by Nancy Ross-Flanigan
photos by Martin Vloet

It's a familiar scenario: a patient comes to the hospital with a baffling set of symptoms, and doctors trying to diagnose the problem are stumped. Just a decade or so ago, a common solution was calling in a surgeon to take a look inside. Now, thanks to advances in medical imaging technology, such invasive exploratory procedures have virtually been eliminated. And that's not all. In addition to aiding diagnosis, state-of-the-art imaging is transforming treatment — and doing it all with less discomfort and inconvenience to patients.

N. Reed Dunnick

It's no exaggeration to call the developments revolutionary, says N. Reed Dunnick, M.D., Fred Jenner Hodges Professor and chair of Radiology. "These advances in imaging are so dramatic," he says, "that they're literally changing the way we practice medicine."

Slimmer, smarter slices

At the University of Michigan Health System, some of the newest additions to the medical imaging arsenal are three machines known as 16-slice CT scanners that work in a flash and offer up highly detailed images of internal anatomy. CT (computed tomography) scanners, which first came into use in the mid-1970s, combine X-rays with computer technology. As a patient lies in the donut-shaped device, a series of X-rays is beamed through the body from many different angles. After the beams have passed through the patient's body, detectors measure their remaining strength. Beams that have traveled through very dense tissue, such as bone, are relatively weak, while those that have zipped through less dense areas like the lungs are stronger. Using this information, a computer in the machine generates images of internal structures, with each image displaying a cross section or "slice" through one part of the body.

With a conventional CT scanner, each rotation of the X-ray equipment inside the donut results in one slice, but "multi-slice" scanners gather many times more information on each pass around the patient's body. The new U-M machine captures 16 slices at a time, and those slices are slimmer than ever before possible — thinner than a business card.

"People often say CT technology is like slicing a loaf of bread. This is like slicing a loaf of bread in incredibly tiny slices and yet slicing the whole loaf in a very short time," says Joel Platt, M.D., professor of radiology. In patients, that translates into scanning entire regions of the body in mere seconds.

Ella Kazerooni and Joel Platt

Patients appreciate spending less time on the table, but the speedy machine's greatest promise lies in accurately assessing their health problems, particularly those related to the heart, says Ella Kazerooni, M.D., professor of radiology. "The faster you can scan, the less blurring there is from motion, and that's especially important in imaging the heart." Even when patients lie perfectly still and hold their breath, getting a clear image of the heart is tricky because of the organ's constant pumping motion. But by using the lightning-fast scanner and synchronizing the scans with the patient's heartbeat, "we can generate near motion-free images of the heart, which we were never able to do before," says Kazerooni.

Speed isn't the only advantage. The ultra-thin slices reveal details of internal structures, such as extremely delicate blood vessels, that couldn't be seen on CT scans before. And thanks to advanced computer technology, information from individual slices can be combined into realistic, three-dimensional images. "The result is what we call a volumetric view of the patient — a 3-D representation of the person's anatomy," Platt explains, clicking a detailed color image of someone's insides onto a computer screen.

"In this patient, we scanned from the top of the chest down to the upper thigh in one breath-hold," says Platt. "That's a lot of distance to cover, yet we could do it at such a resolution that we could see all the blood vessels." What's more, the technology makes it possible to do "all kinds of novel viewing techniques, like virtual fly-throughs," making for a kind of Fantastic Voyage experience, Platt notes.

"It's the Nintendo generation of technology coming to radiology," he says. "It's really a whole new world for us." It's a new world for patients, too, who increasingly are hopping onto the table for a quick scan instead of submitting to more bothersome procedures.

"The better our technology gets, the more we can replace more difficult, time-consuming, expensive tests — which are often less pleasant for the patient — with things that are simpler and more routine," says Platt.

One example is cardiac catheterization, a technique used for diagnosing and treating heart problems. In the usual procedure, a thin, flexible, hollow tube is threaded into an artery in the groin and guided to the heart. Then, contrast material (dye) is injected into the catheter while a series of X-ray images is rapidly recorded. After the procedure, patients must lie on their backs for two to six hours while they're observed for possible complications, and even after they go home, they have to avoid strenuous activity for 48 hours to a week. But imaging the heart with the 16-slice CT — a 20-minute procedure that requires no recovery time — may provide just as much diagnostic information. "We put you on the table for 20 minutes, and you then can go back to work or go out to play golf," explains Kazerooni. With funding from General Electric Medical Systems, Kazerooni and colleagues are comparing the accuracy of cardiac CT with that of cardiac catheterization. Patients who already are scheduled to have cardiac catheterization will be recruited into the study, and all participants will have both tests performed. "We'll use the cardiac catheterization results as the gold standard, and then we'll compare the findings from cardiac CT to see how accurate that method is," says Kazerooni. "We'll also look at patient preferences for the tests — what they experience during and after the procedure, such as pain, anxiety, and recovery time. We want to know what it means to a patient to have one test versus the other."

