Frequently Asked Questions

FAQs about navigation:

FAQS about MRIs and iMRIs

FAQs about the O-arm™ Imaging System

FAQs about Functional Image-Guided Surgery

1. What is navigation? [ Top ]
Using a technology similar to a global positioning system (GPS), navigation provides the surgeon the ability to see a patient’s anatomy in three dimensions and accurately pinpoint a location in the brain or spinal cord with the aid of diagnostic images such as computed tomography (CT) and magnetic resonance (MR), or intra-operative images using the PoleStar^® or O-arm™ systems. It also enables surgeons to track instruments in relation to a patient’s anatomy and track the anatomy itself during a surgical procedure.

The term “navigation” is synonymous with image-guided surgery (IGS), computer-assisted/computer-aided surgery (CAS) and neuronavigation.

2. How does navigation technology work? [ Top ]

You might compare surgical navigation technology to the location and directional tracking systems used for cars and ships today -- it is, in effect, a GPS system for the surgeon. Much as the driver of a car uses the GPS system to find the way on the road, the surgeon depends on these images to confirm the position of his or her instruments in the patient's body.

As the surgeon moves an instrument in the body, its position is precisely calculated. That data is then transferred to a computer in the operating room. The computer then superimposes the position of the instruments as they are used in surgery onto images of the anatomy displayed on a monitor, allowing the surgeon to see the exact placement and direction the instrument is moving.

3. Why is it beneficial for surgeons to use navigation during surgery? [ Top ]
Ultimately, using navigation helps the surgeon accurately detect where he or she is working in the patient's body at every moment during surgery.

This capability enables the surgeon to make smaller incisions. When trauma to the body is minimized, the patient may spend less time in recovery and may experience fewer complications.
By enabling the surgeon to navigate through the delicate landscape of the sinus or brain more accurately, the surgeon can remove a brain tumor or sinus infection, possibly without impacting healthy tissue. During orthopaedic surgery, navigation helps the surgeon align bones at just the right angle.
This precise technology also enables the surgeon to go right to the problem, which may mean the patient spends less time on the operating table.
This technology may mean better long-term results with less need for repeat surgeries.

4. In what ways can the use of navigation affect my recovery? [ Top ]
Trauma, pain and scarring can be minimized due to smaller incisions and the surgeon’s increased ability to avoid damaging healthy tissue. The precise technology can also mean better long-term results and decrease the need for repeat surgeries.

5. What steps are involved in a navigation procedure? [ Top ]
There are four broad steps in a navigation procedure. These steps are summarized here, with more detailed information below.

A diagnostic image (MRI, CAT Scan) of the patient’s anatomy may be loaded into the computer.
The scan is then used to create a 3D model of the patient's anatomy.
Just before surgery, the surgeon maps the patient's anatomy to the 3D model using an image-guided probe. (For spinal surgery, Medtronic software can build this model and make the map automatically.) This process is known as registration
Using the navigation system as a tool, the surgeon can see the instruments on the computer image and confirm the exact point where she or he is operating.

Step 1 - The radiology technician takes a CAT or MRI scan of the patient.

Usually the evening before or day of the surgery, a radiology technician takes the first essential step -- a CAT or MRI scan of the patient's anatomy. The CAT Scan, which captures bony structures, is used most often for sinus or spine surgery, while an MRI, which creates a clear image of soft tissue, is used more often for brain surgery.

Just as you navigate in a city on the basis of landmarks -- a particularly tall building or a small park -- a surgeon uses landmarks in the image scan. In the case of the sinus or spine, the natural landmarks of the body -- the bones -- show up on a CAT Scan. The surface of the head, however, needs artificial markers because, except for facial features, the head is relatively featureless.

In that case, the technician will put artificial landmarks on the patient's head to serve as markers. These tiny, donut-shaped sponges (known as fiducials) are coated with a special compound that shows up on an MRI scan. If the scan is taken the night before surgery, the patient may be required to wear them overnight because they must stay on until "registration" (described in Step 3).

Step 2 - The surgeon builds a 3D model on the computer.

The surgeon downloads the image data from the scan of the anatomy into the computer. For brain or sinus surgery, the surgeon uses the data to build a three-dimensional model of the patient's unique anatomy to be viewed on a computer monitor. For spine surgery, the surgeon may go through this model-building process, unless the hospital uses software from Medtronic, FluoroNav^® Spine. This software makes the images available for immediate use by the surgeon and maps (or registers) them automatically to the patient's body. (See Step 3 for the details.)

Step 3 - The surgeon maps the computer model to the patient's body (registration).

After anesthesia is administered, but before the start of surgery, the surgeon maps the patient's anatomy to the 3D model of the scanned information. This process is known as registration.

