Temporal bone (modified Stenvers view)
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The modified Stenvers view is an oblique radiographic projection used to demonstrate the petrous temporal bone, internal acoustic meatus and bony labyrinth. It is performed as a posteroanterior (PA) projection to minimize radiation to the orbits. This view has succeeded the Stenvers view, which includes more of the mastoid air cells.
This view is primarily used to assess electrode placement following the insertion of a cochlear implant. Specifically, it:
- assesses the integrity, positioning, and depth of insertion of the electrodes 1
- is used as a baseline 2
The more electrodes in the cochlea the better. For the best hearing outcomes, a minimum of 15 intra-cochlear electrodes is required 1.
- the patient is sitting upright or standing erect with the side of interest closer to the image detector or erect bucky
- position infraorbitomeatal line (IOML) (see Figure 1) perpendicular to the detector
- rotate the patient's head 45° so that the cheek of the side of interest is close to the image detector
- posteroanterior oblique projection
- centering point
- to include all petrous and mastoid parts of the temporal bone of the side of interest
- 18 cm x 24 cm
- 75-80 kVp
- 20-25 mAs
- 100 cm
- yes (this can vary departmentally)
Image technical evaluation
The obliquity of the beam positions it in the plane of the superior semicircular canal. In a normally positioned cochlear implant (see cases), the electrodes should be medial to the point of cochleostomy, which is approximated by a line drawn (see Figure 2) downward vertically through the superior semicircular canal 3,4.
- ensure tight collimation is used so that adequate penetration will allow for the visualization of all intra-cochlear electrodes (i.e. dots in a circular configuration on the image)
- learning your skull positioning lines will make reading positioning guides a whole lot easier