The idea is not to completely replace cardiac catheterization with CT, but to use CT for preliminary screening, says Kazerooni. "There's a large group of people out there who have heart disease but are not being diagnosed, and part of the reason may be fear of the procedures that are involved. I see the potential of CT not as a replacement for cardiac cath, but as a way to bring more people in to be evaluated for heart disease." While some patients still may need cardiac catheterization as part of their treatment, others may be spared the discomfort and inconvenience, based on the results of their cardiac CT exams.

Viewing vessels

David M. Williams

Advanced imaging techniques also are transforming the diagnosis and treatment of vein and artery problems, says David M. Williams, M.D., professor of radiology and of internal medicine.

"I'm an interventional radiologist, which means that I do procedures to open up veins and arteries," says Williams. "For those procedures, we rely heavily on the newer imaging methods, such as CT scanning, magnetic resonance scanning, and ultrasound." In the past, it was common to use classic angiography — inserting a catheter into a blood vessel, injecting contrast material and taking X-rays — to develop a sort of roadmap that could be used to plan treatment, such as installing an endograft to reinforce a weak area in a blood vessel. "Nowadays, we use just the CT scan, no angiograms at all, in the planning phase for probably 95 percent of our patients.

When we do the procedure itself and deploy the endograft, we still use the classic angiogram, but for all the planning that goes up to that, we no longer need to use it." The three-dimensional CT images also help physicians tailor endografts to individual patients' internal anatomies. "That allows a precision of measurement that we didn't have before," says Williams.

Big improvements for the smallest patients

In the pediatric radiology waiting room at U-M Mott Children's Hospital, toddlers snuggle on their parents' laps, watching cartoon bunnies on a television screen as they wait to be called in for procedures. Performing imaging studies on these young patients presents particular challenges, says Ramiro Hernandez, M.D., professor of radiology. Some are simply too young to follow instructions like "Take a deep breath," or "Hold still," and even those who are old enough to understand directions may be too fussy and fidgety to follow them. What's more, while minimizing radiation exposure is a goal for all patients, it's especially important in children because their rapidly growing tissues are more vulnerable to radiation damage and because they have so many years ahead in which long-term effects may show up. That's why Mott physicians are excited about a new CT scanner that was installed last spring.

Peter Strouse and Ramiro Hernandez

"We've been using CT in children for the last 15 years, and it has proven itself an essential technique in the management of a wide variety of disease processes, including cancer, bone trauma and deformities, and inflammatory diseases such as appendicitis and post-operative infections," says Hernandez. "The new wrinkle is that we are more dose-conscious, and we try to use the radiation more efficiently than in the past."

The new scanner, developed specifically for pediatric use, is an 8-slice version that combines scanning speed with reduced radiation dose. The machine also has a feature that automatically adjusts the strength of the X-ray beam to the density of the tissue through which it is passing. "For example, you might need a stronger beam in the belly and a slightly weaker beam in the lungs," explains Peter Strouse, M.D., associate professor of radiology. "With previous machines, you had to select one beam strength that would work for the whole region you were scanning, but with its ability to adjust the beam, this machine allows you to idealize the amount of radiation you use."

Another feature of the machine is a boon in imaging children with blood vessel abnormalities, says Strouse. "We can program the machine to sense when the contrast material gets to the vessels we're trying to image" and to wait until then to start scanning. "Some of these kids have bad hearts that don't pump very well, so getting the timing just right has always been a problem. But with a machine that can sense when the contrast gets to the right place, we can get better pictures."

The speed of the new scanner offers yet another advantage. Young children often need sedation to keep them still during scanning, and while the practice is considered very safe, "there's a little bit of associated risk when you sedate a child, so you'd rather not if you don't have to," says Strouse. Since the new scanner has been in use, sedations have been reduced by about 10 percent.

Mixing media

As informative as CT images are, they don't always tell physicians everything they need to know. In cancer diagnosis, for example, CT images help reveal the size, shape and location of tumors, but clinicians rely on positron emission tomography (PET) to help determine whether a tumor is cancerous or benign. Magnetic resonance (MR) — which uses properties of hydrogen molecules to distinguish among different tissues — has unique advantages, too, revealing soft tissue anatomy better than CT, says Marc Kessler, Ph.D., assistant professor of radiation oncology.

Marc Kessler and Barry Shulkin

While each method yields its own sort of valuable information, putting it all together in a form that's easy to understand is a challenge. That's where Kessler and colleagues come in. "Every patient has what's called a treatment planning CT, a digital representation of that patient based on CT images," he says. "We've developed techniques that allow the clinician to outline regions of the disease on an MR or PET scan and then have it mapped onto the treatment planning CT."

Overlaying the images is not as simple as it may sound. Taken with different machines at different times, with the patient in slightly different positions, the images don't neatly line up in all three dimensions. "So computer-based techniques are required to geometrically register the three-dimensional images," Kessler explains.

