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. Author manuscript; available in PMC: 2011 Jan 1.
Published in final edited form as: Otol Neurotol. 2010 Jan;31(1):94–99. doi: 10.1097/MAO.0b013e3181c2f81a

Figure 7.

Figure 7

Measurement technique for estimating the distance from the centerline of the drill trajectory to facial nerve and chorda tympani. On the intraoperative endoscopic photograph a line is drawn over the drill bit, which provides a scale to the true physical size - 2 mm in this case. The distance from the edge of the drill to the chorda tympani and the facial nerve are then digitally drawn and calibrated.