The proliferation of image-guided surgery (IGS) systems has been driven by advances in the technology of image manipulation, development of innovative minimally invasive surgical (MIS) procedures as well as the establishment of IT networks capable of linking areas of image acquisition, such as radiology or orthopedics, to the operating suite. While neurosurgeons were the first clinicians to recognize the benefits of implementation of this sophisticated equipment, other specialists have come to rely upon the exquisite anatomic and increasingly physiologic roadmaps these systems provide.
Naissan Vahman, research analyst of the orthopedics division of Millennium Research Group in Toronto, describes driving forces that have enhanced market penetration for the companies that produce the equipment.
The introduction of non-spinal orthopedic applications for such MIS procedures as knee arthroplasty or hip replacement has begun to propel IGS adoption. Some manufacturers have begun to produce specific software tailored to improve MIS procedures. The benefits of MIS have been well-documented in scientific literature as offering lower cost, shorter hospital stays, and less recuperative time compared to those experienced with traditional procedures.
Although IGS presents a huge benefit to the surgeons who recognize its value, there are limiting forces at work, not the least of which are the financial aspects. In this climate of constant cost containment, hospitals have been relatively slow to adopt these new systems that range from $100,000 for a basic set up to $400,000 for a fully functional system. In many institutions, significant modifications to the IT network infrastructure are required for efficient implementation of the technology.
Many hospitals are housed in older buildings, and laying or modifying a network with sufficient bandwidth to accommodate moving the huge image data files to the OR, is not always an easy task. Most operating suites were considered low on the priority list for inclusion in the IT network up to this point, largely because images were hand-carried on a variety of media (film, CDs, optical disks, or Zip disks) via "sneaker-net" to the OR.
Richard Buscholz, M.D., F.A.C.S., the K.R. Smith endowed professor of neurosurgery for Saint Louis University School of Medicine, is one of the developers and patent holders of the system known as StealthStation (currently produced by Medtronic). With a current installed base of 1,400 units worldwide, the technology is available in a wide array of institutions.
In the original incarnation of the system, StealthStation employed a large series of drive bays specifically programmed to permit receipt of images from each particular scanner in that healthcare setting. This circumstance required significant effort to retrofit all existing StealthStations in the hospital as the institution replaced CT or MRI scanners.
"Now that IT has begun to take off in hospitals, we have found that we can rely on a standardized format [DICOM] to do image retrieval and archiving," says Bucholz. "Having said that, there appear to be certain dialects of DICOM which are still somewhat problematic for our system, but, in general, I would say that an increasing number of scanners now are at least speaking in the same language."
Because image data sets are quite large (for example, a typical CT scan includes 50 to 100 images, each are 512 x 512 pixels in size where each pixel is made up of 16 bits of grey tone) the network must be configured to support image data file transfers. Without sufficient bandwidth in the network, the images would consume a large proportion of the network's capability, and render it useless for other functions such as managing electronic medical records, or other IS activity.
Additionally, without some level of PACS (picture archiving and communications system) connectivity, the scanners do not function as servers, and they are just another presence on the network. Buscholz explains that unless there is a PACS, they cannot patch into the scanners and transmit the images over the network.
Kamal Thapar, M.D., Ph.D., FRCSC, director of the department of neurosurgery at Sacred Heart Hospital, Eau Claire, Wis., explains that their PACS functions quite well to transfer images to their BrainLAB planning station.
"The goal is to fully and faithfully merge virtual space with real space and that's what image guidance allows you to do," says Thapar. "There are relatively few neurosurgical operations that would not benefit from some form of image guidance."
THE IT NETWORK: ESSENTIAL TO SUCCESS
From a philosophical perspective, Sacred Heart's Thapal says that the purpose of the IT department is truly information technology, not just to function as the purveyors of images from the PACS.
"There are so many elements and dimensions to information that we need in order to make the operating room a rich environment in which to work," says Thapal.
"Information technology is well-penetrated in radiology with the PACS. They can generate beautiful 3D image renderings, but then you go to the OR, and what you see is very low tech â?¦ a lightbox on a wall with an x-ray film or a CT scan put up slice by slice," says Nadim Yared, vice president and general manager for Medtronic Surgical Navigation Technologies. "Navigation brings live images that respond automatically to the surgical instruments. This information becomes mission-critical."
Klia Berhman, the area support manager for BrainLAB suggests a minimum of a 10/100 Base T line. Once images have passed through the BrainLAB planning station, they are reduced in format size so they are only 1/10th to 1/20th as large as when they arrived from radiology, but nonetheless, this IT issue becomes important when contemplating the use of an image-guided surgery system in the OR.
