Bone Densitometry & Body Composition Suite

Dual Energy Abosrbiometry (DXA)

The bone and body composition suite operates a Hologic Discovery DXA scanner located in the CCTS Clinical Services. It is a flat-bed, C-arm scanner that uses fan-beam technology to acquire an areal image. DXA analyzes bone mass and body composition (fat and lean tissue) and can be used for children as well as adults.

The Hologic Discovery DXA is capable of producing the following scan types:

  • Total body (subregion analysis also available)
  • A/P lumbar spine pair
  • Supine lateral lumbar spine pair
  • Vertebral fracture assessment (VFA)
  • Proximal femur (Hip)
  • Distal femur
  • Forearm

We have APEX software version 2.3 from Hologic, Inc. for scan analysis and an FDA–approved pediatric reference database. The FDA–approved pediatric reference database provides Z-scores for lumbar spine and whole body bone mineral density (BMD) for children ages 3–20 years. Hip BMD Z-scores are provided for children ages 5–20 years.

Frequently Asked Questions

How long does a DXA take?
Depending on what scans are being acquired, a DXA may take anywhere from 5 to 25 minutes.

What is the effective dose of radiation associated with a DXA?
Effective dose varies with scan type. The National Council of Radiation Protection and Measurements (NCRP) has recommended the annual effective dose limit for infrequent exposure of the general public, including children, is 5,000 µSv and that an annual effective dose of 10 µSv be considered a Negligible Individual Dose.

Scan Type Whole Body A/P Spine Proximal Femur Forearm
Effective Dose (uSv) 2.6 4.0 1.3 0.05

PEA PODAir Displacement Plethysmography (PEA POD)

The bone and body composition suite also offers infant plethysmography via the “PEA POD” (Cosmed), which utilizes air displacement for determining percent fat and fat-free mass in pre-term and term infants. The test consists of measuring the infant’s mass (weight) and volume, which is determined while the infant lies inside the PEA POD chamber. Once the infant’s volume is determined, body density is calculated and the relative proportions of fat and fat-free mass are estimated.

Infants from 1 kg up to 8 kg can undergo PEA POD testing, and testing takes approximately 7 minutes. Watch a demonstration video.

Peripheral Quantitative Computed Tomography (pQCT)

The bone and body composition suite also houses a Norland Stratec XCT 2000 pQCT. pQCT measures bone density at peripheral skeletal sites by acquiring a three dimensional image. Using "CAT" scanner technology, pQCT provides a detailed analysis of both trabecular and cortical bone compartments at the forearm and tibia. Aside from volumetric bone mineral density, other parameters measured include bone mineral content, bone area, cortical thickness and strength, as well as muscle cross-sectional area.

How long is the scan time?
Scan Time is approximately 2.5 minutes per image.

What is the effective dose of radiation from pQCT?
Effective dose at the site of measurement is between 4 and 9 mRem per scan. Averaged over the whole body, effective does is estimated to be 3 μSv per scan in adults.

Quantitative Ultrasound (QUS)

The bone and body composition also houses a Sunlight Omnisense 8000 to evaluate bone strength via quantitative ultrasound (QUS). QUS operates on the axiom that the speed of sound (SOS) is directly proportional to the density of the material through which it travels. The speed at which the sound propagates through the bone is calculated as the time between sound transmission and receipt.

SOS can be done at the mid-shaft tibia or 1/3 distal radius. Three to five consecutive measurement cycles are performed, after which SOS (m/s) is determined and appropriate score (Z-score or T-score) is reported. QUS can be performed on adults, children, term and pre-term infants, is portable, not associated with ionizing radiation, and measurements can be completed on most participants within 30 minutes.

Bioelectrical Impedence Analysis (BIA)

Bioelectrical impedance analysis (BIA) may capture complementary information on adiposity and nutritional status that is not thoroughly captured by anthropometric indices, such as body mass index (BMI) and waist circumference or skinfold thickness. BIA is a simple and non-invasive method of measuring the body’s resistance and cell capacitance to a small electrical current. This technology is based on the axiom that electrical conductivity is greater in fat-free mass (FFM) than fat mass since FFM contains nearly all of the body’s fluids and electrolytes. From the resistance and capacitance, total body water (TWB) can be calculated, yielding an indirect measure of fat-free mass.

Questions?

Please contact Hillarie Slater for more information or with questions about the bone densitometry and body composition suite services.