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Special imaging

Bone Density Scanning (BDS) aka Dual-energy X-ray Absorptiometry (DXA) aka Bone Densitometry And (a totally different thing) Nuclear Bone Scan/Scintigraphy. Special imaging. Purpose. Measures bone mineral density Lean mass, fat mass imaging Women over 65 advised, 60 if high risk

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Special imaging

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  1. Bone Density Scanning (BDS) aka Dual-energy X-ray Absorptiometry (DXA) aka Bone Densitometry And (a totally different thing) Nuclear Bone Scan/Scintigraphy Special imaging

  2. Purpose • Measures bone mineral density • Lean mass, fat mass imaging • Women over 65 advised, 60 if high risk • High Risk individuals: • Hx of fx, smoking, excess alcohol or caffeine, small frame, low body weight, physical inactivity, low estrogen/early menopause/late onset menstruation, hyperthyroid or hyperparathyroid disease, medication which causes bone loss (dilantin etc)

  3. pDXA (Peripheral) Small unit Wrist, heel or finger measurement Types • Central DXA • Large unit • Hip and Spine measurements

  4. pDXA DXA

  5. Courtesy of Intermountain Medical Imaging, Boise, Idaho.

  6. Interpretation • T score — This number shows the amount of bone you have compared with a young adult of the same gender with peak bone mass. A score above -1 is considered normal. A score between -1 and -2.5 is classified as osteopenia (low bone mass). A score below -2.5 is defined as osteoporosis. The T score is used to estimate your risk of developing a fracture. • Z score — This number reflects the amount of bone you have compared with other people in your age group and of the same size and gender. If this score is unusually high or low, it may indicate a need for further medical tests. • Based on caucasian men/women – may need cultural adaptation

  7. Advantages • Accurate measure of osteoporosis and fracture relative risk • Widely available • Radiation exposure very low • 0.001 mSv • Less than 1 day's worth • 2.2 mSv yearly background radiation dose

  8. Disadvantages • Technical expertise varies widely by state, regulations are poor so far • Each manufacturer has different measurement standards • Repeat exams must be done on the same machine to be accurate (same manufacturer may be ok) • Cannot use previous scans on different equipment

  9. “Bone scan” • A confusing term for a DXA scan (bone density scan is slightly better) • Often used for nuclear bone scan (bone scintigraphy) • NOT the same thing as DXA scan or PET scan

  10. Bone Scintigraphy • Competes with PET scan using FDG • Much less expensive • Usually wait 2-3 hours after administration before the scan • Uses Technetium-99m • ~6 hour halflife • 3 mSv (less than a CT, more than 1yr background radiation) • More active bone turnover results in greater radioactivity • Primary usage is for detecting hidden fractures, Pagets, bone cancer, Fibrous dysplasia, bone pain

  11. Metastasis-wide scanning region allows easy discovery of distributed pathology

  12. Fibroma

  13. Normal scansfemale male

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