Ludwig Mies van der Rohe is credited with coining the motto, “Less is more.”

But it is not only architects who have taken it up as a battle cry. Digital imaging product designers also are shrinking the size and weight of ultrasound systems to make them handheld and easily transportable not only in a hospital setting, but in an ambulance or helicopter.

The traditional 800-pound gorillas, refrigerator-sized ultrasound units on wheels, are not about to become obsolete. But as the new generation of five-pound portable scanners with laptop computer footprints is rolled out, it is likely that ultrasound behemoths of limited mobility will become as stationary as MRIs.

The ability to bring the small ultrasound units quickly to a patient in the emergency department, the operating room, the obstetrical delivery room or the nursery, the wards, or the ICU is being looked on as a godsend by many hospital ultrasound departments. Currently, when ultrasound is needed for an emergency elsewhere in the hospital, a spare unit must be found, or an ultrasound suite has to be broken down and brute-forced into an elevator and thence to the patient’s bedside, where space is often at a premium. With use of most ultrasound units tightly scheduled well in advance, moving a unit from radiology to a remote location and back can take an hour or more and necessitate a lot of juggling and tedious rescheduling of patient examinations.

In radiology circles, it has long been conventional wisdom that to achieve portability in an ultrasound system, it would be necessary to compromise the image and clinical capabilities. But the handheld portable units now in use or undergoing validation at beta sites have effectively put those issues to rest.

Have Ultrasound, Will Travel

Despite their small size, light weight, and low price point, portable ultrasounds produce decent images, says Frederick Doherty, MD, chief of ultrasound, New England Medical Center (NEMC) in Boston.

St Paul’s Hospital in Vancouver, Canada, has had a portable unit for 2 years. It is used by the staff doctors and residents rather than the sonographers. “It is perfectly adequate for 95% of what we do, and 100% of what we do portably,” says Peter Cooperberg, MD, professor of radiology at the University of British Columbia and chairman of radiology for the 500-bed hospital, which is all digital and filmless.

However, he adds, “I don’t think that any radiology department would buy one of these machines as its only ultrasound unit. It is not a replacement for a full size machine.”

Barry Goldberg, MD, director of diagnostic ultrasound and professor of radiology at Thomas Jefferson University in Philadelphia, is of the opinion that although the images from handheld units are of lesser quality than those from the best of the big machines, they are nevertheless still diagnostic.

“In theory, the better the image the easier it is to interpret. But that is not always the case,” notes Goldberg, whose division performs 50,000 examinations per year with 35 ultrasound systems, and is a major center for training and hardware evaluation.

“Those using the smaller machines for diagnosis must have diagnostic knowledge and capabilities similar to those who are using the larger machines. No matter what images you have, you still need experience,” he adds. “However, in a small facility with limited volume, I could use portable units and teleradiology to have the images read by experienced radiologists.”

Multipurpose portable ultrasound units for real-time abdominal and pneumothorax examinations are battery-powered, weigh less than six pounds, have a cable-attached transducer, and cost in the range of $20,000 to $26,000. Radiologists who have been using these DICOM-compatible systems say they can do 90% to 95% of the studies that are normally done on a full-size ultrasound system costing upwards of $150,000-$200,000.

There also are two FDA-approved, battery-powered portable ultrasounds based on phased array technology that are targeted at cardiologists and obstetricians. They cost as little as $11,000. One is about 2x14x10 inches with a flip-up display. The other is about the size of a handheld laptop or a Personal Audio Player. It has a 9×9-inch screen but only four or five buttons. Both models weigh about five pounds.

Additionally, there also is an even smaller point-of-care unit under development by a California venture capital startup for emergency vehicle, paramedic, and battlefield use. A suitcase-sized portable system for echocardiography and pediatrics also is being marketed for use in third world countries. It weighs about 20 pounds, costs about $46,000, and plugs into an electrical outlet, or can be used with a battery pack.

Hospital Setting Applications

For general imaging in a hospital setting, small ultrasounds facilitate doing emergency examinations on patients who cannot come to the radiology department. And depending on circumstances, the examination can be done by a sonographer, a radiologist, or a physician trained in its use.

“In our hospital, doctors do the portable imaging, so our technicians don’t use the portable but only do normal ultrasound scanning,” Cooperberg says. “Our staff doctors and residents can just run off to the ICU or emergency department with it and do a perfectly adequate study. It is actually in a knapsack so when a doctor takes off with the unit, it looks like he is going off on a hike somewhere. When he finishes the examination, he brings the unit back to radiology and we upload the images to our PACS.”

St Paul’s 2-year-old battery-powered portable is a closed design that weighs 5.4 pounds and has a flip-up liquid crystal screen and the normal controls you see on a full-size ultrasound unit. It also has direct PC connectivity.

The model can do color flow Doppler, power Doppler, pulsed wave Doppler and M-mode, and the next release will include directional Doppler, Cooperberg says. “We use it for any type of abdominal application,” he notes. “There are very few thyroids that have to be done on an emergency basis. Occasionally there are pregnancies that need to be done while the patient is awaiting delivery. But mostly we use it in the ICU or ER for very straightforward procedures like looking for abscesses or for perforations of blood vessels.”

ER physicians are interested in ultrasound because they can bill for it, notes Cooperberg. “However, I am concerned that they cannot do it with the same degree of diligence or expertise as a radiologist. So, in our institution, if the ER needs it, we come running down and take care of it for them.

