Intro to Radiology Flashcards
The choice of which modality to use depends on… (3)
The clinical question
The body part
Patients age and sex
2 modalities that
- Use ionizing radiation
- Do not use ionizing radiation
- X-rays, CT
2. Ultrasound, MRI
3 general steps of imaging
- Signal is projected at or through body tissue
- Tissue changes signal (absorbs, reflects, etc)
- Changed signal provides info which is used to construct an image
X-rays and CT scans map…
Tissue density
Higher density tissues in X ray are termed…
Radiodense
Lower density tissues in X ray are termed…
Radiolucent
Fluoroscopy
Special type of X ray
Makes a movie rather than a picture
Black and white are reversed!
Can be used to show physiological processes like swallowing
Interventional radiology
Specialty of radiology where minor surgeries are guided by x-rays
3 strengths of X-rays
Relatively cheap
Readily available
Excellent bony detail
2 weaknesses of X-rays
Some ionizing radiation (although low)
Poor soft tissue detail
How does a CT scan work
Scanner rotates around the patient, taking multiple x-rays
Cross-sectional imaging
Can be reconstructed into different planes
4 strengths of CT
Excellent bone detail
Good soft tissue detail
Ability to see each anatomic structure in 3 planes
Avaliable
2 weaknesses of CT
More expensive than x-ray
Exposure to ionizing radiation
Basic principle of MRI
No ionizing radiation
Patient placed in a magnetic field
External low energy applied to the patient
Each tissue absorbs and releases the energy at different, detectable, and characteristic rates
Image acquisition is multi-planar
3 strengths of MRI
No exposure to ionizing radiation
Excellent soft tissue detail
Ability to see each anatomic structure in 3 planes
4 weaknesses of MRI
More expensive than CT
Not readily available
Takes longer to take the images
Uses a very strong magnet
3 types of contrast
For CT and MRI
Intravenous
Enteric
Intra-articular
Ultrasound
Uses high frequency sound waves
Probe receives echoes from tissue interfaces in the body
Sound reflected by body structures is converted to an image
4 strengths of ultrasound
No radiation
Relatively inexpensive
Real-time imaging
Portable
3 weaknesses of ultrasound
Operator dependent
Difficult in larger patients
Takes time
Imaging costs (from cheapest to most expensive)
X-ray
Ultrasound
CT
MRI
