Another major limitation of conventional radiography is the inability to display within the framework of two-dimensional x-ray picture all the information found in the three-dimensional figure under view. Objects seen in the third dimension superimpose losing detail. This is why tomography is used. Tomography is the procedure used when visualizing selected planes within the patient examined. Conventional radiography is a two-dimensional picture of a three-dimensional object. Images of all structures throughout the thickness of the patient in the direction of the x-ray beam are superimposed on the same film. In tomography, a single plane is selected and kept in focus, as structures above and below are blurred and out of focus. This is done by moving the x-ray tube in one direction over the patient. The tube and film are linked and synchronized to move in opposite directions. (See Figures 6 and 7 at end of unit.)
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Carolyn—Marcella, do you know that I will be a better patient? I feel that my attitude has changed too. I think we are in agreement.
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Marcella—Carolyn, don’t get too excited. Now we have the honorable task of creating lesson plans, activities, and hands on experiences for students.
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Carolyn—I know. Let’s pre-test to see how much our students already know about the subject. Then we can start from there.
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Marcella—Let’s drink milk to that. You know we have to keep up our image.
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Medical Imaging
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Questions
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Pre—Post Test
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Answers
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1. What is a radiograph?
____
a) a radio
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b) an x-ray picture
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b
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c) radiation
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2. What are x-rays?
____
a) sound waves
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b) artificial light used in photography
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c
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c) electromagnetic radiation
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3. A convex lens
____
a) bends light rays to meet at a point
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b) spreads parallel rays outward
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b
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c) produces colors
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4. A concave lens
____
a) bends light rays to meet at a point
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b) spreads parallel rays outward
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a
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c) produces colors
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5. Millimeter
____
a) is the smallest unit for measuring length in the metric system
____
b) is the largest unit for measuring length in the metric system a
____
c) is the smallest unit of measuring weight in the metric system
6. Roentgen rays are used in reference to
____
a) color
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b) x-rays
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b
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c) sound waves
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7. Radiation is not given off by
____
a) toasters
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b) manual toys
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b
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c) television sets
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8. X-rays
____
a) because of their extremely short wavelength, are able to penetrate materials that absorb or reflect visible light
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b) do not obey the laws of light
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a
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c) do not produce biological changes in cells
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9. The x-ray tube
____
a) is the fundamental property of x-ray
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b) the most efficient means of generating x-rays
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b
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c) is one of the dual natures of x-ray
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10. One must be an M.D. to
____
a) be a radiation therapy technologist
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b) be a radiologist
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b
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c) be a nuclear medicine technologist
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True or False
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11. Roentgenographic examination is another name for x-ray or radiography.
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T
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12. Persons less trained in radiology than radiologists sometimes tend to allow a primary x-ray beam that gives unnecessary primary and scattered radiation to patients.
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T
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13. X-rays should be taken on a monthly basis.
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F
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14. Improper equipment may lead to poor diagnostic film and cause more x-rays to be taken.
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T
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15. One should always demand an x-ray when a fall has taken place.
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F
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16. X-rays are not potentially harmful to pregnant women.
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F
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17. Lead aprons are unnecessary for protection in the x-ray room.
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F
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18. Scattered radiation can be reduced by beam limitation.
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T
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19. The linear non-threshold hypothesis in radiation exposure argues that any level of radiation, no matter how small is dangerous.
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T
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20. The threshold hypothesis in radiation exposure argues that low levels of radiation are safe, radiation does not become dangerous until larger quantities are used.
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T
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