Bone Densitometry Basics: Equipment

What type of technique does Dual energy x-ray absorptiometry use?

Subtraction Technique

What is the function of the subtraction technique in DXA?

Identify soft tissues and subtract them from the scan results to measure only bone mass

At ____ energy, attenuation of bone is greater than soft tissue

low

At ______ energy, attenuation of bone is similar to soft tissue

high

Thicker, more dense bones absorb _____ energy

more

Thinner more porous bone absorbs ______ energy

less

Scanners first appeared when?

1970s and early 1980s

What does SPA stand for?

Single Photon Absorptiometry

SPA used what to emulate soft tissue?

Water bath

SPA could only be used for what peripheral areas?

heel and wrist

DPA stands for what?

Dual Photon Absorptiometry

DPA used photons of two different energies using which two radiation sources?

Iodine-125 or Gadolinium-153

DPA established the concept of measuring what?

Axial Bone density

DPA produced what type of beam?

Tightly collimated beam

What was a major flaw of Dual Photon Absorptiometry?

Not precise enough to measure bone density changes

What is the equation for BMD?

BMD= BMC/Area

Scanners using xrays became available in what year?

1987

Xray tubes in new scanners replaced what in DPA?

Radioisotopes

GE and Norland Swissray use what to separate the two photon peaks?

K-edge filter

Hologic Uses what to separate the two photon peaks?

Energy-switching system

What are some advantages of using an x-ray tube over using isotope resources? (9)

1) Cost savings

2) Easier maintenance

3) Consistent results overtime

4) No source decay

5) Better collimation

6) Reduced patient dose

7) Imporved image resolution

8 ) Faster scan times

9) Better precision

An x-ray tube produces a beam with a wide range of photon energies, so it must be restricted to how many distinct photon peaks necessary for bone Densitometry?

2