Virtual fly-throughs have long been radiological vignettes—decorative designs skirting the border of clinical relevance. The movies, run back and forth, have entertained exhibit visitors for years. But Viatronix, a start-up workstation manufacturer
Virtual fly-throughs have long been radiological vignettes-decorative designs skirting the border of clinical relevance. The movies, run back and forth, have entertained exhibit visitors for years. But Viatronix, a start-up workstation manufacturer in New York state, may have come up with the means to change the way this technology is viewed.
Founded by researchers at the State University of New York, Stony Brook, Viatronix has developed a two-module visualization system-one part preprocessor, the other interactive display-that allows the operator to segment data into 3-D chunks or slices that can be zoomed or viewed from any angle. The preprocessor, wired into a spiral CT scanner, reconstructs the data into a volume, and the reading station displays the fly-through at different points and perspectives. Prices begin at $100,000 to $115,000 for the preprocessor and $15,000 for the display station.
The first such unit was installed in late February at Open Systems Imaging in Palm Desert, CA. More units are scheduled for installation at eight other sites in the chain of imaging centers, as Viatronix ramps up to market its system to hospitals and imaging chains nationwide. The lack of reimbursement from major payers for screening exams will be challenging but not insurmountable, according to Dr. Mark R. Wax, an associate professor of radiology and chief of body CT at SUNY and Viatronix medical director.
“There is a large group of patients who are willing to pay out of pocket,” Wax said. “For those people who have complaints, you can use codes for CT of the abdomen, pelvis, or 3-D reconstruction.”
The core technology could support a number of clinical applications. Preliminary tests have demonstrated the ability of the Viatronix Visualization System (VVS) to reconstruct the aorta, larynx, bladder, and temporal bone, as well as to do surgical planning. Virtual colonoscopy was chosen as the vanguard commercial application, largely because of the public health imperative, according to Wax. Colon cancer is the second leading cause of cancer mortality in the U.S., accounting for about 56,000 deaths annually. Around 130,000 new cases of colorectal cancer are diagnosed each year. Experts suggest that 90% of these cases could be treated successfully if the disease were detected in its earliest stages. Yet 80% to 85% of the population is never screened for this disease.
Viatronix is not the first company with hopes of whittling that number down through the use of virtual colonoscopy. Other workstation vendors, including Vital Images and AccuImage, as well as CT manufacturers, offer virtual colonoscopy packages. And the colon is not the only option for a fly through.
“If you have real good software, it doesn’t matter what body cavity it is,” said Jeff Sorenson, director of marketing for Imatron. “You can fly-through anything, including coronary arteries.”
Imatron, which makes electron-beam tomography scanners, may hold the high ground. In December the company announced that the FDA had cleared its EBT technology specifically for colonographic use. No modification or upgrade was necessary, since the technology was designed to produce both 2-D and 3-D images of anatomical cavities. Capabilities include cardiac and coronary artery scanning, electron-beam angiography, and low-dose lung scanning.
Viatronix has passed FDA scrutiny as well, but not to the same degree as Imatron. The integrated system-EBT scanner, software, and computing hardware-was submitted by Imatron and cleared by the FDA. Only the reconstruction portion-the VVS system-was submitted by Viatronix.
“It really depends on what level of confidence a person wants,” Sorenson said. “We are specifically cleared for cross-sectional images to perform colonography.”
The difference comes down to scanner capabilities, and on this score, Imatron has an edge. EBT systems are up to 10 times faster than the best mechanical CTs, as an electron beam can be fired every 50 to 100 msec, and the fastest mechanical multislice scanners rotate once every 500 msec. EBT may also deliver thinner slices, resulting in higher resolution.
But speed is not as big an issue in virtual colonoscopy as it is in angiography or cardiovascular imaging. And resolution in a 3-D reconstruction is difficult, some would say impossible, to gauge. For such tentative advantages, EBT scanners, which carry a price tag of close to $2 million, may be difficult to justify, if they are to be used only for virtual colonoscopy. Because EBT scanners have been sold mostly to cardiologists rather than radiologists, the installed base is not likely to expand clinical applications to include a GI application.
Viatronix is not so encumbered. VVS can be hooked up to any spiral CT. The technology evolved from nearly two decades of research conducted at SUNY. An early spin-off turned into a computer board called VolumePro, which became the primary product of Real Time Visualization, a division of Mitsubishi Electric before its purchase in mid-February by TeraRecon (SCAN 2/14/01).
Like its competitors, VVS creates a 3-D rendering and a center line for navigation. The fly through is guided by the operator. Unlike competing products, however, VVS is designed specifically for virtual colonoscopy. Consequently, the product is easier to use and more efficient, and it provides more information. Key to these advantages are the automatic processing algorithms built into the system, including preprocessing capabilities, which dramatically reduce physician time. Exams with the Viatronix system can be completed in 10 to 15 minutes compared with a half-hour to two hours for competing systems, according to Viatronix.
Common to all virtual colonoscopies, the computer flies though the colon along a scripted flight path. Unlike movie-based fly-throughs, the VVS allows the user to take over at any moment, zoom in, and fly around suspicious structures, interactively examining them from any angle.
Interactive volume rendering can be completed at 10 frames per second, according to the company. Speed will reach 15 frames per second in the near term. The few products allowing such interactivity operate at one to five frames per second, according to Viatronix.
The painless, noninvasive nature of virtual colonoscopy is a big plus for patients. Rather than endure the insertion of an endoscope, patients undergo two 40-second scans (one prone, one supine) on a single-slice spiral CT using 5-mm-thick slices, reconstructed at 1 mm, then integrated into a virtual fly-through of the colon. A barium enema, typical of fiber-optic colonoscopy, is not necessary for virtual colonoscopy. Instead, patients examined with the VVS follow a special two-day diet prior to the exam and drink a small amount of barium. Artifacts from stool and other materials in the bowel are “electronically cleansed” using special algorithms, which subtract irrelevant anomalies. Polyps as small as 4 mm can be routinely seen, according to Wax.
Optical colonoscopy might spot even smaller polyps, but their clinical significance is not certain. Physicians may recommend the patient be followed rather than undergo treatment to determine whether the polyp presents a risk, Wax said.
The ability of the Viatronix product to visualize tissue not otherwise seen is an advantage over the optical colonoscope, which might achieve 95% coverage if the scope is twisted and turned expertly and if physical problems do not intervene. Virtual colonoscopy covers close to 100% consistently yet requires no special human skills, according to Wax.
“They look while they are inserting and then while they are pulling back,” he said. “With the computer, it’s like we can turn around 180º to look behind folds.”
Data presented to the FDA supporting the Viatronix 510(k) submission showed 100% sensitivity of polyps over 3 mm with no false positives. Three polyps found by virtual colonoscopy were missed by optical colonoscopy: two located on the back side of folds and one in the cecum of a patient who received an incomplete optical exam due to constructions that blocked the scope.
VVS offers several unique features that could help identify patients at risk for colon cancer. Translucent rendering provides a look inside the suspected polyp for characteristics consistent with polyps.
Viatronix is conducting clinical trials comparing the efficacy of VVS against optical colonoscopy, and Imatron is considering similar trials for its EBT product.
Both companies hope to ride a growing interest in preventive medicine in the U.S., as consumers take a more active role in their own welfare. Imatron has already succeeded in cardiology, having popularized coronary calcium measurements as a prognosticator for heart disease. Imatron, Viatronix, and their competitors are trying to do the same in a different venue-cancer.