Radiology - Introduction to imaging modalities: CXR, US, and CT

Question 1

What causes the blackening of the fracture on an X-ray?

Answer 1

Air is mostly black on an X-ray, whereas bone will attenuate the X-ray

Question 2

What is an AP (anteroposterior) view?

Answer 2

The X–ray is entering the body from anterior to posterior

Question 5

Why do we need two X-rays when looking for pneumonia?

Answer 5

To localize the pneumonia (see which lung is affected)

Question 6

What is ground glass opacity?

Answer 6

A description of the appearance of the lung in cases of of vaping-associated lung disease or Covid-19 (greyish, not so sharp appearance)

Question 7

What are the advantages of using digital radiography?

Answer 7

• Allows magnification
• Better brightness and contrast
• Accessible to multiple sites
• Easier to teach with
• No lost films

Question 8

What is a serious disatvantage of digital radiography?

Answer 8

Serious confidentiality issues (because it is so accessible)

Question 9

What is fluoroscopy

Question 10

What is a CT scan

Answer 10

360 scan around he patient - allows reconstruction of internal structure of an object

Question 11

How does an ultrasound work? What is it usually used for?

Answer 11

When sound reaches a different density than the one it was traveling in, a number of sound waves will be reflected while others will continue. A medical US probe transmits sound waves and receives the reflected echoes. The image is formed by calculating the distance of reflection based on the time of travel of the sound waves

Question 12

What is the frequency of ultrasound, by definition?

Answer 12

Greater than 20,000 cycles per second

Question 13

Sound travels faster through…

Answer 13

dense objects
- solids (Fe 5,120 m/s0
- Liquids (water 1484 m/s)
- Air (340 m//s)
- Human soft tissues (1,540 m/s)

Question 14

What is an MRI?

Answer 14

Magnetic Resonance Imaging

Magnetic field is turned on, causing a small percentage of hydrogen atoms in the body to line up North-South

Then, radio-frequency force is applied, causing these atoms to turn by 90 degrees from North to South

Once this radio-frequency is turned off, they will return back to North-South at different rates based on the type of cell they are. In doing so, they also release energy, which is used to produce the MRI image.

Question 15

What is ionizing radiation?

Question 16

Where does the majority of background ionizing radiation come from?

Answer 16

Radon in the environment

Question 17

What are some sources of radiation other than radon?

Answer 17

cosmic rays
terrestrial sources
internal emissions

Question 18

What is an effective dose (radiation)

Answer 18

It is a dose corrected for the type of radiation and tissue sensitivity (expressed as Sieverts Sv)

Question 19

What is the risk of a CT scan?

Question 20

When requesting an X-ray, what should you ask yourself?

Answer 20

Ask yourself about risk vs benefit (because these tests can cause damage)

Which test is best (do it first instead of doing a bunch of tests)

Which test is most clinically appropriate?

How can I follow acceptable guidelines?

Question 23

“An abdominal helical CT scan in a young girl results in a risk of fatal cancer later in life that amount to about one in a thousand”. What does this mean?

Answer 23

?

Question 23

The data are not available to indicate if there is a threshold below which no harmful effect of ionising radiation will occur…

Answer 23

all ionising radiation is harmful!

Question 24

Lifetime radiation risk is greater for…?

Answer 24

children

Question 25

Is flying dangerous (due to increased exposure to radiation)?

Question 26

What is artificial intelligence?

Answer 26

AI refers to a field of computer science dedicated to the creation of systems performing tasks that usually require human intelligence.

Question 27

Can AI replace radiologists?

Answer 27

No. There is a very narrow target for any AI, either it MUST be perfect, or it will be supervised. A radiologist makes obscure, difficult calls all day long. AI will not replace radiologists, but it will be increasingly utilized BY radiologists.