CT head protocols

Question 1

Indications for CT post contrast

Answer 1

Further characterisation of Space occupying lesion

Mets

Characterisation of intracerebral haemorrhage seen on unenhanced scan

Arteriovenous malformation

Epilepsy

Infections

Seizures (especially recent onset)

Question 2

CT post contrast protocol

Answer 2

Scout: Lat +/- AP

Position with chin tucked towards chest base of skull parallel to x-ray beam

Coverage from base of skull to vertex

Small SFOV

Thin slice acquisition
Pitch will usually be <1. Overlap

Brain and bone, filters and windows

Keep head in same position before and after contrast injection

Question 3

CT post contrast, contrast requirements

Answer 3

Hand or pressure injected

Contrast timing will vary with indication
Standard post contrast brain, hand injected or injector 30-50ml @ 2-3ml/s

Post contrast brain delayed scan. (2+ minutes)

18 gage or 20 gage cannula

Question 4

Possible protocol alterations for a trauma CT brain

Answer 4

-Trauma patient: lots of staff, quick scan, organised room ready to scan
-Contrast volume dependent on patient size
-Fast non-con scan to prevent patient movement and risk of repeating
immobilisation devices

Question 5

Possible protocol alterations for a paediatric CT brain

Answer 5

Paediatric patient: parent in the room, sedations/ GA, secure head, organised and quick scan, simple explanation
Dose reduction techniques
-Contrast volume dependent on patient size
-Fast non-con scan to prevent patient movement and risk of repeating
immobilisation devices

Question 6

Possible protocol alterations for a geriatric CT brain

Answer 6

Geriatrics: secure head, explain simply, organised and quick scan
-Contrast volume: increase dependent on patient size
-Fast non-con scan to prevent patient movement and risk of repeating
immobilisation devices

Question 7

Possible pathologies related to CT post contrast

Answer 7

Cerebral arteriovenous malformations (CAVMs)

Mets

Glioblastoma

Vasogenic cerebral oedema

Question 8

Indications for CT IAMs/PTBs post contrast

Answer 8

Acoustic neuroma

Tinnitus

Question 9

IAMs/PTBs protocol

Answer 9

Scout: Lat +/- AP

Position with chin tucked towards chest base of skull parallel to x-ray beam

Coverage from base of skull to vertex

Small SFOV

Thin slice acquisition
Pitch will usually be <1. Overlap

Brain and bone, filters and windows

Keep head in same position before and after contrast injection

+/ - contrast

Question 10

Contrast requirements for IAMs/PTBs

Answer 10

Hand or pressure injected

Contrast timing will vary with indication
Standard post contrast brain, hand injected or injector 30-50ml @ 2-3ml/s

Post contrast brain delayed scan. (2+ minutes)

18 gage or 20 gage cannula

Question 11

Orbits +/- brain indications post contrast

Answer 11

Infection/Abscess 
Optic nerve mass
Proptosis/Diplopia 
Vision loss 
Melanoma

Question 12

Orbits +/- brain protocol

Answer 12

Scout: Lat +/- AP

Position with chin tucked towards chest base of skull parallel to x-ray beam

Coverage from base of skull to vertex

Small SFOV

Thin slice acquisition

Pitch will usually be <1. Overlap

Brain and bone, filters and windows

Keep head in same position before and after contrast injection

Question 13

Contrast requirements for orbits +/- brain

Answer 13

Hand or pressure injected

Contrast timing will vary with indication
Standard post contrast brain, hand injected or injector 30-50ml @ 2-3ml/s

Post contrast brain delayed scan. (2+ minutes)

18 gage or 20 gage cannula

Question 14

possible pathologies for CT orbits +/- brain

Answer 14

Melanoma

Question 15

CTA-COW indications

Answer 15

Aneurysm
Stroke
AVM

Question 16

CTA COW protocol

Answer 16

Performed as stand-alone study or as part of head and neck CTA

Coverage will vary with indication from COW only to whole brain

Position chin down as per Brain

Soft algorithm and individual window to differentiate between contrast and calcification

Small SFOV

Thin slice

Pitch <1 / overlap

MPR ave. MIP, various 3D rendering methods

Question 17

CTA-COW contrast requirements

Answer 17

Contrast scan in arterial phase

50-100ml @ 4-5ml/sec

Contrast timing can be aided by bolus tracking: ROI over carotid arteries or posterior muscles in neck (once you see carotids fill with contrast, trigger scan)

18 gage cannula: high flow scan

Question 18

CTA COW possible pathologies

Answer 18

Ischaemic stroke

Haemorrhagic stroke

Aneurysm

AVM

Question 19

Instructions to give to patient

Answer 19

Procedure explanation

Remove metal from head. (Dentures, Hairclips, piercings, jewellery)

Consider MAR for permanent metal. (fillings, surgical clips, cochlear implant, etc.)

Question 20

List some dose reduction strategies(12)

Answer 20

Pitch closer to 1 to decrease scan time (critical cases)

Making the non con scan a fast scan: reducing dose and reducing risk of having to repeat scan

Change contrast volume (dependent on patient size)

Change technical factors dependent on patient size

Change tube rotation time

Reduce scan range to reduce radiation exposure and maximise resolution

SFOV is appropriate: tight to maximise spatial resolution

Automatic exposure control

Tight pre and post patient collimation

Bowtie filter

Centre patient in isocentre correctly

Lead shielding if needed

Question 21

What protocol would you do for the following and what are possible pathologies?

• 80 year old female collapsed at home
• Brought in by ambulance
• BP 240/110 (high)
• HR: 99
• On examination: pulsating carotid arteries and throbbing headache
• Pupils that are Equal, Round and Reactive to Light
• Carotid ultrasound: no abnormality detected
• Query cause of headache

Answer 21

Non contrast and then CTA- COW to determine source of headache
- Most likely an aneurysm due to the throbbing headache