Medical imaging and diagnostics refers to a variety of technologies that are used to evaluate the human body in effort to diagnose, monitor, or treat a medical condition. The type of technology used depends on the area of the body that is being monitored or treated, the type of disease, illness, or condition that is being treated. It is important to make note that professionals in these roles do not diagnose, rather, they obtain important clinical information for the clinical care team to make an informed decision about patient care.

Within medical imaging, there are several common types of imaging, these include: X-rays, magnetic resonance imaging (MRI), ultrasound, computed tomography (CT) scan, and nuclear medicine imaging. Each of the imaging types use specific technology and modalities.

X-rays

x-rays use ionizing radiation to create images of the body. This is a non-invasive and painless procedure that allows the healthcare team to diagnose a disease and monitor therapy. The images that are generated help support medical and surgical treatment planning, and they can also be used during procedures to verify correct placement of catheters or other medical devices that could be inside the body. When the x-ray is turned on, radiation travels through the body and the amount that is absorbed by the tissues depends on the radiological density. For example, a bone has a higher radiological density, this allows for the bony structures of our body to absorb x-rays and produce high contrast images, on the black background of the x-ray image, bones appear whiter. On the other hand, tissues that are less radiologically dense, such as muscles or the air-filled lungs, are shown as various shades of gray on the black background of the x-ray.

Computed Tomography

computed tomography (CT) uses traditional x-ray imaging along with a computer to process a series of cross-sectional images or slices. The images produced by CT are far more detailed than traditional radiographs, they allow for the healthcare team to view the structures from many different angles. The cross-sectional images can then be stacked together to create a three-dimensional image of the structure. When a CT is being performed, a patient will lay on a bed that moves in and out of a fixed x-ray tube that rotates while taking the images. While it rotates, x-rays are emitted and go through the patient’s body, the x-ray detectors opposite of the x-ray source are then picked up and an image is transmitted and produced onto a computer. Similar to traditional x-rays, the higher radiological dense structures appear more white, whereas the less radiological dense structures appear in various shades of gray.

Magnetic Resonance Imaging

magnetic resonance imaging (MRI) uses strong magnetic fields and radio waves to produce images of the internal structures of the human body. The magnetic resonance signal comes from the protons that are in fat and water molecules in the body. Throughout the MRI exam, an electrical current passes through coiled wires, creating a temporary magnetic field in the patient’s body. Radio waves are then sent from a transmitter in the MRI machine and the signals are used to create digital images of the area that is being scanned. MRI’S are used to help diagnose disease and monitor treatment that a patient may be receiving. MRI’s are very helpful when evaluating non-bony or areas made up of soft-tissues. Therefore, structures such as the brain, nerves, muscle tendons and ligaments can be viewed much more clearly than traditional x-ray or CT.

Ultrasound Imaging

ultrasound imaging is a specialized type of imaging that uses high-frequency sound waves to view internal structures of the body. When ultrasound is performed, the images that are captured are in real-time. This is extremely helpful when a medical provider needs to evaluate the flow of blood or other movements. What makes ultrasound different from traditional x-ray imaging, is that ionizing radiation is not used. The image that is captured with the ultrasound is produced from the reflection of the soundwaves off of the structures in the body. Other benefits of ultrasound imaging include being non-invasive and is generally less expensive and can be found in a variety of settings. There are some limitations when using this type of imaging, such as if a healthcare provider is needing to evaluate a bodily structure that is surrounded by air, the ultrasound waves can be disrupted by air / gas. The patient’s body composition may not allow for a clear image to be obtained, as the ultrasound waves are weakened when they have to travel through thick amounts of tissue.

Ultrasound is an imaging tool that is used to help healthcare providers, diagnose, evaluate and treat a variety of conditions. There are a number of procedures that utilize ultrasound imaging, these include:

• Abdominal Ultrasound: This type of ultrasound is key in evaluating the various tissues and organs that are found in the abdominal cavity.
• Breast Ultrasound: This type of ultrasound allows for healthcare providers to visualize breast tissue, which can help identify breast cancer.
• Fetal Heart Rate Monitoring: Doppler ultrasound allows for the healthcare team to hear and non-invasively monitor a fetus’ heart rate while in the womb.
• Fetal Ultrasound: This type of imaging that allows healthcare providers to evaluate the growth and overall development of a fetus throughout pregnancy.
• Ultrasound-guided needle placement or intravenous catheter placement: Healthcare providers can use ultrasound to help them ensure that they are placing a needle or intravenous catheter into a specific tissue or vessel.
• Cardiac Echocardiogram: This type of ultrasound provides the healthcare team an image of the heart and the blood flow through the heart.

Nuclear Medicine Imaging

nuclear imaging is a type of medical imaging that uses tiny amounts of material that is considered radioactive that is then combined with a carrier molecule. When combined the product is referred to as a radiotracer. Nuclear medicine imaging is another tool that is used to evaluate, diagnose, and treat various conditions. When the radioactive material is swallowed or injected into the body, the material builds up and the radiotracer compound then goes to the area that is being evaluated, this is used very often when examining areas that are inflamed or that may be suspicious of cancer. Cancerous cells generally utilize a lot of energy through glucose, therefore the imaging device that is used in nuclear medicine detects the excess amount of energy and an image is then generated showing the location of the radiotracer. In addition to helping with diagnosing, nuclear medicine can also be used to treat certain types of cancers and other conditions. The radioactive material that is given to the patient attaches to a specific cell, then delivers a prescribed dose of radiation to the cell, which in turn destroys the cell. Nuclear medicine imaging can also be used to evaluate the function of the heart and amount of blood flow going to it. This can be helpful when the healthcare team is wanting to assess the damage that was caused from a heart attack. Nuclear medicine can also be used to evaluate the lungs, this is helpful when a blood clot is suspected within the pulmonary circulatory system. Other body systems that can be evaluated using nuclear medicine imagine include the gastrointestinal, endocrine and neurological systems.

With a lot of diseases and conditions starting at the cellular level, nuclear medicine allows for healthcare providers to identify disease much earlier in its course, with this information being available earlier, the team can respond quicker, providing treatment and/or therapy to potentially stop or slow down the spread of disease.

Attributions

1. Figure 7.1: image released under the Pexels License
2. Figure 7.2: image released under the Pexels License