MARCH / APRIL 2005

FORUM

Picture this: Diagnostic imaging comes of age

Diagnostic imaging technology has seen stunning advances in recent years. Positron emission tomography (PET), for example, can detect brain activity and give a color-coded image of the body’s metabolism and chemical activities. Computed tomography (CT), meanwhile, provides detailed anatomy of the body’s tissues and organs in multiple planes. Combined, they enable physicians to pinpoint the location of cancer, heart disease, and brain disorders.

The technology is improving every day. In development now are devices that can spot tumors when they are less than a millimeter in diameter by identifying cells that are absorbing glucose at a rapid rate.

From PET to CT, to magnetic resonance imaging (MRI), to ultrasound, diagnostic imaging is one of the most important medical advances of the past century. According to the World Health Organization (WHO), diagnostic imaging is a prerequisite for the correct and successful treatment of at least one-quarter of all patients worldwide. In the developed world, medical imaging is used for diagnosis in the leading causes of death, heart attacks, strokes, and cancer. And as the technology gets better, physicians are able to perform more accurate and less invasive tests.

George Taylor: “The (miniature ultrasound) devices can be used in the bush or in a village. They allow you to make very sophisticated diagnoses in the field—literally.”

But with these monumental improvements come colossal challenges. Like most technological advances, the medical imaging revolution comes at a price, both literally and figuratively. New modalities are prohibitively expensive for many of the world’s health care systems. For example, around 60 percent of all MRI scanners are in the United States, according to Dr. George Taylor, Radiologist-in-Chief and Director of the Kresge Laboratory for Pediatric Imaging Research at Children’s Hospital in Boston. Most countries simply do not have the infrastructure, the specialists, or the resources to invest in and maintain the most basic, let alone the most sophisticated, imaging machines.

Even countries that can afford the technology are struggling with the cost of its use (or, some would say, its “overuse”). In the U.S., for example, the cost of diagnostic imaging is expected to reach $100 billion annually by 2005, up from about $75 billion in 2000, according to the Blue Cross and Blue Shield Association.

This challenge is exacerbated by a growing shortage of professionals who can operate the machines and interpret the images. The American Society of Radiologic Technologists estimates that there are over 30,000 vacancies for radiologic technologists nationwide, and the American College of Radiology reports that the rate of imaging use is growing three times faster than the available pool of radiologists (6 percent vs. 2 percent).

Such inequities and challenges are an inevitable part of this transformation, and only time will tell how the social and political repercussions will play out. Researchers at Children’s Hospital and other teaching hospitals are studying the clinical impact of the technologies and trying to piece together which are the most important and the best way to use them. But today there are more questions than answers.

In the meantime, a handful of technologies are poised to send ripples throughout global health care. HMI World spoke to researchers at Harvard Medical School-affiliated teaching hospitals about four of these breakthroughs and how they are likely to shape the future of medicine.

Portable ultrasound
When most people think of ultrasound they think about looking at babies inside the womb. But sonography—the use of sound waves to construct an image of a body organ—is also used to diagnose breast cancer, appendicitis, abdominal tumors, and a vast array of life-threatening injuries.

Developed in the 1960s, ultrasound scanning involves placing a small device, called a transducer, against a patient’s skin near the area of interest. The transducer produces a stream of inaudible, high-frequency sound waves which penetrate the body and bounce off the organs inside. The transducer then detects the sound waves as they echo back from the internal structures and contours of the organs. The waves are received by an ultrasound machine and transformed into live pictures via computers and reconstruction software.

In the past, ultrasound systems weighed more than 300 pounds, cost between $80,000 and $300,000, and were the size of a washing machine. That’s still true in most instances. But advances in chip miniaturization have led to the development of battery-operated hand-carried ultrasound machines that weigh less than six pounds and are the size of a laptop computer.

“The miniaturization of ultrasound may have a tremendous impact on developing nations,” says Taylor. “The devices can be used in the bush or in a village. They allow you to make very sophisticated diagnoses in the field—literally.”

According to SonoSite, a company that makes the devices, units have been used in combat situations in Afghanistan, Iraq, and Turkey, and on medical service missions in Nicaragua, Guatemala, Kenya, Haiti, Ecuador, the Philippines, and the Ukraine. The company reports it has sold over 15,000 systems since 1999, allowing for new point-of-care applications in thousands of situations where ultrasound was either too cumbersome or too expensive to be used before.

The World Health Organization surmises that roughly two-thirds of patients who need diagnostic imaging can be diagnosed by the use of either X-ray or ultrasound or both. WHO advises that every hospital, from district level to university hospital level, have the capacity to perform these techniques.

Portable ultrasound units allow health care systems and agencies to go beyond this baseline requirement, says Taylor. “What’s important is not that the technology is so advanced,” he points out. “It’s that it can be taken into hostile and distant environments.”

Teleradiology
The world is running low on radiologists. This shortage is particularly pronounced in less technologically-developed nations. According to some estimates, about two thirds of the world's population has little or no access to radiological services.

Teleradiology has the potential to help alleviate this shortage by eliminating the need to have a radiologist on site.

It works like this. Through Picture Archiving and Communication Systems, or PACS, a digital X-ray, CT scan, or MRI scan is sent to a database for storage or is sent over the Internet to another site, where it can be retrieved and viewed on a high-resolution workstation. The advantages are fast report turnaround time, anytime-anywhere access, and a film-less environment. While the technology is not new, it is becoming more widespread and affordable, thanks to dramatically decreased hardware and network costs, the development of communication standards such as HL7 and DICOM, open architecture, and the spread of the Internet. “PACS makes it possible to send images from far-flung places and bring them to an international center,” says Taylor.

