Bone Densitometry Equipment

The Dept of Nuclear Medicine & Bone Densitometry provides a range of equipment for determining bone density. We now operate:

• three bone densitometers in a dedicated bone densitometry suite
• Two of the scanners share a common database on our internal computer network, allowing patients to be seen on either instrument. Scans may also be analysed and reported at other workstations in the department
  
• a mobile bone densitometry service in rural regions
• an ultrasound absorptiometer in the Women's Health Centre and at rural fairs
• a research only scanner at the Institute of Medical and Veterinary Research animal research centre

Reporting of all DXA scans uses the same report format, giving an indication of fracture risk, peer relationship, change since previous scan, and recommendations for followup and therapy. Reports are sent for upload to the hospital database, and from there to the statewide patient database. Reports are also available electronically to physicians via the IMVS.

Dual Energy X-Ray Absorptiometers (DXA)
The principle underlying DXA relies on measurement of the absorption of two different photon energies. By knowing how many photons are transmitted with respect to the number generated, the amount of bone mineral and soft tissue can be determined.

GE-LUNAR DPX-IQ This pencil beam densitometer is used primarily for research and some routine scanning. This older generation was installed in October 2000, to supplement the DPX-L. The primary difference between this scanner and the new instruments is the software platform.
GE-LUNAR Prodigy Vision The replacement for the GE-LUNAR Expert provides the same functionality, but utilises a mini-fan beam and high sensitivity Cadmium-Zinc-Telluride detectors, giving much lower radiation doses The high throughput of this scanner ensures patient waiting times are kept to a minimum
GE-LUNAR DPX-PRO This is the next generation pencil beam densitometer, and the evolution of the DPX-IQ. It uses the same software as the Prodigy Vision, allowing excellent compatibility for all scans performed by the service. Two scanners are in operation: at the RAH campus. This instrument replaced our original DPX-L (installed in 1990) scanner in mid 2005. The DPX-L and DPX-IQ databases have been imported into this system. Correlation studies of the two scanners show almost perfect agreement in the results, with minor discrepancies at the extremes of bone density. in our Mobile Bone Densitometry caravan providing rural South Australia with modern DXA facilities for most of the year. The improved scan times, and full calibration compatibility with the RAH campus bone densitometers ensures all patients, regardless of location, have continuity of care. Patients previously scanned on the Hologic QDR-1000+ have had their scan results converted and added to the DPX-Pro database. All mobile scan data is available at the RAH.
Hologic QDR-2000 This fan beam densitometer is used for research studies and replaces the QDR-1000+ (originally from the Mobile Bone Densitometry service) for routine animal research

 

Our DXA scanners capability and performance times are listed below:

	Scanner
Scan type	DPX-IQ	DPX-Pro	DPX-Pro (mobile)	Prodigy Vision	Hologic QDR-2000
Posterior/Anterior lumbar spine	3-4 minutes	1-2 minutes	1-2 minutes	1 minute	2-3 minutes
Femur (including Dual femur mode)				1 minute	2-3 minutes
Forearm	4-5 minutes	4-5 minutes	4-5 minutes	20 seconds	3-4 minutes
Lateral decubitus lumbar spine	6 minutes	6 minutes	6 minutes	90 seconds
lateral vertebral assessment (morphometry)				3-4 minutes
Orthopaedic (prosthesis monitoring)
Paediatric bone assessment
Hand for monitoring rheumatoid arthritis
Total body & body composition	20-30 minutes	15 minutes		4 minutes	5-7 minutes
Small animal/research mode

Ultrasound Absorptiometers
The principle underlying this method relies on the transmission of sound. The more dense and contiguous a material, the more sound will be transmitted. In addition, the speed at which the sound traverses the material is proportional to the contiguous nature of the material. These two properties can be used to assess the quality of bone. It is not a measurement of bone mineral.
Ultrasound measures of bone are poorly correlated to bone density, however, a number of research studies have shown that it may be a good predictor of fracture.
The limitation with this method is its poor reproducibility compared to DXA, making it unsuitable for monitoring therapy.

• McCue CUBA
  This is a contact ultrasounddevice, and is mainly used for screening. It is often taken to health fairs for promotional purposes. Patients should regard it as a one off measurement for screening purposes only.
  In use, the patient has the heel area of the foot measured, with a small amount of ultrasound gel on each side (patients are required to remove shoes and socks (or stockings). The transducers of the instrument are then placed in contact with the heel, and a sequence of measurements is performed.