New technologies in ultrasound: high-end drives innovation, commodity products ease workflow
Conventional or B-mode ultrasound has been used as a diagnostic imaging tool for over four decades. Over the last few years, however, ultrasound systems have witnessed a blizzard of developments in their underlying technology. This has catalysed a significant change in the patterns of ultrasound usage vis-a-vis other, older imaging modalities, especially in terms of concerns about the latter - for example, radiation risk in X-rays and computer tomography (CT), and cost for both CT and magnetic resonance imaging (MRI).
The ultrasound market is largely driven by innovations in underlying technologies and more sophisticated software algorithms, which allow manufacturers to offer smaller, more powerful and complex systems.
Key developments include an acceleration in processing speed and enhancement in the quality of diagnostic images – coupled to advances in contrast-enhanced imaging and precision in the timing of image capture. This has been accompanied by a sharp reduction in noise-to-signal ratios in the final data to optimize spatial, contrast and temporal resolution, including rotatable views for better visualization.
GE’s cSound technology, for example, offers CT level image quality based on advanced algorithms that capture much larger amounts of data than possible previously (by some estimates, about a DVD worth of data per second). The technology also makes pixel-by-pixel selections of the most precise information to display.
Developments in transducers, beam formation
Ultrasound has also made quantum leaps in factors such as transducer sensitivity and beam formation. For example, line-by-line imaging in beamformers has been replaced in some systems by large zone acquisitions, allowing users to view examinations in greyscale and colour Doppler. Meanwhile, retrospective imaging makes it possible to process raw data multiple times, while retention of channel domain data allows for patient-specific imaging.
Because of all the above, clinicians are able to use ultrasound to image blood perfusion and blood flow in vessels with diameters of 2 mm and less, with small vessel beds displayed via Doppler flow false-colour 3-D or greyscale reconstructions. The result is better assessments of organ perfusion, which have traditionally been difficult on ultrasound.
Take-up of ultrasound has also been recently boosted by a growing commodification trend. Certain categories of ultrasound have become relatively inexpensive, mobile and less demanding of power. Mobility-related innovations include portable hand-held devices, and more recently, the world’s first wireless transducer. Even some low-end machines are now enabled for full bi-directional communication with electronic medical records.
As healthcare reforms and budgetary pressures favour use of cost-effective solutions, this has led to especially sharp growth in the use of low- and mid-range ultrasound systems. It is now commonplace, for example, to see ultrasound systems in a recovery room, next to hospital beds, or equipping NGOs at health outreach projects in developing countries.
For many hospitals, this kind of product/technology mix makes sense, since not all patients require the sophisticated features offered by high end machines, while their smaller, inexpensive counterparts provide solutions for an everyday challenge faced by most hospitals – workflow bottlenecks.
High-end remains motor for new applications
At the other end, the high-end segment is leading innovation not only in ultrasound technologies, but driving the overall medical imaging market, too. Despite their cost, the advanced features of premium systems have moved ultrasound well beyond traditional applications such as ob/gyn to interventional cardiology and internal medicine. Several ER clinicians, for instance, now routinely utilize ultrasound for echocardiograms and abdominal imaging, while radiologists and surgeons use it to guide needle placement or perform bone sonometry.
Some cutting-edge areas – such as matrix transducers - remain ensconced in the premium category. Matrix transducers have direct relevance to two fast-emerging applications, namely volumetric ultrasound and 3-D/4-D applications.
Given below is an overview of key recent developments in ultrasound systems.
Mobility and Ergonomics
Ergonomics and mobility are being addressed by vendors in order to differentiate their systems and grow user volumes. Some surveys suggest that over three out of four of ultrasound users experience work-related pain, with a fifth of these suffering a career-ending injury.
New-generation ultrasound systems stand out in terms of design. Most are noiseless to permit sonographers to minimize distraction and focus on the exam, with settings customized and organized depending on clinical preferences.
Some have slanted bodies to prevent users hitting their knees or feet on the machine, with keyboards that can be raised or lowered depending on user height, probes that are shaped to the human palm and rotatable LCD monitors for sharing the display with colleagues. Other innovations include the possibility of use in both sitting and standing positions, with memory features to accommodate different users.
Some recent ultrasound machines have tablet-sized touchscreen-based interfaces, which significantly reduces the reach and steps (in some cases by 15-20%) in order to start and complete an exam. This enables faster workflow. Touchscreens allow users to tap in order to start functions, pinch and drag to zoom in and out, and swipe to expand the image. Some vendors offer exam presets, with several enhanced functions such as continuous wave Doppler or transducers.
As discussed below, there is an increase in the use of ultrasound as an alternative to CT and MRI in many point-of-care (PoC) settings. One of the reasons for the trend is mobility as well as increasing miniaturization. Smaller ultrasound machines provide solutions to concerns about cables or wheeling bulky machines around patient rooms, and address tight space demands in key hospital settings such as the operating room. Compact models can be transported by being wheeled or atop a cart.
