Diagnostic Imaging

Diagnostic Imaging, also called Medical Imaging, is the use of electromagnetic radiation to produce images of internal structures of the human body for the purpose of accurate diagnosis. Diagnostic imaging is roughly equivalent to radiology, the branch of medicine that uses radiation to diagnose and treat diseases.

X rays, used since 1895, were the first type of radiation to provide images of the interior of the body. X rays pass through bodily tissues and also have the property of darkening photographic film when they strike it. As they penetrate tissues, the X rays are absorbed differentially, with denser objects such as bones absorbing more of the rays and thus preventing them from reaching the film. Soft tissues, on the other hand, absorb fewer rays; the result is that in an X-ray photograph of the interior of the body, bones show up as lighter areas and soft tissues show up as darker ones on the exposed film.

A limiting factor in X rays when used alone is the inability to distinguish between adjacent, differentiated soft tissues of roughly the same density (it is not possible to produce contrasting tones between such objects on the exposed film). To obtain this contrast, a contrast medium -- a liquid or gaseous substance that is comparatively opaque to X rays (radiopaque) or comparatively transparent to them -- is injected into the body. Contrast-medium fluids can be injected into naturally occurring body cavities, injected into the bloodstream and lymphatic vessels, swallowed or introduced by enema for study of the digestive tract, or injected around organs to show their external contour.

Different contrast media thus allow the X ray imaging of particular types of soft internal structures, such as the arteries and veins in angiography, the passage of blood through the heart in angiocardiography, the gallbladder and biliary channels in cholecystography, the spinal cord in myelography. and the urinary tract in urography. Virtually any part of the body can be examined for physiological disturbances of the normal structures by X-ray analysis. X-ray motion-picture films can record the body processes as the contrast media enter and leave parts of the body.

Other imaging techniques have been developed using X rays. In tomography X-ray images of deep internal structures can be obtained by focusing the rays on a specific plane within the body. A more complex variation of this technique is computerized axial tomography, known as a CAT scan.

The scanning of radioactive isotopes that have been injected into the tissues is a medical specialty called nuclear medicine. Both isotope scanning and X-ray photography are used in brain scanning. An imaging technique related to isotope scanning is positron emission tomography. Another type of diagnostic imaging is nuclear magnetic resonance, which creates images of thin slices of the body using very-high-frequency radio waves. Ultrasound is a technique in which high-frequency sound waves are used for detecting abnormalities in internal organs. The varieties of radiation that are used in diagnostic imaging continue to expand, along with the techniques for using them.

Exercise 18. Give Ukrainian equivalents to the following words and word combinations:

soft internal structures, limiting factor, to distinguish between, to obtain the contrast, gaseous substance, to swallow, to absorb differentially, property of darkening photographic film, accurate diagnosis, to treat diseases, to diagnose, to produce images, opaque, disturbances, varieties of radiation, external contour, to detect abnormalities, high-frequency sound waves, specific plane, thin slice, transparent, to create image.

Exercise 19. Answer the following questions:

1. What is Diagnostic Imaging?

2. What is the purpose of Medical Imaging?

3. What was the first type of radiation?

4. What properties do X rays have?

5. Which structures of the human body absorb more X rays?

6. Which structures of the human body absorb fewer X rays?

7. What is a limiting factor of X rays?

8. What ways can contrast-medium fluids be injects into the body?

9. What other imaging techniques do you know?

10. What is computerized axial tomography?

11. What is positron emission tomography?

12. What is nuclear magnetic resonance?

Exercise 20. Open the brackets paying attention to the usage of the Passive Voice.

1. The X rays (to absorb) differentially.

2. Any part of the body (to examine) for physiological disturbances of the normal structures by X-ray analysis.

3. Radioactive isotopes (to inject) into the tissues.

4. X-ray photography (to use) in brain scanning.

5. They (to emit) from the nucleus of some radioisotopes.

6. Contrast-medium fluids (to inject) into naturally occurring body cavities.

7. In tomography X-ray images of deep internal structures (to obtain) by focusing the rays on a specific plane within the body.

8. Each detector (to operate) in multiple coincidence with many detectors across from it.

9. One element (to convert) into another.

10. The varieties of radiation (to use) in diagnostic imaging.

Exercise 21. Complete the sentences.

1. __________ absorb more of the rays.

2. __________ pass through bodily tissues.

3. ___________________ are injected into naturally occurring body.

4. _____________ absorb fewer rays.

5. _______________________ record the body processes as the contrast media enter and leave parts of the body.

6. _________________________allow the X ray imaging of particular types of soft internal structures.

7. ________________________ creates images of thin slices of the body using very-high-frequency radio waves.

8. _______________________are used for detecting abnormalities in internal organs.

9. ___________________________ is a medical specialty called nuclear medicine.

10. ___________________________ are used in brain scanning.

11. ____________________ continues to expand.

Exercise 22. Retell the text “Diagnostic Imaging”.

Exercise 23. Put all possible special questions to the following sentences:

1. The technician waits for the computer to compile the picture.

2. Each scan takes only a few seconds.

3. The dye is filtered out of the bloodstream by the kidneys.

4. A radiologist will examine the pictures from the scan.

5. A CT scan usually involves from 10 to 30 different pictures.

6. The differences in densities appear as different shades of grey similar to a black and white photograph.

7. A patient will be asked to drink two more glasses of the dye just before the procedure.

8. The x-ray tube rotates around your body.

9. CT scans are performed in the radiology department by technicians specially trained to operate CT scanning equipment.

10. The computer measures from each angle the amount of energy absorbed by a patient’s body tissue.

11. The computer converts the analysed information into a picture of the internal organs of the body.

12. An x-ray tube or "camera" is mounted inside a ring surrounding the doughnut hole.

Exercise 24. Read the text and discuss it using questions after the text.