Saturday, September 19, 2015
Indications for MRI brain
Contraindications
Patient preparation for MRI brain
Positioning for MRI brain
Protocols and planning
Localiser
A three plane localizer must be taken in the beginning to localise and plan the sequences. Localizers are usually less than 25sec. T1 weighted low resolution scans.
T2 tse axial
Plan the axial slices on the sagittal plane; angle the position block parallel to the genu and splenium of the corpus callosum. Slices must be sufficient to cover the whole brain from the vertex to the line of the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
T2 FLAIR axial
Plan the axial slices on the sagittal plane; angle the position block parallel to the genu and splenium of the corpus callosum. Slices must be sufficient to cover the whole brain from the vertex to the line of the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
T1 SE coronal
Plan the coronal slices on the sagittal plane; angle the position block parallel to the brain stem. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane on a tilted head (perpendicular to mid line of the brain). Slices must be sufficient to cover the whole brain from the frontal sinus to the line of the occipital protubernce.
T2 tse sagittal
Plan the sagittal slices on the axial plane; angle the position block parallel to midline of the brain. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane on a tilted head (parallel to the line along 3rd ventricle and brain stem). Slices must be sufficient to cover the brain from temporal lobe to temporal lobe.
DWI epi3scan trace axial
Plan the DWI axial slices on the sagittal plane; angle the position block parallel to the line from the glabella to the foramen magnum. This angle will reduce air-bone interface artefacts from the Para nasal sinuses. Slices must be sufficient to cover the whole brain from the vertex to the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
Indications for contrast enhancement brain scans
Use T1 SE axial and coronal after the administration of IV gadolinium DTPA injection(copy the planning outlined above). The recommended dose of gadolinium DTPA injection is 0.1 mmol/kg, i.e. 0.2 mL/kg in adults, children and infants.
- Transient ischaemic attack (TIA), syncope, collapse , stroke
- Brain Tumour, Suspected brain tumour, metastases, papilloedema
- CNS infection, abscess, meningitis, AIDS,&TB
- Congenital malformation of brain or meninges
- Post-operative follow-up after brain surgery
- Dementia, neurodegenerative disorder
- Demyelinating disease of the brain
- Encephalopathy, encephalitis
- Cerebellar, or brainstem lesion
- Head trauma, epilepsy,stroke
- CVA, altered mental status
- Suspected leukodystrophies
- Ataxia, bipolar disorder
- Multiple sclerosis
- ENT problems
Contraindications
- Any electrically, magnetically or mechanically activated implant (e.g. cardiac pacemaker, insulin pump biostimulator, neurostimulator, cochlear implant, and hearing aids)
- Intracranial aneurysm clips (unless made of titanium)
- Pregnancy (risk vs benefit ratio to be assessed)
- Ferromagnetic surgical clips or staples
- Metallic foreign body in the eye
- Metal shrapnel or bullet
Patient preparation for MRI brain
- A satisfactory written consent form must be taken from the patient before entering the scanner room
- Ask the patient to remove all metal objects including keys, coins, wallet, cards with magnetic strips, jewellery, hearing aid and hairpins
- If possible provide a chaperone for claustrophobic patients (e.g. relative or staff )
- Contrast injection risk and benefits must be explained to the patient before the scan
- Gadolinium should only be given to the patient if GFR is > 30
- Offer earplugs or headphones, possibly with music for extra comfort
- Explain the procedure to the patient
- Instruct the patient to keep still
- Note the weight of the patient
Positioning for MRI brain
- Head first supine
- Position the head in the head coil and immobilise with cushions
- Give cushions under the legs for extra comfort
- Centre the laser beam localiser over the glabella
Protocols and planning
Localiser
A three plane localizer must be taken in the beginning to localise and plan the sequences. Localizers are usually less than 25sec. T1 weighted low resolution scans.
T2 tse axial
Plan the axial slices on the sagittal plane; angle the position block parallel to the genu and splenium of the corpus callosum. Slices must be sufficient to cover the whole brain from the vertex to the line of the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
T2 FLAIR axial
Plan the axial slices on the sagittal plane; angle the position block parallel to the genu and splenium of the corpus callosum. Slices must be sufficient to cover the whole brain from the vertex to the line of the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
T1 SE coronal
Plan the coronal slices on the sagittal plane; angle the position block parallel to the brain stem. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane on a tilted head (perpendicular to mid line of the brain). Slices must be sufficient to cover the whole brain from the frontal sinus to the line of the occipital protubernce.
T2 tse sagittal
Plan the sagittal slices on the axial plane; angle the position block parallel to midline of the brain. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane on a tilted head (parallel to the line along 3rd ventricle and brain stem). Slices must be sufficient to cover the brain from temporal lobe to temporal lobe.
DWI epi3scan trace axial
Plan the DWI axial slices on the sagittal plane; angle the position block parallel to the line from the glabella to the foramen magnum. This angle will reduce air-bone interface artefacts from the Para nasal sinuses. Slices must be sufficient to cover the whole brain from the vertex to the foramen magnum. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane on a tilted head (perpendicular to the line of 3rd ventricle and brain stem).
Indications for contrast enhancement brain scans
- Tumour, Metastases, Cranial nerve lesion, Indeterminate intracranial lesion, IAC mass
- Cavernous angioma, Amyloid angiopathy, Neurocysticercosis
- Meningitis, Encephalitis, Leptomeningeal spread
- Multiple Sclerosis, AVM, HIV, Infection Abscess
- Leukodystrophies, Delayed development
- Syringomyelia(Syrinx)
Use T1 SE axial and coronal after the administration of IV gadolinium DTPA injection(copy the planning outlined above). The recommended dose of gadolinium DTPA injection is 0.1 mmol/kg, i.e. 0.2 mL/kg in adults, children and infants.
