2b. MRI - Head Radiology

Question 1

what are the 7 advantages of MRI

Answer 1

no ionizing radiation
versatile with multiple modes/sequence types
good for prenatal brain
contrast can be manipulated
acute ischaemia demonstrated ealy when CT is normal
Angiography with/without contrast
multiplanar

Question 2

what are the 8 disadvantages of MRI

Answer 2

long acquisition time (10-120min)
poorer access
expensive
motion sensitive
need high level of expertise to acquire
complex examinations = substantial post-processing times
safety issues
artifacts from metals

Question 3

what is the safety concern for MRI

Answer 3

magnet on all the time and metal objects near it could be turned into a projectile

Question 4

how does the MRI work in terms of the nuclei

Answer 4

body placed in powerful magnetic field and some proton nuclei align with direction of field and act as tiny bar magnets

Question 5

how does the MRI work in terms of how the radiofrequency pulse is applied and what results from this

Answer 5

radiofrequency pulse is applied perp to main field which flips direction of aligned nuclei

Question 6

how does the MRI work in terms of what happens once the RF pulse is removed

Answer 6

nuclei realign with the main magnetic field and lose energy as they do so and they emit their own signal

Question 7

what 2 factors vary the signal produced by the nuclei in MRI

Answer 7

tissue type

pulse sequence used

Question 8

what can be done to the energy produced in MRI production

Answer 8

energy manipulated and collected in a number of ways resulting in designed image contrast/info

Question 9

what are the 2 most basic types of MRI sequences

Answer 9

T1 weighted and T2 weighted

Question 10

what is CSF and fat intensity on T1 MRI

Answer 10

CSF = hypointense (dark)
fat = hyper intense (bright)

Question 11

what is CSF and fat intensity on T2 MRI

Answer 11

CSF = hyperintense (bright)
fat =  hypointense (dark)

Question 12

after administering contrast the areas with compromised BBB does what on T1W imaging

Answer 12

it enhances

Question 13

what does bone look like in terms of intensity MRI

why is it like that

Answer 13

bone is black as it has few mobile protons and so not much signal

Question 14

what does scalp look like in terms of intensity MRI

why is it like that

Answer 14

scalp is bright and white as its high signal from the fat etc

Question 15

what does eyeball look like in terms of intensity MRI

Answer 15

eyeball is bright and white as its high signal

Question 16

malignant tumors in MRI has what intensity for the rim and what does the border look like

Answer 16

enhancing from contrast so is bright

rim is irregular

Question 17

tumor is always affected by contrast in which MRI T type

Answer 17

always affected by contrast in T1

not T2

Question 18

what does multiple metastases look like in MRI

Answer 18

multiple lesions and enhanced with contrast media and lot of oedema around them

Question 19

if the MRI image looks like metastases but weren’t metastases or cancer what else could it be

Answer 19

infection due to bacteria/fungi/parasite

Question 20

what can you see in DWI MRI imaging

Answer 20

get sequences from MRI and process in different ways to get different info out of it

can see direction of nerve fibres and produce white matter tract maps using DWI data

Question 21

what is DWI MRI imaging

Answer 21

diffusion west image

Question 22

within mins of a stroke the DWI signal is bright due to what reason

Answer 22

restriction of movement of water out of the cell caused by cytotoxic oedema

Question 23

what 3 feature identifies abscesses on MRI

Answer 23

enhancing round lesion

uniform rim

Question 24

what does meningitis look like on a MRI T1

how enhancing is it and why

Answer 24

Lots of bright areas in the brain and basal cisterns is where blood goes if you have a subarachnoid haemorrhage

Meninges have swollen and lots of leaky blood vessels so enhancing with contrast agent -> hugely enhancing

Question 25

what does tapeworm look like on a MRI in terms of appearance and location

Answer 25

Multiple bilateral lesions throughout all lobes of brain and also in soft tissues

Very extensive , at least 50% of brain is replaced by cysts by tape worm and in other soft tissue of body

Question 26

what does TB look like in a T1&2W MRI image and what features signify it in the image

2 features

Answer 26

Vertebral body destroyed

anterior collection of fluid - pus with Tb bacteria in it

Question 27

when TB in the spine is more advanced you get what to the spine and what is this called

Answer 27

When its more advance you get angulation of spine due to collapse of vertebrae - gibous

Question 28

what does multiple sclerosis look like on a MRI in terms of appearance

Answer 28

enhancing lesions in the brain

Question 29

what does Alzheimer’s look like on a MRI in terms of appearance and location

3 features

Answer 29

gross atrophy in brain (could be global/whole brain)

reduced tissue and ventricles are huge

could have focal tissue loss in hippocampus

Question 30

what does functional MRI do and what is it useful for

Answer 30

locates brain activity

useful for surgical planning

Question 31

what can be demonstrated and done with anatomy with FMRI for surgical planning

Answer 31

reconstruction from MRI and functional activation

demonstrates location of tumor in relation to cortex responsible for hand and foot control (ie can tell if remove tumor from this location in cortex, could lead to loss of hand/foot function)

Question 32

what is the difference between the machine appearance for MRI and CT

Answer 32

CT is like a donut

MRI head coil is longer

Question 33

is CT or MRI better for stroke imaging

Answer 33

MRI

Question 34

is CT or MRI better for tumor imaging

Answer 34

MRI

Question 35

is CT or MRI better for bony reconstruction

Answer 35

CT

Question 36

is CT or MRI better for angiography

Answer 36

MRI (doesnt need contrast) or CT (needs contrast)