Dual Energy X-Ray Absorptiometry (DXA) Imaging
The General Clinical Research Center of Cincinnati Children's Hospital Medical Center operates three Hologic QDR-4500A densitometers, Hologic Inc., Bedford, MA. The main DXA Facility is located on A3South, Room 171. An additional DXA facility is located at our satellite in the Cincinnati Center for Clinical Research (CCCR) at 619 Oak Street, Room 2669. Our hours of operation are:
Monday - Friday, 8:30 AM – 5:30 PM and
one evening per week until 7:00 PM by request
Saturdays 8:30 AM - 1:30 PM
1st & 3rd Saturday of the month at CCCR/Oak
2nd & 4th Saturday of the month at GCRC
Appointments may be made by calling (513) 636-6204 or faxing (513) 636-2866.
The staff members, Gemma Uetrecht, Arin Fletcher, and Donna Buckley, are Ohio Department of Health licensed General X-Ray Machine Operators. Gemma and Donna are also Certified Densitometry Technologists (CDT) from the International Society for Clinical Densitometry. Our Saturday technician, Miranda Elmore, is a full time licensed Radiology Special Imaging Technician from the Radiology Department.
IRB/Radiation Safety approval and GCRC Advisory Committee approval are needed for all research protocols. Physicians may complete an Ancillary Order Form, obtained from the DXA staff, to order DXA scans for clinical patients. All females who have started their menses will have a pregnancy test performed before they are scanned. There is a weight limit of 300 lbs. on the densitometers.
DXA has become increasingly popular for measurement of total body bone, lean and fat mass and for measurement of regional bone mass and density. It is highly accurate, precise and sensitive in both pediatric and adult populations. Scans available include:
Whole Body, Lumbar Spine, Lateral Spine,
Proximal Femur or Hip, Distal Femur and Forearm
We have the latest software (version 12.6) from Hologic, Inc, for scan analysis and an FDA approved pediatric reference database. The software includes a new "Auto Low Density" mode for analyses of spine, hip and whole body scans. This new analysis mode uses lowered thresholds at which the algorithms determine bone and soft tissue to account for smaller body sizes. The analysis program automatically determines which threshold to use based on the body size it detects. This allows for a more accurate and reliable assessment of pediatric bone density and body composition.
The FDA approved pediatric reference database (12/04) gives updated Z-scores for lumbar spine and whole body bone mineral density (BMD) ages 3–20 years and for hip BMD ages 5–20 years. Reference data on BMC-for-height are not yet available. In the last 10 years, there have been several technological changes in DXA scan acquisition and analysis that affect the appropriateness of the original Hologic reference database. The new reference database was developed from scans acquired on modern fan beam systems and analyzed with the new software.
Our precision data were calculated from scanning 20 adults and 16 children < 12 years of age. BMD for all scans and body composition measurements from the total body scan in adults have %CV's of 1.0% or less. %CV's for pediatric scans are slightly higher as follows:
Lumbar Spine BMD = 0.853
Total Hip BMD = 3.21
Total Body BMD = 1.30
Total Body Lean Mass = 0.98
Total Body Fat Mass = 3.39
Total Body % Fat = 2.48
Scan results are available either as a hard copy report or as a database export in MS Access.
Radiation exposure from DXA scans is minimal. The National Council of Radiation Protection and Measurements (NCRP) has recommended the annual effective dose limit for infrequent exposure of the general public that would include children is 5,000 µSv and that an annual effective dose of 10 µSv be considered a Negligible Individual Dose. The average annual background radiation exposure in the United States is 3,000 µSv/yr or about 8 µSv/day. The following table lists the\Effective Doses for DXA scans:
| Age (yrs) | Effective Dose (µSv) |
|---|
| Lumbar Spine | Hip Scan,
Male | Hip Scan,
Female | Whole Body Scan, Male | Whole Body Scan, Female | Forearm Scan |
|---|
| 1 | 4.7 | 15.2 | 6.4 | 3.4 | 3.5 | 0.14 |
| 5 | 3.3 | 13.2 | 6.1 | 2.9 | 3.0 | 0.10 |
| 10 | 2.7 | 8.3 | 5.6 | 2.5 | 2.7 | 0.066 |
| 15 | 2.2 | 6.3 | 4.7 | 2.0 | 2.2 | 0.03 |
| Adult | 2.2 | 5.1 | 4.6 | 1.8 | 2.1 | 0.03 |
Contact Us
For more information about the General Clinical Research Center Body Composition Core Laboratory at Cincinnati Children's Hospital Medical Center, please contact Donna Buckley, (513) 636-8549, or donna.buckley@cchmc.org.
