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Nutrition plays a vital role in human health and is often considered to be a primary factor in the development of or protection from disease. As such, research investigators frequently incorporate a component of nutrition assessment as part of their overall research methodology.The role of the Bionutrition Core at the Clinical Translational Research Center is to assist these investigators in obtaining research-quality data in the area of nutrition.
The Bionutrition Core staff provides the following services to clinical investigators:
What is a metabolic kitchen?
A metabolic kitchen prepares nutrient-controlled meals for subjects participating in research studies. Meals are designed by the research dietitian and can be controlled for any one or a number of nutrients depending upon the research question. Subjects can be free-living and pick up pre-packaged food to take home, or they can be fed from the kitchen while staying in the hospital as an inpatient.
How is it different from a regular hospital kitchen?
The metabolic kitchen adheres to important operational and food safety guidelines used by institutional kitchens. However, metabolic kitchens are required to be more precise in food usage, measurement and preparation. For example:
Who uses the metabolic kitchen?
Any research approved by the CTRC Scientific Advisory Committee has access to the metabolic kitchen, as long as their needs have been well-defined in the protocol and reviewed by the research dietitian.
The CTRC at Cincinnati Children’s currently has the only metabolic kitchen in our area. Nutrition studies are on the rise nationwide, and we hope to support this trend among local researchers by providing access to such a facility.
The Body Composition Core Lab provides access to imaging techniques using:
The Clinical Translational Research Center (CTRC) of Cincinnati Children’s Hospital Medical Center operates three Hologic QDR-4500A densitometers by Hologic Inc., Bedford, MA. The main DXA facility is in Location E, floor 2, room E2.328. . An additional DXA facility is at our satellite in the Cincinnati Center for Clinical Research (CCCR) at 619 Oak St., Room 2669.
Our hours of operation are:
Appointments may be made by calling 513-636-6204.
All core staff are Ohio Department of Health-licensed general X-ray machine operators. In addition, two of our staff also are certified bone densitometry technologists (CBDT) from the International Society for Clinical Densitometry.
Institutional Review Board (IRB), radiation safety and CTRC Scientific Advisory Committee approval are needed for all research protocols requesting DXA services. Physicians may complete a diagnostic testing order form and fax to 803-1111 to order DXA scans for clinical patients. There is a weight limit of 350 pounds 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, AP lumbar spine, lateral spine, proximal femur or hip, distal femur and forearm.
We have the latest software (Apex) 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.
Additionally, we have high-power whole-body software to be used in people >250 pounds. This allows for more accurate analysis of lean and fat tissue in larger body sizes but also increases the radiation exposure by a factor of three for total body scans.
The FDA-approved pediatric reference database gives updated Z-scores for lumbar spine and whole body bone mineral density (BMD) for ages 3-20 years and for hip BMD ages 5-20 years. Reference data on BMD-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 percent or less. %CV’s for pediatric scans are slightly higher as follows:
Lumbar spine BMD = 0.85 Total hip BMD = 3.21 Total body BMD = 1.30 Total body lean mass = 0.98 Total body fat mass = 3.39 Total body percent 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:
Effective dose (µSv)
Hip scan, male
Hip scan, female
Whole body scan, male
Whole body scan, female
Thomas, S., Kalkwarf, H., Buckley, D., & Heubi, J. (2005). Effective dose of dual-energy X-ray absorptiometry scans in children as a function of age. Journal of Clinical Densitometry, 8(4), 415-422.
Peripheral Quantitative Computed Tomography (pQCT) Imaging.
The Clinical Translational Research Center at Cincinnati Children’s Hospital Medical Center operates a Stratec XCT 2000 pQCT (Orthometrix, White Plains, NY). It is operated by the same technologists and during the same hours as the DXA equipment. IRB / radiation safety approval and CTRC Advisory Committee approval are needed for all research protocols. The pQCT is available for research scans only. It is not available yet for clinical purposes as there is no pediatric reference database (normal range) available for interpretation.
The pQCT densitometer measures volumetric bone mineral density (BMD) (mg / cm3) and cross-sectional bone dimensions at peripheral skeletal sites: the radius and tibia. The pQCT allows for selective measurement of cortical and trabecular density, bone area, cortical area, cortical thickness, periosteal and endosteal circumference, muscle cross-sectional area and biomechanical strain strength indices. Bone density measurements by DXA (a two-dimensional technique) are affected by skeletal size, and changes in density may be obscured by changes in skeletal size. Measurement of volumetric BMD is advantageous because it is independent of skeletal size.
A pQCT scan takes about 10 minutes and is therefore generally not feasible in children under 6 years of age. Radiation exposure expressed as effective dose per scan site is approximately 0.3µSv.
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