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Flashcards in Imaging Deck (18)
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1
Q

What are benefits and features of T1 weighted MRI of the brain?

A

Good for anatomy, fluid has a dark signal intensity, white matter is brighter than gray matter

2
Q

What are benefits and features of T2 weighted MRI of the brain?

A

Good for pathology, fluid has a bright signal intensity, gray matter is brighter than white matter, and Gas, calcium, ferromagnetic particles, and flow show up dark

3
Q

What is the benefit of using T2 weighted FLAIR sequences?

A

Good for looking for cerebral edema (CSF appears dark, but edema will show up white)

4
Q

What is diffusion weighted imaging (DWI) on MRI used for?

A

To look for cell death (areas of cell death appear whiter due to cellular edema and diffusion restriction) - it is the most sensitive imaging modality for detection of acute ischemia (can detect within 15-30 minutes of the insult)

5
Q

At what point does Acute ischemic stroke become conspicuous on CT?

A

6-8 hours

6
Q

What is the best screening tool for brain aneurysms?

A

MR angiogram

7
Q

How is cavernous sinus thrombosis diagnosed?

A

MRI (with gadolinium and MR venography), or can also be diagnosed with CT angiography and CT venography

8
Q

Why does myelin show up white on T1 weighted MRI?

A

Because fat shows up bright

9
Q

How do the time to echo (TE) and time to repetition (TR) differ on T1 and T2 weighted MRIs?

A

T1: short TE and TR
T2: long TE and TR
(TE is the time interval that signal intensity is measured following radiofrequency (RF) pulses. TR is the time between RF pulses)

10
Q

What does contrast enhancement indicate?

A

A breakdown in the BBB (may be due to areas of inflammation, infection, or tumor)

11
Q

What areas of the brain is MRI especially useful for imaging over CT?

A

The posterior fossa and the craniocervical junction due to artifact from surrounding bone on CT

12
Q

How does the nephrotoxicity of CT iodinated contrast agents compare with gadolinium for MRI?

A

Iodinated agents are more nephrotoxic

13
Q

What is the imaging modality of choice for acute intracranial bleed?

A

CT without contrast

14
Q

How does MR angiography compare with conventional angiography?

A

MRA uses blood flow as a contrast agent, whereas angiography uses contrast dye. MRA is also less invasive and can be performed more quickly and less expensively, but it is less sensitive and specific

15
Q

Where is hypometabolism seen on FDG-PET scans of patients with Alzheimer’s?

A

The temporal and parietal lobes

16
Q

Where is hypometabolism seen on FDG-PET scans of patients with frontotemporal dementia?

A

The frontal and temporal lobes

17
Q

Where is hypometabolism seen on FDG-PET scans of patients with dementia with Lewy bodies?

A

The occipital region

18
Q

What MRI technique is most sensitive for detecting blood breakdown products?

A

Susceptibility or gradient-echo imaging