1. Imaging Of
Musculo-Skeletal
System

2. Introduction
• “Imaging” excludes direct visualization of the
body… for e.g. arthroscopy.
• For all the right reasons Plain Roentgenography
is termed the mother of imaging in medical
science.
• Roentgen’s discovery of X-rays in 1895.

3. Imaging modalities
• Plain X ray
• Computerized Axial Tomography
• Magnetic Resonance Imaging
• Others  PET, Bone scan.

4. • EM spectrum ranges from cosmic waves to radio
waves.
• Visible spectrum  VIBGYOR
• Principle of vision  interpretation of chemical
reaction induced by visible light on retina.
• Possibility to expand the visible spectrum???
• “See” the effects of the non-visible spectrum.

5. R
o
e
n
g
e
n
o
g
r
a
p
h
y

6. Plain X ray imaging
• Principle based on a particular property of
electromagnetic waves  Penetrance.
• Penetration potential of EM waves α frequency.
• Objects which absorb/reflect EMW are termed
radio-dense objects.
• Radio-density depends on the composition, and
thickness a given object.

7. Pb
BaSO4
Bone
Muscle
Blood
Liver
Butter
Fat
Air
E
M
W

8. Object
EMW

9. How is a X-ray image taken?
F
i
l
m
X Ray
source
Object

10. X ray…
• Summation of shadow layers.
• Negative of the true image commonly used
• Shows structures closest to the film with the best
clarity.
• Clear anatomical knowledge is essential to
interpret a X ray.
• Should be obtained prior to any other imaging
techniques.

12. Tomography
• Is basically glorified Roentgenography, which
shows the anatomy much superiorly than a plain
X ray with the drawback of increased radiation
exposure.
• Conventional Tomography is a technique by
which an image is procured with the use of X
rays  emphasizing a particular plane of
interest and blurring the rest. (obsolete)

13. CAT
• CAT focuses on multiple planes of pre-
specified thickness around a particular pivot
line, usually the Axis being the pivot.

14. Advantages of CAT Disadvantages of CAT
• Excellent image resolution
• Faster procuring time (v/s
MRI)
• 3D reformations are possible
• Best imaging tech to detect
cortical pathology
• Radiation effectiveness (100-
200 times a plain X ray)
• Cost effectiveness
• Requires contrast to visualize
vessels.

15. M
R
I

16. Introduction
• Unlike the yet discussed techniques, it doesn’t
use ionizing radiations.
• As the name suggests, MRI incorporates two
physical principles, Magnetism and resonance.
• Magnets in discussion  H+ ions in our
body and the external magnetic field source.
• Resonance  b/w the magnetic moment of the
H+ ions and the magnetic impulse produced by
the external magnet.

17. The external magnetic field
• Strengths range from 0.3 – 1.5 Tesla
• 1 Tesla = 10,000 Gauss
• Earth’s magnetic field = 0.5 Gauss

18. “Outline” of the technique
• H+ ions in random rotation and alignment 
external magnetic field aligns them to a vector.
• Energy as radio wave pulse  applied to such a
setting, certain number of H+ ions 
knocked out of their alignment  eventually
return back as the ext energy wades off.
• Return phase  H+ ions emit energy  final
phase, resonates together  pattern picked up
by electronic devices and visualized.

19. T1 and T2????
• Time intervals pertaining MR scan include
Time of echo ; TE
Time of repetition ; TR
• T1  short TE + Short TR
• T2  short TE + Short TR
• Still ????

20. Practical purpose
• T1 weighted images depict Normal anatomy at
its best.
• T2 weighted images picks up “pathology” better
than T1.

22. Other differences
T1 T2
• Fat
• Marrow
• Brain WM
• Liver, pancreas
• Brain GM
• Kidney
• Spleen
• CSF
• Water, lung
• Bone, air, flowing blood
• CSF, water
• IVD
• Brain, GM
• Spleen
• Brain, WM
• Liver
• Fat
• Iron in basal ganglia
• Bone, air, flowing blood

23. MR in Orthopedics
• THE BEST method to detect soft tissue
pathology.
• Not of much use in cortical bone studies, as bone
cortex contains minimal H+ ions.

25. Pros and cons
Pros Cons
• Best soft tissue detailing,
contrast
• No ionizing rad:
• Possibility of creating infinite
no: of virtual planes
• Virtual arthroscopy +
• Cost
• Procuring time is high
resulting in more movement
blur
• Claustrophobia/ magnetic
implants
• Bone cortex poorly visualized

26. Other investigations
• USG  useful in detecting joint pathology like
effusion
• New generation high frequency probes can
detect hair line cracks which are not picked on X
rays.

27. Summarize
• X ray  absolute necessity in Ortho invest:
• CT  currently the best modality for cortical
studies.
• MRI  best to detect soft tissue pathology.
• None of these have a complete dominance over
the other.
• Cost  Pelvis Xray = Rs 135/-
CT = Rs 2000/-
MRI = Rs 6000/-

28. T
h
a
n
k
Y
o
u