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Fig. 7 2D single-slice QCT of L3 with a slice thickness of 10 mm. Volumetric BMD
measurements were performed in the cortical and trabecular compartment of L3 (white contours).
Note the calibration phantom in the table mat
to convert
the voxels
'
attenuation values in
Hounseld Unit into BMD values in mg/cm calcium hydroxyapatite
plane is selected through the middle of each vertebra parallel to the endplates. The
radiation dose for scout image and 3 slices of 10 mm thickness range between 0.2
and 1.0 mSv [
29
,
46
]. Alternatively, 3D QCT measurements can be obtained
allowing more sophisticated analysis of cortical and trabecular bone and the
imaging of trabecular bone microstructure. However, 3D QCT scans are associated
with higher radiation doses (about 1.5 mSv) [
29
,
46
]. Reproducibility errors for 2D
single-slice QCT at spine expressed as coef
cient of variation (CV) range between
1.4 and 4.0 %, those for 3D QCT between 1.3 and 1.7 % [
46
]. Compared to DXA,
the drawbacks of QCT are the higher radiation dose and the fact that the WHO
de
2.5 using DXA) is not applicable. Therefore,
QCT is not as commonly used as DXA and is predominantly performed in selected
patient populations and clinical trials [
48
].
Since routine thoracic and abdominal MDCT is one of the most frequently used
radiologic examination, it would be bene
nition of osteoporosis (T-score <
−
cial to use the obtained MDCT images to
conduct additionally BMD measurements of the spine [
49
]. Thus, further radiation
exposure is avoided. Particularly, patients with cancer would bene
t, since they
routinely undergo MDCT and are at increased risk of osteoporosis due to the cancer
related treatment [
50
]. Most routine thoracic and abdominal MDCT examinations
are performed with intravenous contrast medium. Therefore, the obtained BMD
values have to be converted to standard QCT equivalent BMD values which are
better useable for fracture risk prediction. Bauer et al. [
51
] and Link et al. [
52
]
demonstrated the feasibility to determine BMD values at the lumbar spine in axial
images of non-dedicated routine abdominal contrast-enhanced MDCT. Baum et al.
described lumbar BMD measurements without dedicated software and with
