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Clinical Medicine > Bone Scans > Flashcards

Bone Scans Flashcards

1
Q

What does a DEXA scan measure?

A

bone mineral density (bone mass)

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2
Q

What is considered the gold standard of bone scans for patients with suspected osteoporosis?

A

DEXA

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3
Q

Osteoporosis =

A

decreased osteoblastic activity + increased osteoclastic activity

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4
Q

Osteoblastic

A

formation of bone

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5
Q

Osteoclastic

A

resorption of bone

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6
Q

Is osteoporosis an increase or decrease in total bone mass or density?

A

decrease

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7
Q

What does osteoporosis increase the risk of?

A

fractrures

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8
Q

DEXA generates x-ray beams at which two different energy levels?

A

soft & bone tissue

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9
Q

Computer software reconstructs a DEXA scan to produce an image and quantifies the three components of total body composition? What are the three components on total body composition?

A
  1. bone mineral density
  2. total fat mass
  3. lean mass
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10
Q

What are the general recommendations for a DEXA scan?

A
  • females 65 y/o or older
  • males 70 y/o or older
  • fx sustained after age 50
  • female of menopausal age w/risk factors
  • post-menopausal female under 65 w/risk factors
  • male 50-69 w/risk factors
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11
Q

What is considered lean mass?

A

muscle, water, proteins & internal organs

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12
Q

What are common areas for DEXA imaging?

A
  • hip
  • heel
  • lower back
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13
Q

What two computed scores are given to patients in their DEXA report?

A

t-score & z-score

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14
Q

T-score

A

a comparison of an individual’s bone density to that of an average, young, healthy adult

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15
Q

Z-score

A

compares the patient’s bone mineral density with that of an age-matched healthy adult

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16
Q

The ______ the density, the _________ the risk of the fracture.

A

lower, greater

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17
Q

What does a T-score greater than -2.5 indicate?

A

osteoporosis

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18
Q

What does a T-score between -2.5 to -1 indicate?

A

low bone density

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19
Q

What does a T-score greater than -1 indicate?

A

normal bone density

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20
Q

1 SD =

A

approx. 10% difference in bone mass

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21
Q

What does a standard deviation of 0 indicate?

A

does not deviate from the average

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22
Q

What does a standard deviation of +1 or +2 indicate?

A

bone mass is 10-20% above the average, young, healthy adult

23
Q

What does a standard deviation of -2 or -3 indicate?

A

bone mass is 20-30% below the average, young, healthy adult

24
Q

What does a Z-score greater than -2.0 indicate?

A

normal bone density

25
Q

What patient populations would one use the z-score instead of the t-score?

A
  • children
  • teens
  • women w/periods
  • younger men
26
Q

What is bone scintigraphy?

A

nuclear medicine imaging of the skeleton

27
Q

What is used in bone scintigraphy to diagnose disease?

A

radiopharmaceuticals

28
Q

What is bone scintigraphy based on?

A

physiological or functional changes of the skeletal tissue

29
Q

What are the two types of imaging that can be obtained from bone scintigraphy?

A

whole body & spot imaging

30
Q

What is whole body imaging helpful with?

A

non-focal complaints
- bony metastases
- diffuse arthralgia

31
Q

What is spot imaging helpful with?

A

focal complaints
- isolated stress fx
- unexplained rib pain
- indeterminate tumor on x-ray
- multiple projections

32
Q

Explain the science behind bone scientigraphy.

A
  • patient inject w/radioactive tracer
  • radioactive substance travels through the body & binds to sites of osteogenesis
  • radiation in substance is detected by a gamma camera in areas of increased blood flow & bone formation
33
Q

What are the four phases of bone scientigraphy?

A
  1. flow phase
  2. blood pool phase
  3. delayed phase
  4. fourth phase
34
Q

What is the timeframe for the flow phase?

A

60-90 secs post injection

35
Q

What are the results of the flow phase?

A
  • perfusion & tissue vascularity
  • blood flow to an area
36
Q

What is the time frame for the blood pool phase?

A

approx. 10 mins post injection

37
Q

What are the results of the blood pool phase?

A
  • blood pool
  • inflammation causes capillary dilation & increased blood flow
  • increased soft tissue activity
38
Q

What is the time frame for the delayed phase?

A

2-6 hours post injection

39
Q

What are the results of the delayed phase?

A
  • reflects rate of bone turnover
40
Q

What is osteogenesis?

A

nonspecific response of bone to range of stimuli such as
- physiological growth or rebuilding
- mechanical stress or injury
- infection or tumor

41
Q

Can you diagnose w/ a bone scan alone?

A

No - you should combine w/clinical exam & follow-up w/PCP

42
Q

On a bone scan, how does normal bone appear?

A

transparent & grey

43
Q

On a bone scan, how does abnormal bone appear?

A

darker black areas (radiotracer has been increasingly absorbed)

44
Q

What are normal bone scan findings?

A

symmetric uptake
- increase uptake in articular surfaces (shoulders, hips, knees, ankles, feet, etc.)
- areas closer to camera
- epiphyseal plates in children

45
Q

What are abnormal bone scan findings?

A
  • subtle fx
  • avascular necrosis
  • metabolic bone disease
  • occult fx
  • osseous metastatic tumors
  • infections
46
Q

On a bone scan, how do we differentiate between shin splints versus a stress fx?

A

shin splints = linear activity along tibial cortex

versus

stress fx = isolated hot spot

47
Q

What to keep in mind when considering an individual for bone scintigraphy?

A
  • requires adequate kidney function
  • requires adequate hydration
  • requires adequate injection into blood stream NOT soft tissue
48
Q

When do we typically utilize bone scintigraphy?

A

when patients are unable to communicate area of pain or discomfort

49
Q

Is bone scintigraphy best used as a sensitivity or specificity test? Why?

A

sensitivity - it provides us w/an early indicator of increased bone activity.

lacks specificity because we are unable to identify WHY the increased uptake has occurred

50
Q

What does a PET scan help visualize & measure?

A

normal vs. abnormal cellular function

51
Q

Why is a PET scan used?

A

it can obtain imaging of metabolism at a molecular level before the disease or condition appears

52
Q

What is a PET scan sometimes combined with?

A

CT or MRI

53
Q

What is the science behind a PET scan?

A
  • radioactive tracer via injection, inhalation, or swallowing
  • traces bound to carrier molecule
  • areas of body that normally absorb glucose absorb the tracer
  • tracer decays & emits positron that interacts w/electrons
  • releases gamma rays
  • detected by gamma camera
  • converted to 3D image
54
Q

In a PET scan, how do areas w/increased metabolic/chemical activity appear?

A

areas w/a high energy demand appear as “hot spots”

Clinical Medicine (5 decks)

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