General radiology

Question 1

What is CT?

Answer 1

Computed tomography- produces cross-sectional images by scanning a slice of tissue from multiple directions using a fan X-ray beam

Question 2

How do we described white and dark on CT? What does it mean in terms of x-ray absorption?

Answer 2

increased attenuation/hyperdensity= white (more X rays absorbed)Decreased attenuation/hypodensity= dark (less X rays absorbed)

Question 3

Axial scan orientations for CT?

Answer 3

imagine you are looking up from the feet. So the right hand side of the image is often the left of the patient

Question 4

What are the Houston units for bone, haemorrhage, water and air?

Answer 4

Bone >500Haemorrhage +50-80Water= 0Air= -1000

Question 5

What is windowing in CT?

Answer 5

We can select certain tissues/fluids etc on the image by selecting the housten units. for example, if you wanted to see just soft tissue, then you would set the HU to +40

Question 6

What contrast agents are used for CT?

Answer 6

positive agents that include iodine and barium

Question 7

What are some advantages of CT?

Answer 7

good resolution and quick to perform

Question 8

What are some disadvantages of CT?

Answer 8

high radiation dose and adverse SE to contrast

Question 9

How do we know that contrast has been delivered?

Answer 9

when blood vessels appear more dense (whiter) than muscle or brain

Question 10

If we wanted to see an arterial phase or venous phase- after contrast has been delivered, how would we see this on CT scan?

Answer 10

After contrast is injected, it would go through the arteries first–> use early scans, then go to the veins next–> see later scans.

Question 11

What does anechoic mean on U/s? what substances lead to this?

Answer 11

dark- fluids like blood, bile, urine

Question 12

What does echogenic mean on U/s? what substances are echogenic?

Answer 12

bright. fat, connective tissue etc.

Question 13

What are U/s usually used for?

Answer 13

gallbladder (looking for stones), liver, obstretrics etc

Question 14

What is a doppler u/s used for?

Answer 14

looking at blood flow

Question 15

What is a hot spot?

Answer 15

focal area of increased isotope uptake–> darker

Question 16

What are radioisotope imaging used for?

Answer 16

bone scans (reflects OB activity), thyroid scans and lung scans (V/q)

Question 17

What do we use PET for?

Answer 17

PET used for detecting tumours and staging cancer. It is capable of demonstrating metabolic activity and function to a much greater extent than the modalities.

Question 18

What are the most common applications of MRI?

Answer 18

CNS, spine, musculoskeletal

Question 19

Difference between T1 T2 weight?

Answer 19

T2= fluid is bright (CSF, bile, urine)

Question 20

what is flair MRI?

Answer 20

T2 image but CSF is nullified

Question 21

How do we describe increased whiteness or blackness on a MRI?

Answer 21

hyper intensity and hypointensity respectively

Question 22

What contrast is used in MRI contrast?

Answer 22

Gadolinium

Question 23

What do we use DWI MRI for?

Answer 23

looking at ischaemic stroke and abscesses

Question 24

What is MRA?

Answer 24

looking at angiography and flow of blood

Question 25

MRCP?

Answer 25

MRI imaging of biliary system and pancreatic ducts. Less risky than ERCP

Question 26

What is a danger of contrast administration in MRi?

Answer 26

Nephogenic systemic fibrosis in renal impaired individuals

Question 27

Advantages of MRI?

Answer 27

no radiation, high resolution, superior soft tissue contrast than CT, does not need contrast for angiography/cholangiography.