New applications made possible by improved transducer technology and system software are having an impact on radiologists' practice patterns Premium ultrasound carries a significant price tag, thanks to its configuration rich with applications intended to deliver real-time views of the anatomy. Nonetheless, price appears to pose no impediment to an expanding group of imaging departments and imaging centers sold on the idea of possessing ultrasound technology so advanced that it can, in some instances, rival or surpass the utility and diagnostic value of MRI or multidetector CT. For the purposes of this article, premium ultrasound is defined as a high-quality, general-radiology ultrasound system capable of compound and advanced harmonic imaging, with dedicated applications for abdominal, breast, small-parts, and vascular ultrasound, based on an advanced architecture with software-based updating and multifrequency transducers, priced at or above $100,000. Ronald S. Adler, MD, PhD, is chief of the division of ultrasound and body CT in the radiology and imaging department at the Hospital for Special Surgery, New York. “Most often MRI, and to a much lesser extent CT, feeds into ultrasound for guided interventions. An abnormality initially identified on, say, an MRI, such as a paralabral cyst in the shoulder, may then be referred for an ultrasound-guided intervention,” he explains. “Not infrequently, however, we are asked to evaluate a suspected abnormality directly using ultrasound and inject if appropriate. An example might be a patient with wrist pain who is clinically suspected of having a ganglion cyst. The guided interventions are largely cortisone shots, but these may also refer to aspirations or even targeted anesthetic injections.” In those instances when ultrasound stands in for MRI or CT, the greater clarity and resolution provided by premium systems pays dividends. “I recently handled a case where both an MRI and an ultrasound were taken in order to help us ascertain the presence of a suspected ulnar-nerve abnormality. The quality of the MRI we get here is usually exquisite, and thus the modality is ideal for making this kind of determination, but in this instance, the patient had indwelling metallic hardware. While there have been improvements in MRI—and CT, for that matter—to address the indwelling-metallic-hardware issue, the fact remains that indwelling metallic hardware produces artifact, always.” Adler continues, “This, in combination with the claustrophobic patient’s difficulty remaining motionless while in the MRI gantry, resulted in an MRI image that was virtually uninterpretable. We then took an ultrasound using one of our high-end machines. It beautifully depicted the abnormal ulnar nerve—and the precise location of that abnormality,” shown in Figure 1.
Figure 1 Adler and many others have come to recognize premium ultrasound as a tool for producing definitive answers that obviate any need for further diagnostic procedures. “In some cases, ultrasound proves to be the only way to get the answer,” he says. A similar view is held by Margaret Szabunio, MD, director of breast imaging and ultrasound at the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Fla. “High-end ultrasound enables us to see lesion morphology in remarkable detail, which is very important in order to characterize breast lesions correctly, so that we can determine into which ACR BI-RADS® category we will place them,” she says. “A key part of the evaluation of a breast lesion is the margins. You can see these very nicely with high-end ultrasound.” Economically Justifiable Premium ultrasound is also prized by decision makers at Johns Hopkins Medical Institutions in Baltimore; they elected to acquire roughly a dozen such systems. Robert deJong, RDMS, RDCS, RVT, radiology technical manager of ultrasound, says, “Yes, premium ultrasound is very expensive, but we have several ways of justifying the cost. One way is by taking into consideration the marketing edge that premium ultrasound gives us. In our messages to the referring-physician community and to consumers, we’re able to trumpet the fact that we possess the technology and related expertise to perform certain diagnostic tests better, more safely, and more rapidly.” He adds, “We believe this is a strong selling point that opens the door to increased case volume. It ties directly into the Johns Hopkins brand; patients come here because they see us as the best of the best and, as such, they have high expectations that the equipment we use is likewise going to be the best of the best.” The diagnostic tests that deJong mentions being able to perform better include exams for gallstones, portal hypertension, cysts, and masses or tumors that can be visualized. “It formerly was the case that our image-guided biopsies were performed mainly with CT,” deJong says. “In recent years, however, as ultrasound technology at the high end has improved, we’ve progressively moved away from CT and toward ultrasound as the predominant modality for these image-guided biopsies.” Ultrasound-guided biopsies, by themselves, are a key component in the economic justification for premium ultrasound. “With an ultrasound of the abdomen or liver, our professional and technical fees combined might total under $1,000,” deJong notes, “but an ultrasound-guided biopsy of those same areas commands fees at least triple those we’d receive for performing just the ordinary ultrasound.” Further, the increased procedural speed of premium ultrasound may contribute to reduced absenteeism and worker’s compensation claims among equipment operators. “A serious and well-documented problem for sonographers is repetitive stress injury resulting from long periods of sometimes incredibly awkward positioning of the handheld transducer,” deJong says. “The fact that we can complete an exam in significantly less time reduces the amount of stress-injury potential that sonographers are exposed to each day. In addition to reducing the risk of injury, we also think that this will help extend the productive years of the sonographer.” Patients Appreciate It Patient satisfaction represents another justification for the steep investment in premium ultrasound. “Patients who’ve had both CT-guided biopsies and ultrasound-guided biopsies have much better things to say about their experiences with the ultrasound type,” deJong says. “What’s more, ultrasound involves zero exposure to radiation, so the sonographer can be right there with the patient, coaching and reassuring him or her throughout the entirety of the procedure, instead of having to disappear repeatedly behind a lead shield.” He explains, “This is important because there is deeper emotion associated with a biopsy than with most other types of diagnostic procedures. Typical biopsy patients are scared and upset. It means a lot to them to have us remain there, continually at their sides, during the procedure. It’s unsettling—and for some, devastating—to