The World Within

The World Within

What can be done with medicine today is truly astounding. In just a little over a century, we have gone from crude, anaesthetized surgery with non-sterilized instruments to the ability to delicately rebuild a hand or bypass a major artery with little risk to the patient and without even leaving a large scar. These great heights to which we have ascended are based upon a number of breakthroughs in sanitation and sterilization, antibiotics, and any number of other small discoveries that make possible today's operating room - but by far the most powerful and groundbreaking advances have been made in the field of human imaging.

For over sixteen hundred years, the edicts and guidelines of the Catholic Church forbade the exploration of the human body. This sad state of affairs effectively limited our knowledge of the body to studies performed upon stolen cadavers and the rather inaccurate classical-era studies of Galen. Even when the ban upon anatomical study was lifted, by the end of the nineteenth century we had still progressed no further than an understanding of the basic anatomy as observed by dissection. Then, in the last five years of the nineteenth century, two important discoveries ushered in a new era in medicine: Roentgen's discovery of x-rays in 1895 and Bequerel's discovery of "Uranium rays" - nuclear radiation - in 1896. These forms of electromagnetic radiation, and their derivatives, form the basis of today's most prevalent and important imaging technology - X-rays, Computed Tomography (CT), and nuclear medicine.

At its most basic level, x-ray technology works by using a high-voltage current to generate a burst of x-rays (high-frequency electromagnetic radiation), which are then focused and directed through the human body. Certain materials, such as bone and cartilage, absorb more of the radiation than other tissues, which creates a "shadow" in the x-ray beam that is recorded on a special cassette containing photographic film, situated on the other side of the patient. Upon development of the film, the image of the bone structure (and some other tissue) can be studied to diagnose any apparent pathologies (Wolbarst 33). Today, this technology is wildly popular - almost everyone has had at least one x-ray during his life. However, the two-dimensional nature of an x-ray does create some limitations in its usefulness - but a further development of this technology has eliminated these.

Computerized Tomography, invented in 1963, is essentially a development of x-ray technology that allows a physician to observe highly detailed "slices" of the human body, and today is "highly reliable, non-invasive, painless, quick, and available on an urgent, 24 hour-a-day basis at most hospitals (Kelly 50)." The imaging system surrounds the patient with a large number of sensitive radiation detectors much like those that record x-rays. An x-ray tube projects a fan-shaped beam of radiation through the body, turns about one degree, then sends another burst through, until it has traversed 180 degrees (Wolbarst 101). Computers then digest this information and produce a highly detailed "slice" of the patient's body for analysis. CT is "the established imaging modality for the diagnosis of solid-organ injury (Obeid et al. 706)," but has been shown to be rather more inaccurate when dealing with soft tissue. Thus, doctors have had to turn to other forms of radiation for soft-tissue analysis, leading to the development of nuclear medicine.

Essentially, nuclear medicine involves introducing radioactive isotopes into the body and using radiation detectors to follow their path and behavior. often, the isotopes of technetium are used because they produce intense gamma radiation for a very short period of time, and are thus ideal for use in the human body with little risk of overexposure. Several methods are utilized, such as having the patient inhale radioactive gas to study lung pathologies, or "perfusion", which involves attaching radioactive isotopes to blood protein and injecting the mixture into the patient. The images produced allow doctors to observe such things as a beating heart (Prvulovich et al. 1140), but there is some risk involved in exposing the patient to radiation - a risk eliminated by another popular imaging system, MRI.

Magnetic Resonance Imaging essentially performs the same operation as CT, but utilizes magnetic fields and radio waves rather than x-rays and can better distinguish soft tissues. Images are produced by recording the behavior of sensitive water molecules in the tissue (Torricelli et al. 23). MRI's are highly effective and can diagnose such things as hip fractures where other technologies fail (Rizzo 396). They are virtually risk free unless the patient has metal implements such as surgical pins or a pacemaker in his body; these would be forcibly removed by the powerful magnetism of the MRI.

MRI's and CT's are