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Precise measurement of vertebral bone density using computed tomography without the use of an external reference
S D Boden1, D J Goodenough, C D Stockham
1Department of Radiology, George Washington Medical Center, Washington, DC Washington, DC 20037.
Journal of Digital Imaging
|February 1, 1989
Summary
This study introduces an improved quantitative computed tomography (QCT) method using internal reference tissues, like muscle and fat, to enhance bone density measurement accuracy. This technique offers better precision than external phantoms, crucial for detecting small annual bone density changes.
Area of Science:
- Medical Imaging
- Radiology
- Biomedical Engineering
Background:
- Quantitative computed tomography (QCT) for bone density measurement typically relies on external reference phantoms.
- External phantoms can introduce inaccuracies due to their peripheral location and susceptibility to artifacts like beam hardening and scatter.
- These limitations affect the precision and accuracy of bone density measurements.
Purpose of the Study:
- To develop and evaluate a computer program utilizing internal reference tissues (paraspinal muscle and fat) for QCT bone density measurement.
- To eliminate the need for external reference phantoms in QCT scans.
- To improve the accuracy and precision of QCT by using tissues proximal to the target bone.
Main Methods:
- A computer program was developed to use paraspinal muscle and fat as internal reference standards.
- A user-interactive computerized histogram plotting technique was employed to derive CT numbers for muscle, fat, and trabecular bone.
- Reproducibility was assessed using 165 images with varying degrees of region-of-interest (ROI) mispositioning.
Main Results:
- The use of internal reference tissues and histogram technique demonstrated improved scan-to-scan reproducibility and inter-scanner precision.
- Precision of better than 1% for normal patients and 1% to 2% for osteoporotic patients was achieved with ROI mispositioning.
- This represents a twofold improvement in precision compared to the standard technique using external phantoms.
Conclusions:
- Internal reference tissues offer a more accurate reflection of local X-ray spectra and scatter compared to external phantoms.
- The developed histogram technique with internal references significantly enhances the precision of QCT bone density measurements.
- Improved precision is critical for QCT's clinical utility in detecting subtle annual changes in bone mineral density, aiding in osteoporosis management.