What is Bone Densitometry? (DEXA/ DXA)

Bone mineral content and density are assessed using a bone density test. X-rays, dual-energy X-ray absorptiometry (DEXA or DXA), or a specialised CT scan that makes use of computer software to assess the hip or spine’s bone density are possible methods. For a number of factors, the DEXA scan is regarded as the “gold standard” or most precise test. Let’s learn about Bone densitometry (DEXA).

This measurement informs the medical professional whether there has been a loss of bone mass. In this condition, bones are more fragile and prone to breaking or fracture.

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COMPOSITION OF HUMAN BONE

To begin with, our bodies utilise bones for a variety of purposes. The support of organs is one of the most crucial roles. The production of red, white, and platelet cells, as well as the storage of calcium (which the brain needs), are additional roles. A mineral layer and a hard layer make up the bone. The Haversian canal is one of the structures that make up the mineral layer of the bone’s tube-like features. This structure carries organic nutrients necessary for the bone system. The Haversian canal is encircled by tiny plates, or lamellae, that house the bone marrow.

The red marrow is particularly formed of tissue that contains blood cells, while the yellow marrow is made of fat. Collagen makes up the bony hard layer. This stratum accounts for 70% of bone density. In adults and 30% in children, the musculoskeletal system is made up of bones and muscles. The functional component of the bone is made up of three cells. Osteoblasts, osteocytes, and osteoclasts are some of them. The osteoblasts build the bone by producing collagen. The mineral balance in the body is managed by the osteocytes. In the process known as bone turnover, osteoclasts obliterate bone mineral tissue. Excessive bone turnover is a disorder called osteoporosis.

BONE DENSITOMETRY (DEXA/DXA)

The calcium and other minerals in your bones are measured using a bone density scan, sometimes referred to as a DEXA scan. The measurement aids in displaying the strength and thickness of your bones also referred to as bone mass or density.

As people age, their bones typically become thinner. Osteopenia refers to thinning of the bones beyond normal. You are more susceptible to osteoporosis, a more severe condition if you have osteopenia. Osteoporosis is a condition that progressively weakens and fractures bones. Osteoporosis typically affects elderly individuals and is more prevalent in women over 65. Patients are more likely to experience fractures (broken bones), particularly in the hips, spine, and wrists.

THE WAY BONE DENSITOMETRY (DEXA) IS COMPLETED

You may eat regularly on the day of the exam. Before your exam, you should wait at least 24 hours before taking calcium supplements.

Avoid wearing clothes with metal belts, zippers, or buttons; instead, dress comfortably and loosely. Remove anything that might be in the area being scanned, such as wallets or keys.

For the exam, you might have to take some of your clothes off and/or change into a gown. Remove any metal jewellery, removable dental equipment, eyeglasses, or clothes that could obstruct the x-ray pictures. Notify your doctor if you recently had a barium exam, a contrast material injection, a computed tomography (CT) scan, or a radioisotope scan. You might need to hold off on getting a DXA test for 10 to 14 days.

Women should always disclose their pregnancy to their doctor and the technician. To prevent radiation exposure to the foetus, medical professionals will not do numerous tests during pregnancy. If an x-ray is required, the doctor will take measures to limit the baby’s exposure to radiation. For further details on x-rays during pregnancy, visit the Safety in X-ray, Interventional Radiology, and Nuclear Medicine Procedures page.

WHEN IS A BONE DENSITY (DEXA) SCAN REQUIRED?

Bone density testing can be used to:

• Confirm an osteoporosis diagnosis if you’ve previously had a bone fracture
• Predict your risk of breaking a bone in the future
• Establish your pace of bone loss
• Evaluate the effectiveness of therapy

There are numerous osteoporosis risk factors and densitometry test indications. The following are some typical osteoporosis risk factors:

Age-related factors, such as women over 65 and males over 70, smoking, and a family history of hip fracture, as well as post-menopausal women who are not taking oestrogen

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HOW DO RESULTS FOR DENSITOMETRY LOOK LIKE?

You’ll receive a T-score for the outcomes of your scan. It reveals whether your bone density is much more or lower than that of a healthy 30-year-old, the age at which bones are at their strongest. Your bones are weaker the lower your score is.

• Normal bone density is defined as a T-score of -1.0 or higher.
• A T-score of -1.0 to -2.5 indicates osteopenia or low bone density.
• Osteoporosis if the T-score is -2.5 or lower.

You may occasionally receive a Z score as a second DXA scan result from your doctor. It contrasts your bone density with the average value for someone your age and size.

Image source: sites.edb.utexas.edu

DISEASES DIAGNOSED BY DXA/DEXA

DEXA scans, as opposed to standard X-rays, can detect minute decreases in bone density. As a result, osteoporosis can be identified early on, before a bone is broken. In addition to using a low dosage of radiation, DEXA scans also pose significantly fewer health concerns than conventional X-rays.

The results of bone density scans are used by doctors to determine whether low bone density requires therapy.

Men can get osteoporosis, despite the fact that older women are more prone to the ailment. Your doctor might suggest a bone density test, regardless of your gender or age, if you’ve:

• Height loss

  . Osteoporosis is one of the main causes of compression fractures in the spine, which can occur in those who have lost at least 1.5 inches (3.8 cm) of height.

• Broke a bone

  . When a bone becomes too brittle, it breaks far more easily than is normal, leading to fragility fractures. An especially strenuous cough or sneeze may occasionally result in fragility fractures.

• Used certain medicines

  . Prednisone and other steroid drugs should not be used long-term because they interfere with bone regrowth, which can cause osteoporosis.

• Hormone levels dropped

  . In addition to the dip in hormones that naturally happens after menopause, oestrogen levels in women can decrease as a result of several cancer treatments. Male testosterone levels can be decreased by several prostate cancer therapies. Lower quantities of sex hormones damage bone.

SIDE EFFECTS OF DEXA

Bone densitometry (DEXA) comes with a few drawbacks:

Risks come with bone scans.

Radiation is released during a bone density test in a very small proportion. It is best to avoid radiation whenever possible because its negative effects might accumulate.

Risks come with the medications used to treat bone loss.

Fosamax (generic alendronate), Boniva (generic ibandronate), and Actonel are the most often prescribed medications for treating bone loss (generic risedronate).

These medications are significantly overprescribed and carry numerous dangers. Heartburn, swallowing issues, and upset stomach are typical adverse effects. There are a few uncommon adverse effects, such as fissures in the femur (thighbone), bone loss in the jaw, and irregular heartbeat.

The test can be a financial waste.

A DEXA scan typically costs $125. Additionally, you waste money if your doctor prescribes a medicine when you just have minimal bone loss. Generic alendronate can cost up to $75 for a month’s supply. The same medication sold under Fosamax can cost twice as much.

SUMMARY

To summarize, X-rays, dual-energy X-ray absorptiometry (DEXA or DXA), or a specialised CT scan that assess the hip or spine’s bone density are possible methods. The DEXA scan is regarded as the “gold standard” or most precise test. Excessive bone turnover is a disorder called osteoporosis. The calcium and other minerals in your bones are particularly measured using a bone density scan, sometimes referred to as a DEXA scan. Women should always disclose their pregnancy to their doctor and the technician. To prevent radiation exposure to the foetus, medical professionals will not do numerous tests during pregnancy.

Thanks for reading

Team MBD

Further reading- Bone Densitometry | Johns Hopkins Medicine