Lecture 2: intro to radiology Flashcards
Interworking of X-Rays
XR tube, beam, and film used to create X-ray
Xray photons released from behind tube and strike film behind it
X rays may be absorbed or scattered
Radiopaque (xray image)
Dense metal or bone shows up more white on x ray
*atomic weight of target plays role in density
Radiolucent (xray image)
skin and fat appear more gray or black on x ray
Affect of distance on Xray
closer to film, better the picture.
Larger distance from film will warp imaging.
X ray view: AP
Anterior-Posterior (front to back)
X ray View: Lateral
side to side
X ray view: PA
Posterior to anterior (front to back)
Advantages of Xray (7)
Fast, inexpensive, readily available provides global view of area being examined low risk of adverse effects minimal pt prep no sedation required
Disadvantages of Xray (3)
insensitive and non-specific
image is affected by positioning
2D image
not all structures can be seen (gas and feces and affect image)
CT scan
*computed tonography
Uses several x-ray images and converts them into pictures
Used digital geometry processing to create 3D images
CT scanner emits series of narrow beams through the body, producing more detail than single beam from xray
Spiral CT
machine moves continuously around the body in a spiral, creating cross sectional images of body
able to detect small abdominal areas with precision
Helical CT
patient transported continuously through gantry while data are acquired during sevral 360 scans
Axial (CT view)
top to bottom
Coronal (CT view)
front to back
Sagital (CT view)
side to side
When to use CT… (5)
1) Rule out stroke (non contrast headCT)
2) detect internal injuries and bleeding
3) Diagnose bone disorders such as bone tumors and fractures
4) detect and monitor diseases and conditions such as cancer, heart disease, lung nodules, and lung masses
5) guide procedures such a sx, bx, and radiation therapy
Advantage of CT (5)
Readily available
Quick and painless
Shows bone changes better than any other method
only method to provide detailed images of bone, soft, tissue, and blood vessles
Can detect life threatening conditions
Disadvantage of CT (6)
exposure to radiation, allergies to contrast materials, more expensive than x ray, misinterpreted test results, limitations, unsuitable for pregnant women (unless dire situation)
***CT radiation exposure known to have enough radiation to increase cancer risks
MRI
Magnetic field used to align H protons in body
Radio frequency waves absorbed by protons and emitted as a signal
radio frequency currency coil picks up the signal and transmit it
computer processes data and an image is generated
MRI safety
MAGNET ALWAYS ON
- all implants must be checked before entering MRI
- patients with pacemakers and coclear implants must not have MRI or even enter room
- Medication pathced can cause burns
- ALL foreign objects must be checked by a tech