DEXA Bone Density Test (Densitometry Scan)

WHAT IS A BONE DENSITOMETRY SCAN (BONE DENSITY TEST)?

Bone density scan/test (or “Dexa bone densitometry test”) uses low-dose x-rays to view how dense or strong your bones are. Bone density scan is an improved form of x-ray technology, used to measure bone loss. DEXA bone density test is the established standard for measuring bone mineral density (BMD) today. 

Other names for bone density test are:

• Dual-energy x-ray absorptiometry (DEXA) bone density scan.
• Bone densitometry.

Bone density test is most often done on the lower spine and the hips. However, in children and some adults, the whole body might be scanned.

BENEFITS OF DEXA BONE DENSITY SCAN

The pros of DEXA bone densitometry scan include:

• Standardized and accurate diagnosis of osteoporosis.

• It assesses someone’s risk of developing fractures.

• There are usually no side effects.

• It monitors treatment effects for osteoporosis and other conditions that cause bone loss.

• No radiation remains in your body after the scan.

• No anesthesia is required.

• It is simple, quick, and noninvasive.

ELIGIBILITY FOR DEXA BONE DENSITOMETRY SCAN

Bone density test is required if you:

1. Are a post-menopausal woman.
2. Are not taking estrogen.
3. Happen to be a woman above 45 years, who is tall (over 5ft7ins.) or thin (weighing less than 125 pounds).
4. Are you a woman aged 65 or older?
5. Have a personal or family history of hip fractures.
6. A male with clinical conditions related to bone loss, such as:

• Rheumatoid arthritis.
• Liver disease.
• Chronic kidney disease.

Take medications known to cause bone loss, including:

• Corticosteroids, such as Prednisone.
• High-dose thyroid replacement drugs.
• Various anti-seizure medications, such as:
• Dilantin.
• Certain barbiturates.

1. Are you a smoker (or chain-smoker)?
2. Are a type 1 diabetes patient and have kidney disease or liver disease.
3. Have a family history of osteoporosis.
4. Show evidence of high bone turnover, which appears in form of excessive collagen, in urine samples.
5. Suffer from a thyroid condition, such as hyperthyroidism.
6. Had experienced a fracture after only mild trauma.
7. Show x-ray evidence of vertebral fracture or other symptoms of osteoporosis.
8. Suffer from a parathyroid condition, such as hyperparathyroidism.

A low-dose x-ray examination of the spine, the Vertebral Fracture Assessment (VFA) to screen for vertebral fractures, performed by a DEXA bone densitometer machine, may be used to the advantage of older patients, especially if:

• They have unexplained back pain.
• They have lost more than one inch in height.
• Their DEXA images of the spine imply a vertebral deformity or fracture.
• The DEXA bone densitometry scan gives borderline readings.

PREPARATIONS FOR A DEXA BONE DENSITY SCAN

When preparing for a DEXA bone density test, the following preparatory steps are required.

• You may eat normally on the day of the scan.

• Don’t take calcium supplements for at least 24 hours to the exam.

• Wear loose, comfortable garments not having zippers, belts, or buttons made of metal.
• Objects like keys, wallets, or metal components, should not go with you into the scanning area.

Before bone density scan, you will be asked to:

• Change into a gown, during the exam.
• You will not wear your jewelry, dentures, eyeglasses, and any other metal objects.

Inform your doctor if you had a barium examination or have been injected with a contrast material for a CT scan or radioisotope scan.

Inform your doctor if you are pregnant, before the exam.

THE DEXA BONE DENSITY SCAN EQUIPMENT

There are two types of DEXA bone densitometers:

A Central Device.

This is commonly found in hospitals and medical offices. It is used to measure bone density in the hip and spine. A central device has a large, flat table and an “arm” suspended overhead.

• A Peripheral Device.

This is used to measure bone density in the wrist, heel or finger, and is common in drugstores and mobile health vans. Peripheral DXA is smaller, of a portable box-like structure with a space for the foot or forearm to be placed for imaging. 

Peripheral DXA (pDXA), notwithstanding, the central DXA is the standard technique. The CPT codes for central DXA and peripheral DXA are 77080 and 77081 respectively.

THE CENTRAL DEXA SCAN PROCEDURE

Duration: 10 to 30 minutes

Specialist: An orthopedic doctor or surgeon

Conductor: A radiographer or radiologist

• You will lie on your back on a flat, open x-ray table.
• You will be asked to keep very still during the scan, so the images won’t be blurred.
• A large scanning arm will be placed over your body, to measure bone density in the center of the skeleton.
• While the scanning arm is moved slowly over your body, a narrow beam of low-dose x-rays will be passed through the part of your body being examined (hip and lower spine).
• An x-ray detector inside the scanning arm measures the number of x-rays that have passed through your body. 
• The information gotten will be used to produce an image of the scanned area.

RESULTS OF THE BONE DENSITY TEST

A radiologist, who oversees the conduct of the radiology exam, will analyze the images and send a signed report to your doctor, who will discuss the result with you. Results of a DEXA bone densitometry scan adopt a scoring system. The scan’s scoring system measures your bone loss against that of a healthy young adult, according to the WHO standard. This is called your “T-score”. 

A T-score shows how much higher or lower your bone density is than that of a healthy 30-year old. The lower your score, the weaker your bones are. 

The T-score shows:

–1.0 or above	Normal bone density
–1.0 to –2.5	Low bone density
–2.5 or lower	Osteoporosis

Certain times doctors will give you another DEXA bone densitometry scan result, a Z-score, which compares your bone density to a normal score for an individual of your same age and body size.

RISKS OF DEXA BONE DENSITY SCAN

The risk of undergoing a DEXA bone density test is low, but may include:

• Slight chance of cancer from radiation exposure. However, the benefit of an accurate diagnosis far outweighs the risk.
• Radiation exposure likely affects a woman’s fetus, causing some complications.

DEXA BONE DENSITY TEST COST

As usual, the cost of tests or scans varies in different parts of the world and hospitals. But in the U.S, bone density scan cost ranges between $100 to $200.

FAQs

• How is a DEXA bone densitometry test done?

During the DEXA bone density test, a large scanning arm is passed over your body to measure your bone density in the center of your skeleton. When the scanning arm is moving slowly over your body, a narrow beam of low-dose x-rays will be passed through the part of your body being examined.

• What is the DEXA bone density scan used for?

Bone density scans (DEXA scans) help to work on your risk of breaking a bone. They help in diagnosing bone-related health problems, such as osteoporosis, or to assess the risk of having them.

• Is DEXA bone densitometry not harmful due to radiation?

Usually, the DEXA bone density test has no side effects. Virtually no radiation remains in your body after the scan (except there’s a baby in your womb). 

Although there are seems to be a slight chance of cancer (as a result of radiation), the benefit of an accurate diagnosis far outweighs the risk. 

Women should inform their doctors if they are pregnant, before performing the test, due to the risky incidence of exposing the developing fetus to radiation (which may result in certain birth defects or gene alteration).

• Who are the right candidates for a bone density test?

DEXA bone densitometry scan (bone density test) is for women over the age of 65 and men over the age of 70. 

DEXA bone densitometry tests are only appropriate for those with moderate risk of fracture or when the results will change the patient’s healthcare plan. 

Younger women and men aged 50─60 should consider the test if they have any risk factor of serious bone loss, including osteoporosis.

• How often can someone get a DEXA bone densitometry scan?

You are expected to get a DEXA bone density scan at most once in two years and should be nothing more than that. Initial screening for osteoporosis should be performed according to National Osteoporosis Foundation (NOF) recommendations.