VIENNA, Austria — Just as high-end ultrasound machines were reaching maturity with the menace of commodity market pricing a break-through opens new applications for tissue characterization with elastography.
The immediate potential for this technology is rapid diagnosis of tumors for breasts, prostate and the liver that may dramatically reduce the need for interventional biopsies.
Yet tissue characterization with elastography is a vast field in medical research stretching further than anyone can see at this moment.
Already seen as the "must-have" feature among ultrasound manufacturers the lines are being drawn in a classic fight for distinguishing product quality among competitors and a renewed exploring for setting value against the clinical benefits.
For example, what is it worth for the U.S. to eliminate, according to a conservative estimate, over one-third of the two million breast biopsies performed annually?
Elastography begins with old-fashioned finger-poking by a general physician to see how stiff a patient's liver may be, or a woman feeling a lump in her breast.
Stiff tissue is neither normal nor healthy.
Hitachi (Tokyo) introduced elastography for ultrasound in a symposium at the European Congress of Radiology in 2004, using a simple physical manipulation and some powerful algorithms in its software.
The radiologist pushes down on a breast, for example, and the software analyzes how the sound waves bounce against underlying tissue, rendering an image of troublesome stiffness.
This compression method, relying only on a software upgrade, was matched by competitors to the point that elastography was a significant theme at ECR 2009, with scientific papers and product demonstrations.
Hitachi continues to lead in the compression technique available on its Hi-Vision line with the HI-RTE (Real-time Tissue Elastography) and has been followed by Toshiba (Tokyo) with its Differential Tissue Harmonics (DTH) on the high-end Aplio line, which has now been migrated as well to the portable Viamo. (Medical Device Daily, March 10, 2009).
Ellison Ribby, Hitachi Europe's manager for ultrasound, told Medical Device Daily, that speed for processing is a good question to be ask about the quality of other systems, adding "Our algorithm has stood the test of time since 2004."
"Multicenter studies have shown the accuracy and reproducibility of results with HI RTE," she said, and it has emerged as a key capability for biopsy in guiding fine needle aspiration.
Hitachi sponsored a special session for a standing room only crowd to hear abstracts presented from studies using HI RTE capabilities in procedures for non-invasive, quantitative evaluation of diffuse liver disease, results from a multi-center study of prostate exams and elastography in musculoskeletal applications.
GE Healthcare (Waukesha, Wisconsin) has not yet entered the elastography competition and the elastography picture at Philips was confused at ECR 2009.
Yet Radjen Ganpat, sales development manager for Ultrasound with Philips Healthcare EMEA (Böblingen, Germany), told MDD, "we will have elastography on the IU22 by the end of 2009."
Oddly, product literature promoting Philips' Compact Extreme 50 (CX-50) for cardiologists claims capabilities for "tissue motion quantification, including functions like annular excursion, velocity, and regional shear," and also for strain quantification, both principles that speak specifically to elastography.
Riding the shear wave
Two manufacturers stand out from the crowd with a different approach to elastography that does not depend on operator-induced compression but uses a shear wave pulse from the transducer to compress tissue.
Both Siemens (Erlangen, Germany) and Supersonic Imagine (Aix-en-Provence, France) quickly dismiss the operator compression technique because results are highly dependent on the skill level and experience of a given operator.
Results from compression examinations are not reproducible, even by the same operator with a second exam, they agree.
Jacques Souquet, the founder of SuperSonic, said operator compression ultrasound provides "only a global assessment of deformation where shear wave pulse provides a local assessment of specific lesion stiffness."
SuperSonic began deliveries in Europe of the Aixplorer with elastography capabilities on board and Souquet told MDD, "Our sales funnel has exceeded our expectations for the first three months of this year and we are building up the capacity to meet this kind of demand. "
"I know that both GE and Philips are suffering right now because they do not have this capability," he said.
"We won two contracts in France, beating them out because of elastography," he added. "It is true we have a home court advantage there. But we also won in Germany and will be delivering the Aixplorer there next month."
