Investigators: Gary S. Beaupré, PhD and Robert T. Whalen, PhD

Project Staff: Norbert Pelc, PhD; Tammy Cleek, MS; Chye Yan, PhD; and Cliff Les, PhD

Project Category: Osteoporosis - 2000

Summary: Clinical treatment strategies need to be developed to maintain and/or restore bone mass in the elderly and in patients such as those sustaining spinal cord injuries. A mathematical-based theory for bone maintenance and remodeling has been developed by us and qualitatively validated through computer simulations of bone development, bone adaptation, and bone remodeling after prosthetic implantation. The objective of this project is to quantitatively validate and refine the model by measuring bone loss in the calcaneus of persons who have sustained a spinal cord injury.

Objectives: The objective of this project is to use quantitative computed tomography (QCT) imaging of the calcaneus (heel bone) to study functional adaptation of bone to mechanical stimuli. In this study we will investigate the nature of bone remodeling and the related issue of reversibility of changes in bone density and structure in cancellous and cortical bone.

Research Plan: This project will involve the use of QCT to measure serial changes in bone mass. This study requires the development of new techniques, that are both precise and accurate, to measure bone density and changes in bone density with time. The two main techniques are image registration software and beam hardening correction software. In addition, a novel foot immobilization fixture is required to minimize motion artifact during scanning.

Methods: Accurate image registration software involves realigning two images of the same bone taken at two different times. Image registration will be based on the assumption that the surface of the calcaneus does not change with time, while the internal distribution of bone density does change with time. Beam hardening correction software is needed to insure that measured changes in bone density reflect real changes and are not simply artifacts from differences in beam hardening characteristics between images. Finally, a foot immobilization fixture has been developed that relies on a dilational cast technology used in conjunction with an inflatable membrane.

Findings: Our productivity on this project is indicated by the following selected publications:

Yan CH, Whalen RT, Beaupré GS, Yen SY, Napel S: Modeling of polychromatic attenuation using computed tomography reconstructed images. Med Phys, 26(4):631-642, 1999.

Giddings VL, Beaupré GS, Whalen RT, Carter DR: Calcaneal loading during walking and running. Medicine and Science in Sports and Exercise 32(3):627-634, 2000.

Yan CH, Whalen RT, Beaupré GS, Yen SY, Napel S: Reconstruction algorithm for poly-chromatic CT imaging: with application to beam hardening correction. IEEE Transactions on Medical Imaging, 19(1):1-12, 2000.

Les CM, Whalen RT, Yan CH, Cleek TM, Beaupré GS, Willis JS: The x-ray attenuation characteristics of human calcaneal marrow do not change significantly during adulthood. Submitted to the Journal of Bone and Mineral Research.

Funding Source: NASA

Updated 02/02/2001