Intro To Medical Imaging Flashcards
What is radiology?
A medical specialty that uses imaging to diagnose and treat diseases seen within the body
Examples of imaging modalities:
- Radiographs (conventional or digital )
- CT scan
- Magnetic resonance imaging MRI
- Contrast studies
What are radiographs?
X-rays are a form of electromagnetic radiation, able to pass through the human body and produce an image of internal structures. The resulting image is called a radiograph, more commonly known as an x-ray or plain film
How is an x-ray produced?
Image production by x-ray results from attenuation of those x-rays by the material through which they pass
Attenuation is the process by which the x-rays are removed from a beam through absorption and/or scatter. Absorption is influenced by the atomic number if the structure
What are the types of radiography densities?
Radio-dense/ plaque: less photons can pass through the structure and they appear white on X-ray
Radiolucent: photons easily pass through structures and they appear black on X-ray
Score the main materials in order of the most radiodense first?
Metal or contrast (appears bright white on x-ray)> bone> sift tissue> fat> gas(air) (appears black)
When is standing position important in X-rats?
When area of interest is in the chest
What is a CT scan?
Computed tomography (CTj imaging combines the use of a digital computer together with a rotating x-ray device to create detailed cross-sectional images or slices of the different body parts such as the lungs, liver, kidneys, pancreas, pelvis, extremities, brain, spine and blood vessels
CT scan can be used to produce detailed images of many structures inside of the body, including the internal organs, blood vessels and bones
‘Contrast’ dye can be used to enhance structures such as blood vessels
What is an MRI?
MRI uses the magnetic properties of spinning hydrogen atom s to produce images. Much of the complexity of MRI arises from the fact that the MR signal depends on many varied properties of the tissues and structures being examined, including:
- Number of hydrogen atoms prevent in tissue(proton density)
- Chemical environment of the hydrogen atoms e.g. whether I’m free water or bound by fat
- Flow: blood vessels or CSF
- Magnetic susceptibility: T1 relaxation time and T2 relaxation time
Why do tissues with less water appear darker in MRI?
Tissues containing less water have pure hydrogen protons that will emit signals and therefore, they will appear darker in the image
What is the orientation for CT & MRI on the axial. Plane?
In the axial plane we view images moving from inferior (toe) to superior (head) as though you were standing at the patients feet looking up
What is the orientation for CT & MRI on the Sagittarius plane?
In the Sagittarius plane we view images from right to left, as though you were standing on the patients right and progressively seeing through them
What is the orientation for CT & MRI on the coronal plane?
In the coronal plane we view images from anterior to posterior, as though you were standing to the front of the patient and progressively seeing through them
What are contrast studies?
To examine studies that don’t have inherent contrast differences from the surrounding tissues, contrast agents must be used e.g. (abdominal structures, blood vessels). Contrast agents are available in several different forms, but in general a contrast agent is a pharmaceutical which is radiopaque (attenuated x-rays and therefore shows up as white )
Some examples of contrast studies include:
Barium enema: gastrointestinal tract
Subtraction angiography: circulatory system