Siemens offers operator compression elastography and also began shipping its shear wave technology, called ARFI (Acoustical Radiation Force Impulse), in Europe in May 2008.
ARFI is not approved by the FDA, though Siemens said it is in the filing process.
Roee Lazebnik, Director for Ultrasound Product Development, Siemens Medical USA (Mountain View, California) said elastography is "the most exciting change in ultrasound in a long time."
"It is rare in any imaging modality to get a truly new source of information," he said, explaining that "usually we get better at looking at existing information."
He explained that a shear wave created with an ultrasound pulsation is the same as ripples in a pond with waves passing faster through stiff tissue and more slowly through soft tissue, just as sound waves will vibrate more quickly through a brick than a sponge.
ARFI renders a 2-D image displayed side-by-side in gray scale for the operator with a standard ultrasound B-mode image.
Siemens offers two versions of shear wave elastography under the brand Virtual Touch with ARFI running in one mode to quantify the shear wave and in a second mode to quantify the effect on the tissue, resulting in tissue characterization, which is "very new," according to Lazebnik.
Lazebnik said ARFI is doing very well in Europe with liver tumors proving to be the hot application.
Souquet, a pioneer in ultrasound at ATL Ultrasound who served five years as chief scientific and technology officer (CTO) with Philips after ATL was acquired, said that elasticity changes the paradigm ultrasound, yet without hardware.
The Aixplorer takes advantage of this by streamlining technology even further with no hardware for beam formation and using only one acquisition board instead of the five to 10 found on competitive machines.
"The board we use for acquisition is what I call a 'dumb' board, though I should probably not say that," he said.
"The data is transferred over a BUS to an off-the-shelf board developed for the video gaming industry giving Aixplorer a configuration that more flexible and can be programmed with new modes for very, very fast imaging," Souquet said.
The Aixplorer transducer is made of a composite materials by Vermon (Tours, France), he said, that is "every bit as good as a single crystal transducer."
"Developing our elastography platform we have a relationship with the École Supérieure de Physique et de Chimie Industrielles (ESPCI), which is located in the Nobel Prize Corner of Paris where Marie Curie did her work, along with many others," he said.
"Working with this lab we have developed unique patents on shear wave, 11 of which are our own and 10 which we purchased from the Centre National de Recherche Scientifique (CNRS)," he said.
This intellectual property becomes key to entering the shear wave market, he said.
"Anyone who is going to generate a true ultrasound shear wave, as opposed to the compression method sooner or later must talk with Armen Sarvazyan, who holds the key patent," he said adding that Sarvazyan is a founder of SuperSonic Imagine.
"Even when they receive FDA approval for the ARFI system, Siemens will not be able to put those units on the U.S. market, because they do not yet have an agreement with Armen," he smiled.
SuperSonic is currently conducting a multicenter study of the breast using shear wave from the Aixplorer.
Seventeen leading research and reference hospitals are participating, with seven in the U.S. and 10 in Europe.
Exams from 1,000 have been completed with the study design calling for 2,300 exams, which SuperSonic expects to complete by July.
The endpoint for the study is to demonstrate the specificity of the shear wave exam in detecting tumors in the breast.
"The gold standard for mammography remains X-ray examination," said Souquet.
"When a tumor is suspected, the patient is then sent to a diagnostic center for an ultrasound exam to characterize the tumor. In the United States there are 2 million breast biopsies performed each year, yet 80% of these biopsies return negative results. That is a heavy cost to the healthcare system," he said.
"If we are able to clinically demonstrate that we can reduce the number of biopsies required, that could represent significant savings for healthcare systems not only in the United States but around the world," Souquet said.
Physicians at Hammersmith-Charring Cross Hospital (London), who are participating in the study, estimate the reduction in biopsies could be as high as 50%, he said, while partner hospitals in the U.S. are more conservative saying it could be reduced by 30% to 40%.
"If we demonstrate the effectiveness for breast examinations we plan to move on to the prostate and the liver," Souquet said.