Medical Imaging Techniques: Types & Uses

Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

What is medical imaging and how is it used? Learn about the different types of imaging used in medicine and how they've changed healthcare, then take a quiz to test your knowledge.

What Is Medical Imaging?

Aside from Superman with his x-ray vision, people generally can't look at a sick person and instantly figure out the problem. Most medical issues occur inside the body, so making a diagnosis can be a challenge. Medical imaging has made that challenge far easier over the last century. Medical imaging is the technique of producing visual representations of areas inside the human body to diagnose medical problems and monitor treatment. It has had a huge impact on public health.

Types of Medical Imaging

There are many types of medical imaging, and more methods for imaging are being invented as technology advances. The main types of imaging used in modern medicine are radiography, magnetic resonance imaging (MRI), nuclear medicine, and ultrasound. We'll discuss these in further detail below.

Radiography uses electromagnetic radiation to take images of the inside of the body. The most well-known and common form of radiography is x-ray. For this procedure, an x-ray machine beams high-energy waves onto the body. The soft tissues, such as skin and organs, do not absorb these waves, whereas hard tissue like bones do absorb the waves. The machine transfers the results of the x-ray onto a film, showing the parts of the body that absorbed the waves (the bones) in white and leaving the unabsorbed materials in black.

Medical x-ray
Medical x-ray

Magnetic resonance imaging involves radio waves and magnetic fields to look at the organs and other structures in the body. The procedure requires an MRI scanner, which is, simply put, a large tube that contains a massive circular magnet. This magnet creates a powerful magnetic field that aligns the protons of hydrogen atoms in the body. Those protons are then exposed to radio waves, causing the protons to rotate. When the radio waves are turned off, the protons relax and realign themselves, emitting radio waves in the recovery process that can be detected by the machine to create an image.

MRI scanner
MRI scanner

Nuclear medicine is a rather general term that involves any medical use of radioactive materials. But in terms of imaging, it usually refers to the use of radioactive tracers, which are radioactive materials that are injected or swallowed so that they can travel through the digestive or circulatory system. The radiation produced by the material can then be detected to create an image of those systems.

Radioactive tracer image
Radioactive tracer image

Ultrasound utilizes high-frequency sound waves, which are reflected off tissue to create images of organs, muscles, joints, and other soft tissues. It's kind of like shining a light on the inside of the body, except that this light travels through the skin layers and can only be viewed using electronic sensors.

Ultrasound image
Ultrasound image

Uses and Benefits of Medical Imaging

Each technique is used in different circumstances. For example, radiography is often used when we want images of bone structures to look for breakages. MRI scanners are often used to take images of the brain or other internal tissues, particularly when high-resolution images are needed. Nuclear medicine is used when you need to look inside the digestive or circulatory systems, such as to look for blockages. And ultrasound is used to look at fetuses in the womb and to take images of internal organs when high resolution is not necessary.

MRI brain scan
MRI brain scan

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