Imaging principles

Risks of radiation ( 😎

Considerations	Explanation
Relevance	Any indication for imaging ?  Influence on management ?
Modality	Alternative imaging modalities more appropriate + lower dose of radiation?  MRI/ USS  X ray/ CT  → reduced exposure w/ low dose CT
Size of area required	Whole spine vs Cx sp
Anatomical region	Reproductive organs ( lumbar sp imaging )
Dosage effects	Single vs cumulative dose
BMI
Age	Radiation risk for younger ppl > elderly ( cancer takes time to develop )
Initial/ advanced imaging	Need to be done w/ contrast? → referral

Schemes for imaging rebates

	Situation
Rebated imaging	Medical benefits rebates by non-medical practitioner → spine  Qld public health facilities:  → accredited physios to refer in the public health system  → facility based on need + experience
Non-rebated imaging	MRI X rebate but typically accepted if clinically relevant

Pros + cons ( X ray )

Pros	Cons
Quick overview ( full series of 6 views )  Easily available  Inexpensive Min contraindications  Less radiation dose Rebate available  Multiple views	Poor soft tissue definition  → X see neural tissues  Repeated images needed to be taken for a full views → radiation exposure  Can be rebated

Pros + cons ( CT scan )

Pros	Cons
Relatively quick for whole Cx  Moderate availability  Reduced dosage of radiation  Good anatomical information Good bony detail ( thin slices of image ) Good for multiple fractures	X refer Less soft tissue detail

Pros + cons ( MRI )

Pros	Cons
**Soft tissues Different weightings	Limited availability  Higher cost  Lower bony definition  X rebate X eligible for degenerative neck pain Contraindications:  Pacemaker Metal in eye  Metallic stents  Aneurysm clips  Neural stimulators  Inner ear implants

Applications ( X ray )

Vertebrae  Relative canal size  Soft tissue shadows  Alignment  → straightening of lordosis from muscular spasm → anterior/ retrolisthesis  Views:  Planar: 2 views → AP/ lateral  Oblique → intervertebral foramen Open mouth/ odontoid Swimmer’s view: C7- thoracic junction   Stability views ( neutral/ flexion/ extension )

Applications ( CT scan )

1. Bone 

2. Large region → skull base to mid T1 ( cervical sp ) 

Applications ( MRI )

Muscle/ tendon Ligament  Neural tissues  Bony reactions  T1: √ anatomical detail T2: √ nerves ( water based structures)

CTA vs MRA

	CTA	MRA
Radiation	Y	N
Contrast	Y	N
Applications	Coronary artery disease  Pulmonary embolism  Aortic aneurysm	Cerebral vascular disorders  Stroke  Peripheral vascular disease
Availability	More	Less

ACR guidelines for imaging

	Appropriate imaging
Cervical pain/ radiculopathy	X ray MRI w/o contrast
Neck pain/ cervical headaches	Chronic cervical pain:  X ray  MRI X contrast  Cervicogenic headache: MRI X contrast
Increasing neck pain/ radiculopathy	X ray MRI X contrast

Canadian C spine criteria

Criteria ( if you have )	Imaging
High risk factors:  Age > 65 years  dangerous mechanisms  Paraethesias in extremities	Y
Low risk factors allowing for safe Ax of RoM  Simple rear-end MVC Sitting position in emergency department  Ambulatory at any time  Delayed onset of neck pain  Absence of midline C sp tenderness	N
Able to actively rotate neck  → 45’ bilaterally	N

When to image

1. Guidelines 

2. Red flags 

3. Persistent/ unresponsive symptoms → new symptoms in chronic conditions? 

4. Neurological deficit ( cord signs ) 

5. Implications for treatment → will imaging findings change treatment

Basic information from imaging

 

1. Name 

2. DoB + date of image 

3. View

• Sagittal 

• Axial 

→ use both to match findings → where does the sagittal view match to axial view  

4. Anatomical 

• General alignment 

• Vertebral bodies 

• Discs 

• Nerve roots 

• Canal 

Items to look at ( X ray )

Anterior ( prevertebral ) soft tissue: 

1. 6 mm @ C2 

2. 2cm @ C6 ( w/ trachea 

→ any swelling

→ Sharp soft tissue contours 

1. Anterior body line 

2. Posterior body line 

3. Facetal line → equally stacked 

4. Spino-lamina line 

5. Spinous process line

Myelopathy + degeneration of Cx sp on imaging

Myelopathy: white parts in the vertebral foramen —> excess fluid

Degeneration: contours of the bone rough

Source + mechanism of trauma

Source of trauma	Mechanism of injury
MVA: speed/ ejected  Sports  Others	Hyperflexion Hyperextension  Hyperextension + rotation  Vertical compression  Lateral flexion  Diverse/ imprecisely understood

Classification of cervical sp injuries 

Denis 3 column model 

3 columns: anterior column/ middle column/ posterior column 

Instability only happens when there is > 1 column unstable

Structures in ant. column	Structures in middle column	Structures in post. column
Anterior longitudinal lig Ant. annulus  Ant. ½ vert body	Post longitudinal lig Post annulus  Post ½ vert body	Pedicles  Facets  Laminae  Post lig complex  → supra + infraspinous lig → ligament flavum  → Z capsules

Classification of craniocervical dislocation

1. Power’s ratio ( basion-C1 arch/ OA ) 

→ normal: 0.8 

→ > 1= anterior subluxation 

→ < 0.8 = distraction/ post subluxation 

2. Harris measurements 

→ Basion-densinterval ( vertical ) ; basion-axial interval ( horizontal ) < 12 mm → craniocervical instability 

→ atlantodental interval < 3mm  → > 7 mm: alar ligament disruption

Classification of odonotid #

Type	Location	Stability	Prognosis
I	Upper  part of odontoid peg  → above transverse band of cruciform lig	Stable	/
II	Base of odontoid  → below transverse band of cruciform lig	Unstable	High risk of non-union
III	Through odontoid to lateral masses of C2	Relatively stable if X displaced excessively	Best → large SA of #

What is a jefferson #

Jefferson fracture → burst fracture of atlas ( X odontoid but craniocervical junction # )

Displacement of the atlas laterally  → anterior + posterior arches from axial loading

Signs on imaging + prognosis for hyperflexion + hyperextension injury

	Signs on imaging	Prognosis
Hyperflexion	Increased interspinous distance  Flexion tear drop fracture  → fracture in the ant vertebral column/ possibly other columns	Commonly serious
Hyperextension	Extension tear drop #  → inferior part of the vert body displaced forwards	→ can disrupt ALL

Disruptions to facet joint + signs on imaging

Disruptions to facet joint	Signs on imaging
Perched facet	X evenly stacked facet joints/ regularity of appearance
Facet dislocation	Hamburger sign → space bwt the facet joint
Bilateral locked facet	Facet coming up + over to the superior  level