DEXA

A normal BMD is

-1 or greater

Why does a patient require a DEXA scan?

-Assess risk of fractures, to decide whether therapy is needed. -Tracking effects of treatment

Advantages of DEXA

-Cheap -Low radiation dose -More sensitive and accurate at measuring the subtle changes in BMD over time

List the risk factors for osteoporosis

-Female sex -Advanced age -Estrogen deficiency -Caucasian race -Low bodyweight/BMI -F hx of osteoporosis -Smoking -Hx of # as an adult -Low calcium -Inadequate PA -Glucocorticosteriod use

How long are DEXA scans?

Spine- 1 min Hip- 2 mins Total body- 4 mins

What two things (equipment wise) constantly switch during a BMD exam?

kV and filtration

How much radiation exposure does a patient receive for a BMD?

About 1/3 of that of a CXR

Define T score

A measure of how dense a patient's bone is, compared with a normal, healthy 30 year old of the same sex

Define Z score

A measure of how dense a patient's bone is, compared with a person of the same age, sex and race

What type of radiation is used?

A single energy x-ray used with two different filters

BMD correlates with what?

Bone strength and ability to bear weight

Define osteopenia

Low BMD, but not as severe as osteoporosis.

Define osteoporosis

Low BMD. Bones become brittle, fragile and more prone to fractures

What does DEXA measure?

Patient's bone mineral density (BMD). Demonstrates the attenuation differences between bone and soft tissue

What is one positioning feature of DEXA?

Patient's lower limbs need to be rotated 15-20 degrees internally

What type of x-ray beam is used?

Pencil beam

An osteopenia BMD is

-1 to -2.5

An osteoporotic BMD is

-2.5 or less

What two things can make someone estrogen deficient?

1. Early menopause (<45 years) 2. Prolonged premenopausal amenorrhea (>1 year)

DEXA stands for

Dual Energy X-ray Absorptiometry

Define BMD

The absolute amount of bone as measured by BMD.