CT Protocol For The Temporal Bone And Inner Ear | Beginners Tips

CT Protocols- Beginners Tips

Protocol- Temporal Bone and Inner Ear

Indications 

• Fractures
• Preoperative evaluation of the cholesteatoma and otitis media
• Otosclerosis 
• Postoperative follow-up
• lesions in the cerebellopontine angle cistern
• Prior to cochlear implant 

Patient Positioning
Supine with Headfirst, with Arms beside the trunk. 

Topogram Position/Landmark
Lateral; level of the vertex.

Mode of Scanning 
Helical.

Scan Orientation
Craniocaudal. 

• Starting Location - Cranial limit of the petrous bone. 
• End Location - Level of the mastoid tip. 

Gantry Tilt
Nil.

Field of View  
Just fitting the temporal bone. 

Contrast Administration 
Nil. 

Slice Thickness for Reconstruction  
0.5-1 mm.

 

Slice interval for Reconstruction 
0.25-0.5. 

Reconstruction Algorithm / Kernel
UltraSharp. 

3D Reconstruction
MPR, subtraction images for the ossicles.

Comments

• The use of a Headrest is recommended for head positioning.
• It is important to avoid the eye lens from unnecessary radiation exposure. So the position should be such that the orbits are avoided with no need for the gantry tilt as well. However, if such a position is not possible, then a gantry tilt can be given to avoid the lens. 
• MPR is prepared in the oblique coronal and oblique sagittal plane parallel and perpendicular to the long axis of the petrous and squamous temporal bone respectively separately for the two sides. 
• 3-D reconstruction is prepared for the planning of cochlear implant surgery. 
• Image data can also be reconstructed at the smooth kernel if the soft tissue visualization is also of interest. 

Criteria of Good Image Quality 

• Symmetric position with the orbital plates overlapping with each other.
• Absence of the motion artefacts.
• Optimally delineation of the ossicular chain, facial nerve canal, and tympanic cavity.