“You need a trained doctor or sonographer to use a portable unit,” he adds. “You don’t give it to a secretary.

“We could use it for biopsies to guide a needle. It probably wouldn’t be as good as a high-end machine for liver metastases or pancreatic cancer, but then CT does most of that these days anyway. I don’t think I would want to use it for fetal anomalies in early pregnancy or subtle, difficult procedures,” Cooperberg says. “But it is perfectly adequate for 95% of what we do. The $200,000 machines do not have that much over the mini for general purpose examinations.”

St Paul’s has nine full-size ultrasounds in its Radiology Department and there are also units in the interventional suite and delivery room. The cardiologists have four units. Ultrasound is booked 2 weeks in advance; the sonographers do 100 examinations per day, on average. There also is a second portable unit in the hospital, which is used by nephrologists to find the veins for dialysis and by vascular surgeons following an operation. “The OR formerly had a full-sized ultrasound system but there was no place to store it,” Cooperberg explains.

The same portable ultrasound used at St Paul’s has also proven itself in a small, rural hospital with limited resources. Alan Hirshberg, MD, head of the five-physician emergency department at Martha’s Vineyard Hospital, normally sends severe trauma patients on a 90-minute helicopter flight to one of the Boston trauma centers. But late one November evening, the sole survivor of an automobile crash that had killed two others arrived at the emergency department. He was complaining more of abdominal pain than about his severely injured leg. With the radiologist and the sonographer off duty, Hirshberg’s options seemed to be to immediately airlift the patient without understanding the cause of his abdominal pain, or to do a CT scan and use a teleradiology service to read the images. Making either choice would seriously delay the start of treatment, so Hirshberg opted for a third-to use the hospital’s recently acquired portable ultrasound. He had completed 30 practice examinations with it but had not yet used it to help diagnose a patient.

Within a minute he was able to positively identify fluid in the peritoneal cavity. The patient underwent an emergency splenectomy and, after being stabilized, was flown off the island for extensive surgery on his fractured leg. “If we had opted to transport him immediately to Boston, he could have rapidly deteriorated,” Hirshberg notes. “Instead, the quick diagnosis allowed us to operate just as the situation became more critical and save the young man’s life.”

User-Friendly and Portable

For two other portable ultrasound users, Goldberg and Doherty, ease of operation and portability are the key issues for their hospitals. Both are testing the same 128-channel PC-based model. It has a microminiaturized 10-ounce probe with proprietary software that has been integrated with the open architecture of a 4.5-pound laptop computer with IEEE 1394 compatibility that is running on a Windows 2000 operating system. The probe and its connected transducer plugs into the PC like a digital video-camera. Thus, the model is immediately teleradiologically Internet-capable.

“It is very, very easy to operate,”? Doherty explains. “It is intuitive. Anybody who knows Windows can use this thing.” He feels that with some training EMTs and ambulance paramedics would be able to use the device to answer some important questions and forward answers to the hospital emergency department by wireless Internet so it can be ready to start treatment as soon as the patient arrives.

At the 350-bed New England Medical Center, Doherty has four ultrasound rooms and four scanners that do about 35 examinations a day, or about 8,300 a year. Of that total, about 15%, or 1,250 examinations, are done outside radiology. In the past, this has required breaking down and moving an ultrasound room. Now NEMC will not have to lose one quarter of its ultrasound capacity whenever there is an emergency. It can send the portable. A plus benefit, says Doherty, will be the ability to better schedule its four conventional scanners.

While agreeing that the PC-based model being evaluated at Thomas Jefferson could be carried in a backpack, Goldberg noted that staff radiologists and sonographers are more comfortable having it on a small stand with wheels, which can also accommodate a recording device, primarily because there is often no place to set anything down in a patient’s room. “In hospital rooms the tables are filled with other things, and you can’t put it on the bed, as it could fall off.”

The Cardiology Connection

At the present time the PC-based ultrasound does color Doppler, mean velocity Doppler, spectral Doppler, pulse Doppler, and blind Doppler. CW Doppler, which is mainly of interest to cardiologists, is to be added in the future.

The cardiology-targeted portables are basically designed to be used as a visual stethoscope for the heart, says David Liang, MD, an assistant professor of cardiology at Stanford University, which has been a beta site for two different cardiology units. “I have used a portable optimized for heart examinations to look at kidneys, the aorta, the liver, and gallbladder, but it is certainly not the ideal tool for looking at those parts of the body.”

He feels such units will become part of a typical heart examination. Physical examinations of the heart using only a stethoscope typically are notoriously unreliable. They are only about 20% to 25% accurate. But a Stanford study with residents indicates that by also using a portable ultrasound, diagnostic accuracy can be increased 50 to 60%.

At another beta site, Duke University Medical Center, cardiologist Joseph Kisslo, MD, sees inexpensive portables being used as an adjunct to a physical examination increasing correlation to 65%.

“The concept is not to do complete examinations, it is to provide a simple answer to a simple question: Is the heart big or little?” he asks. “Do you really need to send a patient for a full examination when your question is limited? Do we have to incur these costs? Why can’t it simply be done by the doctor providing the care?

“We are advocating that they be used for limited goals in the patient care process-to provide answers right on the spot to limited questions,” says Kisslo, a professor at the Duke University Medical School. “I think there are going to be a lot of people saying they don’t think that is right. In cardiology, we are saying we don’t think handheld ultrasound has to be used only by total experts.”

Richard Elsberry is a contributing writer for Decisions in Axis Imaging News.