopes of an element have the same atomic number, and their chemical behavior is very similar. For example, 3H (tritium) can substitute for 1H (hydrogen), and either 125iodine or 131iodine can substitute for 126iodine in chemical reactions.
Several procedures that are used to determine the concentration of substances, such as hormones, depend on the incorporation of small amounts of radioactive isotopes, such as 125iodine, into the substances being measured. These procedures enable clinicians to more accurately diagnose disorders of the thyroid gland, the adrenal gland, and the reproductive organs.
Radioactive isotopes are also used to treat cancer. Some of the particles released from isotopes have a very high energy content and can penetrate and destroy tissues. Rapidly growing tissues, such as tumors, are more sensitive to radiation than are healthy cells. Thus, radio-active isotopes can be used to destroy tumors. Medical facilities also use radiation to sterilize materials that cannot be exposed to high temperatures (e.g., some fabric and plastic items used during surgical procedures). In addition, radioactive emissions can be used to sterilize food and other items.
X-rays are electromagnetic radiations with a much shorter wavelength than visible light. When electric current is used to heat a filament to very high temperatures, the energy of the electrons becomes so great that some electrons are emitted from the hot filament. When these electrons strike a positive electrode at high speeds, they release some of their energy in the form of x-rays.
X-rays do not penetrate dense material as readily as they penetrate less dense material, and x-rays can expose photographic film. Consequently, an x-ray beam can pass through a person and onto photographic film. Dense tissues of the body absorb the x-rays; on the film, these areas are underexposed and, so, appear white or light in color. By contrast, the x-rays readily pass through less dense tissue, so the film in these areas is overexposed and they appear black or dark in color. In an x-ray film of the skeletal system, the dense bones are white, and the less dense soft tissues are dark, often so dark that no details can be seen. Health professionals use x-rays to determine whether bones are broken or have other abnormalities.
Soft tissues can be photographed by using low-energy x-rays. Mammograms are low-energy x-rays of the breast that can reveal tumors because tumors are slightly denser than normal tissue.
Radiopaque substances are dense materials that absorb x-rays. If a radiopaque liquid is given to a patient, the liquid assumes the shape of the organ into which it is placed. For example, if a patient swallows a barium solution, the outline of the upper digestive tract can be photographed using x-rays to detect any abnormality, such as an ulcer.