ISCD CBDT - Fundamentals Exam With Questions And 100%
Correct Answers
Central Devices
- Types
- What do they measure? - Answer Two x-ray based technologies: DXA and QCT
(quantitative computed tomography)
Measures hip and spine (DXA may also measure forearm and total body)
Peripheral Devices
- Types
- What do they measures? - Answer Two primary technologies: X-ray and Ultrasound
Peripheral DXA (pDXA), Single x-ray absorptiometry (SXA), Quantitative ultrasound
(QUS), Radiographic absorption (RA), Peripheral QCT (pQCT)
Measures phalanges, metacarpals, forearm, or calcaneus
Pros of peripheral DXA - Answer Smaller devices, more portable, less radiation, shorter
scan times, easier to operate, less expensive
Cons of peripheral DXA - Answer May miss early bone loss, no agreement for the
threshold BMDs that should be used to classify patients
Attenuation
- What is it?
, - Determined by
- Allows for what to be measured - Answer The reduction in the number and energy of
photons in an x-ray beam (it's intensity)
Determined by the tissue density and thickness
Allows for tissue density to be measured
At low energy (30-50 keV), bone attenuation is _______ than that of soft tissue - Answer
greater
At high energy (>70 keV), bone attenuation is ______ than that of soft tissue - Answer
about the same
Principle behind DXA: Absorptiometry - Answer The denser the tissue, the more
electrons it contains
Denser material attenuates more photons in the x-ray beam and the beam is weaker
What use dual energy x-rays? (3) - Answer Bone and soft tissue are differentially
absorbed (eliminates the need for uniform object thickness)
Allows you to suppress the impact of overlying soft tissue
Partially corrects for presence of varying amount of fat
Why are BMD results from different manufacturers not comparable? (5) - Answer There
are two different approaches to producing dual-energies (filtered x-ray and switched
x-ray)
Correct Answers
Central Devices
- Types
- What do they measure? - Answer Two x-ray based technologies: DXA and QCT
(quantitative computed tomography)
Measures hip and spine (DXA may also measure forearm and total body)
Peripheral Devices
- Types
- What do they measures? - Answer Two primary technologies: X-ray and Ultrasound
Peripheral DXA (pDXA), Single x-ray absorptiometry (SXA), Quantitative ultrasound
(QUS), Radiographic absorption (RA), Peripheral QCT (pQCT)
Measures phalanges, metacarpals, forearm, or calcaneus
Pros of peripheral DXA - Answer Smaller devices, more portable, less radiation, shorter
scan times, easier to operate, less expensive
Cons of peripheral DXA - Answer May miss early bone loss, no agreement for the
threshold BMDs that should be used to classify patients
Attenuation
- What is it?
, - Determined by
- Allows for what to be measured - Answer The reduction in the number and energy of
photons in an x-ray beam (it's intensity)
Determined by the tissue density and thickness
Allows for tissue density to be measured
At low energy (30-50 keV), bone attenuation is _______ than that of soft tissue - Answer
greater
At high energy (>70 keV), bone attenuation is ______ than that of soft tissue - Answer
about the same
Principle behind DXA: Absorptiometry - Answer The denser the tissue, the more
electrons it contains
Denser material attenuates more photons in the x-ray beam and the beam is weaker
What use dual energy x-rays? (3) - Answer Bone and soft tissue are differentially
absorbed (eliminates the need for uniform object thickness)
Allows you to suppress the impact of overlying soft tissue
Partially corrects for presence of varying amount of fat
Why are BMD results from different manufacturers not comparable? (5) - Answer There
are two different approaches to producing dual-energies (filtered x-ray and switched
x-ray)
