Week 12: CT Spine and Soft Tissue Neck

Question 1

Spine Protocols

Answer 1

• MRI is modality of choice for imaging of the some but in some situations (bony abnormalities of the the spine) CT is considered superior
• proper localization is essential for spine CT (all studies must have AP and Lat scout)
• visualization of intradural structured is improved by intrathecal administration of CM

Question 2

Patient Position C-spine

Answer 2

• supine, head first, use head scoop, ask patient to lower shoulders as much as possible
• laser lights at labella
• scan just above skull base to mid T1 (include all c-spine vertebrae unless a level is specified
• recons: always include a bone window
• reformats: coronal and sagittal
• smaller DFOV
• helical

Question 2

Patient Position T-spine

Answer 2

• supine, knees bent, feet first, arms raised above head
• laser lights 2 inches above jugular notch
• scouts AP and Lat
• scan just above T1 to just below T12 (include all t-spine vertebrae unless a level is specified)
• recons: always include a bone window
• reformats: coronal and sagittal
• helical

Question 3

Indication for CT Spine

Answer 3

• disc herniation
• spinal stenosis
• spinal infection
• trauma (fracture, dislocation)
• intraspinal tumours

Question 4

IV Contrast CT Spine

Answer 4

• yes: post-op lumbar spine, inflammatory and neoplastic lesions
• IV CM only used when specific by the rad (Romans says 100ml at 1.5ml/s. scan when injection is finished)
• no: any other pathologies (disc lesions, spinal trauma, congenital anomalies)
• oral contrast not needed

Question 5

Patient Position L-spine

Answer 5

• supine, knees bent, feet first, arms raised over head
• laser light diploid process (T10)
• scouts Ap and Lat
• scan above L1 to mid sacrum (include all L-spine vertebrae, unless a level is specified)
• recons: always include a bone window
• reformats: coronal and sagittal
• helical

Question 6

Spine Windowing

Answer 6

• soft tissue: 350ww/50wl
• bone window: 2000ww/500wl

Question 7

Intracathecal Administration of CM for Spine Imaging

Answer 7

• CT exams are performed after myelography to enhance or clarify findings
• a delay of 1-3 hours between the intrathecal injection and scanning is recommended to allow CM to dilute so that the CM is not too dense and doesn’t mask intradural structures

Question 8

CT Myelography

Answer 8

• patient may be required to roll
• injection done in fluoroscopy
• some patients cannot have MRI so myelography is used instead
• demonstrates CSF leaks
• widely used for operative planing
• best suited for: dynamic stenosis, postoperative leg pain, severe scoliosis, spondylosthesis, metallic implants

Question 9

CTA Spine

Answer 9

• indications: arteriovenous (AV) fistulas, arteriovenous malformation (AVM), blunt trauma (vascular incident)
• scan skull base to sacrum
• 120 mL of contrast at 6mL/s
• 2 sets of scans: 1.) arterial scan delay = bolus tracking ROI in aorta just below diaphragm 2.) played scan immediately after first arterial scan

Question 9

CT Neck Patient Position

Answer 9

• supine, head first
• ask patient to lower shoulders as much as possible (to reduce artifacts around lower neck)
• extend neck slightly to position hard palate perpendicular to table or angle the gantry to hard palate
• center on glabella
• scan mid orbits to clavicular heads

Question 10

Neck CT Indications

Answer 10

bone:
- tumours
- infection
- trauma
soft tissue:
- tumours
- congenital defects
- enlargement of glands
- infection
- abscess
- vasculature

Question 11

Neck Protocol

Answer 11

• DFOV 18 cm
• helical mode most often
• neck soft tissue window: 450ww/75wl
• bone window: 4000ww/400wl
• recons slice thickness 2.5 mm at 1.25 mm intervals

Question 12

IV Contrast Enhancement for CT Neck

Answer 12

• always used in the neck unless contraindicated
• goal is to allow sufficient time for CM to enhance: mucosa, lymph nodes and pathological tissue while acquiring images with the vasculature opacified
• spil bolus used: total 125mL at 2.0 mL/s
• first bolus: 50mL, 2 minute delay to allow for structure that are slower to enhance
• second bolus: 75mL, scan delay 25 sec (arterial phase) to allows for all vessels to be fully opacified

Question 13

Oral Contrat for Neck CT

Answer 13

• usually not given unless in combo with other exams
• entire procedure usually takes 5-10 minutes, may take additional 10-15 minutes with IV, oral IV need to be given an additional 45-50 minutes prior to exam

Question 14

Breathing Instructions for CT Neck

Answer 14

• perform modified Valsalva maneuver: puff cheeks out to distend pyriform sinuses
• pronounce long “e” during scanning to evaluate aryepiglottic folds and pyriform sinus
• OR hold your breath, don’t swallow

Question 15

Possible Combo Exam

Answer 15

• combination could be C/A/P/N/H – neck done
  @95 secs
• starts with arms up
• at the end of the pelvic scan the patient lowers their arms to their sides being careful not to move their head
• glabella to SC joints if in combo with chest
• could be done 3mL/sec to compliment C/A/P scan injection rate

Question 16

CTA for Neck

Answer 16

• arterial pase
• evaluate vessel walls, relationship of lesions and surrounding structures, valuable for surgical planning
• cerebral catheter angiography (digital subtraction angio) can be diagnostic and therapeutic (but more time, money and risk of complications)

Question 17

Advantages of CTA for Neck

Answer 17

• non-invasive
• widely available
• time saving (especially with stroke)
• can combine with brain perfusion scans
• less expensive

Question 18

CTA for Neck Goal Summary

Answer 18

• CTA can be used to evaluate and measure stenosis of carotid and vertebral arteries ad their branches
• for neck and head evaluate the circle of willis for completeness in 3D
• detect vascular lesions, dissections, occlusions

Question 19

CTV for Neck

Answer 19

• CT venous phase (a modification of CTA)
• used to visualize venous anatomy
• same protocol but acquired in venous enhancement (longer scan delay 40-50 seconds)