The surgeon does this by first touching a "landmark" on the patient with an image-guided pointer or probe. This can either be a natural landmark, a bony structure such as the outer point of the eye or between the two front teeth, or an artificial donut-shaped marker (fiducial). Then he or she touches that point on the screen with the instrument. The camera for the image-guided surgery system transfers a signal from the probe to the computer to "register" the specific location being touched.

Point by point, on the patient's body and then on the monitor, the surgeon builds a correlation between the body and the screen image. By matching the scan to the real anatomy during surgery, the surgeon, using special image-guided instruments, can "see" the location of the instrument tip in the body accurately as he or she operates.

Step 4 - The surgeon uses the image-guided system during surgery

During surgery, the tip of the surgical instruments will be displayed dynamically as cross-hairs in all three of the anatomical views on the monitor. (Remember, the image is three-dimensional.) As the surgeon moves the instruments, the views shift to show their new position. This also enables the surgeon to visualize the proximity of the instruments to critical anatomic structures, such as the brain, carotid arteries, optic nerve, spinal chord, etc.

6. How do patients benefit from navigation in brain surgery? [ Top ]

Navigation gives surgeons image-guided precision for delicate procedures like tumor removal or Deep Brain Stimulation (DBS). During tumor removal, navigation and intra-operative imaging allow the surgeon to “see” whether he or she has successfully removed the entire tumor and avoid damage to surrounding healthy tissue. During DBS, the surgeon is able to confidently and precisely target the exact point on the brain necessary for the treatment of Parkinson’s disease or other neurological disorders.

7. How do patients benefit from navigation in spine surgery? [ Top ]
Absolute precision is needed in spine surgery because of its proximity and relation to the spinal cord. Navigation helps the surgeon navigate through the bone, while avoiding the spinal cord and other nerves. This not only helps the surgeon perform a minimally invasive procedure, it allows him or her to visualize the exact incision and screw placement and precisely track surgical instruments in relation to anatomy.

8. How do patients benefit from navigation in ear, nose and throat (ENT) surgery? [ Top ]

The primary advantages to using navigation during ENT surgery is that the procedures are much less invasive compared with the open surgical operations that were once standard, and it provides an enhanced level of patient safety, physician convenience, and procedural versatility.

For patients, this means the surgery will be less invasive because the affected tissue can be more effectively targeted. Fewer and smaller scars, less tissue trauma, and faster healing time have led to increased patient confidence.

For surgeons, this means they will be able to navigate on patient CT or MRI images with more clearly defined lesion borders. This will allow them to more precisely guide their instrumentation to the exact location that needs to be worked on, and remove the diseased tissue while leaving the surrounding healthy anatomy undisturbed.

9. How do patients benefit from navigation in joint replacement surgery? [ Top ]
Navigation is beneficial in joint replacement surgery because it allows the surgeon to more accurately place implants and align bones. This precision helps the surgeon minimize procedure invasiveness and recovery time, ensure that soft tissue and muscle surrounding the implant is balanced, and improve the overall longevity of the implant.

10. How widely used is navigation? [ Top ]
More than 2,300 medical facilities worldwide use Medtronic’s navigation systems to improve the precision of the procedures their surgeons perform and raise their patient care to the highest level.

11. Is navigation covered through my insurance or Medicare? Must I pay any additional fees for the navigation system? [ Top ]
Since every patient’s insurance coverage is different, you will need to contact your insurance provider to discuss your specific coverage.

12. What is Magnetic Resonance Imaging (MRI)? [ Top ]
An MRI is a procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as CT or X-ray. MRI is especially useful for imaging the brain, spine, the soft tissue of joints, and the inside of bones.

13. What is intra-operative Magnetic Resonance Imaging (iMRI)? [ Top ]
An iMRI is an "MRI guidance" system available in operating rooms designed to function with an MRI scanner. It allows the surgeon and clinical team to take MRI scans of the patient’s soft tissue and organs during a surgical procedure.

14. What are the benefits of using iMRI scans? [ Top ]
iMRI scans are beneficial because they allow the surgeon to track changes in a patient’s anatomy as the surgery takes place, while providing updated images and tracking the placement and trajectory of surgical instruments in relation to the anatomy.

15. How do patients benefit from the use of iMRI scans during brain surgery? [ Top ]
During tumor removal, iMRIs can be an enormous benefit because the intra-operative scans (scans taken during surgery) can track the shift in brain tissue that occurs when the skull is opened. Since the iMRIs have the ability to distinguish between cancerous and healthy tissues, the iMRI scans help the surgeon's accuracy in successfully removing the entire tumor while minimizing damage to surrounding healthy tissue.

