This document provides an overview of various imaging techniques used in orthopaedics, including their history, uses, and classifications. It discusses techniques such as x-rays, CT, MRI, ultrasound, bone scans, and DEXA scans. For each technique, it covers the basic principles, advantages, disadvantages, and applications in orthopaedics such as diagnosis, surgical planning, and monitoring treatment.

1. IMAGING TECHNIQUES
Presented by
Dr Binod Chaudhary
Department of Orthopaedics
WRH, PoAHS

2. Contents
• Introduction
• Historical perspective
• Classification of different types of imaging techniques
• General application of imaging in orthopaedics
• Conclusion

3. INTRODUCTION
• A veritable tool in the evaluation of surgical patients.
• Many surgical diagnoses can be made with clinical assessment.
However, radiological investigations remains vital to the diagnosis,
preparation and follow up of patients
• A myriad of imaging options are available.
• Initial application of radiography lay in the demonstration of fractures
and radio-opaque foreign bodies.
• Subsequent parallel development of Radiology and Orthopaedics had
broaden the scope.
• Today, high precision interventional therapeutic procedure can be
carried out.

4. HISTORICAL PERSPECTIVE
• Wilhelm Conrad Rontgen: discovered x-rays(1895). Nobel prize in
1901 (father of radiology).
• 1920: use of contrast for x ray studies
• 1950s: nuclear medicine was born
• 1970s: ultrasound came into use
• Sir Godfrey Hounsfield invented CT in 1975.

5. USES OF RADIOLOGICAL TECHNIQUES
• To aid diagnosis of a medical and/or surgical disorder
• To guide a surgical procedure
• Monitoring
• Interventional radiological techniques

6. CLASSIFICATION OF IMAGING TECHNIQUES
Current techniques in practice of orthopaedics include:
• Clinical photograph
• X-rays (plain radiographs)
• Fluoroscopy
• Ultrasound
• Computed tomography
• Magnetic resonant imaging
• Radionuclide scanning
• Bone densitometry

7. CLINICAL PHOTOGRAPH
• First line imaging
• For documentation and monitoring
• Uses
In trauma with soft tissue
involvement
In management of clubfoot pre-,
intra- and post correction
Angular deformities of the limb,
etc

8. X-RAYS (PLAIN RADIOGRAPHY)
Electromagnetic radiation
• Travel at speed of light ~3,00,000 km/s
• Not affected by electric or magnetic fields
• Travel through vaccum

9. X-RAYS (PLAIN RADIOGRAPHY)
Definition
• High energy radiation which undergo differential absorption by
tissues as they pass through the body
• Generated via interactions of the accelerated electrons with electrons
of tungsten nuclei within the tube anode.
• 2 types of x-rays generated: Characteristic radiation and
Bremsstrahlung radiation.

10. Characteristic Radiation Bremsstrahlung radiation

11. • Quantity of x-rays generated: directly proportional to number of
moving electrons.
• Quality of x-rays generated: proportional to the speed of the
electrons
• 2 outcomes when x-rays interacts with matter
1. Photoelectric absorption
2. Compton scattering

12. Basics of X-ray physics
• Travel in straight lines
• Body parts further away
from the detector are
magnified compared with
those that are closer and
vice versa.
• A source tat is too near the
patient will further
exaggerate the size of
structures nearest to that
sources.

13. Tissue densities
• an x-ray image is a map of x-
ray attenuation
• Attenuation of x-rays is
variable depending on
density and thickness of
tissues
• Describing x-ray
abnormalities in terms of
density may help in
determining the tissue
involved.
• The greatest contrast is
found in areas of greatest
difference in density of
adjacent structures.

14. Uses
• Invaluable investigation in orthopaedics
• Have wide application such as
Diagnosis
Planning of surgery
Intraoperative assessment of fixation of fractures
Monitoring of treatment and healing
Occasionally for interventions eg. Vertebroplasty, SNRB.
Advantages
• Cheap
• Easily available
• Good in assessing bone due to its high calcium content and intrinsic
contrast.

15. COMPUTED TOMOGRAPHY(CT) SCAN
• One of the major advances in radiology
in recent years.
• Uses a computer to create an image
from an integration of multiple xrays
exposures taken in a circle round the
patients.
• Heavy ionizing radiation dose.

