d03a.jpg (11559 bytes)Digital runs rampant in radiology these days. Whatever isn’t digital needs to be, and whatever is digital needs to be better. While the work in digital radiography has reached a commercialization period, the work in digital fluoroscopy is still taking place in the R&D centers for the most part.

Because it is used to image moving anatomy, fluoroscopy, by its nature and application, cries for digital capabilities. For that reason, fluroscopy was one of the earliest modalities to gain some digital capabilities to provide dynamic, digital images of moving anatomy.

That technology, however, looks to be greatly modified in the near future, as vendors use CCD and flat-panel technologies perfected for digital radiography to improve digital fluoroscopy. While most OEMs’ digital fluoroscopy products are some time from commercialization, radiology department buying teams need to stay abreast of their progress.

The flat panel trend
Fluoroscopy is looking to follow the move of its radiographic cousin and using flat-panel detectors to replace the image intensifier, optic system and TV camera for digital acquisition and processing of images.

d03b.jpg (12331 bytes)Marconi’s Mx8000 multislice CT scanner is part of the company’s Venue suite.

Marconi Medical Systems Inc. (Highland Heights, Ohio), for example, is developing this technology with its Venue suite of products. Venue includes a FACTS (fluoro-assisted computed tomography) fluoroscopic C-arm, as well as a PinPoint articulated frameless stereotactic arm and a CT scanner.

Charles Cassudakis, Venue and interventional product line manager at Marconi, says the Venue interventional suite is used in special procedure rooms for a variety of minimally invasive techniques. “The [flat] panel [detector] allows better patient access without barriers,” he adds.

John R. Haaga, M.D,. chairman and professor at University Hospitals of Cleveland and Case Western Reserve University (Cleveland), views the Venue suite as a micro surgery system.

“We use it to do biopsies and put tubes in place for drainages,” Haaga says. “Our biggest use is in the treatment of fluid collections, both infectious and malignant. For example, recently we had a patient with pancreatic cancer, who had a biliary stent in place that developed a small abscess in the head of the pancreas right next to the metal biliary stent. This was in a tight site between the vena cavae, the common bile duct and the portal vein.”

Haaga says the Venue suite allows him to get into those very tight, virtually inaccessible areas successfully and perform the necessary catheter insertion.

Cancer treatment is a target application for the Venue suite as well. James M. Hevezi, Ph.D, director of medical physics at the Cancer Treatment and Research Center (San Antonio), uses the Venue for CT-guided, 3D brachytherapy, a cancer treatment technique that involves implanting radioactive iodine seeds into solid tumors. The delicacy of placing the seeds requires extreme accuracy from an imaging modality.

Hevezi’s department received its system in the fall of 1998 and performed its first CT-guided implant in February 1999.

“This is a new technique for certain kinds of tumors ? for people with recurrent tumors after radiotherapy,” explains Hevezi. “We’ve used this for treating inguinal nodes, recurrent lung tumors and ovarian tumors.”

The facility eventually plans to move to prostate seed therapy. Although the follow-up times to date are only for a year, the hospital has enjoyed success with most patients showing no evidence of recurrence. Two of 10 treated patients have died, but both patients had extensive metastatic disease.

In addition to outpatient brachytherapy, Hevezi also plans to use the unit for diagnostic studies, because of the good image quality. The facility can follow tumors in patients undergoing chemotherapy, which makes the equipment utilization economically feasible.

photoVarian Medical Systems Inc. (Palo Alto, Calif.) supplies the flat-panel digital detectors to Marconi. “Varian has focused on fluoroscopic, high-speed, 30 frames per second [equipment],” says Chuck Blouir, marketing manager of imaging products for Varian. Blouir touts several features to flat-panel image acquisition, including higher contrast resolution, subtle differences in density, which provide better visualization of an anomaly or tumor, and improved spatial resolution that is useful for small stents.

“We are developing a larger panel [which] should have around RSNA 2000 to replace a 16-inch image intensifier,” he adds.

As with flat-panel digital radiography systems, durability and reliability is a concern in digital fluoroscopy. Because flat-panel receptors are manufactured of glass and electronic components, they are relatively fragile compared to existing radiographic and fluoroscopic equipment.