She has seen institutions transfer images from radiology to the BrainLAB planning station over either the hospital or radiology network depending on the IT infrastructure, but then transport the output from the planning station to the OR on CD, MOD, or 4mm dat-tape if their ORs are not networked.
"Some of the older facilities are having to upgrade to a 1000BaseT or a gigabit (Gb) network," explains Donald Gravlin, vice president and CTO of the health practice for Cap Gemini Ernst & Young in New York. "That is no easy feat to get that kind of high bandwidth from a core network."They have seen corporations like Hewlett-Packard and Cisco begin to offer consulting services for new construction of surgical units to optimize their IT utilization.
Gravlin estimates that over the next 18 months, wireless networks will permit serious retrofitting in existing facilities. However, wireless presents its own challenges, such as adhering to HIPAA regulations for patient confidentiality. (For more information on wireless networks, see "Riding the Wireless Wave" on page 18.)
Yared from Medtronics proposes a solution, "Our vision in the OR would be to have an operating room that would be totally wireless and shielded by a firewall. Then the connection from the OR to radiology could be either wired or wireless." If it's wireless, either Wi-Fi network or Bluetooth technology would work in this setting for these applications.
Berhman explains that wireless solutions require careful management of the network capacity, because routers now have a 2.6 GigaHz capacity. In some settings, they have circumvented the problem by placing the BrainLAB system on a specific LAN, given the traffic it must support as images are pushed across the network.
Yared predicts that in ORs of the future, there will be a propagation of "intelligent" equipment, each piece acting as either a server or a client. Every piece of equipment will have to communicate with the others, yet be shielded from the outside world to avoid contamination from external viruses and to prevent the distribution of information to non-secure places.
"Whatever happens, inside the OR has to remain inside the OR, except for filtered influx and outflux of information," Yared concludes. Information will include not only images, but other clinical data and patient demographics and intraoperative videos.
Few would dispute the phenomenal impact that an image-guided surgery system affords to surgeons who perform intricate precision-driven, often minimally invasive procedures. Access to the latest 3D images enhances the surgeon's capability. IT plays a key role in the efficient and effective management of images to and from the different components of the image-guided surgery system in the OR.
There are two basic methods for navigation systems to indicate the position of surgical instruments, notes Nadim Yared, vice president and general manager for Medtronic Surgical Navigation Technologies.
One is based on "line of sight" that employs an optical camera equipped with infra-red detection technology to visualize the LED dots on the instruments. The relative position of the dots in space gives the computer an indication of where the instruments are in space and which instrument is being used.
The second technology uses an electromagnetic field, and the receiver collects differing quantities of electromagnetic signal to permit the computer to locate the instrument in space.
"Both have advantages and inconveniences," Yared explains. The technique selection is based primarily on the specific surgical procedure being performed, but might include surgeons' preference.
Importing Images Step By Step
Using the example of a brain tumor resection, neurosurgeon Kamal Thapar, M.D., Ph.D., FRCSC, the director of the department of neurosurgery at Sacred Heart Hospital in Eau Claire, Wis., explains the steps to perform an image-guided surgical procedure using the BrainLAB VectorVision system.
- Import MRI or CT images onto the planning station.
- Use the planning station to mark the lesion, segment the blood vessels, indicate operative hazards, and indicate any structures that are relevant to the trajectory of the procedure.
- Integrate the initial DICOM image data set into the native software of BrainLAB, and transfer that information to a 100-megabyte zip disk.
- Transport the data to the operating room and load it onto the VectorVision system.
- Once the patient is anesthetized, use a feature called Z-touch, a laser that is beamed onto the patient's face to capture several anatomic landmarks. This creates a "mask" which the system can recognize and superimpose on the preoperative image data set. Surgical implements such as scalpels are equipped with markers, so the system indicates where the instrument is in relation to the lesion as visualized on the pre-operative image data set.
- Images are infused into the eyepiece of the operating microscope in a technique known as image injection.
- When the doctor looks into the eyepiece, he or she sees the lesion super-imposed on the operative field. Note: One of the challenges of cranial surgery is that once the surgical incisions are made, and cerebral-spinal fluid drains, brain shift occurs, moving the soft tissue within the skull. To accommodate for brain-shift, intraoperative ultrasound guidance is used to identify key anatomical structures and morph the existing data set to account for brain shift.