DEXA and REMS: a quick guide

One of the first steps in diagnosing osteoporosis is a scan – but which one should you choose?
DEXA scan

There are two types of scan commonly used to diagnose osteoporosis – DEXA and REMS. 

Traditionally, DEXA (Dual Energy X-ray Absorptiometry) has been the ‘gold standard’ for measuring bone density1. However, a newer technology, REMS (Radiofrequency Echographic Multi-Spectrometry), is emerging as a promising option.

There are two types of scan commonly used to diagnose osteoporosis – DEXA and REMS. 

Traditionally, DEXA (Dual Energy X-ray Absorptiometry) has been the ‘gold standard’ for measuring bone density1. However, a newer technology, REMS (Radiofrequency Echographic Multi-Spectrometry), is emerging as a promising option.

DEXA

A DEXA scan is a medical imaging test used to measure bone mineral density (BMD) and body composition, including fat and lean muscle mass. They are routinely used by the NHS for diagnosing and monitoring osteoporosis and fracture risk. 

DEXA uses X-rays to measure BMD. The radiation dose of current DEXA systems is small, so much that the operator can stay in the room while the scan takes place. 

 

DEXA

A DEXA scan is a medical imaging test used to measure bone mineral density (BMD) and body composition, including fat and lean muscle mass. They are routinely used by the NHS for diagnosing and monitoring osteoporosis and fracture risk. 

DEXA uses X-rays to measure BMD. The radiation dose of current DEXA systems is small, so much that the operator can stay in the room while the scan takes place. 

 

Procedure

The scan is very simple and painless. You should wear comfortable clothing without any metal, and take out any piercings that may impact the areas that are scanned. 

You may be asked to avoid calcium supplements 24 hours before the scan, since undissolved calcium tablets can falsely increase bone density measurements2.

You will lie on a padded table or bench, with the X-ray scanner above you. The scanning arm will pass over your body and take images of your lumbar spine and hips – the two most common places for a fracture to occur. You may be asked to adjust your legs to get a clear picture. 

The DEXA scanner consists of three distinct pieces:

  1. X-ray generator: this produces two different X-ray beams, one with high and one with low energy. The various energy levels allow for differentiation between bone and soft tissues.
  2. X-ray detector: the detector captures the X-rays that pass through the body and sends the data to a computer.
  3. Computer system: the computer system processes the data to build up images of bone density or body composition based on the absorption of X-rays by different tissues.

 

The whole process usually takes between 10 and 20 minutes. 

Procedure

The scan is very simple and painless. You should wear comfortable clothing without any metal, and take out any piercings that may impact the areas that are scanned. 

You may be asked to avoid calcium supplements 24 hours before the scan, since undissolved calcium tablets can falsely increase bone density measurements2.

You will lie on a padded table or bench, with the X-ray scanner above you. The scanning arm will pass over your body and take images of your lumbar spine and hips – the two most common places for a fracture to occur. You may be asked to adjust your legs to get a clear picture. 

The DEXA scanner consists of three distinct pieces:

  1. X-ray generator: this produces two different X-ray beams, one with high and one with low energy. The various energy levels allow for differentiation between bone and soft tissues.
  2. X-ray detector: the detector captures the X-rays that pass through the body and sends the data to a computer.
  3. Computer system: the computer system processes the data to build up images of bone density or body composition based on the absorption of X-rays by different tissues.

 

The whole process usually takes between 10 and 20 minutes. 

Understanding your DEXA result

Results from your DEXA scan are given as a ‘t score’, which is the standard deviation of your bone density compared to the average bone density of a young and healthy person of the same sex as you. It is usually a good predictor of how likely you are to break a bone. 

What your t-score means:

  • +1 to -1 – your bone density is in the normal range
  • -1 to -2.5 – your bone density is in the osteopenia range
  • -2.5 and below – your bone density is in the osteoporosis range

Understanding your DEXA result

Results from your DEXA scan are given as a ‘t score’, which is the standard deviation of your bone density compared to the average bone density of a young and healthy person of the same sex as you. It is usually a good predictor of how likely you are to break a bone. 

What your t-score means:

  • +1 to -1 – your bone density is in the normal range
  • -1 to -2.5 – your bone density is in the osteopenia range
  • -2.5 and below – your bone density is in the osteoporosis range
REMS ultrasound scanner

REMS

REMS uses ultrasound technology to provide a radiation-free assessment of bone health. This is ideal for populations that need frequent monitoring or are sensitive to radiation exposure, such as young children and pregnant women. 

Some private clinics offer REMS, but it is not currently available on the NHS. 

REMS devices are often portable and can be used in various clinical settings, making bone health assessments more accessible.

