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MSK Exam I > Lecture 2: Intro To Medical Imaging > Flashcards

Lecture 2: Intro To Medical Imaging Flashcards

1
Q

What type of imaging uses photons that pass through the body to expose the recording plate?

A

X-rays

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2
Q

With x-rays, the greater the exposure, the ________ the density

A

Darker

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3
Q

With X-rays, the greater the absorption of the photons, the _______ the density

A

Lighter

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4
Q

How will organs, bones, soft tissue, and water appear on an x-ray?

A

Organs with air appear dark

Bones appear white

Soft tissues and water have intermediate density

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5
Q

What are 2 very important concepts to consider while examining an x-ray?

A

Plane of view

Orientation

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6
Q

The __________ view of a CXR shows magnification of the heart and mediastinum, so the ___________ view is preferred

A

Anteroposterior (AP)

Posteroanterior (PA)

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7
Q

What type of imaging uses a continuous stream of x-rays to view movement in real time?

A

Fluoroscopy

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8
Q

With fluoroscopy, the x-ray source is _______ the patient, and the data capture equipment are ______

[above/below?]

A

Below; above

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9
Q

What type of imaging uses x-ray images generated as the patient moves through a rotating x-ray tube while detectors on the opposite side collect the passing rays?

A

Computed tomography (CT)

[Multi-detector computed tomography]

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10
Q

With CT scans, mathematical algorithins are used to reconstruct _____ images of the body from the data collected.

Images in the ______ and _____ planes and renderings are reconstructed by computer from the serial slices

The gray-scale image can then be manipulated by the monitor

A

Axial

Sagittal; coronal

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11
Q

How is CT density measured?

A

Hounsfield scale

Density of water is 0
Density of air is ~1000
Compact bone is +3095
Soft tissues between -100 and 100

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12
Q

Why is it a potential problem with CT that the monitors only show 256 levels of gray?

A

Only a portion of the Hounsfield scale can be displayed; this window can be adjusted

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13
Q

A Hounsfield scale set to middle gray is referred to as the ______ ______; the range of gray scale mapped onto the Hounsfield scale is called the ______ ______

A

Window level; window width

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14
Q

CT numbers below the window with display as _______; CT numbers above the window width are _______

A _____ window width is good for imaging bone

A ______ window is better for soft tissue

A

Black; white

Wide

Narrow

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15
Q

What are some advantages to CT imaging in terms of time and motion?

A

Very quick (a few seconds for whole-body imaging)

Motion is not as much of a problem as things like simple x-ray

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16
Q

What are some advantages to CT in terms of ability to manipulate, degree of resolution, and availability?

A

Gray scale can be manipulated from viewing screen

Resolution excellent for many areas

Widely available and cheaper than MRI

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17
Q

What are some disadvantages to CT imaging in terms of patient risk?

A

Uses ionizing radiation

Renal function may be affected by contrast

Some patients are allergic to iodine contrast

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18
Q

What are the 2 most common contrast agents used in CT imaging?

A

Barium sulfate (administered orally or rectally)

Iodine compounds (administered IV)

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19
Q

What type of imaging relies on application of a strong magnetic field and pulse radio waves to knock nuclear spin of atoms out of alignment?

A

MRI (Magnetic Resonance Imaging)

20
Q

What type of contrast agents are often used with MRI?

A

IV gadolinium

Oral agents (juice, H2O)

21
Q

How does MRI technology generate an image?

A

When pulse waves knock nuclear spins out of alignment, atoms return to equilibrium and radiofrequency energy emitted is measured in a receiver coil to create images

Tissues have different relaxation times depending on water content and composition

22
Q

Almost any tissue can be viewed by MRI by varying magnetic ________ and ________ strengths

A

Gradients; pulse

23
Q

How would the items listed below appear on a T-1 weighted MRI image:

Tumor
Inflammation
Infection
Hemorrhage

A

Dark

24
Q

How would the items listed below appear on a T-2 weighted image:

Increased water, as in edema
Tumor
Inflammation
Infection
Subdural collection
A

Bright

25
Q

How would the items listed below appear on a T-1 weighted image:

Fat
Subacute hemorrhage
Melanin
Protein-rich fluid
Slowly flowing blood
A

Bright

26
Q

How would the following appear on a T2-weighted MRI image:

Calcification
Fibrous tissue
Protein rich fluid

A

Dark

27
Q

What are some advantages to MRI, especially as compared with CT, imaging?