In development
Philips Medical Systems North America (Shelton, Conn.) is banking on a bright future for flat-panel digital fluoro and has invested heavily in the production of flat panels, reports Tom Giordano, business unit director for radiography.

Working collaboratively with Siemens AG Medical Engineering Group (Erlangen, Germany) and Thomson Tubes Electroniques (Meudon-la-Foret, France), Philips and their partners have commissioned Trixell S.A.S. (Moirans, France) to manufacture flat panels to integrate into their imaging systems.

Philips’ Digital Diagnost is a DR system that uses a flat-panel detector from Trixell. Philips considers the dynamic use of flat panels for fluoroscopy as a works-in-progress at this point. The company currently is testing the use of dynamic flat panels for RF and cardiac applications at clinical sites in Europe.

GE Medical Systems (GEMS of Waukesha, Wis.) began development of flat-panel technology for fluoroscopic application as far back as 15 years ago, notes Brad Fox, global cardiac product manager. GEMS is using its successes in other flat-panel products to fuel the development of flat-panel fluoroscopy. In fact, according to Fox, GEMS began working on its flat-panel fluoro system before the digital radiography and full-field digital mammography products it currently offers commercially.

“We developed a fluoro-ready panel and, from that, developed as an off-shoot the two other products” Fox says.

In fluoro work, Fox explains that a high frame rate is important to create high-quality images and low X-ray dose compared with mammography and chest X-ray. GEMS currently is collecting clinical data to optimize that technology and develop products.

Fox says GEMS considers the product at a works-in-progress stage. EG&G (Santa Clara, Calif.) has an exclusive agreement to provide GEMS with its flat-panel technology. The current panel format is 20 cm by 20 cm for fluoro applications.

Toshiba America Medical Systems (Tustin, Calif.) is another company actively engaged in a works-in-progress application of flat-panel technology, but is taking a different approach from the others.

As in digital radiography, the debate between direct conversion and indirect conversion is alive and well in digital fluoroscopy. Raymond Dimas, Toshiba’s senior product manager of vascular systems, reports that the company is developing a prototype flat-panel fluoro system, which uses a two-step direct conversion process. Indirect conversion systems use three layers – a cesium iodide layer, a photo diode layer and a matrix of thin-film transistors to produce images. With the Toshiba process, there is one layer that converts X-ray to charge (amorphous selenium) coupled with a laminated thin film transistor (TFT) layer.

“With three layer [panels], you lose information in the middle layer,” says Dimas. “With direct conversion, [there is] very little, if any, loss of information.”

Toshiba has been able to leverage its expertise in the manufacture of laptop computers which use TFTs.

Toshiba anticipates this technology will be most helpful in vascular studies because of increased resolution capabilities, especially in renal, neurological or angiographic applications.

“Estimates are that it will be cost-competitive with what’s on the market today, especially if you do a lifecycle cost analysis,” Dimas asserts. “The physician side benefit is that there are consistent images and no interruption from preventive maintenance or service calls.”

At the Radiological Society of North America (RSNA) show in 1999, Shimadzu Medical Systems (Torrance, Calif.) unveiled plans to develop a flat-panel fluoroscopy system. While the project is still in the early stages, the company said very small panels had been used to image small animals. The plan is to have a larger panel that is used on a C-arm for a variety of applications. Clinical studies are expected to begin in less than two years.

Cardiac Mariners (Los Gatos, Calif.) is yet another vendor that has designed a new approach to fluoroscopic imaging, which gained FDA clearance in October 1998. Rather than employing the traditional method of projecting a diverging X-ray beam from a single focal spot to a large detector in close proximity to the patient, Cardiac Mariners’ system, based on a technology called scanning beam digital X-ray – or SBDX – employs a large scanning

X-ray source to project converging X-ray beams onto a small detector located a distance from the patient.

The benefits of the system, other than producing digital images, include reduced radiation exposure to patients, improved image quality and lower operating costs. The SBDX technology includes continuous cooling functions to prevent system shutdowns due to overheating. The relative cost of the equipment is comparable to conventional X-ray fluoroscopy systems.

Barclay N. Dorman, Cardiac Mariners’ vice president of marketing and sales, says the company expects to have production units out in the latter half of this year. Because images are produced in three dimensions, quantification of spaces is facilitated. With a 3D data set, a physician can select the correct size of stent to place, because they are working from actual measurements rather than estimates.

