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CT Navigation Setup for Image Guided Surgery - Sinus and Skull Base

last modified on: Tue, 11/14/2023 - 15:47

return to: Paranasal Sinus Surgery Protocols or Sinus and Rhinology

Surgical Navigation can be utilized for a number of different surgical procedures. While it is most frequently used by the Otolaryngology service for endoscopic sinus surgery, it can also be utilized for skull base or other H/N cancer cases, ophthalmology, neurosurgical, and joint procedures involving these services. Surgical Navigation at UIHC is currently achieved with Medtronic Fusion IGS (Image Guided Surgery) system. For the purposes of this protocol, the setup for Endoscopic sinus surgery will be described.

Indications for Surgical Navigation

  • The AAO-HNS currently maintains surgical navigation systems are deemed appropriate in "select cases to assist the surgeon in clarifying complex anatomy during sinus and skull base surgery."
  • Examples of appropriate cases listed by the academy include, but are not limited to:
  1. Revision sinus surgery
  2. Distorted sinus anatomy of development, postoperative or traumatic origin
  3. Extensive sinonasal polyposis: pathology involving the frontal, posterior ethmoid and sphenoid sinuses
  4. Disease abutting the skull base, orbit, optic nerve or carotid artery
  5. CSF rhinorrhea or conditions where there is a confirmed or suspected skull base defect
  6. Benign and malignant sinonasal neoplasms
  • The AAO-HNS website regarding surgical navigation was reaffirmed 12/8/2012: 

Imaging Platforms

Fusion: Standalone, electromagnetic based ENT image guidance system. This unit has a smaller footprint and at UIHC is utilized in the ASC.

Stealth 7 (S7): Utilized in the main OR at UIHC. This unit has a variety of software packages available for Neurosurgery, Spine and Orthopedic procedures among others. This unit has both electromagnetic and optical capabilities. The optical capability refers to the infrared light based camera that monitors reflections from the spheres placed on the surgical instrumentation.

Treon Plus: Infrared light based unit currently utilized at the VA in Iowa City.

Preoperative Workup

  • CT scan of the paranasal sinuses with Stealth protocol should be ordered prior to the patients surgery date.
  • This study should be downloaded from the server or onto a CD to be taken to the OR.
  • The surgeon should ensure the desired patient, date of study, and anatomical location are obtained.
  • If a Stealth protocol CT cannot be obtained, a normal sinus CT can be utilized but may not provide the same level of accuracy.
  • Surgeon and OR staff ensure the appropriate equipment are available and present in or near the OR room prior to transport of the patient to the OR.


AxiEM System power box with cords for connecting to the base unit.
Image 1: AxiEM System power box with cords for connecting to the base unit.

Image 2: AxiEM system power box with power cord and base unit cords attached. To the left of the picture are inputs for the EGM cords (shown in figure 4).

Image 3: The equipment shown here is required for the positioning the Electromagnetic Field Generator (EMG seen in figure 4) within the space adjacent to the surgical field. At UIHC, this is equipment is kept in a mobile storage unit that can be positioned outside the room prior to the start of the case.

Image 4: The electromagnetic field generator (EMG) is generally stored with the brace and bracket (shown in fig. 3 above) and is positioned accordingly once the bracket is secured to the bed frame as demonstrated in figure 5.

Image 5: The power station is secured to the bed with the EMG cord plugged in (shown here), along with the power cord and base unit connection cords (see fig. 2).

Intraoperative Setup

  • The patient should be positioned in the bed, head generally positioned to the right for FESS.
  • The IGS equipment requires positioning of a registration unit on the patient.
  • For FESS, this is generally placed on the patients mid-forehead.
  • The IGS instrumentation and registration protocols will vary with based on the brand and model of the system used.
  • The Images should be loaded onto the base unit prior to the registration process and the appropriate exam selected
  • It is imperative that the correct patient, study from the desired date and the appropriate anatomical study are selected.

Intraoperative Utilization

  • Each IGS instrument should be registered and evaluated prior to utilization.
  • The endoscopic view obtained of the surgical field and positioned instrumentation should be the primary focus while performing the surgery. The IGS serves as a useful tool in assisting with difficult areas, but the system itself is inherent to built in and user error. Thus, it should be utilized as the adjunct and should not be viewed as a substitute for surgical knowledge and anatomical familiarity with the surgical region.
  • Keep in mind that the images provided are based on the anatomy at the time of CT scan and the surgical anatomy may have changed prior to the start of the procedure (resolution/progression of infection, change in size of masses, etc). The anatomy will certainly change with the progression of the procedure.
  • Recognition and utilization of surgical landmarks is imperative for the surgeon.