Bone Marrow Density: Meaning and Implications
Bone marrow refers to the flexible tissue which is present in hollow interior of the bones. Generally in adults, the marrow present in large bones leads to formation of new blood cells. This component of bone makes up 4% of the overall body weight.
Bone marrow density is a medical term that describes the amount of matter per square centimeter of bones. This quantity can be measured using a procedure called densitometry which is generally conducted in radiology or nuclear medicine departments of hospitals or clinics. Besides this, the measurement is also painless; non-invasive and involves minimal exposure to radiations. Generally, the measurement is done over the upper part of lumbar spine and hip. On an average, the bone marrow density is about 1500 kg/m3.
A number of techniques are utilized for measuring bone marrow density. These include dual photon absorptiometry, single energy X-ray absorptiometry, single photon absorptiometry, qualitative ultrasound, dual energy X-ray absorptiometry, digital X-ray radiogrammetry and quantitative Computed Tomography. From all the techniques that are utilized for measuring bone density, ultrasound remains a cost-efficient approach to measure the bone density.
The technique of dual energy X-ray absorptiometry has certain limitations with respect to the measurement of bone density. Firstly, the size of the patient and thickness of the tissue that covers the bone can affect the measurement of bone density. Although bone density is considered to be an alternative to the bone strength; bone density remains a poor indicator of bone strength under specific conditions. Moreover, crushed vertebrae can cause abnormally high bone-density and must not be incorporated in the analysis.