CT head protocols Flashcards
Indications for CT post contrast
Further characterisation of Space occupying lesion
Mets
Characterisation of intracerebral haemorrhage seen on unenhanced scan
Arteriovenous malformation
Epilepsy
Infections
Seizures (especially recent onset)
CT post contrast protocol
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
CT post contrast, contrast requirements
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
Possible protocol alterations for a trauma CT brain
-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
Possible protocol alterations for a paediatric CT brain
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
Possible protocol alterations for a geriatric CT brain
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
Possible pathologies related to CT post contrast
Cerebral arteriovenous malformations (CAVMs)
Mets
Glioblastoma
Vasogenic cerebral oedema
Indications for CT IAMs/PTBs post contrast
Acoustic neuroma
Tinnitus
IAMs/PTBs protocol
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
Contrast requirements for IAMs/PTBs
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
Orbits +/- brain indications post contrast
Infection/Abscess Optic nerve mass Proptosis/Diplopia Vision loss Melanoma
Orbits +/- brain protocol
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 requirements for orbits +/- brain
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
possible pathologies for CT orbits +/- brain
Melanoma
CTA-COW indications
Aneurysm
Stroke
AVM
CTA COW protocol
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
CTA-COW contrast requirements
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
CTA COW possible pathologies
Ischaemic stroke
Haemorrhagic stroke
Aneurysm
AVM
Instructions to give to patient
Procedure explanation
Remove metal from head. (Dentures, Hairclips, piercings, jewellery)
Consider MAR for permanent metal. (fillings, surgical clips, cochlear implant, etc.)
List some dose reduction strategies(12)
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
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
Non contrast and then CTA- COW to determine source of headache
- Most likely an aneurysm due to the throbbing headache
