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MSK Test 2 Extra > Introduction to Medical Imaging > Flashcards

Introduction to Medical Imaging Flashcards

1
Q

How do X-Rays work?

A

Photons from tungsten target pass through body to expose the recording plate

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2
Q

X-Ray Rule:

Greater the absorption of photons by tissues, the …

A

Whiter the density will appear

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3
Q

On an x ray __ will appear white

A

Bones

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4
Q

On an x-ray ___ will have intermediate density

A

Soft tissues and water

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5
Q

The greater thickness of bone or soft tissue on an X-ray, the ___ density

A

Whiter

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6
Q

What is an AP Plain film radiograph?

What is closer to recording plate?

A

AP: Anteroposterior
goes from front to back

-back is closer to plate
So heart is farther away = enlarged

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7
Q

What is a PA Plain film radiograph?

What is closer to the recording plate?

A

PA: Posteroanterior
Goes from back to front

-front is closer to recording plate so heart is closer = normal size heart

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8
Q

If you want to keep an organ the right size, where would you put the plate?

A

Closer to the plate

I.e. Use AP view for kidneys

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9
Q

What is fluoroscopy?

A

Real time x-ray imaging
Shows movement of structure in real time
-has c arm so the whole apparatus can be rotated to give 3D info

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10
Q

When would you use fluoroscopy?

A

Is used for barium contrast studies of GI, variety of Angiographic, catheter and tube placement, fracture repair adn apparatus placement in ortho surgery

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11
Q

How many frames are taken per second for a peripheral vascular study using fluoroscopy?

A

2 to 3 frames/second

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12
Q

How many frames are taken per second for a coronary artery studies?

A

15-30 frames per second

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13
Q

What is Digital Subtraction Angiography (DSA)?

A

Form of fluoroscopy (real time x rays)
Tissues and structures not of interest = digitally subtracted
Allows for better imaging of vessels

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14
Q

What is DSA used for?

A

For diagnostics like balloon angioplasty, stent placement, guiding catheter placement

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15
Q

What is the downside of DSA?

A

Invasive bc artery must be entered percutaneously

(Unlike CTA and MRA which are relatively noninvasive procedures that only require IV catheter in arm vein for contrast injection)

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16
Q

What is an upside to DSA?

A

Quicker than an MR study

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17
Q

How does CT work? (Basic)

A

Patient slides thru a donut, x rays pass thru patient ina helical fashion and are detected on opposite side of tube
Algorithm reconstructs in 3D image

Grayscale image can be manipulated on monitor as well

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18
Q

What are the advantages and disadvantages to CT?

A

Quick, motion not a problem, gray scale can be manipulated, resolution excellent, widely available and cheaper than MRI

Disadvantages: uses ionizing radiation, must evaluate renal function if contrast used, allergy to iodine contrast

19
Q

What is the hounsfield scale?

What is middle gray? Scale for middle gray?

What is window width

A

Scale for CT

Window level; -1000 to +3095

Range of gray so-called mapped onto housnfield scale

20
Q

The narrower the width the ___ the contrast

A

Higher

21
Q

If the CT is ABOVE the window width image will appear ____

A

White

22
Q

If the CT is BELOW the window width, the image will appear ___

A

Black

23
Q

you would use a narrow window width for __

A

Soft tissue

24
Q

You would use a wide window width for __

A

Bone

25
Q

What is the window level and width for Lungs?

A 
Level = -550
Width = 1600
26
Q

What is the window level and width for soft tissue?

A 
Level = 70
Width = 450
27
Q

What is the window level and width for bone?

A 
level = 570
Width = 3077
28
Q

If you wanted more contrast and not as much detail on a CT, what would you do to the width?

A

Make it narrower

will give more contrast and not as much detail

29
Q

Does a MRI use Ionizing radiation?

A

No

30
Q

How doe an MRI work?

A

Big magnet that atoms will align with
It will hit tissues with radio frequency so they all go out of alignment
Then relaxation time occurs where they all eat back into alignment

Depending on density of tissues, return to realignment will occur at a different rate

Different rate of return = different gray scale in image

31
Q

What is the difference between T1 and T2 weighted MRIs?

How will fluid appear in each?

A

T1= longitudinal relaxation time = fluid is dark

T2 = transverse relaxation time = fluid is light

32
Q

What are the advantages and disadvantages to MR?

A

Advantages: no ionizing radiation, better soft tissue contrast than CT, extremely versatile

Disadvantages: longer time for sequencing, more expensive, images cannot be manipulated on viewing screen, narrow matching (claustrophobia), no metal in body, no gadolinium contrast with pregnant women, increased risk for NSF in those with renal dysfunction, noisy

33
Q

What will give more depth in an angiography study? CT or MR?

A

CT

34
Q

What is nuclear medicine?

A

Radioactive molecules attached to other compounds to form radiopharmaceuticals.
Administered orally or intravenously
Designed to bind or be uptakes by specific cells in specific organs (esp. highly metabolic cells, i.e. CANCER)
Detector used to look at hot spots

35
Q

What is one application of nuclear medicine?

A

look at breast cancer

36
Q

What is an ultrasound?

A

A non invasive imaging technique using sound waves that echo back after being reflected from tissue interfaces within the body

37
Q

When would you use a high frequency on an Ultrasound?

A

to visualize structures near the surface

I.e. neck vessels, thyroid gland, breasts, and testes

38
Q

When would you use a low frequency on an Ultrasound?

A

Will have greater penetrating power, can image deeper structures in abdomen and pelvis

39
Q

How does air show up on an ultrasound?

A

Black

40
Q

What are the benefits to using ultrasound?

A

Low risk, portable, good for emergency situations, cheap

41
Q

What is barium sulfate used to visualize as a contrast agent?

A

Hollow organs

I.e. for upper Gi study, colon study

42
Q

What is iodine compounds used to visualize as a contrast agent?

A

Vessels (angiography)

I.e. for celiac arteriogram, hysterosalpingogram

43
Q

What kinds of contrast agents does MR use?

A 
Intravenous gadolinium 
oral agents (juice, H2O)

MSK Test 2 Extra (5 decks)

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