MRI Diffusion Weighted Temporal Bone (Cholesteatoma protocol)
Cholesteatoma
Cholesteatoma is a medical condition characterized by the presence of an abnormal, non-cancerous growth of keratinizing squamous epithelium (skin cells) in the middle ear or mastoid region of the skull. This growth forms a cyst-like or sac-like structure that can gradually expand, erode surrounding bone, and cause various symptoms.
On MRI, cholesteatomas typically appear as well-defined, round or oval lesions with low signal intensity on T1-weighted images. They often demonstrate high signal intensity on T2-weighted images due to the presence of inflammatory or granulation tissue within the lesion. On DWI with a b-value of 1000, cholesteatomas may appear as hyperintense (bright) lesions, indicating restricted diffusion, while the surrounding normal tissues typically show lower signal intensity. On DWI with a b-value of 0, cholesteatomas may also appear as hyperintense (bright) lesions. On ADC maps, cholesteatomas often demonstrate restricted diffusion, appearing as regions of low ADC values.
Indications
- Cholesteatoma recurrence
Contraindications of DWI Temporal Bone MRI scan
- 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 Cholesteatoma MRI
- 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 Cholesteatoma MRI scan
- 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
Recommended DWI IAM'S Protocols, Parameters, and Planning
localiser
A three-plane localizer must be taken at the beginning to localize and plan the sequences. Localizers are usually less than 25 seconds and are T1-weighted low-resolution scans.
T2 tse axial
Plan the axial slices on the sagittal plane and position the block parallel to the genu and splenium of the corpus callosum. Verify the planning block in the other two planes and ensure that an appropriate angle is maintained in the coronal plane, making it perpendicular to the line of the midline of the brain and the 4th ventricle. Ensure that the number of slices is sufficient to cover the entire brain from the vertex to the line of the foramen magnum.
Parameters
TR 3000-4000 | TE 100-120 | SLICE 5MM | FLIP 130-150 | PHASE R>L | MATRIX 320X320 | FOV 210-230 | GAP 10% | NEX(AVRAGE) 2 |
T2 TSE coronal 2 mm small fov
Plan the coronal slices on the axial plane and position the block parallel to the line along the right and left internal acoustic meatus (IAMS) as indicated in the diagram. Verify the planning block in the other two planes to ensure proper alignment. Set an appropriate angle in the sagittal plane, parallel to the brain stem. The number of slices should sufficiently cover the internal acoustic meatus and mastoid air cells, extending from the posterior border of the sphenoid sinus up to the line of the fourth ventricle.
Parameters
TR 3000-4000 | TE 100-120 | SLICE 2 MM | FLIP 130-150 | PHASE R>L | MATRIX 256X256 | FOV 150-170 | GAP 10% | NEX(AVRAGE) 2 |
T2 HASTE DWI coronal 2mm small fov b0
Plan the coronal slices on the axial plane and position the block parallel to the line along the right and left internal acoustic meatus (IAMS) as indicated in the diagram. Verify the planning block in the other two planes to ensure proper alignment. Set an appropriate angle in the sagittal plane, parallel to the brain stem. The number of slices should sufficiently cover the internal acoustic meatus and mastoid air cells, extending from the posterior border of the sphenoid sinus up to the line of the fourth ventricle.
Parameters
TR 1500-2000 | TE 200 | FLIP 130 | NEX 15 | SLICE 2 MM | MATRIX 192X192 | FOV 150-170 | PHASE R>L | GAP 10% | b value 0 |
T2 HASTE DWI coronal 2mm small fov b1000
Plan the coronal slices on the axial plane and position the block parallel to the line along the right and left internal acoustic meatus (IAMS) as indicated in the diagram. Verify the planning block in the other two planes to ensure proper alignment. Set an appropriate angle in the sagittal plane, parallel to the brain stem. The number of slices should sufficiently cover the internal acoustic meatus and mastoid air cells, extending from the posterior border of the sphenoid sinus up to the line of the fourth ventricle.
Parameters
TR 1500-2000 | TE 200 | FLIP 130 | NEX 15 | SLICE 2 MM | MATRIX 192X192 | FOV 150-170 | PHASE R>L | GAP 10% | b value 1000 |
T1 TSE coronal 2mm small fov
Plan the coronal slices on the axial plane and position the block parallel to the line along the right and left internal acoustic meatus (IAMS) as indicated in the diagram. Verify the planning block in the other two planes to ensure proper alignment. Set an appropriate angle in the sagittal plane, parallel to the brain stem. The number of slices should sufficiently cover the internal acoustic meatus and mastoid air cells, extending from the posterior border of the sphenoid sinus up to the line of the fourth ventricle.
Parameters
TR 400-600 | TE 10 | FLIP 130 | NEX 3 | SLICE 2 MM | MATRIX 256X258 | FOV 150-170 | PHASE R>L | GAP 10% |
For accurate diagnosis and proper mapping of the apparent diffusion coefficient (ADC), it is crucial to ensure that the slice thickness, field of view (FOV), and number of slices are consistent across T1, T2, HASTE DWI with b0, and HASTE DWI with b1000 sequences. Any deviation in these parameters can hinder the accuracy of diagnosis and ADC mapping.