have the people who were present in the room with you suddenly all disappear around the corner, leaving you there alone.” In addition, premium ultrasound expunges certain challenges associated with image-guided biopsy. The main one is accuracy of needle positioning. “In a CT-guided biopsy, the radiologist positions the needle, the patient holds his or her breath, and the CT scan is taken to confirm positioning—but after that, you’re almost working blind through the remainder of the biopsy procedure,” deJong says. “Compare that with a premium ultrasound-guided biopsy: Because it is a real-time image, the clinician performing the biopsy can see, from start to finish, what he or she is doing after having located the target lesion. Ultrasound makes it possible truly to document that the needle is entering the lesion and, more specifically, from what part of the lesion the sample is taken. We can go in, collect the sample, and then very easily reposition the needle to be able to sample another part of the lesion, so as to ensure the fruitfulness of our search for diagnostically helpful cells.” Premium ultrasound can be used to assist with the biopsy of virtually every type of cancer. “This includes thyroid and kidney tumors, liver lesions, deep abdominal lymphadenopathies, pleural-surface lung lesions, and even some bone lesions,” deJong says. “Our basic rule of thumb for choosing whether to go with ultrasound or CT is that if we can visualize it in ultrasound, then that becomes our preferred biopsy-guidance modality.” Ultrasound also contributes to greater accuracy and safety of the biopsy, deJong believes. Take, for instance, a tissue sample sought from the deep abdominal lymph nodes. “It’s imperative that we avoid placing the needle in the surrounding vessels,” deJong says, “but it’s very difficult to avoid them using CT for needle-positioning guidance. Fortunately, many premium ultrasound systems include a color Doppler feature that affords an excellent view of those surrounding vessels, making it far easier to avoid them.” Another example is lung biopsy. “We see fewer complications with ultrasound because it allows us to do a better job of positioning—the needle can enter the lesion without also penetrating aerated lung. This decreases the risk of pneumothorax,” deJong says. Stretching the Limits One of the more intriguing applications available for premium ultrasound is elastography (Figure 2). An important characteristic of tissue is its elasticity, which can be affected by aging or by inflammation. It can also be affected by malignancy. The ability to visualize changes in that elasticity is thus deemed useful in diagnosing cancer, proponents of elastography contend. A small, but growing, body of evidence suggests that lesions can be characterized more rapidly and with a higher degree of accuracy when elastography is incorporated into the routine patient-examination process.
Figure 2 “Especially for breast imaging, the value of elastography has been significant,” Szabunio says. “We have not yet fully proven its effectiveness, but elastography appears to allow us to be more definite about whether we are dealing with benign or malignant lesions. If, for example, we are dealing with a lesion that does not seem particularly worrisome (based on its grayscale characteristics), it is hoped that elastography will provide confirmation that we have little or nothing to be concerned about, and can perhaps avoid having to perform a biopsy on the patient. We hope that elastography will decrease the number of biopsies performed each year. There is great interest in reducing biopsies because of their direct and indirect cost burdens on the health care system.” Elastography is not a substitute for mammography; of that, Szabunio is already quite certain. “Mammography and ultrasound are complementary techniques,” she says. “It has been proven that mammography is an effective screening tool—so much so that it cannot, at this time, be replaced with anything else. This is not to say that at some point in the future, a better modality for breast screening won’t come along, but at present, ultrasound is not that modality.” Elastography also is creating a buzz in the realm of prostate-cancer detection. Researchers are now learning that elastography may increase the ability to identify not only malignancies in suspect tissues, but also those present in tissues that are not suspect. Prostate elastography is something of a challenge to perform, however, in part because the transducer must be sharply angled while within the narrow confines of the rectum. Moreover, the accuracy of the elasticity measurement is heavily dependent on the skills of the sonographer: specifically, the procedure requires someone who can properly maintain consistent transducer pressure throughout the exam, regardless of the severity of the angles involved. Further applications for elastography are emerging, as are new techniques and tools for those applications that have already arrived. Szabunio, for one, is excited about what is in store with regard to transducers and probes. “The type of elastography we currently use relies on a freehand probe technique,” she says. “Its limitation is that accuracy and consistency depend, to a significant degree, on the skill of the sonographer. There is, however, a new technology called shear-wave elastography. The quality of scan results is not operator dependent. That is going to be very helpful.” Added Dimension Perhaps even more exciting than elastography are the new volume-imaging applications for premium ultrasound. “Volume imaging transforms ultrasound into slices that can be manipulated and turned into 3D reconstructions, very much like a CT scan,” deJong says. “A big difference, though, is that the sonographer can acquire the necessary volumes of data in 5 to 10 minutes, as opposed to 30 to 45 minutes. This will greatly affect our patient throughput. Volume imaging will also help reduce the frequency of repeated exams by giving the radiologists or interpreting physicians the ability to manipulate the slices to obtain the information they really need.” Szabunio says, “3D ultrasound may be helpful in that it will allow us to evaluate the size and extent of the tumors and their respective responses to treatment.” Adler expresses delight at the potential of 3D ultrasound to expedite diagnosis of musculoskeletal problems, such as rotator-cuff tears. “When you look at the tear, you want to get a true sense of its morphology and cross-sectional area, which is very difficult when you’re limited to looking at it in two planes,” he says. “Obviously, 3D would overcome this difficulty; however, I don’t think the technology for it is quite there yet. Some of the 3D systems that are part phased array and part mechanical provide a decent view, but not quite at the resolution I’d like. Some of the new matrix-array configurations, as they improve, may, in fact, allow us to do that.”