16. • Attenuation: amount of x-rays absorbed by tissues
(different for different tissues)
• Hounsfield units describe the attenuation co-
efficient of tissues
• Bone=1000 Hu
• Water= 0 Hu
• Air= -1000 Hu
• There is a much wider range of attenuation co-
efficient than the greyscale a human eye can
perceive
• Different windows for different tissue types
allowing the whole range of attenuation to be
displayed and improves overall detail.

17. Advantages
• Reconstruction possible in any plane desired
• Good for surgical planning in complex fractures-
3D reconstruction
• Exellent resolution of cortical bone
• Better soft tissue attenuation than plain x-ray
• CT guided biopsy
• CT with contrast
Disadvantages
• Availability
• High resolution dose
• Claustrophobia

18. MRI
• Newest of the imaging techniques
• Does not use ionizing radiation
• Principle: body tissues consists of
protons/electrons. In a strong uniform
field such as MRI scanner, these nuclei
align themselves with the main magnetic
field.
A brief radiofrequency, pulse is applied
to alter the motion of the nuclei. When
removed, the nuclei realign with the
main magnetic field, emitting energy(RF
signal).

19. • T2 signal
• Time taken for the protons to loose
their coherence once radiofrequency
turned off
• Water rich tissues have longer T2 time
as they contain more protons
• Hence they release energy for a
longer time and give a high signal
• T1 signal
• Time taken for 63% of the protons to
return to the longitudinal spin axis

20. • Repitition time (TR) (msec)
• The time between repetition of pulses
• T2 images have very high TR time
• Otherwise the water dense tissues will not have released enough
energy to detect pulses are given frequency though, fat appears
white rather than water.
• Time to echo (TE) (msec)
• Time from when the pulse is stopped to when the signal is
measured.

21. • Differential sequences
• T1 weighted- short TR (TR<1000 ms), short TE(<60 ms)
fat=bright
fluid= dark
defining anatomy
• T2 weighted- long TR (TR>1000ms), long TE (TE>60 sec)
Fluid= bright
Defining pathology
• Proton density (PD)- long TR(TR>1000ms), short TE(TE<60ms)
• Part T1, Part T2
• Useful in certain situations e.g. the meniscus

22. • Contrast (Gadolinium)
• High net magnetic moment
• More strongly affects hydrogen
ions in close proximity to the
contrast.
• Enhances the image and results in
high signal on T1 scans as well.
• Shows pathologic fluid collections
better.

23. • Advantages
• No ionizing radiation
• High quality image
• Can be used with contrast
• Abscesses and intra-articular pathology
• Disadvantages
• Claustrophobia
• Noisy
• Not tolerated well by children
• Availability
• Contraindication to MRI e.g. aneurysm
clips and pace makers, internal hearing
aids,
• Metal artifacts: MARS sequence
• Over diagnosis of asymptomatic

24. ULTRASOUND
• Second most common method of
imaging
• Relies on high frequency sound waves
generated by a transducer containing
piezoelectric material
• Principle:
generated sound waves are
reflected by tissue interfaces and, by
ascertaining the direction and the time
taken for a pulse to return, it is possible
to form an image.

25. Acoustic impedance
• Impedance between tissues creates echo
• Minimal differences between fat and
muscle(most waves pass through)
• Large difference between air and
skin(most waves reflected-use gel)
• High impedance=bright
• Low impedance= dark

26. Advantages
• Non ionizing
• Cheap
• Portable
• Dynamic imaging
• Very good for cystic structures
• Biopsy, injection, aspiration
Disadvantages
• Highly operator dependent
• Only for superficial structures (cannot
penetrate cortical bone)
• Limited field of fiew
• Poor resolution comparatively

27. BONE SCAN(RADIONUCLIDE IMAGING)
• Gamma rays emitted from a radioactive isotope
of technetium 99 bound to a phosphate to give a
map of blood flow and osteoblastic activity
Technetium-99
• Unstable radioisotope
• Emits gamma rays
• Derived from the decay of molybdenum 99
• Short half life of 6 hours
• Excreted via kidney (bladder hydration and

28. Mechanism of action
• Technetium-99 is attached to methyl
diphosphonate(MDP) when injected iv
• The MDP interact with HA crystals in bone-
depending on adequate vascularity to the area
in question.
• Because HA crystals are generated by
osteoblasts mineralizing bone it is a direct
reflection of osteoblastic activity.
• The gamma rays emitted by the T-99 are dected
by a gamma camera
• A digital image is created giving a map of blood
flow and osteoblastic activity

