Today there are radiographic techniques such as DEXA, CT and MRI that allow you to directly view and measure the variables of body composition (adipose tissue, bone tissue and muscle tissue).
The main limitation of these equipment is that they are not very accessible and very expensive.
DEXA Scan is a means of measuring bone mineral density (BMD) using digital X-rays. DEXA is the most extensive and in-depth study of bone density measurement technology. This technique can measure osteoporosis.
Through electromagnetic interference, we can also scan and analyze the body composition, such as measuring the total fat content of the body. Athletes, models and health-conscious people usually like this type of scan. This type of scan requires an appointment in advance.
It is based on the principle of differential attenuation of an X-ray beam, at two energy levels, as it passes through the tissues. This attenuation is recordable and correlated to the body composition of the examined subject.
The device uses a coincident X-ray beam with no dispersion in the environment.
The radiation dose per single exam is minimal. There is therefore no risk for both the patient and the operator and it is possible to repeat the examination within a short time.
The scanning inspection may take up to 20 minutes.
Is DEXA scan the same as bone scan?
Although the names sound similar, the purpose and method of the two inspections are quite different. Bone scan is a "nuclear medicine exam" (nuclear medicine exam), it is generally used to observe tumors and stress fractures, not for bone density measurement.
Besides DXA, what other methods are available for measuring bone density?
Although there are also ultrasound or lower dose X-rays for "screening" of bone density, or more complex algorithms to analyze the results of CT images to obtain bone density (QCT), the accuracy of these methods is still not as good as DEXA scan, Therefore, it has not been widely used in direct diagnosis in hospitals.
What do I need to do before doing a bone density test?
Do not take calcium tablets within 24 hours before the examination.
2. Wear loose and comfortable clothes during the inspection (try not to have metal zippers, belts or buttons), and remove metal objects such as keys and wallets before the inspection.
3. If you have recently performed a barium or contrast agent-enhanced examination, it will take another two weeks before the DEXA examination.
4. Pregnant women are not recommended to do DEXA examination.
How does DEXA instrument measure bone density?
The DEXA instrument emits a beam of low-dose X-rays with two energy peaks on the bones of the arm or torso on the workbench. One energy peak is mainly absorbed by soft tissue, and the other is mainly absorbed by the bone.
By this method, the soft tissue part can be quickly subtracted from the total amount of the entire arm or torso, and the bone X-ray penetration is obtained. Through the software algorithm, the bone density of this part is obtained.
Is there a risk in DEXA inspection?
If the inspection is too frequent and the radiation exposure is excessive, there is a risk of cancer. However, the contribution of this test to accurate diagnosis is far greater than the risk of disease.