DEXA/DXA (Bone Density Scan)

What is a DEXA/DXA (Bone Density Scan)?

Dual Energy X-Ray Absorptiometry, called DEXA is a scientific way of measuring your bone density. DEXA uses low dose x-ray from different angles projected at bones in the spine, hip, or wrist. Low dose x-ray determines the density or mass of the bone. Other names for this test are Bone Mineral Density (BMD) or Dual X-ray absorptiometry (DXA). The dose of the x-ray is so minimal that the technologist sits next to you during the entire exam. 

Why is Bone Density Important?

Our peak bone mass is usually achieved in young adults between 25-30. This peak density varies between women and men, and among different ethnicities. This peak density assumes your peak bone mass by comparing your density to a large database. This database includes women (or men) of similar height, weight, and ethnic groups. Therefore, there are different database references for caucasian women compared to African American men.

What Conditions Affect Bone Density?

Our genetics, diet, and sex hormones allow us to achieve a greatest density in our mid-twenties. After that time, the density decreases over time. We can see the greatest changes in women's de-nsity after menopause. This is because their hormones are much lower during menopause. Men exhibit the greatest decrease in density after age 50 when testosterone decreases. Our diet and nutritional access play a significant role in the development of peak bone density. Our diet and nutritional access also help the maintenance of normal bone mass. A diet rich in calcium is essential at all age levels. Foods that are rich in calcium include:

  • Milk products
  • Most vegetables
  • And most supplemented foods.

How Aging Affects Bone Density

The average American has an adequate calcium intake until they become older. The elderly have several obstacles to overcome with meeting adequate dietary calcium intake. For example, as we age, we lose our sense of taste and have other medical problems. Medication may make it harder to maintain adequate intake. Thus, many patients who struggle with the aging cons, supplement with over-the-counter calcium. We do not make our own active Vitamin 3. Thus, we can either have enough sun exposure to allow our skin to convert the inactive to the active form. Or we can consume supplemental vitamin D3. Vitamin D3 levels are not tested but in some conditions may be recommended such as:

  • Underlying renal
  • Liver
  • Small bowel absorption problems
  • Or thyroid conditions.

How Does Family History Influence My Future Fracture Risk?

We know that family history is a significant risk factor for osteoporosis. If your first-degree relatives have been diagnosed with osteoporosis, you may be at risk. For example, if a close relative suffered an osteoporotic fracture, that is considered an even stronger indication of your future fracture risk. The opposite is also true. If your close family members had excellent bone density, you may too.

Hereditary factors also influence peak bone density. Your body weight and height affect the stimulation of bone cortical thickening. A thicker bone cortex is necessary to hold a heavier frame. But, low body weight is a significant risk factor for low bone density. A loss of height of greater than 1/2 inch over a one-year interval is also considered a significant risk factor. 

Do Prior Fractures Affect My Density?

Your history of prior fractures may influence your future risk for fracture. It depends on the circumstances that caused the fracture in the first place.  If you suffered a fracture from minor trauma, your fracture may be considered a “fragility” or “insufficiency” fracture. If you had a traumatic injury such as a car accident, then this history should not be used to predict your future risk. 

What Other Factors Affect My Bone Density?

Some medicines like corticosteroids and overtreatment with thyroid supplements can affect bone density. Smoking and excess alcohol consumption also affect bone density. Many medical conditions affect bone density including:

  • Liver disease
  • Kidney disease
  • Celiac disease
  • Small bowel absorption issues
  • Autoimmune conditions such as:
    • Rheumatoid arthritis
    • Hyperthyroidism
    • Hyperparathyroidism, among others.

When to Start a Bone Density Scan?

The International Society of Bone Densitometry (ISCD) and

the National Osteoporosis Foundation (NOF) recommends bone density scans to start by:

  • Age 65 for most women
  • 70 for most men of average risk.

The radiologist may schedule a woman as early as age 50 for a low bone density screening. This is because most women become menopausal after age 50. The radiologist uses menopausal and family history risk factors to see if she needs a DEXA test

A radiologist may schedule a woman for a low bone density screening depending on: 

  • If she does not take hormone replacement therapy
  • And if she has a family history of osteoporosis.

But, if it is the opposite case where;

  • A woman who goes onto hormone replacement a
  • And does not have any family history
  • Or other significant risk factors

she may wait until age 65 if her clinician advises. 

