Bone Scans (Final)

What are the results of the blood pool phase?

- BLOOD POOL - inflammation causes capillary dilation & increased BLOOD FLOW - INCREASED SOFT TISSUE ACTIVITY

When are z-scores indicated versus t-scores?

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

What are the limitations to a PET scan?

- limited spatial resolution - limited anatomical information - slow growing, less active tumors may not show up - RADIATION EXPOSURE IS HIGH - caution for diabetics

Explain the science behind bone scientigraphy.

- 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 - tracer is later excreted in the urine

What is the science behind a PET scan?

- 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

What are the results of the delayed phase?

- reflects rate of BONE TURNOVER

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

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

What are abnormal bone scan findings?

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

What are normal bone scan findings?

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

There are four imaging phases in bone scintigraphy. What are the first three?

1. flow 2. blood pool 3. delayed

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

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

What are the results of the flow phase?

- PERFUSION & tissue vascularity - BLOOD FLOW to an area

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

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

What is the time frame for the delayed phase?

2-6 hours post injection

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

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

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

soft & bone tissue

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

t-score & z-score

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

whole body & spot imaging

What is the timeframe for the flow phase?

60-90 secs post injection

What is a PET scan sometimes used in conjunction with?

CT or MRI

Can you diagnose w/ a bone scan alone?

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

What does a standard deviation of 0 indicate?

does not deviate from the average

What is spot imaging helpful with?

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

Osteoblastic

formation of bone

What does osteoporosis increase the risk of?

fractures

What is the time frame for the blood pool phase?

approx. 10 mins post injection

1 SD =

approx. 10% difference in bone mass

What are common areas for DEXA imaging? Why?

hip, heel, & lower back increased risk of fx in these areas for people with osteoporosis & bone density of hip and spine can predict the likelihood of fx's in other bones

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

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

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

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

What does a DEXA scan measure?

bone mineral density (bone mass)

T-score

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

Z-score

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

Why is a PET scan used?

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

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

low bone density

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

lower, greater

Osteoporosis =

metabolic bone disease characterized by decreased osteoblastic activity + increased osteoclastic activity

What is considered lean mass?

muscle, water, proteins & internal organs

What is whole body imaging helpful with?

non-focal complaints - bony metastases - diffuse arthralgia

What is osteogensis?

non-specific response of bone to range of stimuli - physiological growth or rebuilding - mechanical stress or injury - infection or tumor

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

normal bone density

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

normal bone density

What does a PET scan help visualize & measure?

normal vs. abnormal cellular function

PET scan

nuclear medicine imaging of specifically targeted tissues that uses radioactive tracer

What is bone scintigraphy?

nuclear medicine imaging of the skeleton

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

osteoporosis

What is bone scintigraphy based on?

physiological or functional changes of the skeletal tissue

What is used in bone scintigraphy to diagnose disease?

radiopharmaceuticals

Osteoclastic

resorption of bone

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

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

DEXA

specialized, non-invasive type of x-ray examination

On a bone scan, how does normal bone appear?

transparent & grey

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

DEXA

On a bone scan, how does abnormal bone appear?

darker black areas (radiotracer has been increasingly absorbed)

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

decrease

When do we typically utilize bone scintigraphy?

when patients are unable to communicate area of pain or discomfort