Download Diagnostic Techniques

Diagnostic
Imaging
Techniques
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Today’s Topics
Forms of imaging techniques used to
view subcutaneous structures
 Other diagnostic testing (NCS/EMG)

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Imaging process
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Radiographs
100+ years of use
 Low cost
 Limitations

◦ Eg, scaphoid fracture

Ionizing radiation
◦ Absorbed or dispersed
◦ Bone (high density) absorbs more radiation

Protect reproductive organs
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Interpreting Radiographs
Alignment:
1. Normal continuity
of bones & joint
surfaces
2. Relationship of one
bone to another
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Interpreting Radiographs
Bones:
1. Normal density patterns
2. Uniform color
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Interpreting Radiographs
Cartilage:
1. Appreciated for what
does NOT appear
2. Smooth spaces,
uniform & of equal sizes
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Interpreting Radiographs
Soft tissue:
1. Swelling
2. Outlines & pockets of
edema w/adjusted
exposures
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Other X-ray
Techniques

Stress x-rays:
1. Assess joint’s ligamentous integrity
2. Requires application of force to open
joint to measure ___?___
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Other X-ray
Techniques
Contrast imaging: Radioopaque dyes absorbed by
the tissues
Examples:
arthrograms
myleograms
angiograms

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Radiography: Best Use

Standard: Bone lesions, joint surfaces,
joint spaces

Arthrogram: Capsular tissue tears &
articular cartilage lesions

Myleogram: Pathologies w/in spinal
canal
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Computed
Tomography

To determine and quantify
the presence of specific
pathology

X-ray source and detectors
rotate around the body
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Computed
Tomography

Computer determines
density of tissues

Creates 2-dimensional
image (slice) or 3-D image
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CT: Best Use
Bony and articular cartilage lesions
 Chest, abdomen & pelvis
 Different cancers (lung, liver, pancreatic)
 Vascular diseases (artery or vein pathology,
including stenosis, aneurysms and clots)

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Magnetic Resonance Imaging

Detailed picture of
soft tissues

To identify specific
pathology
◦ Sprains, fluid, nerve
entrapment

To visualize soft
tissue structure
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Magnetic Resonance Imaging
MRI tube produces magnetic
field
 Body’s hydrogen nuclei align
w/magnetic axis
 Tissues bombarded w/radio
waves

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Magnetic Resonance Imaging
Nuclei resonate (absorb energy)
 Nuclei return to state of equilibrium
 Energy released & detected by MRI unit

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Magnetic Resonance Imaging

No known harmful effects

Contraindications
◦ Claustrophobia
◦ Some types of metal
implants (eg, pacemaker)
 Other metal implants are
acceptable if in place for
longer than 4 – 6 weeks
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MRI: Best Use

Soft tissue structures,
especially ligamentous &
meniscal injuries
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Bone Scan

Form of nuclear medicine

Detect bony abnormalities not visible on
normal x-rays
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Bone Scan

Radionucleide injection
Tc-99m: technectium-99
-tracer element

Absorbed by remodeling bone — “hotspot”

Pathologies identified by bone scan
◦ Degenerative disease
◦ Bone tumors
◦ Stress fractures
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Bone Scan
Appear as darkened
spots
 Correlate w/clinical S/Sx


Used to identify
degenerative disease,
bone tumors, stress fxs
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Bone Scan: Best Use

Acute bony change
determination

MAY produce false-positive
findings!
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Diagnostic Ultrasound

Visualize internal organs & identifies soft
tissue defects

Similar energy to therapeutic US but lower
frequency
◦ 1–15 MHz
 Superficial structures (7–15 MHz)
 Internal organs (1–6 MHz)

Computer detection of reflected sound
(away from tissues) & creates 2-D image
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Ultrasonic Imaging:
Best Use

Tendon, internal
organ & other soft
tissue imaging
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Nerve Conduction Study (NCS)/
Electromyography (EMG)

Detect pathology in nerves and the muscles
they innervate
 Pathologies identified by NCS or EMG

Peripheral nerve entrapments
 Nerve root injury
 Muscle disease
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NCS
Peripheral nerve is stimulated and muscle
activity is detected
 Latency

◦ Time it takes for the impulse to travel to the
muscle

Amplitude
◦ Magnitude of the nerve’s response
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NCS

Best use:
◦ Function of motor and sensory nerves
◦ Nerve pathology
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EMG

Invasive
◦ Electrode needle inserted into muscle
◦ Electrical activity within muscle is noted
Normal muscle = electrically inactive
Pathological muscle = spontaneous
activity or depolarization at rest
 Patient asked to contract muscle


◦ Shape, size, and frequency of motor unit action
potentials are noted
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EMG

Best use:
◦ Muscle physiology at rest and w/activity
◦ Pathology of muscle 2° to nn supply
dysfunction
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Comparison of Imaging and Clinical Examination for
Knee Pain
Injury
Radiological Examination
Physical Examination
Sensitivity
Specificity
Sensitivity
Specificity
Fracture
Plain
Radiography
85-100%
88-92%
100%
54%
Meniscal tear
MRI
79-89%
80-91%
86-88%
72-92%
Ligamentous
tear
MRI
75-87%
91-93%
74-81%
95%
Cartilage
damage
MRI
84%
90%
51%
96%
Results from a meta analyses of data published from
1986 to 1999 (Jackson et al, 2003)
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Next time…..

Emergency procedures
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