In some cases, smaller portable machines can also be moved between departments within a hospital or clinic - on a user’s back.
Enhanced quality drives ultrasound to point of care
Ultrasound images today are available with far-higher resolutions than in the early 2000s, when most physicians were used to pictures being fuzzy. One of the key reasons is enhancement in real-time computer processing of images.
Superior image quality has also driven ultrasound to the point-of-care (PoC) setting – both for diagnostic and interventional procedures. PoC ultrasound is now widely available in operating theatres and emergency rooms. Between 2010 and 2013, anesthesiologists are reported to have doubled the use of ultrasound procedures, and ultrasound is also far more common today in certain interventional procedures such as image-guided biopsies and ablations, previously dominated by CT and MRI.
Volumetric ultrasound development
Volumetric ultrasound allows superior characterizing of tissue and the performance of procedures with far greater accuracy.
Ultrasound was previously only able to capture a single imaging plane, but it can currently acquire volumes. This is because transducers which enable the acquisition of real-time volumes of tissue and allow imaging in multiple planes such as the transverse and sagittal have recently become available. For instance, transducers can detect the altered speed of high-frequency sound waves through adipose layers versus other tissue, and make the system aware of increased adipose content.
Though several new-generation transducers remain expensive, in areas where they make a difference, the added price tag is becoming justified. For instance, high-resolution matrix transducers are finding use in interventional cardiology applications such as trans-esophageal echocardiogram (TEE) and 4D imaging.
While 2-D continues to be widely used in clinical applications, recent technological advances such as matrix transducers have been enabling factors and triggered interest in 3-D and 4-D ultrasound.
3-D/4-D ultrasound has a more rapid acquisition rate of datasets and subsequent improved image visualization.
4-D imaging consists of the three spatial dimensions as well as the element of time. It projects a cinematographic, motion picture view of an organ or a specific part of an organ, and is emerging as the next generation in advanced imaging.
In combination with advanced visualization functions, 4-D ultrasound aids complex surgical applications and interventional procedures. Multiplanar reconstructed (MPR) images are now available for review in the same manner as CT and MR scans.
Leading imaging vendors already offer 4-D imaging products - across all modalities, PET/CT, MRI and ultrasound. However, 4-D ultrasound is capturing a great deal of interest in applications where ultrasound has already made a case for itself, due to cost, mobility or radiation concerns.
The close connection between 4-D and ultrasound dates back to cutting edge efforts in the early 1980s, when a Duke University team determined that although MRI was faster, ultrasound was the closest to “achieving 3D real time acquisition.” The researchers, led by Dr. Olaf von Ramm, developed a single-transmit, multiple-receive ultrasound scanner called Explosocan to increase data bandwidth.
One of the most revolutionary technologies in ultrasound consists of elastography, which utilizes B-mode ultrasound to measure the mechanical characteristics of tissues, which are then overlaid on the ultrasound image. This provides physicians the ability to view stiffer and softer areas inside of tissue, with image quality and clinical outcomes equivalent to X-Ray, MRI, and CT.
Elastography techniques include strain elastography and shear wave elastography (SWE). It has begun proving its use in the characterization of thyroid nodules, lymph nodes and indeterminate breast lumps as well as the detection of prostate cancer. None of these were achievable via conventional ultrasound.
The application which has generated maximum attention is liver fibrosis staging. Biopsies are not only invasive but carry bleeding and infection risks. Elastography, which can be repeated as often as required, is being seen as a way to get the data needed by clinicians to diagnose and stage liver diseases without the associated complications. Elastography is also used to predict complications in patients with cirrhosis.
SWE in particular is also seen as a tool to assist in earlier detection of conditions such as Hepatitis C, and both fatty liver and alcoholic liver disease. Alongside lab studies, it offers a means to closely monitor the impact of treatment and assess if the liver will normalize. For many hepatologists, fighting a liver condition before Stage 4 cirrhosis provides a good chance of reversibility.
SWE can also provide information on which Hepatitis C patients might benefit from viral therapy.
From smartphone apps to AI: the future
App-based ultrasound have recently been showcased. These use transducers connecting via a USB port to a mobile device and a downloadable app. The transducer performs data acquisition, processing and image reconstruction. The result is an ultrasound feature in a consumer-grade smartphone.
Some vendors have launched artificial intelligence systems to enhance speed and automatically take image volume data from 3-D echo to recreate optimized diagnostic views. In cardiac echo in particular, the result offers major potential by permitting reproducibility of imaging.
Nevertheless, such cutting edge technologies are still in their infancy. Only time and user experience will determine their eventual success.