Hospital of Saint John & Saint Elizabeth > Services > Imaging Services

QCT Bone Densitometry

This service is available to all patients referred by a medical practitioner.
You can also refer yourself to this service if you meet our referral criteria.
Please call 020 7078 3834 for more information and appointments.

Osteoporosis screening and QCT bone densitometry

As part of its range of diagnostic services, the Imaging Department offers QCT bone densitometry as a screen for osteoporosis and for monitoring the progress of treatment regimes.
QCT bone densitometry is used to assess osteoporosis in the same way a cholesterol measurement is used for coronary heart disease or blood pressure for stroke. The data is used to measure an important risk factor and determine the necessity, choice and efficacy of therapy.

What is osteoporosis?

Osteoporosis is a condition that causes loss of bone mineral to a point where fractures can occur following minor injury, such as a fall.
One in four women and one in twenty men will suffer bone fractures as a result of osteoporosis. Most do not have any symptoms (ie. pain) before a fracture occurs.
Some fractures can be life-threatening in later life, especially hip fracture, yet early detection and preventative treatment at a younger age can avoid the most serious consequences of osteoporosis.

image of a normal, healthy bone The inside of bone looks like honeycomb, with blood vessels and bone marrow in the spaces between bone.

Facts and figures

1 in 3 women and 1 in 12 men in the UK will have osteoporosis over the age of 50
Every 3 minutes someone has a fracture due to osteoporosis
An estimated 3 million people in the UK suffer from osteoporosis
Each year the numbers of people with osteoporosis include over
- 70,000 hip fractures
- 50,000 wrist fractures
- 40,000 spinal fractures
Osteoporosis costs the health service over £1.7 billion each year, that's £5 million each day!

What is QCT bone densitometry?

QCT (Quantitative Computed Tomography) Bone densitometry is specialised CT scanning procedure that measures bone density to detect early signs of osteoporosis.

How does QCT differ from DEXA?

QCT and DEXA both measure spinal bone mass - spinal bone is a mixture of high-turnover, metabolically active trabecular (spongy) bone and slowly-changing cortical (compact) bone.
Trabecular bone is approximately eight times more metabolically active than cortical bone and is therefore highly sensitive to changes in skeletal density. For this reason, measuring the trabecular bone mass gives the best indicator of osteoporosis.
DEXA is a well-established and valuable tool in the diagnosis of osteoporosis but cortical bone and any aortic calcification overlying the spine, or degenerative changes and osteophytes in the lumbar spine will be included in the area being assessed and cause inaccuracies in the density measurements.
QCT on the other hand produces 3D cross sectional images that can be analysed to give separate bone mineral density measurements of the trabecular bone - free from other artefacts, such as aortic calcification and osteophytes. The measurement of the trabecular bone is important because this bone has a high metabolic activity and is thus a very sensitive indicator for early bone loss and effects of treatment.
QCT provides highly accurate assessment of the bone mineral density, thus aiding the early detection of osteopenia and osteoporosis, identification of fracture risk and monitoring the effect of treatment

How accurate is QCT?

With proper technique and specialised analysis software, the precision error for QCT is very small (about 1-2%), so ongoing monitoring patients at yearly intervals yields clinically useful results.
Because of its accuracy, QCT is considered to be the “Gold Standard” in bone density measurement.

What about the X-ray’s?

All bone density measurements excepting ultrasound use small amounts of radiation to determine the amount of bone present. In all cases, the typical x-ray doses received from QCT or DEXA examinations are small in comparison to other common radiation sources and are believed to represent no significant health risk.
A common misconception is that QCT x-ray doses are much larger than DEXA x-ray doses. In reality, x-ray doses from QCT and DEXA are comparable—especially when considering that a DEXA study is often accompanied by a lateral spine x-ray.
The exposure given during QCT Bone densitometry is only slightly more than that for a chest x-ray and considerably less than that of a conventional spinal x-ray.
At these levels, QCT does not involve significant exposure to radiation and the benefits (diagnosis and subsequent treatment of osteoporosis) outweigh the risks posed by the small amount of radiation.

Who should have an osteoporosis screen?

The ageing process affects everyone's bone mass and for women in particular, bone loss can accelerate around the time of the menopause when the body ceases to produce oestrogen.
Bone density assessment should ideally take place at around age 40 or above in those at risk of osteoporosis to identify early bone loss, take action to improve this and prevent fractures.

What happens at a QCT osteoporosis scan?

You will be given a gown to change into. No other preparation is necessary.
You will be positioned in the CT Scanner and images will be taken of the Lumbar vertebrae in your lower back.
The scan is painless and gives a negligible radiation dose.

How long does a QCT osteoporosis scan take?

The scan takes approximately 10 minutes.

When do I get the results?

A Consultant Radiologist with a specialist interest in bone disease will read and report your scan and you will know the result by post within seven days.
A copy of the report will also be sent to your GP.
If the report recommends further action, such as referral to a Consultant Rheumatologist or Gynaecologist, your GP will be able to arrange this with you.

What is the treatment for osteoporosis?

Osteoporosis does respond to treatment and it is possible to reduce the risk of fracture with appropriate treatment.

Common treatment / prevention measures include:

hormone replacement therapy (HRT)
medicines such as bisphosphonates or selective oestrogen receptor modulators (SERMS)
vitamin D and calcium (especially in the elderly)
lifestyle advice and measures to reduce falls, such as keeping fit and having eyes tested in old age.

All treatments should be supervised by your doctor or a specialist in osteoporosis.

How often can I have a QCT osteoporosis screen?

After an initial scan, usually around age 40-45, a subsequent scans may be required after an interval of one to three years. The timing of the follow-up scan will depend on the degree of osteoporosis and the treatment given.
In low-risk patients who do not require treatment, this is to provide a better overall view of lifetime risk, and in high-risk patients, this is to assess the effects of lifestyle changes and treatment.

I would like a QCT osteoporosis screen

This service is available to all patients referred by medical practitioner and as a “self referral” test for those meeting our referral criteria (see below).

Notes about Self referral

We always advise you to discuss your health and medical concerns with your GP or Hospital Consultant first, but you may also refer yourself for a QCT osteoporosis screen without going through your doctor, provided you meet our referral criteria. The CT scanning staff will discuss this with you when arranging your appointment.
If you “self refer” for this test, we will require you to provide us with your GP or Consultants details, so that a copy of the report can be forwarded for inclusion in your medical records, and any follow-up treatment planned.

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