Presentation delivered via Skype during the International Conference on Innovative Computing and Information Processes – 2012

1. MR Imaging Techniques
for the Assessment
of Osteoporosis
Renato Toffanin
Advanced Research Centre for Health,
Environment and Space
ICICIP 2012, Mahendrapuri, Tamil Nadu, India
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2. Osteoporosis is a metabolic disease
characterised by low bone mass
and structural deterioration with
an increased fracture risk.
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3. ARCHES

4. Atraumatic
osteoporotic fractures
mainly affect the
proximal femur, the
spine and the distal
radius.
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5. Osteoporosis represents a major
public problem, with a high impact
on quality of life and high rates of
morbidity.
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6. The osteoporosis landscape
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7. A big health worry for India
Over 30 million Indians have
osteoporosis and 80% are women.
The number of cases has almost
doubled in the last 10-15 years.
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8. Clinical diagnosis
The established modality to
diagnose and monitor
osteoporosis is dual-energy X-ray
absorptiometry (DXA), which
provides areal bone mineral
density (BMD).
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9. BMD measurement sites
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10. WHO guidelines
Peak Bone Mass
Normal
Osteopenia
Osteoporosis
T-Score -2.5 -2 -1 0
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11. Fracture risk
BMD is a limited predictor of
fracture. It explains about 70% to
75% of the variance in strength.
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12. Additional factors such as bone
architecture, tissue composition
and micro damage determine
bone strength.
Accordingly, high resolution
imaging techniques are needed
for measuring bone quality.
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13. Magnetic resonance imaging
(MRI) is an emerging technology
for acquiring high-resolution
images of cortical and trabecular
bone in vivo.
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14. In conventional MRI, bone yields a
low signal and appears dark due
to the relatively low abundance of
protons and an extremely short T2
relaxation time (< 1 ms).
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15. The MR signal stems largely from
the marrow, and depends on the
pulse sequence used and the fat
content of the marrow (fatty vs
hematopoietic bone marrow).
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16. Sagittal T1-weighted fast spin-echo image of the
calcaneus with an in-plane resolution of 195 µm.
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17. Quantitative MRI
Information regarding structure,
topology and orientation of the
trabecular bone network can be
extracted from the images by
applying digital processing
techniques.
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18. Image analysis
Analysis of trabecular bone images
involves several post-processing steps:
outlining of the ROI, correction of the
coil sensitivity, bone/marrow
segmentation, structural calculations
and, if needed, serial image
registration.
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19. Trabecular bone analysis
Structural parameters are commonly
divided into 3 classes including scale
(e.g. volume of bone and thickness),
topology (e.g. plate- or rode-like
structure) and orientation (e.g. degree
of anisotropy).
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20. High-resolution MR image of the calcaneus acquired
at 3 T and a selected ROI. The color-coded map
illustrates the different assignments of bone voxel to
their closest junction based on minimum geodesic
distance (Source: Carballido-Gamio et al. Magn
Reson Med, 2009, 61: 448)

21. T2* measurements
Alongside high-resolution MRI for
structural analysis, T2* measurements
can be performed to assess bone
quality.
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22. T2* is sensitive to inhomogeneities
caused by susceptibility differences at
the interface between bone marrow
and trabecular bone.
T2* depends on trabecular bone
density and is shorter in normal
trabecular bone than in osteoporotic
tissue.
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23. T2* mapping of the calcaneus
The preferred site for T2* relaxometry
is the heel bone, mostly composed of
spongy bone (95%). T2* mapping of
the calcaneus is extremely sensitive in
identifying changes in bone quality
that are not revealed by BMD.
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24. ST
CC TC
T2* map showing the examined calcaneal sites: cavum
calcanei (CC), tuber calcanei (TC) and subtalar region
(ST).
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25. T2* mapping of the spine
Trabecular bone is also prominent in
the vertebral body (up to 90%). The
spine certainly represents the most
critical site for quantitative MRI since
vertebral fractures are the most
common type of osteoporotic
fractures.
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26. MRI: sagittal plane T2*W
5 SLICES
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27. Image analysis: sagittal plane
Monoexponential Levenberg-Marquardt fit algorithm
Dahnke and Schaeffter, Magnetic Resonance in Medicine, 20052

28. MRI: axial plane
L2 T2*W
5 SLICES
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29. Image analysis: axial plane

30. Contacts
E-mail: toffanin@arches-centroricerca.org
E-mail: retoffanin@gmail.com
Skype: arches02
www.arches-centroricerca.org
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