My research interests mainly involve techniques for extracting bone strength information from x-ray image data and the application of those methods in clinical research. The initial development work was done on dual energy gamma ray absorptiometry scanners and most of the remaining work has used dual energy x-ray absorptiometry (DXA) based. The techniques mainly involve the extraction of structural geometry of bone cross-sections for use in engineering analyses. The method has been widely used in research studies in both children and adults at centers around the world. The technique has been applied to studies of gender differences in growing children, the effects of exercise and skeletal load in children and adults, prediction of stress fractures in military recruits, evaluation of general aging effects and studies of dietary supplements and osteoporosis treatments etc. Work has been funded by the US National Institutes of Health, the US Naval Health Research and the US Army (for prediction of stress fractures). The method has recently been licensed by Hologic Inc of Waltham MA, and has gotten FDA approval for incorporation into their commercial DXA scanner software.

My interests extend to the optimization of DXA scanners and their underlying physics for use in providing better measurements of bone geometry. Image quality and the limitations of a single projection image limit the accuracy and precision for measurements of bone geometry using DXA scanners which are designed and optimized for bone densitometry not structural assessment. Toward that end work has been done under funding from the National Biomedical Space Research Institute (NSBRI) in collaboration with engineers at the Johns Hopkins Applied Physics Laboratory on the development and testing of DXA scanner designs specifically configured to measure bone geometry extended to 3D using multiple projection data.

My most recent efforts have been dedicated to extending the bone structural analysis method to the evaluation of the human hip using multi-slice quantitative computed tomography methods. This work is designed to be a stand-alone application as well as reference for validating the 3D DXA methods under development.
 

• Bone mechanical properties using X-ray imaging technique

Curriculum Vitae

Biosketch

Personal Pages

Software:

• Tom Back's Handy Dandy Bone Geometry Simulator Program (download)

The bone geometry simulator program is distributed free-of-charge for any interested individual.  The purpose of the program is to illustrate how the dimensions of a cylindrical bone influence its structural geometry and its BMD as would be measured by a DXA scanner (aBMD) or by a CT scanner (vBMD).   The cross-sections are elliptical and can be adjusted by the user.  The inner and outer cortices are simulated by ellipses.  The position of the inner ellipse center can be adjusted to produce asymmetric cortices, the outer ellipse remains centered on the coordinate axis.  The volume fraction of both the trabecular core and of the cortices can be adjusted as can the average mineralization of the bone (throughout trabeculae and cortex).  The program provides scale drawings of simulated cross-sections.  There are three tabbed screens in the program. Tab 1 permits you to determine the geometry of a cross-section then produce a drawing.  Tab 2 is similar except that two cross-sections are produced so that changes can be made to dimensions to evaluate the effect on BMD/BMC geometry etc.  The third tab can simulate a homeostatic process whereby one property can be kept fixed while a selectable dimension is changed.  Then another selected dimension is adjusted until the property returns to its original value. 

This is a beta version of the program and while the results should be accurate, I am sure that there are ways to cause erroneous values in this version so if you discovery any problems please e-mail me (tjbeck@jhmi.edu).  Also please write with comments, suggestions and critiques.   If you use the program in your publications, I would appreciate an acknowledgement.  Hope you find it useful.  

The programming was done by Ms. Alia Khaled.

In the future I plan to post improved versions with a help file as well as a complete listing of the math used in calculations.