Osteoporosis - Spinal Imaging and Image Analysis - page 71

cortical margins, can be directly visualized by using MDCT. It is less expensive
than MRI and may provide important information for differentiating between
osteoporotic and malignant fractures and assessing bone matrix changes [ 34 ]. Low-
dose MDCT protocols for the visualization of the spine were reported with a dose
of 2.2 mSv for men and 3.3 mSv for women [ 35 ]. Therefore, radiographs should be
primarily used for the initial assessment of osteoporotic vertebral fractures. How-
ever, clinicians have to be aware that MDCT can more accurately assess vertebral
fractures than standard radiographs and has to be used in unclear cases. Bauer et al.
compared the performance of lateral radiographs and sagittal reformations of axial
MDCT images in detecting osteoporotic vertebral fractures [ 35 ]. They examined 65
vertebrae which were harvested from 21 human cadaver spines with a 64-row
MDCT scanner. Ninety- ed by using

sagittal reformations of 1 mm slice thickness, but 18 % of the fractures were missed
on the radiographs. Thus, the authors concluded that sagittal MDCT reformations
could more accurately assess vertebral fractures than standard radiographs. Fur-
thermore, sagittal reformations of axial MDCT in-vivo images of the spine sig-
ni

ve percent of the fractures could be identi

cantly improved the detection of osteoporotic vertebral fractures and other spine
abnormalities, compared to axial images [ 36 ].
However, osteoporotic vertebral fractures often occur in absence of a speci

c
trauma and are asymptomatic. Thus, they frequently do not come to clinical
attention and dedicated imaging for the diagnosis of osteoporotic vertebral fractures
is not performed. Consequently, initiation of appropriate therapy is delayed.
Therefore, it is highly important to report prevalent osteoporotic vertebral fractures
in routine chest radiographs and routine thoracic/abdominal MDCT images, which
are one of the most frequent performed radiologic examinations (Fig. 4 ). However,
osteoporotic vertebral fractures are underdiagnosed in these non-dedicated images
[ 37 40 ]. Therefore, the International Osteoporosis Foundation (IOF) and the

European Society of Musculoskeletal Radiology (ESSR) have started a teaching
initiative to raise the awareness of radiologists to report prevalent osteoporotic
fractures at the spine, which is well suited to improve the accurate diagnosis and
reporting of prevalent vertebral fractures on lateral chest radiographs [ 41 ]. Fur-
thermore, the development of semi-automatic segmentation techniques for lumbar
radiographs and MDCT images as computer-assisted detection tools may support
radiologists to correctly diagnose and report prevalent osteoporotic vertebral frac-
tures [ 42 , 43 ]. Roberts et al. [ 42 ] presented a semi-automatic determination of
detailed vertebral shape from lumbar radiographs using active appearance models.
The vertebral body outlines were manually annotated by radiologists in 670 lumbar
radiographs to obtain a training set. This was used to build statistical models of
vertebral shape and appearance using triplets of vertebrae. In order to segment the
vertebrae, the models were re

-

tted using a sequence of active appearance models of
vertebral triplets. The accuracy achieved on normal vertebrae was good. However,
the accuracy performance deteriorated with increasing fracture grade, but even in
fractured vertebrae, point-to-line accuracy was below 2 mm in 79 % of the cases.
The authors concluded that the located detailed vertebral shapes may enable the
development of more powerful quantitative classi