"This," says Kessler, clicking side-by-side images on his computer screen, "is a CT scan showing a patient's lungs, part of the aorta and the liver. Over here is a similar view from PET. They each show us different features of the patient, but they have enough information in common to allow us to register them in three dimensions."

The process results in a composite representation of the patient that can be used to precisely plan treatment and assess its effectiveness. "Each of the imaging modalities has its own strengths," says Kessler. By merging them, "we combine all their strengths to create as complete a model of the patient as possible. That, in turn, helps us define as accurately as we can the diseased tissue we want to treat and the healthy tissue that we want to avoid."

The approach is so useful, in fact, that a new breed of machine has been developed to perform more than one type of imaging scan on a patient in a single session and to combine the information into either side-by-side or merged images.

U-M has one such machine, a PET/CT scanner in use since 2002 to detect and plan treatment for a variety of cancers, including breast, esophageal, cervical, ovarian, lung, colorectal, head and neck, melanoma and lymphoma. Several studies at other institutions have shown the PET/ CT combination to be highly effective at detecting and precisely locating tumors.

"The PET/CT scanner helps us more accurately characterize the disease, and that's good not only at the time of diagnosis, but also during its management," says Barry Shulkin, M.D., professor of radiology. By tracking metabolic processes such as the uptake of glucose — a source of fuel for cell activity — PET detects "hotspots" where cells are particularly active. Because tumors consist of actively growing cells, this information is a tip-off to a tumor's status, Shulkin explains. "By knowing how fast glucose uptake is decreasing, we have an idea of whether the tumor is responding to therapy."

Targeting tumors, refining radiation

Pinpointing tumors doesn't do much good unless treatments can be targeted just as precisely. Fortunately, radiation therapy methods are advancing in step with imaging techniques, making for more effective treatment with fewer side effects. Using 3-D and intensity modulated (IMRT) treatment plans generated with the PET/CT scanner or Kessler's integrated image method, radiation oncologists can custom shape radiation beams to conform to the area being treated, homing in on tumors and tissues where the cancer may have spread, while sparing normal tissue.

Avraham Eisbruch and Ted Lawrence

"This is an exploding area — the union of radiology and radiation oncology," says Ted Lawrence, M.D., Ph.D., the Isadore Lampe Professor and chair of Radiation Oncology. "The close collaborations we've always had are just becoming closer and closer."

Lawrence 's patient Richard Magers is grateful for the kind of accuracy that results from that union. Magers, an 80-year-old Farmington Hills resident whose full life includes working part time as a proofreader, flying, and making monthly jaunts to the casino, was treated at U-M for pancreatic cancer five years ago. "I had no problems at all from the radiation," recalls Magers, who also appreciated being shown just where his cancer was and what would be done to treat it. "I'm a curious person," he says. "I wanted to know what was going on."

In head and neck cancer patients, use of the highly precise technique, called conformal radiation therapy, has enormous implications for quality of life after treatment, says Avraham Eisbruch, M.D., associate professor of radiation oncology.

"When we treat cancer of the head and neck, we need to treat both the cancer and the surrounding areas that may contain microscopic disease, as well as lymph nodes in the neck — the first place where microscopic disease goes," Eisbruch says. "The standard way to do it is to use two big beams that cover everything — all the neck, all or most of the mouth, the oropharynx and the nasopharynx. The problem is that because the salivary glands are very sensitive to radiation, the doses of radiation that are required to treat even microscopic cancer wipe out the function of the salivary glands permanently." The distressing result for patients is a lifetime tethered to a water bottle. That may not sound like much of a problem in an age when lots of fitness-minded folks are toting Evian and Absopure to the gym and on errands, but patients with severe dry mouth (xerostomia) often have trouble talking, eating and swallowing without constantly sipping something, and their teeth are more vulnerable to decay.

Not so for Eisbruch's patient Frank Galea, 58, of Livonia, who was treated for squamous cell carcinoma of the tonsil in 1996 with a highly conformal radiation therapy technique. "I have very good saliva function," says Galea. "I don't have to drink water, and I don't have any problems with eating or swallowing." Patients like Galea are the rule now, not the exception, says Eisbruch. While conventional radiation therapy leaves 50 to 75 percent of head and neck cancer patients with extremely dry mouths, "we don't see severe xerostomia" now that the more precise method is being used, Eisbruch says.

Beyond 3-D

Impressive as today's techniques are, even more exciting possibilities are ahead, says Lawrence. "With the newest generation of CT scanners, images can be obtained so rapidly that we can get a sense of how tumors move as a patient breathes. That will allow us to undertake a whole new level of targeting, working out a model of a breathing patient in the computer and then targeting the tumor as it moves during breathing. The new high-speed image acquisition, along with conformal radiation therapy, will allow us to do that." And that ability will move imaging and treatment into a whole new dimension, says Lawrence. "We've been in the era of 3-D radiation, and now this is 4-D, with time being the fourth dimension."

Whether 3-D, 4-D or more — it's a promising picture of the future of patient care.