Bone Scans

Question 1

What does a DEXA scan measure?

Answer 1

bone mineral density (bone mass)

Question 2

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

Answer 2

DEXA

Question 3

Osteoporosis =

Answer 3

decreased osteoblastic activity + increased osteoclastic activity

Question 4

Osteoblastic

Answer 4

formation of bone

Question 5

Osteoclastic

Answer 5

resorption of bone

Question 6

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

Answer 6

decrease

Question 7

What does osteoporosis increase the risk of?

Answer 7

fractrures

Question 8

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

Answer 8

soft & bone tissue

Question 9

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?

Answer 9

1. bone mineral density
2. total fat mass
3. lean mass

Question 10

What are the general recommendations for a DEXA scan?

Answer 10

• 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

Question 11

What is considered lean mass?

Answer 11

muscle, water, proteins & internal organs

Question 12

What are common areas for DEXA imaging?

Answer 12

• hip
• heel
• lower back

Question 13

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

Answer 13

t-score & z-score

Question 14

T-score

Answer 14

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

Question 15

Z-score

Answer 15

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

Question 16

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

Answer 16

lower, greater

Question 17

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

Answer 17

osteoporosis

Question 18

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

Answer 18

low bone density

Question 19

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

Answer 19

normal bone density

Question 20

1 SD =

Answer 20

approx. 10% difference in bone mass

Question 21

What does a standard deviation of 0 indicate?

Answer 21

does not deviate from the average

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

normal bone density

Question 25

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

Answer 25

- children - teens - women w/periods - younger men

Question 26

What is bone scintigraphy?

Answer 26

nuclear medicine imaging of the skeleton

Question 27

What is used in bone scintigraphy to diagnose disease?

Answer 27

radiopharmaceuticals

Question 28

What is bone scintigraphy based on?

Answer 28

physiological or functional changes of the skeletal tissue

Question 29

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

Answer 29

whole body & spot imaging

Question 30

What is whole body imaging helpful with?

Answer 30

non-focal complaints - bony metastases - diffuse arthralgia

Question 31

What is spot imaging helpful with?

Answer 31

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

Question 32

Explain the science behind bone scientigraphy.

Answer 32

- 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

Question 33

What are the four phases of bone scientigraphy?

Answer 33

1. flow phase 2. blood pool phase 3. delayed phase 4. fourth phase

Question 34

What is the timeframe for the flow phase?

Answer 34

60-90 secs post injection

Question 35

What are the results of the flow phase?

Answer 35

- perfusion & tissue vascularity - blood flow to an area

Question 36

What is the time frame for the blood pool phase?

Answer 36

approx. 10 mins post injection

Question 37

What are the results of the blood pool phase?

Answer 37

- blood pool - inflammation causes capillary dilation & increased blood flow - increased soft tissue activity

Question 38

What is the time frame for the delayed phase?

Answer 38

2-6 hours post injection

Question 39

What are the results of the delayed phase?

Answer 39

- reflects rate of bone turnover

Question 40

What is osteogenesis?

Answer 40

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

Question 41

Can you diagnose w/ a bone scan alone?

Answer 41

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

Question 42

On a bone scan, how does normal bone appear?

Answer 42

transparent & grey

Question 43

On a bone scan, how does abnormal bone appear?

Answer 43

darker black areas (radiotracer has been increasingly absorbed)

Question 44

What are normal bone scan findings?

Answer 44

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

Question 45

What are abnormal bone scan findings?

Answer 45

- subtle fx - avascular necrosis - metabolic bone disease - occult fx - osseous metastatic tumors - infections

Question 46

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

Answer 46

shin splints = linear activity along tibial cortex versus stress fx = isolated hot spot

Question 47

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

Answer 47

- requires adequate kidney function - requires adequate hydration - requires adequate injection into blood stream NOT soft tissue

Question 48

When do we typically utilize bone scintigraphy?

Answer 48

when patients are unable to communicate area of pain or discomfort

Question 49

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

Answer 49

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

Question 50

What does a PET scan help visualize & measure?

Answer 50

normal vs. abnormal cellular function

Question 51

Why is a PET scan used?

Answer 51

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

Question 52

What is a PET scan sometimes combined with?

Answer 52

CT or MRI

Question 53

What is the science behind a PET scan?

Answer 53

- 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

Question 54

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

Answer 54

areas w/a high energy demand appear as "hot spots"