Medical Imaging

Medicine progresses very rapidly and it advances exponentially. Due to scientific discovery, changes in what we perceive to be traditional healthcare are constantly being redefined and modified, and consequently, treatment standards are forced to undergo change.

In the past, it took decades of research so as to make new discoveries as in the fields of microbiology and virology. Now, it takes us only months to map out DNA and come up with genetic markers for common diseases (Reiser, 2004).

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It is even possible that with the rate that scientific progress is moving along, new findings are already rendering it obsolete. Remarkable advances have been made in the diagnosis and treatment of human diseases. For example, computerized axial tomography (CAT), magnetic resonance imaging, and X-rays have greatly improved diagnostic precision for many disorders (Weck, 1999).

Diseased, atrophied, or malformed tissue can often be detected by analysis of radiographic film, or by directly viewing the body organ by means of fluoroscopy, which utilizes the ability of medical imaging to illuminate a fluorescent screen (Fishman, 1997).

Radioactive substances are used in diagnosis and treatment. X-ray treatment of disease has been increasing as newer techniques of dosage control are discovered. Certain cancerous growths have been arrested by the use of X-ray dosages which will kill the malignant cells without harming healthy tissue. X-rays are used to diagnose skeletal and chest disorders and follow X-ray opaque substances through the intestine, kidneys, and blood vessels (Fishman, 1997).

Other methods trace small amounts of radioactive substances in tissues. Giving radioactive iodine orally and measuring subsequent thyroid gland radioactivity is used to assess thyroid function. Larger doses can be used to destroy cells in overactive glands.

Because this isotope has a half-life of only 8.1 days, it poses no long-term hazard. Radioactive substances can be placed closed to a tumor where their emissions destroy malignant cells with little risk to normal cells. Radium, which emits alpha particles, and cobalt, which emits both beta particles and gamma rays, are used in this way. X-rays also destroy malignant cells (Fishman, 1997).

Tissue changes that result from disease or degeneration will change the density of the tissue in different degrees, depending on the severity of the destruction. Density changes, in turn, affect the penetrability of the X-rays; hence, when diseased tissue radiograms, or X-ray exposed films, are compared with normal, healthy tissue radiograms, an experienced diagnostician can determine the type of disease or malfunction involved and proceed to treat the ailment (Fishman, 1997).

As an example, a fluid-filled lung has greater X-ray absorption capabilities than a healthy lung. The radiogram of a person suspected of having tuberculosis will show a darker lung area in an X-ray radiogram of that region because of the denser fluid in the lungs.

Skeletal fractures and malformations are easily seen in radiograms. The soft tissues of the abdominal system can be viewed after a preparation of  X-ray absorbent barium sulfate is ingested. Gastrointestinal movements may then be seen as the barium sulfate courses through the system (Fishman, 1997).

Neurological disorders can affect the brain, spinal cord, and cranial and spinal nerves. Many disorders can be diagnosed by imaging techniques and by abnormalities in reflexes. The newest imaging technique is nuclear magnetic resonance (NMR), also referred to as magnetic resonance imaging (Sajid, et al., 1994).

For example, osteoarthritis, also degenerative joint disease or simply old-age disease, is the most common form of arthritis. Usually, the symptoms are confirmed osteoarthritis-related when the medical doctor discerns them through the latest imaging techniques. Imaging exams, like x-rays, permit the physician to verify for changes in a patient’s bones and joints, although the distinctive upshots of osteoarthritis may not be manifest early in the disorder.

The physician may also employ other imaging assessments, like magnetic resonance imaging or computerized tomography scans, to identify soreness and other deformities in the person’s joints (Stewart, et al., 1992).

To obtain such an image, the patient is placed in a chamber within a very large magnet. The strong magnetic field, as much as 40,000 times as strong as the earth’s magnetic field, causes hydrogen molecules to spin very rapidly. Energy from spinning molecules is translated by a computer into a visual image. MRI is particularly useful for visualizing soft tissue, distinguishing between gray and white matter, for example. It can also be used to study metabolic reactions as they occur in living tissue (Weck, 1999).

Though MRI provides much clearer images of soft tissues than CAT scans, it has some disadvantages. Its magnetic force can, at highest power, pull metal objects, loose tooth fillings, pacemakers, joint prostheses, and the like, out of the body, and some evidence suggests that it may actually cause tissue damage. Finally, it is much more costly than other imaging techniques (Weck, 1999).

A bone scan is often done on individuals who have had bone cancer or who may have metastasis from another site to the bones. In a bone scan, a dose of a radioactive substance is given, and radiographs are taken over the nest few minutes while the substance if being incorporated into the bone marrow.

The radioactive substance, which shows up as black dots on the developed film, is greatly concentrated in malignant tissues because these tissues take up the radioactive substance more rapidly than normal tissues (Weck, 1999).