How Do I Prepare For My DEXA Scan?

  • Do not take calcium tablets or other large mineral tablets. The tablets may still be in the bowel and overlap on images of the spine.
  • Avoid wearing clothes with metal buttons or naval jewelry. A two-piece outfit with an elastic band is optimal.
  • Download the BONE DENSITY Forms under the Resources tab within “Patients forms” on the first page of our website. 
    • Please bring the forms completed to your appointment and wear an appropriate outfit for your visit. If you cannot prepare for this, don’t worry, come at least 15 minutes early and we will have you complete the questionnaire onsite and change you into comfortable medical scrubs. 

How is a Bone Density Scan Performed?

You will lie on a soft paddled table starting on your back. The technologic will position you in the middle of the beam. The medical x-ray tube moves across your spine. Another scanning device in the table called a photo generator passes beneath you. This is where the name “Dual Energy” in the name DEXA comes from. After the lumbar spine bone density image is acquired, you will be positioned on your side to obtain the Lateral Vertebral Assessment (LVA).

Historically, the left hip is typically selected to measure bone density. If there is a reason that your hip densities would not be symmetrical (such as one leg much shorter than the other), let the technologist so that she can measure both hips. The exam will only take 10 - 15 minutes to complete. 

If I Had a Hip or Joint Replacement, Will it Affect My Bone Density Scan? 

If you have had a hip joint replacement, we can scan the opposite hip. If you have had both hips replaced, then we can omit that score and select the forearm instead. 

What About If I Have Any Underlying Medical Problems?

If you have an underlying medical problem with your serum calcium, then we will scan your forearm. Having hyperparathyroidism also applies here and we will need to scan your forearm.

If you cannot assume these positions, please let your technologists know in advance. They will be able to alter the examination to accommodate your needs.  

Who Will Be Reading My Bone Density Test? 

At The Women’s Imaging Center, our specialized radiologists are certified by the International Society of Clinical Densitometry (ISCD). They have undergone additional rigorous training and certification specifically to interpret complex medical diagnostic imaging scans. This is unlike most other radiology centers which perform the examination and rely primarily on the machine’s software to construct the report. Our radiologists recognize when a patient’s positioning may be affecting the test results or if the bone mass seems too low for the patient’s Body Mass Index (BMI). Denver’s most experienced radiologists will be interpreting your imaging scan.

When Can I Expect to Have My Results?

Once the exam is complete, the results will be determined by a specialized radiologist. Once complete, the results will be sent via letter to the patient and their desired physician.

What Do The Bone Density Results Mean?

  • A T-Score of -1.0 or higher is normal.
  • A T-score -1.0 to -2.5 is low bone density (osteopenia).
  • A T-score -2.5 or greater (more negative) is osteoporosis.

How Can I Treat Osteopenia or Osteoporosis?

At a very least, increase your weight-bearing or resistive exercises. Not all exercise is capable of achieving this. Walking up a hill carrying a backpack will improve bone density. While biking will decrease your density. Biking is not resistive since you are using a machine to decrease your work. The muscles are not resisting a force. Also, take enough Vitamin D3. For most healthy adults, taking 1,000 IU/day is enough but some people may need to take more. If there is a medical reason why you may not be able to absorb Vitamin D appropriately (like with celiac disease). Or convert it to its active form (liver disease), you may want to have your vitamin D3 level measured. 

Are There Any Medications That Can Help Treat Osteopenia or Osteoporosis?

Many medications are available today that improve bone density. These medications work by either reversing the proportion of bone turnover or by anabolic building new bone (PTH). Bone is a dynamic organ-it is always building up by osteoblasts or breaking down (called remodeling) by osteoclasts. The balance of building and breaking down is normal. Specialists have discovered that by slowing the caustic activity, the blastic activity wins. This results in increased bone density. 

Medicines called bisphosphonates are common for treating low bone mass. Bisphosphonates help decrease the rate of bone loss. This process can take around five years to see an increase in bone density. The most common bisphosphonates include Fosamax and Actonel. Other medicines like Boniva can be given as a pill or IV infusion quarterly. Prolia can be used in people with decreased kidney function or in patients who can’t take oral medications. Another drug, Reclast uses IV infusion once yearly. Other anabolic medicines help “build new bone” like Forteo. We recommend all patients speak with their radiologist or primary doctor before taking a new medication. 


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