“Because the X-ray detector is three feet above the patient, in an emergency, staff has phenomenal access to the patient,” concludes Dorman.

Establishing a base
The benefits that may come with the advent of flat-panel digital fluoroscopy will build on existing features of current digital fluoroscopy systems. Like many of its competitors, Siemens Medical Systems, Inc. (Iselin, N.J.) currently is developing a flat-panel digital fluoroscopy system.

Siemens feels its current digital fluoro line provides a good stepping stone to the flat-panel revolution, says Richard Ruoff, product manager of angiography systems.

While not as advanced as flat-panel detectors, Siemens’ current system offers computer-controlled image processing that digitizes the signal. In a fluoroscopic suite – where typical studies such as barium enemas, upper GIs and swallow evaluation examinations are routinely performed – the ability to run all images on a digital system improves efficiency, since images and films need not be developed.

In addition to a digital signal, Siemens equipment offers a pulsed fluoroscopy capability, designed to reduce the amount of radiation the patient receives. Pulsing comes into play when advanced interventions are performed, such as embolization of an aneurysm in the brain or angioplasty in heart vessels. Because these procedures take a long time to accomplish, the patient could be exposed to large doses of radiation without pulsing.

Siemens’ proprietary Carevision can generate between three pulses and 30 pulses per second, depending on the application. Instead of running in a continuous mode of fluoro (which might use 30 pulses per second), if the rate were decreased to 15 pulses per second, half of the radiation dose would be eliminated.

d03d.jpg (4410 bytes)A digital fluoroscopic image from Marconi’s flat-panel fluoro device (FACTS) shows a needle in position for a vertebroplasty procedure.

The radiology department at Hutcheson Medical Center (Fort Oglethorpe, Ga.) is equipped with four Siemens digital fluoro radiography (DFR) remote tables for a variety of fluoroscopic examinations.

“Originally, people thought that remote tables were just for walking/talking patients [for outpatient procedures],” says Joseph J. Busch, M.D., Hutcheson’s chief of radiology. “We use ours for pediatric, elderly and very sick patients, because these tables provide more access to the patient.”

Busch prefers the digital remote configuration, because it permits angulation of the tube for gastrointestinal contrast studies, sinuses other fluoroscopic studies. He asserts that a major advantage to being able to angle the tube includes the ability to examine different anatomical positions, offering efficiencies in work completion.

“We showed that with this technology, we can get patients on and off the table faster, and get them in and out of the department with more comfort and higher precision,” Busch adds.

Busch’s comments bring to light one of the primary benefits to digital fluoroscopy. In a digital environment, the radiologist views images in real-time, which facilitates diagnostic and interventional evaluation.

“The bottom line is that with a remote DFR system we can do more work, faster, in less space, with fewer people,” Busch explains. “In today’s world of reduced reimbursements, this is the way to stay ahead of the game.”

The upgrade path
While the jump to a new digital fluoro system may be a bigger financial burden than some facilities can afford, the idea of upgrading an existing system to give it digital capabilities is gaining acceptance among customers. This trend not only makes the jump to digital easier today, but looks to set a precedent for the flat-panel systems of tomorrow.

InfiMed, Inc. (Liverpool, N.Y.) provides digital upgrades to conventional fluoro rooms with its GoldOne line. InfiMed makes a camera that converts digital information through a computer into a stored image.

Steven Wetzner, M.D., chairman of radiology at the New England Baptist Hospital (Boston), had a goal of eliminating film in his department. He was tired of lost films and wanted to allow numerous people to view the image at one time in different locations, and save the time of processing, storing, and retrieving film images. He saw the digital upgrade as a way to do that.

Wetzner explains that the InfiMed system allows the radiologist to select which images become part of the record. “If you obtain 40 images, and after review find that only 12 are really relevant, you just store or print those images,” he adds. Timothy Stevener, vice president of radiology for InfiMed, quotes a typical base RF room upgrade at $69,000, including installation and a one-year warranty. And if the costs of flat-panel digital fluoroscopy systems go the way of their radiography cousins, that price could make an enticing alternative. end.gif (810 bytes)