Region 02 · Radiationbodycomposition.com.au

DXA and radiation

A DXA scan uses ionising radiation, and ARPANSA gives the typical dose in DEXA scans as between 0.001 and 0.01 millisieverts (mSv). Its Radiation Health Committee says that a scan done only to find body fat and lean tissue, with no clinical indication behind it, does not justify that radiation, because it brings no net benefit.

Typical dose: 0.001 to 0.01 mSv, ARPANSA
Comparison: Roughly one day of the general environment, for bone density testing (Better Health Channel, Victoria)
Code: RPS14 in ARPANSA’s 2016 statement; since superseded by RPS C-5 (2019), together with RPS C-1

General information Not medical advice. Call Triple Zero (000) in an emergency, or go to the emergency department of your nearest hospital. For health information, see healthdirect; for radiation safety, see ARPANSA: Code for Radiation Protection in Medical Exposure (RPS C-5).

Method

Why the scan uses radiation at all

DXA is an x-ray imaging technique. ARPANSA describes it as a way to work out the mass of one material when another is also present, using what is known about how each one weakens an x-ray beam at different energies. For body composition, two images are made at a low and a high average x-ray energy and compared electronically to derive measures such as fat mass and lean soft tissue mass. To assess overall body composition, ARPANSA says, a total body scan is needed. The x-rays are what make the measurement possible, and they are also the dose this guide is about.

Dose

The dose, in two official descriptions

Radiation note

ARPANSA’s statement on DXA gives the radiation dose in DEXA scans as typically between 0.001 and 0.01 mSv.

Victoria’s Better Health Channel, writing about bone density testing, calls it a safe procedure and says its radiation dose is about what the general environment would give you over roughly one day.

The range ARPANSA’s statement gives for the dose in DEXA scans. The bar shows the range only; it is not a reading from any scan.

The two pages describe the dose in different terms: ARPANSA as a range in millisieverts, the Better Health Channel against a day of ordinary life. The first comes from the national radiation agency’s statement on DXA, the second from the Victorian Department of Health’s consumer page on bone density testing, and both are listed at the foot of this page.

ARPANSA statement

ARPANSA’s committee on body composition scans

ARPANSA’s Radiation Health Committee has considered the use of DXA to work out relative body tissue composition. It says it is concerned about the scan’s increasing use in the fitness and weight loss industry. Its statement then makes three points.

Position

A scan for body fat and lean tissue with no clinical indication behind it is “not a justified use of ionising radiation”, since it brings no net benefit.

Alternatives

Other methods of measuring lean body mass, which involve no ionising radiation, are available.

Code

In its 2016 statement, ARPANSA said DXA as a medical procedure was regulated by its code RPS14, which required appropriate referral, justification and approval by appropriately qualified medical practitioners. ARPANSA has since superseded RPS14 with its Code for Radiation Protection in Medical Exposure (RPS C-5, 2019), together with RPS C-1.

Victoria builds a code of practice into its licensing. Its Department of Health’s page makes complying with the code of practice on radiation protection in the medical applications of ionizing radiation a condition of the use licences it issues to bone mineral densitometry operators. ARPANSA calls that code RPS 14. Who may run a DXA scan sets out the rest of Victoria’s licensing.

Victoria

Victoria’s condition for body composition scans

For body composition, Victoria’s condition M1758 requires management licence holders to follow the Department of Health’s “Requirements for the assessment of body composition using DXA”. These are Victoria’s requirements; other states and territories set their own.

Pregnancy

Victoria’s Better Health Channel says there are several things to talk through with your doctor before bone density testing. Its list includes:

your medical history
your risk factors for bone disease
whether you are pregnant: the page says pregnant women should not have bone density testing
any special instructions to follow beforehand.

The list is introduced with “including”, so read the Better Health Channel’s page for its context. Its caution on pregnancy is written for bone density testing, and its advice is to raise these points with your doctor before the test.

Children

Radiation note

ARPANSA’s statement says scans of children need additional attention to technique, to avoid an increased radiation dose.

Referral

Where a referral comes in

For a bone density scan, healthdirect says you will need your doctor or specialist to refer you. Before a DXA scan walks through the referral, Medicare’s bone density items and the day itself, and What a scan measures explains what the scan measures.