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Flashcards in Intro to Radiology Deck (21)
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1

The choice of which modality to use depends on... (3)

The clinical question
The body part
Patients age and sex

2

2 modalities that
1. Use ionizing radiation
2. Do not use ionizing radiation

1. X-rays, CT
2. Ultrasound, MRI

3

3 general steps of imaging

1. Signal is projected at or through body tissue
2. Tissue changes signal (absorbs, reflects, etc)
3. Changed signal provides info which is used to construct an image

4

X-rays and CT scans map...

Tissue density

5

Higher density tissues in X ray are termed...

Radiodense

6

Lower density tissues in X ray are termed...

Radiolucent

7

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

8

Interventional radiology

Specialty of radiology where minor surgeries are guided by x-rays

9

3 strengths of X-rays

Relatively cheap
Readily available
Excellent bony detail

10

2 weaknesses of X-rays

Some ionizing radiation (although low)
Poor soft tissue detail

11

How does a CT scan work

Scanner rotates around the patient, taking multiple x-rays
Cross-sectional imaging
Can be reconstructed into different planes

12

4 strengths of CT

Excellent bone detail
Good soft tissue detail
Ability to see each anatomic structure in 3 planes
Avaliable

13

2 weaknesses of CT

More expensive than x-ray
Exposure to ionizing radiation

14

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

15

3 strengths of MRI

No exposure to ionizing radiation
Excellent soft tissue detail
Ability to see each anatomic structure in 3 planes

16

4 weaknesses of MRI

More expensive than CT
Not readily available
Takes longer to take the images
Uses a very strong magnet

17

3 types of contrast

For CT and MRI
Intravenous
Enteric
Intra-articular

18

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

19

4 strengths of ultrasound

No radiation
Relatively inexpensive
Real-time imaging
Portable

20

3 weaknesses of ultrasound

Operator dependent
Difficult in larger patients
Takes time

21

Imaging costs (from cheapest to most expensive)

X-ray
Ultrasound
CT
MRI