Dual energy absorptiometry [DEXA or DXA] employs different photons from two energy sources.
Provides good precision for all sites of osteoporotic fractures.
Radiation dose is much less than a standard chest x ray.
Whole body scans by DEXA measure total body calcium, lean body mass and fat mass.
Computed tomography[CT] for bone density :
Radiation exposure is higher than with DEXA.
Measurements of femur are not available although very accurate measurements of the spine are possible.
The best information is provided by DEXA technique to give a precision of 1% measuring the 3 sites of greater interest the radius, the hip the spine.
T score:
Standard deviations between pt and average peak young adult bone mass.
The more negative the greater the risk of fractures.
Z score: S.d. between pt and average bone mass for age and wt. A z score lower than -2.0 ( 2.5% of normal population of same age) requires diagnostic evaluation for causes other than post menopausal boneloss.
Definations are based on bone mineral density:
Normal 0 to -1 s.d. from the reference standard (84% of population).
Osteopenia -1 to -2.5 s.d. Osteoporosis below -2.5 s.d.
The clinical relevance of a bone density measurement in a menopausal women is estimated by using T score.
For young women,interpretation utilizes the Z score.
Changes of bone remodeling
Pathophysiology
Signs and symptoms
Risk factors and investigations
Investigations
Diagnostic tests and biochemical markers
Hormonal treatment
Estrogen modulators, calcium
Vitamin D
Bisphosphonates
Calcitonin, Fluoride, Tibolone
Prevention
Provides good precision for all sites of osteoporotic fractures.
Radiation dose is much less than a standard chest x ray.
Whole body scans by DEXA measure total body calcium, lean body mass and fat mass.
Computed tomography[CT] for bone density :
Radiation exposure is higher than with DEXA.
Measurements of femur are not available although very accurate measurements of the spine are possible.
The best information is provided by DEXA technique to give a precision of 1% measuring the 3 sites of greater interest the radius, the hip the spine.
T score:
Standard deviations between pt and average peak young adult bone mass.
The more negative the greater the risk of fractures.
Z score: S.d. between pt and average bone mass for age and wt. A z score lower than -2.0 ( 2.5% of normal population of same age) requires diagnostic evaluation for causes other than post menopausal boneloss.
Definations are based on bone mineral density:
Normal 0 to -1 s.d. from the reference standard (84% of population).
Osteopenia -1 to -2.5 s.d. Osteoporosis below -2.5 s.d.
The clinical relevance of a bone density measurement in a menopausal women is estimated by using T score.
For young women,interpretation utilizes the Z score.
Changes of bone remodeling
Pathophysiology
Signs and symptoms
Risk factors and investigations
Investigations
Diagnostic tests and biochemical markers
Hormonal treatment
Estrogen modulators, calcium
Vitamin D
Bisphosphonates
Calcitonin, Fluoride, Tibolone
Prevention
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