Today, hospitals in the U.S. are using PACS for emergency room and off-hours radiology coverage and for second opinions. But less than one-tenth of one percent of radiology work is transmitted outside the country for interpretation, reports Dr. James H. Thrall, head of the Department of Radiology at Massachusetts General Hospital (MGH). He adds that no MGH work is offshored.

The hospital does, however, provide services to health care providers in other countries. MGH has a teleradiology division whose mission is to bring “real-time expert sub-specialty radiologic opinions to all corners of the globe.” The division provides a primary diagnostic service for all imaging modalities or a second opinion service to referring physicians who request specific sub-specialty opinions. It has clients in Cyprus, Jordan, Lebanon, Saudi Arabia, the United Arab Emirates, and Yemen.

There are a number of medical and legal issues involved in using teleradiology, including the need for constant vigilance to maintain quality, controversies surrounding the outsourcing of jobs in the U.S., malpractice disparities, privacy concerns, and confusion for patients. Licensure issues are another major stumbling block, says Thrall. The only radiologists outside the U.S. who can provide interpretations for U.S. patients are those who have been trained and licensed in the U.S. Still, with the promise of creating a global health care network, these technologies are here to stay.

PET/CT
PET and CT scans are standard imaging tools that physicians use to locate disease states in the body. A PET scan demonstrates the biological function of the body, while the CT scan provides information about the body's anatomy. By combining these two scanning technologies, physicians are able to more accurately diagnose and stage cancer, provide a more personalized course of treatment, and monitor response to therapy.

“Having both of these types of information in the same place is better than the sum of the parts,” explains Dr. J. Anthony Parker, associate professor of radiology at Beth Israel Deaconess Medical Center and Harvard Medical School. Parker recently took part in the dedication of the first PET/CT scanner installed in Greece at Hygeia Hospital in Athens.

Medical research published in the New England Journal of Medicine indicates that integrated PET/CT exams provide extra information beyond that gathered with individual PET and CT merged together in 41 percent of cases because of its accuracy in locating disease.

PET has been used in research for years, says Parker. But recently, the discovery of a radioisotope, fluorodioxyglucose (FDG)—which allows scientists to see where the body metabolizes sugar—has made the technology clinically useful. The addition of CT makes it possible to see more precisely where in the body sugar is being taken up (for example, in the bowel wall versus simply the abdomen).

PET/CT used with a patient who has lung cancer: (A) the CT image, (B) the PET image, and (C) the fused PET/CT. In the middle image, the black dot represents increased FDG uptake and indicates cancer. In the third image, this is represented by the colorful area.

Parker notes that PET/CT has many applications. For example, it can save patients with advanced lung cancer from undergoing unnecessary surgery. It has also become a method of evaluating, following, and directing lymphoma therapy.

The cost of PET/CT scanners is in the $1.5 million range, so this is not a technology that is likely to be globally available in the next five years, according to Taylor. In addition, while the U.S. has an industry built up around producing FDG, other countries do not. Parker notes that in Greece, for example, a single dose of FDG costs over $1,000, as opposed to $200 in the U.S. Of course, as additional hospitals in Greece purchase their own scanners, the FDG manufacturer will be able to lower its prices because it will be able to better distribute the costs of its initial capital investment.

Parker says that another challenge to the proliferation of PET/CT is the lack of physicians and technologists certified in both radiology and nuclear medicine. But in the U.S. boards in both areas are working on addressing this demand. Meanwhile, the technology is spreading. GE Healthcare, a unit of General Electric Company, reports that more than 350 of its Discovery PET/CT systems have been installed worldwide in the last two years, including one at the Tata Memorial Hospital in Mumbai, India.

Images from the Center for Molecular Imaging Research at Massachusetts General Hospital

Molecular imaging
Perhaps the most spectacular development, and one that puts science on a new threshold of discovery, is molecular imaging—a multidisciplinary field that integrates patient- and disease-specific molecular information with traditional anatomical imaging readouts. By noninvasively imaging the molecular (proteomic and genetic) profiles of disease in individual patients, a physician may one day be able to design a personalized, molecularly-guided treatment plan.

Farouc Jaffer: “We think integrating molecular imaging with molecular medicine is going to revolutionize the way that doctors take care of patients.”

“Molecular imaging is being fueled by the potential of personalized medicine,” says Dr. Farouc Jaffer, director of the Cardiovascular Molecular Imaging Program in the MGH Center for Molecular Imaging Research. “We think integrating molecular imaging with molecular medicine is going to revolutionize the way that doctors take care of patients.”

Improvements in imaging hardware—such as PET/CT, single-photon emission computed tomography (SPECT)/CT, MRI, and optical imaging—and new imaging agents, such as superparamagnetic iron oxide for MRI, are making this new wave of medicine possible. These “smart” contrast agents make otherwise hidden microscopic abnormal cells visible.

Already, molecular imaging is leading to advances in disease detection, drug discovery, and biomedical research. And MGH’s Center for Molecular Imaging Research has demonstrated that iron oxide enhanced MRI can detect prostate cancer that has traveled to the lymph nodes with 90 percent accuracy (up from 35 percent accuracy using MRI alone). In addition, says Jaffer, the technology has shown promise for detecting other metastatic cancers, atherosclerosis, rheumatoid arthritis, and other inflammatory diseases such as colitis. There are applications anticipated in infectious disease and neurological disease as well, he adds. “We expect the clinical applications of iron oxide to rapidly grow once the agent is FDA approved.”

As with other modalities, molecular imaging creates challenges with regard to education and training. Moreover, because it requires a large investment in imaging hardware and imaging agent synthesis, it is unlikely to be widely available globally, at least initially. Still, even if it is concentrated in a few institutions, over the next five years, molecular imaging is expected to lead to new drugs and therapies that could significantly affect healthcare worldwide.

Copyright 2006 Harvard Medical International