HEADS UP Surgeons prefer to know exactly where their instruments are located when maneuvering around delicate structures.

Once a month. I use image-guided technology during most sinus surgeries, but that's how often I'm truly grateful to know I'm approaching the thin membrane that sits between my probe and a catastrophic ending to a difficult case. Image guidance has rapidly become sinus surgery's standard of care during reoperations or procedures performed on patients with complicated anatomy, because it adds a level of safety and efficiency to the surgeon's movements. In modern health care and in your facility, those factors add up to value.

Working with an image-guided system is like driving with a navigator program in your car. You know the general direction you're headed, but the technology gives you an added degree of certainty in finding the best route to get there. Image guidance gives surgeons more confidence as they approach delicate anatomy. They have a better idea of how close they're getting to the dura that lines the brain adjacent to the nasal cavity and can easily identify critical structures to work around.

There are 2 options in image-guidance systems used during ENT cases. I'm able to operate equally effectively with both, so the one that's best for you comes down to surgeon and facility preference.

• Electromagnetic systems do not require a direct line of sight between instruments and the image processor, meaning images will continue to be transmitted and displayed even if someone walks between the surgeon and the system's unit. A potential drawback: Surgeons must use proprietary instruments. Although the instruments were limited in the past, the toolkit is expanding. Most systems have multiple probes, suction devices and powered shavers that can be programmed for use.
• Infrared systems demand a clear line of sight between instruments and the system's imaging unit. Fiducial markers are placed on the patient's forehead and instruments reflect infrared light back to the system's camera to track locations, so you have to be aware of how the rest of the equipment in the room is set up. With electromagnetic instruments, that's not an issue. Surgeons can move the device as close to or as far as from the patient as they'd like without losing the signal, which can be an important factor in ORs with limited space.

Before surgery with either system, patients undergo dedicated pre-op CT or MRI scans with fiducial markers placed at anatomical landmarks. Surgeons then use the scans to plot their preferred approaches to targeted pathology. On the day of surgery, the images are loaded into the image-guided system. The setup, registration and verification of known anatomical structures take about 5 minutes to complete.

ROAD MAP Image guidance helps surgeons plot courses through a patient's specific anatomy.

Finding my way
Most of the compartments surgeons work in during sinus surgery are big air spaces filled by pathology — a polyp or tumor. Is that an air pocket? Is that soft tissue? Am I in the cranial cavity? Am I in the orbit? Without image guidance, surgeons probe the sinus cavity with instruments that put pressure on, but do not injure, anatomy. The slow and steady approach certainly works, but it's a tedious way to operate. With image guidance, I know exactly where my instruments are at all times and can move at a safe, steady pace. Confidence breeds efficiency.

During sinus and skull base procedures, different approaches work better for different patients. Image guidance helps with the big-picture pre-op planning, letting me plot my basic course through the patient's specific anatomy before entering the OR. For example, during skull base surgery, it's often preferred to start far posterior and work forward, because blood flows to the back of the skull in patients lying in the supine position. With image guidance, I can determine if that approach would be best.

Patients with tumors or inflammatory disease present with chronic tissue inflammation, which increases blood flow in the operative field. Surgeons must work to keep the field as clear as possible as they navigate close to delicate structures. Suction instruments are designed for that task, but image guidance offers another level of safety. It's nice to know for certain if there is one more plane of cells between instruments and the dura, especially when disease has eroded layers of bone. When the field is bloody, it's hard to differentiate dura from inflamed nasal tissue, especially if the tissue is scarred from disease or previous surgery. Image guidance eliminates those question marks and removes uncertainty from the surgeon's mind.

The fusion of CT scans and MRI images, which is available in some systems, capitalizes on the advantages of 2 imaging modalities. CT scans are very accurate for bone and soft tissue interfaces. For example, at the skull base, you want to know if there's a bone between the nasal passage and the brain. When working near the orbit or the optic nerve, you want to know if a bony plate is protecting those areas. (Actually, you really want to know if one is not).

MRIs pick up soft tissue and show a lot more soft tissue detail than a CT scan allows, which is especially helpful when viewing structures in the eye or brain. The problem is that bone shows up as a void.

Working off fused images gives surgeons detailed information about all layers of the anatomy they're working in and around. It's an interesting imaging modality, but might be more applicable in brain surgery, when you're operating in different sub-area compartments of the brain. In my view, it doesn't offer the same benefit during routine sinus surgery.

SURGEON SATISFIER More docs expect to have image-guided technology in their ORs.

What's next?
The original generation of proprietary instruments used with electromagnetic systems were variations of the powered rotary instruments used in orthopedics. They've been adapted further, but are still fairly cumbersome. Suction devices are relatively comfortable to use, but some instruments that cut and seal to remove polyps and tumors in a relatively bloodless field need to be designed with ergonomics in mind. There's certainly a limit to how small and flexible powered instruments can be made, but this is an area of needed improvement.

Will image-guided instruments someday be able to guide surgeons along a pre-programmed surgical path? Perhaps, but there's an interim step that needs to be taken first. The technology's next advancement should involve capturing real-time images in the OR.

Images of patients' anatomy taken during pre-op CT scans and programmed into the image-guided systems provide extremely accurate snapshots of a patient's unique nasal and skull base anatomy. But after surgeons remove the targeted pathology, the images on the screen are suddenly inaccurate. Surgeons still see the exact location of critical structures, but can't tell for certain if they've completely removed the pathology they set out to excise.

Patients often undergo post-op CT scans or MRIs the afternoon or morning after surgery to confirm the removal of pathology. If surgeons could determine a procedure's outcome while the patient was still sedated in the OR, they'd avoid having to order new scans (and the associated costs), could remove residual pathology cells immediately or set a plan for doing so in the future. Until MRI and C-arm designs become more compact or image-capture technology evolves altogether, real-time image capture during sinus surgery is not yet ready for prime time.

Surgeons currently maneuver laterally through the ear to get to the central part of the brain stem and skull base, because the anatomy is familiar. Researchers are exploring the potential of using image-guided technology to work through the sinuses to safely perform extensive surgeries in previously unreachable areas of the skull base. For example, brain aneurysms are currently treated endovascularly or with a craniotomy. Surgeons approach through an artery to place a coil in the weakened vessel wall or remove a portion of the skull to locate and clip the vessel. Image guidance might allow for passage through the sinuses, a potentially safer and more effective route. It would require removing a lot of bone, but it's an exciting potential application of the technology.