Week 15: CT Facial Bones and Sinuses

Question 1

CT Sinuses Indications

Answer 1

• inflammatory sino/nasal disease
• chronic sinusitis
• road mapping for sinonasal disease endoscopic surgeries (using the coronal images)

Question 2

Sinuses CT Protocol

Answer 2

• exam is focused on frontal, ethos, sphenoid and maxillary sinuses and also the nasal passages, turbinates and septum
• sinus screening is low cost, low radiation and accurate
• scan plane coronal positioning: prone, chin extended or supine and drop head back or can Ange gantry if coronal cannot be achieved
• scan plane axial: common one
• scan range: above the frontal sinus to below the hard palate, include mid sella through frontal sinus
• hard palate perpendicular to table or to OML (position patient or angle gantry)
• no contrast for screening, some indications may need IV contrast or additional scans in axial plane

Question 3

Chronic Sinusitis

Answer 3

• no IV contrast
• axial acquisition (may have to angle gantry)
• coronal postion
• demonstrates air fluid levels

Question 3

CT Imaging of the Face

Answer 3

-preferred modality for imaging go the face because it is more sensitive for fracture detection (show significant soft tissue injury)
- easier to perform, quicker than complete view of general x-rays
- pre-surgical planning for complex injuries
- disadvantage of CT imaging for facial bones: can miss subtle tooth fracture along the axial plane, additional orthopanthogram may be used as well

Question 4

CT Facial Bones Indications

Answer 4

• facial fractures and soft tissue injury
• foreign body
• infection (IV contrast)
• masses (IV contrast)
• CT of the facial bones, orbits, mandible and sella are focused exams that provide better detail of the region of interest, characterization of facial fractures and soft tissue injury

Question 5

CT Facial Bones Protocol

Answer 5

• helical
• just above mandible to just above frontal sinus
• no IV contrast used unless specified (ex: infection and masses)
• smaller areas like orbits can be done, if contracts is used then a split bolus technique is used
• patient will tuck chin (some clinics say IOML parallel to gantry)

Question 6

CT Angio Indications

Answer 6

• CTA: arterial phase, may be combined with brain perfusion strides to asses brain parenchyma and vascular supply
• cerebrals
• carotids and vertebral (measure stenosis)
• circle of willis (COW) for aneurysm or AVM in patient with SAH/ICH
• lesions, dissection and occlusions
• surgical planning

Question 7

CTA Protocol

Answer 7

• circle of willis
• scan 2 sets of images
  1. non contrast head first
  2. arterial phase CTA (80mL 4.0mL/sec or 60mL of higher concentration and 20mL saline)
• timed bolus using ROI of carotid artery at approx. C4
• scan range: at the level of C! to just above skull vertex (or in clinical may see skull base to just above frontal sinus)
• helical
• no gantry tilt

Question 8

CTV (CT Venography)

Answer 8

• a modified CTA scan, similar just in venous phase
• indications: cerebral venous disorders, dural sinus thrombosis
• helical (no gantry tilt)
• 100mL 4.0mL/sec 45sec delay on 64 slice scanner (30 sec on 16 slice scanner)
• scan just below skull base to just above vertex
• hard palate perpendicular to table top

Question 9

The Circle of Willis (COW)

Answer 9

• the Circle of Willis is circle of anastomosed major blood
  vessels that is located at the base of the cerebrum.
• the circle of Willis is formed by the RT & LT internal carotid
  arteries, anterior cerebral arteries, anterior communicating
  arteries, basilar artery & posterior communicating arteries.
• if one of the main arteries that make up the circle of Willis is
  occluded, the distal smaller arteries that it supplies can
  receive blood fr