Dual X-ray absorptiometry
The dual X-ray absorptiometry ( dual energy X-ray absorptiometry DXA , formerly DEXA , German double X-ray absorptiometry ) is an X-ray diagnostic method for determining body composition . Some authors refer to it as a reference method ( gold standard ) in this area.
principle
Two images are made with different X-ray energies. The portion of the soft tissue in the X-ray absorption can thus be subtracted.
The standard measurement of bone density is carried out in two areas: hip joint and lumbar spine and takes about 15 to 30 minutes.
Whole-body DXA measurements can be used to determine not only bone density and mass, but also the composition of the entire body. A model of the human body with three compartments (delimited parts) is used: fat mass, bone mass and other mass. The skeletal muscle mass can also be calculated on this basis .
Areas of application
DXA enables bone density measurement and thus the detection of osteoporosis . It is a widely used method to identify osteoporosis as early as possible.
Whole-body DXA is also used in connection with nutritional examinations, especially in the case of obesity .
In Germany, measurements on children and adolescents using this method are not allowed due to the radiation exposure. The method is also ruled out for pregnant women. The radiation exposure for a whole-body measurement, which takes between 5 and 20 minutes, is around 5–7 µSv .
costs
Measurements are only paid for by the health insurances in certain cases (cost factor: approx. 40-60 €), namely for:
- Broken bones
- a disease of osteoporosis
- special gastrointestinal diseases ( Crohn's disease , ulcerative colitis , malabsorption )
- Long-term use of cortisone
- a parathyroid disease
Individual evidence
- ^ A b Manfred J. Müller: Nutritional Medicine Practice: Methods - Prevention - Treatment. Springer, Heidelberg 2007, ISBN 3-540-38230-5 , pp. 40-42.
- ↑ a b Christine Becker: Formulation of population-specific algorithms for determining the body fat mass of children, adolescents and adults, based on field methods with air displacement plethysmography as a reference . Diss., Kiel 2002 (pdf 1.9 MB)