Figure 3 Fusion imaging—or image registration—is another emerging application for premium ultrasound. “It’s common for patients who will be receiving injections or undergoing biopsy to bring with them target-site images produced outside our institution,” Adler says. “While this is appreciated, the problem with it is that you cannot always be sure the ultrasound you generate yourself is giving a view of exactly the same area of interest depicted on the patient-supplied images. This could be solved with an image-registration capability. There are various ways of accomplishing it, some better than others. One system I know of is already commercially marketing image registration, but whether or not it achieves true accuracy is a question that remains to be studied fully.” Practice Patterns Shift Applications such as elastography, volume imaging, and others made possible by premium ultrasound are engendering shifts in practice patterns. “In the pediatric world, for instance, I would fully expect to see CT utilization diminish in favor of premium ultrasound,” deJong says. “The goal, in pediatrics, has been to minimize CT scanning in order to reduce the child’s exposure to radiation. If ultrasound can give the same information as a CT scan, then why subject a child to any radiation at all?” Szabunio finds that premium ultrasound streamlines the process of making the diagnosis and initiating treatment. “High-end ultrasound exams can bring us to a definite diagnosis with fewer steps,” she says. “For example, if we detect an abnormality in the breast, we can very conveniently—and in the same exam session—investigate other nearby areas, such as the axilla, at the same time. The results may prompt a biopsy of those abnormal lymph nodes, and therefore help in staging the patient’s disease, if possible.” An added benefit of more efficient, more definitive diagnosis is that it spares the patient days (or even weeks) of anguish over not knowing whether the detected mass is benign or malignant. “We want our patients to suffer as little anxiety as possible throughout this time. The shorter we can make that time, the better,” Szabunio says. Practice patterns could shift even more if the FDA approves the use of contrast with ultrasound-guided biopsies. “Ultrasound contrast,” deJong says, “has been shown in other parts of the world—with liver lesions, for instance—to have superior sensitivity and specificity over CT for determining benign versus malignant status. Because ultrasound provides real-time images, we can observe the contrast entering these lesions and then characterize the flow patterns. Contrast is nowhere near winning approval, though. I hope it will happen in our lifetimes; there is a strong core of professionals working closely with the FDA on this.” Szabunio remains skeptical about the value of contrast for her set of patients. “Contrast is difficult to use in the breast, so it makes for a more cumbersome exam, in general,” she says. “In other areas, such as the liver, I think contrast definitely gives a better view and more information, and it can help distinguish between different tumors or help evaluate responses to treatment.” Complementary Modality No matter what the fate of contrast may be, premium ultrasound is fast emerging as an indispensable modality for a great many imaging centers and imaging departments. “You always do better with the high-end systems,” Adler says. “The anatomy is much better seen (Figure 3), and you have much greater flexibility in terms of what kind of transducer you can use. There are circumstances where things seen with ultrasound cannot easily be resolved until you refer the patient for MRI or CT. For the large majority of interventional cases we work on here, ultrasound is complementary to CT and MRI—the latter two define the abnormality; the former guides the intervention.” There is, though, a clear drawback to using premium ultrasound. Once an organization tries it, it can be painfully difficult to return to reliance on less advanced ultrasound systems, with their less-vivid images. “I’ll admit we are somewhat spoiled by using only high-end ultrasound systems here,” Szabunio says. “When we review images from outside institutions that do not have high-end ultrasound, it’s then that we realize how lucky we are to have what we have. This is wonderful technology.”