REMS ultrasound scanner

REMS

REMS uses ultrasound technology to provide a radiation-free assessment of bone health. This is ideal for populations that need frequent monitoring or are sensitive to radiation exposure, such as young children and pregnant women. 

Some private clinics offer REMS, but it is not currently available on the NHS. 

REMS devices are often portable and can be used in various clinical settings, making bone health assessments more accessible.

Procedure

Minimal preparation is needed for a REMS scan. You can continue your routine as normal in the lead up to your appointment.

You will typically lie down on a bed, and the ultrasound probe will be placed on the skin over the bones being examined, typically the lumbar spine and femur. 

Ultrasound scans use sound waves at a high-frequency, so high that you cannot hear them. 

The probe transmits the waves into the body and creates echoes when they bounce off different parts of the body. These echoes are used to build up an electronic picture of bone density. 

The procedure is quick and painless, usually only taking a few minutes.

REMS ultrasound scanner on spine

Procedure

Minimal preparation is needed for a REMS scan. You can continue your routine as normal in the lead up to your appointment.

You will typically lie down on a bed, and the ultrasound probe will be placed on the skin over the bones being examined, typically the lumbar spine and femur. 

Ultrasound scans use sound waves at a high-frequency, so high that you cannot hear them. 

The probe transmits the waves into the body and creates echoes when they bounce off different parts of the body. These echoes are used to build up an electronic picture of bone density. 

The procedure is quick and painless, usually only taking a few minutes.

REMS ultrasound scanner on spine
REMS fragility score graph

Understanding your REMS result

A REMS scan, like DEXA, will also give you a t-score; a low result might mean you are at risk of osteoporosis and fracturing a bone easily. 

REMS will also provide a ‘Fragility Score’, which is an assessment of bone quality. This fragility score is presented on a graph – if you are in the ‘green zone’, the likelihood of sustaining a fracture is very small, whereas if you are in the ‘red zone’, the quality of your bone is similar to the quality of bone of people who have sustained fragility fractures, and you are therefore at high risk of fracturing a bone. 

REMS can also provide a 5-year fracture risk assessment. The fracture risk score derived from this can help clinicians to make informed decisions about your care.

REMS fragility score graph

Understanding your REMS result

A REMS scan, like DEXA, will also give you a t-score; a low result might mean you are at risk of osteoporosis and fracturing a bone easily. 

REMS will also provide a ‘Fragility Score’, which is an assessment of bone quality. This fragility score is presented on a graph – if you are in the ‘green zone’, the likelihood of sustaining a fracture is very small, whereas if you are in the ‘red zone’, the quality of your bone is similar to the quality of bone of people who have sustained fragility fractures, and you are therefore at high risk of fracturing a bone. 

REMS can also provide a 5-year fracture risk assessment. The fracture risk score derived from this can help clinicians to make informed decisions about your care.

While both DEXA and REMS have been determined as clinically valid means of determining bone density, they each offer unique benefits. 

DEXA remains the gold standard due to its widespread acceptance and extensive research backing, providing highly accurate and reproducible results. However, REMS is emerging as a promising alternative, particularly for its portability, radiation-free approach, and potential to provide a measure of bone quality. As technology advances, REMS may become more prevalent, offering new opportunities for bone health monitoring in various settings. Ultimately, the choice between DEXA and REMS should be guided by the specific needs of the patient and the clinical context, ensuring the most effective and personalised care in the assessment and management of bone health.

While both DEXA and REMS have been determined as clinically valid means of determining bone density, they each offer unique benefits. 

DEXA remains the gold standard due to its widespread acceptance and extensive research backing, providing highly accurate and reproducible results. However, REMS is emerging as a promising alternative, particularly for its portability, radiation-free approach, and potential to provide a measure of bone quality. As technology advances, REMS may become more prevalent, offering new opportunities for bone health monitoring in various settings. Ultimately, the choice between DEXA and REMS should be guided by the specific needs of the patient and the clinical context, ensuring the most effective and personalised care in the assessment and management of bone health.

References

  1. Johns Hopkins Medicine. Bone Densitometry. [online] Available at: hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
  2. Lenihan, D.J. and Alencar, A.J. (2006). Cardiac toxicity from breast cancer treatment. Heart Failure Clinics, 2(2), pp.145-156. Available at: sciencedirect.com/science/article/abs/pii/S1094695006000217

References

  1. Johns Hopkins Medicine. Bone Densitometry. [online] Available at: hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
  2. Lenihan, D.J. and Alencar, A.J. (2006). Cardiac toxicity from breast cancer treatment. Heart Failure Clinics, 2(2), pp.145-156. Available at: sciencedirect.com/science/article/abs/pii/S1094695006000217