16. Are iMRI systems covered through my insurance or Medicare? Must I pay additional fees for the iMRI system? [ Top ]
Since every patient’s insurance coverage is different, you will need to contact your insurance provider to discuss your specific coverage.

17. What is an intra-operative O-arm™ Imaging System? [ Top ]
The O-arm™ Imaging System is a multi-dimensional (2D and 3D) surgical imaging tool that produces high-resolution images of bony anatomy. The O-arm™ system is optimized for use during spine and orthopaedic surgeries.

18. What are the benefits of using an intra-operative O-arm™ system? [ Top ]
The O-arm™ system produces the high-resolution surgical imaging needed to achieve minimally invasive procedures and consistently improve surgical results. It can produce 3D images of bony anatomy during surgery in seconds to help guide the surgeon’s instrument trajectory and implant placement. It also produces a post-operative 3D scan to confirm the final results and success of the surgery before the procedure is concluded.

19. How do patients benefit from the intra-operative O-arm™ system in spine surgery? [ Top ]
Absolute precision is needed in spine surgery because of its proximity and relation to the spinal cord. Intra-operative imaging coupled with navigation helps the surgeon navigate through bony anatomy while avoiding the spinal cord and other nerves and see any changes in patient anatomy as the surgery takes place. This not only helps the surgeon perform a minimally invasive procedure, it allows him or her to visualize the exact incision and screw placement and precisely track surgical instruments in relation to anatomy throughout the procedure.

20. Is the use of an O-arm™ system covered through my insurance or Medicare? Must I pay any additional fees for the intra-operative O-arm™ system? [ Top ]
Since every patient’s insurance coverage is different, you will need to contact your insurance provider to discuss your specific coverage.

21. What is functional image-guided surgery? [ Top ]
Functional image-guided surgery is when a functional MRI scan is taken of a patient’s brain prior to surgery that shows what areas of the brain are associated with each specific function (i.e. speech, vision and hand movement). The data from the scan is then used during surgery so the surgeon can avoid potential damage to each functional part of the brain.

22. What steps are involved in a functional image-guided surgery? [ Top ]
A functional MRI (fMRI) scan is performed:

The patient is asked to perform certain repetitive tasks, or "paradigms", such as finger tapping, reading a word list, or even to think about certain types of objects.
Areas of the brain that control these functions will show "increased activation" on the scan, which can be turned into an image showing the anatomical location of interest.
This combined scan is transferred to a surgical navigation computer in the operating room.
Using this device, neurosurgeons routinely can guide incisions, skull openings, and brain tumor removal by the use of a special pointer whose position on a patient’s head is matched to the corresponding point on an MRI or CT scan. With functional image-guided surgery, not only the location of the tumor can be noted, but that of critical brain areas as well.

This functional scan is then "registered" or combined directly with a conventional MRI scan, in which an injection of a contrast medium is used to show the outline of a tumor.

23. How accurate is functional image-guided surgery? [ Top ]
We have compared the predicted location of motor cortex (the part of the brain where movement on the opposite side of the body is initiated) with conventional techniques of brain mapping using sensory stimulation. In every patient we have found the location of the motor cortex to be predicted accurately by functional image guidance.

24. What are the advantages of functional image-guided surgery? [ Top ]
Functional image guidance can give the neurosurgeon increased confidence that the tumor removal has been accomplished without giving a patient new neurological deficits, such as weakness on the opposite side of the body or difficulty speaking. In some cases, it may prevent inappropriately aggressive surgery that may injure a patient.

While the conventional methods of brain mapping described above are widely available, functional image guidance with fMRI allows for accurate, noninvasive preoperative assessment and planning for brain tumor surgery.

25. Who can benefit from functional image-guided surgery? [ Top ]
Any patient who has a tumor near a critical area of cerebral cortex, especially areas involved in controlling movement, sensation, speech, or vision. There are no additional risks, and the only additional step is that of the functional MRI scan, which takes less than one hour to perform.

We have also begun to use functional image-guidance for patients undergoing stereotactic radiosurgery. This allows for the mapping of critical cortex on the radiosurgery planning computer, so that the delivery of potentially dangerous radiation doses to eloquent brain areas will be avoided.

"We have patients now that come in who have explored this topic on the Internet. So the public is becoming much more aware of the accuracy the computer can provide... it is actually bringing patients into our practice looking for this type of technology."

Alfred Tria, MD
St. Peter's Hospital
New Jersey

Medtronic Glossary

Questions about a term? Check the glossary for help.

[ View Glossary ]

Questions?

Contact a Medtronic Sales Rep.

[ Contact Us ]

Important Safety Information