Errors in measuring trabecular bone by computed tomography due to marrow and bone composition

Abstract

The linear attenuation coefficient (mu in cm-1) of trabecular bone was modeled for different conditions of bone and marrow composition in order to assess their influence on computed tomography (CT) quantitation. A large relative change (10% of TBV at 15% TBV) of bone concentration resulted in small changes of mu: 2.3% at 60 keV, 3.4% at 44 keV, 5.2% at 29 keV. Relative changes of trabecular bone volume (TBV) on the order of 3% could be detected in vivo by CT were it not for errors of relocation and for compositional influences on accuracy. The mu (and density) depended critically not only on amounts of bone substance and marrow but on their compositions. Normal variation in the composition of bone substance produced an uncertainty in mu equivalent to 0.5 to 1% TBV. Increases of yellow marrow produced a decrease of mu which could be mistaken for a decrease of bone concentration. The biological variation (90% confidence limit) of marrow composition gives an uncertainty at 15% TBV of about 2.4% TBV at 60 keV, 1.7% at 44 keV, and 1.3% at 29 keV. These correspond to relative uncertainties of 16, 11, and 9% respectively. These factors help explain the large accuracy errors (30%) observed in all studies of trabecular bone where single-energy CT was used. Marrow composition also can affect precision of bone measurement. Systematic shifts of red and yellow marrow could mask biological changes such as those occurring with aging or treatment.

Bone Densitometry for Diagnosis and Monitoring Osteoporosis

“…It is possible to reduce this 5-fold (66,69). A high kilovoltage also is undesirable because it increases the large accuracy errors (at least 15-25%) associated with variable marrow fat and varying osteoid (83)(84)(85)(86)(87)(88)(89)(90)(91)(92)(93)(94)(95)(96)(97)(98). Gluer et al (99) showed an error of ash density of 8 mg/cm3 for every 100 mg/cm3 change of marrow fat, but the error at higher energies is 10-13 mg/cm3, i.e., 30-50% greater (85,92,(99)(100)(101).…”

Quantification of bone mineral measured by single-energy computed tomography

“…Reich et al (1976) were also using the CT single-energy tech-nique, and their report is in agreement with our findings. As earlier stated (Mazess 1983) dual-energy computed tomography increases the accuracy, but the precision may be reduced compared with single-energy computed tomography. Mechanical tests have shown that rotational and axial loading of the femur have the highest correlation with the QCT bone-massrelated measurements (Alho et al 1988, Husby et al 1989).…”

Rotational strength of the femoral neck: Computed tomography in cadavers

“…Earlier reports have mainly dealt with CT measurements of mean density within a defined volume of bone, thus including both cortical bone and bone marrow (Mazess 1983, Bentzen et al 1987. Our approach, by defining a lower density threshold limit, may, to some extent, reduce this error.…”