MEDICAL IMAGING OF THE BODY
Cadavers (preserved human bodies used for scientific research) can be sliced into sagittal, frontal, or transverse slices to allow for easier observation of interior structures, while living bodies cannot. This has been a source of consternation for medical experts who must evaluate if internal organs are damaged or sick. In certain situations, thorough exploratory surgery is the only guaranteed approach to discover a lesion or deviation from normal. Fortunately, recent developments in medical imaging have enabled surgeons to see interior body components without risking damage or other problems associated with major surgery. Some of the more popular methods are briefly discussed here.
Radiography
Radiography, often known as x-ray photography, is the oldest and most extensively used noninvasive method of photographing interior body structures. Energy in the x band of the electromagnetic spectrum is blasted through the body to photo graphic film in this approach (Figure A). The x-ray image depicts the contours of bones and other solid structures that absorb some of the x-rays. Instead of photographic film, a phosphorescent screen sensitive to x rays is utilised in fluoroscopy. As x rays pass through the subject and cause the screen to shine, a visual picture is created. Fluoroscopy allows medical professionals to see the interior components of a moving subject's body.
Using radiopaque contrast material to highlight soft, hollow structures such as blood arteries or digestive organs is one method. Substances that absorb x-rays, such as barium sulphate, are injected or eaten to fill the hollow organ of interest. The empty organ appears as clearly as a thick bone on the screen in Figure A.
Computed Tomography
Computed tomography (CT) or computed axial tomography (CAT) scanning is a modern version of classic x-ray photography. In this approach, a device having an x-ray source on one side of the body and an x-ray detector on the other is spun around the subject's body's central axis (Figure B). A computer interprets the information from the x-ray detectors and creates a video picture of the body as though it were sliced into anatomical parts. The phrase computed tomography literally means "computer-aided cutting." Because CT scanning and other recent breakthroughs in diagnostic imaging generate pictures of the body as if it were divided into sections, students of the health sciences must be especially conversant with sectional anatomy. The study of structural connections apparent in anatomical sections is known as sectional anatomy.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a kind of scanning in which a magnetic field induces tissues to produce radio frequency (RF) waves. An RF detector coil detects the waves and transmits the data to a computer, which creates sectional pictures similar to those produced by CT scanning (Figure C). Because various tissues produce distinct radio signals, they may be differentiated. MRI, also known as nuclear magnetic resonance imaging (NMR), eliminates the use of potentially hazardous x-rays and frequently gives clearer pictures of soft tissues than other imaging modalities.
Ultrasonography
High-frequency (ultrasonic) waves are reflected off interior tissues to create a picture known as a sonogram in ultrasonography. Ultrasonography has been widely utilised since it does not use x-rays and is very affordable and simple to use—particularly in investigating maternal or foetal anatomy in pregnant people. However, the picture generated is not as crisp or sharp as that produced by MRI, CT scanning, or conventional radiography (Figure D).
Later chapters will cover variations on these and other technical developments that have increased the capacity to investigate the structure and functioning of the human body.
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