What is a Bone Density Test

What is the definition of bone density? It is formally defined as: the amount of matter per cubic centimeter of bones. Bone density is measured in three parameters, namely - bone density in g/cm², the 'z-score' ("standard deviation above/below the mean of the patient's sex and age") and the 't-score' ("standard deviation above/below the mean of the normal healthy person of the same age and sex"). The bone density is measured by a technique called 'densitometry', in the radiology department. Densitometry is the second name of bone density test. It is used to diagnose osteoporosis; a disease in which the bones become very fragile and stay at a high risk of breakage.

Bone Density Test

A bone density test is very helpful when it comes to the diagnosis of osteoporosis. Before the advent of the technology, it was really hard to diagnose the disease. In older times it was detected a very later stage. But, with this test, it is easy to diagnose the disease and prevent it accordingly. Performing a timely test can reduce the bone breakage risk and give the exact idea of the state of the patient's bones and how the type of treatment they require.

With the passing of age, we human beings lose certain amount of bone mass. The bones simply get thinner and lose their normal density, this process is called 'Osteopenia'. This happens due to the loss of calcium and such bone minerals. All this, is a gradual process that in the end makes the bones weaker and prone to bone fracture. This gradual process of osteopenia eventually leads to osteoporosis. According to research statistics, women above the age of 65 years are more prone to osteoporosis's as compared to the men of same age.

The test actually calculates the density of the bone minerals, mainly calcium, which is the most important bone mineral of all. The test is performed using various methods, that use CT scan (computer tomography scan), X-ray or ultrasound technique. Some of these bone mineral density tests are explained here briefly:

Ultrasound Tests
This is the most basic bone density test performed, in order to diagnose any primary bone related problem. If the ultrasound test finds any defect in the bone density, then the DEXA test is recommended. An ultrasound machine uses sound waves of different frequencies through water or air, to perform the task. The test is painless, fast and has no harmful radiations. Ultrasound is the most basic test and hence is unable to detect complicated bone problems and hence there are others, that are capable of detecting the more complicated ones.

Dual Energy X-ray Absorptiometry (DEXA test)
This is a very successful method of measuring the bone density and hence no doubt it is the most popular one. The DEXA test utilizes two different X-ray beams to determine the bone density and is preferred when it comes to the testing of the spinal and hip bones. The amount of light that is able to pass through the soft bone tissues is the interpretation of the bone density. This test can measure as little as 2% loss of bone density, per year. DEXA test is fast but is costly than the ultrasound testing. For the bones of forearms and heel, the Single Energy X-ray absorptiometry (SEXA) is used.

Peripheral Dual Energy X-ray Absorptiometry (P-DEXA test)
This is a form of DEXA test that is used to measure the density of the bones in arm, wrists and legs. P-DEXA test machines are portable, so, most of the physicians have them and one need not to go to a radiology center for the tests. P-DEXA cannot find out the effect of medication on the bones, hence, they are not as popular as DEXA test.

Dual Photon Absorptiometry Test (DPA test)
DPA test is done to estimate the bone density in the hip and spinal region. It uses certain special radioactive elements, for the measurement of the density. The DPA test also uses low radiations but it is less popular, due to its slow test results.

Quantitative Computer Tomography Scan (Q-CT scan)
Q-CT scan is done to measure the bone density in the vertebral (spinal) region. The peripheral quantitative computer tomography scan is used to measure the bone density of the arms and legs. The Q-CT scan is a not-so-famous form of a bone density test because it is expensive, utilizes a high amount of radiation and its accuracy is minimum.

Women are generally advised to get this test done after their menopause because after the menopause women start losing calcium form their bodies rapidly. These tests are very helpful because if the bone density of a person is less than normal then he can start taking precautionary measures in order to increase the strength of the bones. Some of the best measures of increasing and retaining the remaining bone's density are, weight training exercises, walking, taking Vitamin D and calcium supplements but only after proper consultation.