Biology Reference
In-Depth Information
structure, as well as the material properties of bone density. Medical imaging technologies
can be used for additional applications of differential disease diagnosis, for the nondestruc-
tive analysis of mummies, or for the imaging of bones from fleshed remains to aid in forensic
investigations. There is obviously no radiation risk to individuals who are deceased, thus
higher resolution images are possible. Existing medical images of living subjects offer the
researcher an opportunity to access data on populations, such as subadults, who are not as
well represented in modern skeletal collections. Bones can be imaged easily and these images
can be used for nondestructive analysis of functional adaptations, to reveal skeletal
pathology and trauma, and provide opportunities to study the skeletons of living subjects.
All of these reasons substantiate why you should consider applying medical imaging to
research in human skeletal biology.
First discovered in 1895 by the German physicist Rector Wilhelm Conrad R
¨
ntgen,
X-rays amazed the world with images of the inside of opaque objects, including the
body. By presenting an X-ray image of his wife's ringed hand, R¨ntgen unknowingly
founded the practice of medical radiology in January of 1896 (
Assmus, 1995
). “Men of
science in this city [New York] are awaiting with the utmost impatience the arrival of
English technical journals which will give them the full particulars of Professor Roentgen's
discovery of a method of photographing opaque bodies” (The New York Times, 1896). It
took another 30 years for science to even understand the full nature of X-rays (
Assmus,
1995
). Traditional X-ray, computed tomography (CT), and dual energy X-ray absorptiom-
etry (DEXA) are all different types of medical imaging that incorporate X-rays, which have
the specific wavelength to penetrate the body. Biplanar radiography essentially takes
a traditional X-ray image of an individual (or bone) from two separate directions (e.g.,
both AP and ML).
Other types of rays can pass through the body and are used for medical imaging modal-
ities. In magnetic resonance imaging (MRI), radiofrequency waves pass through the body as
a large superconducting magnet spins around the subject (
Szabo, 2005
). Computed tomog-
raphy and magnetic resonance are two types of cross-sectional tomography. Tomography
is the process of performing multiple two-dimensional image slices of three-dimensional
objects (
Szabo, 2005; Brant and Helms, 2007
). The idea of tomography was first suggested
in 1914, but the principles of axial tomography were developed in the mid 1940s (
Seynaeve
and Broos, 1995
). The clinical use of MRI began in England in 1967. The Englishman Godfrey
Hounsfield invented computed tomography in 1972 and his name is still used for the units of
measure used to interpret CT images (i.e., Hounsfield units). In 1984, the Food and Drug
Administration approved the commercial use of MRI in the United States (
Seynaeve and
Broos, 1995
).
There are additional modalities of computed tomography potentially useful for the skel-
etal biologist, which include: peripheral quantitative CT (pQCT) and micro-CT. It is impor-
tant for our purposes that radiographic technologies (e.g., traditional X-ray, CT, and DEXA)
provide a superior image of the internal structures of the more dense skeletal tissues than
magnetic resonance imaging (MRI) and ultrasonography (
Brant and Helms, 2007
). Only
the various medical imaging methods that are most relevant to the skeletal biologist are
described in further detail below. Other medical imaging modalities exist but are outside
of the scope of this text.