A

No ionizing radiation

Better soft tissue contrast than CT

Extremely versatile: variety of pulse sequences can be used for visualizing specific tissues and pathology

28
Q

What are some disadvantages to MRI imaging in terms of time, cost, and ability to manipulate images?

A

Longer time for sequences (many minutes)

More expensive

Images cannot be manipulated on the viewing screen like CT windows; parameters must be set before each scan

29
Q

What are some disadvantages to MRI in terms of patient comfort and safety?

A

Gantry is narroer than CT - worse for claustrophobic patients

Gadolinium constrast risky for pregnant women or patients with renal dysfunction (risk of nephrogenic systemic fibrosis)

Noisy

30
Q

How would bone appear on a CT soft tissue window vs. a T1 weighted MRI (both without contrast)?

A

White on CT

Dark on MRI

31
Q

What are T2 weighted MRIs most useful for?

A

Detecting pathological process that have fluid accumulation (e.g., edema)

CSF will appear white

32
Q

What imaging method measures physiological (functional) activity rather than anatomy and involves radioactive molecules attached to other compounds to form radiopharmaceuticals administered orally or IV designed to be taken up by specific cells?

A

Nuclear medicine

33
Q

With nuclear medicine, what records the degree of radioactivity and what detects the pathology?

A

An external gamma camera

Pathology detected by identifying focal areas of various activity (hot spots/cold spots)

34
Q

Nuclear medicine images can be superimposed on ____ or _____ images to combine functional and anatomical information

A

CT; MR

35
Q

Where would you always expect to see spots on a nuclear medicine image?

A

In the kidneys and bladder, because this is how the contrast is excreted

36
Q

What type of imaging is based on “pulse-echo” sound wave energy using a transducer that emits pulses of sound and functions as a receiver?

A

Ultrasound

37
Q

What is the difference between high-frequency and low-frequency transducers in terms of what they visualize?

A

High-frequency visualize structures near the surface

Low-frequency have greater penetrating power but lower resolution; used for deeper structures

38
Q

T/F: Ultrasound is a good method for visualizing air and tissues deep to bone

A

False

39
Q

What type of ultrasound can visualize and measure blood flow?

A

Doppler ultrasound

40
Q

What are some advantages to ultrasound technology?

A

Portable

Relatively inexpensive

No ionizing radiation

Good at capturing motion

41
Q

What type of imaging is a form a fluoroscopy involving the rapid series of x-rays viewed in real time?

A

Digital Subtraction (DS) Angiography

[images taken before contrast injection is used to digitally “subtract” bones and other tissues from the view after contrast is administered]

42
Q

What is the biggest disadvantage associated with DS Angiography?

A

It is an invasive procedure requiring access to arteries with some methods requiring use of an IV catheter for contrast injection

43
Q

What is the difference between CT and MRI angiography?

A

CT angiography shows depth perspective because image can be manipulated

MRI angiography shows maximum intensity projection, and depth perspective can only be obtained by rotating the view

44
Q

What type of imaging detects changes in blood oxygenation and flow?

A

Functional MRI (fMRI)

45
Q

What is functional MRI (fMRI) often used for?

A

Producing activation maps of the brain; more active brain areas have increased blood flow

46
Q

With functional MRI, hemoglobin is ____________ when oxygenated, but ____________ when deoxygenated; this difference leads to small differences in MR signal

A

Diamagnetic; paramagnetic

47
Q

Where would you expect to see cortical activity on an fMRI in a person using their right hand?

A

Left postcentral gyrus (somatosensory)

Frontal lobe (primary motor)

MSK Exam I (18 decks)

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