29. Radionuclide imaging….
3 phases of triple bone scan
• Vascular phase (1-2min)
• Blood pool phase (3-5 min)
• Static phase(4 hrs)

30. Radionuclide imaging…
• Single photon emission computed tomography-CT (SPECT-CT)
• Gamma camera with CT component on the same scanner
• Multi-planar imaging
• Increasing resolution, decrease noise and increase localization
• Positron emission tomography-CT (PET-CT)
• Exploiting increase metabolic rato of tumors i.e glucose
consumption
• E.g deoxyglucose labelled 18 Fluorine (1/2 life-112 min)

31. Radionuclide imaging…
• WBC scan
• Labelling patient’s own WBC with radioactive tracer such as
indium
• Accumulation in the reticuloendothelial system e.g. bone marrow
liver and spleen but also areas of active infection
• Hybrid PET-MRI
• Potential increase bone metastasis assessment and response to
treatment

32. Useful for
• Tumors (metastatic and primary esp in spine)
• Infection-osteomyelitis
• Stress fractures
• Prosthetic loosening/pain
• Paget’s disease
Disadvantages
• Poor specificity although very sensitive
• Radiation dose is fairly high
• False negative in areas of low blood supply-e.g avascular bone, lytic
tumors

33. DEXA scan
• Dual energy x-ray absorbimetry
• Utilizes xrays of different energies
• Absorbed in different proportions by
bone and soft tissues
• Used to assess bone mineral density

34. Result interpretation
• Units of bone mineral density are g/cm3
• Values are related to the peak bone mass density of a young adult or
matched by age
• The T score represents comparison with peak BMD of a young adult
• The z score represents the age-matched score
• Sex and race are matched in both (only difference is age matching in
the Z score)
• The T score is used to determine whether there is osteoporosis
• The Z score is used to assess whether the reduced BMD is related to
another cause i.e lower than expected for age

35. WHO criteria for osteoporosis relies
on T score
• 0 to -1 =normal
• -1 to -2.5= osteopenia
• <-2.5 = osteoporosis
• <-2.5 +fragility fracture=severe
osteoporosis
Disadvantages
• No differentiation between cortical
and cancellous density
• Falsely high BMD in fractured
sclerotic vertebrae and degenerate

36. GENERAL APPLICATION OF IMAGING IN
ORTHOPAEDICS
General applications
• Diagnosis, classification and staging of diseases
• Preoperative planning and templating
• Intraoperative monitoring
• Therapeutic purposes
• Monitoring of treatment and healing process

37. Diagnosis
• Almost all the modalities are used to make or confirm diagnosis
• Plain radiography plays an invaluable role especially in trauma
• CT scan usuallu augments plain radiograph, though plays important
role in complex trauma
• Biopsies can be US, fluoroscopic or CT-guided
• DDH, Joint collection by US scanning
• Bone scans
• Bone densitometry

38. Pre operative planning
• Plain radiographs, CT scans with 3D reconstruction and MRI
• Plain radiographs used in templating
• MRI especially in spine, ligamentous injuries, oncology

39. Intraoperative
• Fluoroscopy in fracture fixations
• Limb reconstructions
• Corrective osteotomies
• Spine fixations
• Minimally invasive surgeries and closed reductions and fixation

40. Therapeutic/interventional procedures
• Arthrography/Diagnostic-therapeutic injections
• Facet injections
• Discography
• Vertebroplasty

41. Monitoring
• Fracture healing and status of the implants
• Endoprosthesis
• Effect of treatment e.g rickets, osteoporosis

42. Risks
• Cell death and distorted replication
• Cancers-Thyroid (85% of papillary cancers –radiation related), skin
and breast cancers
• Cataracts
Reducing risk(measures)
• Justify, optimize (ALARA), limit
• PPE
• Scatter
The annual whole body dose equivalent limit for occupationally
exposed persons is 20mSv

43. Take home message
• Imaging is paramount in orthopaedic practice
• Sound knowledge and broad understanding of radiological techniques
as they applied to orthopaedics is paramount for the orthopaedic
surgeons

44. References
• Ramachandran M, Ramachandran N and Saifuddin A. imaging
techniques.
• Berquist TH. Imaging of Orthopaedic Fixation Devices and Prostheses.
• Rockwood and Green’s Fractures in Adults, 9th edition