CT has experienced spectacular growth over the last five years, spurred by steadily advancing technology, a voracious demand for faster diagnostic imaging, and an accommodating reimbursement environment. Both manufacturers and users expect growth to continue, but some experts warn that economic factors and a short-sighted approach to the use of the modality could cause the rate of growth to slow dramatically.

According to a study published in April (Radiology 2003;227[1]:113-117), CT grew from about 7% to 8.8% of noninvasive radiological studies performed between 1993 and 1999. The number of CT scans performed across the country during the same period increased by 29.9%.

Some radiologists have experienced even greater increases in their practices.

"Our volume from 1996 to 2000 was up almost 40%," said Dr. Bruce McClennan, chair of diagnostic radiology at Yale University. "We averaged 4800 (head and body) CT exams in the month of June, up from over 4000 a year ago, which was itself a marked increase. And I can tell you, my day reflects that now."

The growth rate for CT procedures has exploded over the last three years, said Dr. Stanley Fox, manager of CT advanced applications and chief clinical officer at GE Medical Systems.

"For almost all of my 20 years here, CT procedures in the U.S. have grown by about 10% per year. In the last three years, it went to 12% or 13%, then 15% or 16%. In 2002, CT procedures grew 19%," he said.

CT has become the modality of choice in many situations, particularly when speed is key. The heavy demand for CT in emergency room settings is a big factor driving the modality's growth, according to Thomas van Elzakker, vice president of CT radiology products for Philips Medical Systems. When the number of visits per year to an emergency room reaches a certain level, the facility usually decides to install a dedicated CT.

Yale-New Haven Hospital pioneered the use of dedicated multidetector scanners in the emergency room. Patient management has evolved as emergency medicine doctors and trauma surgeons have acquired the ability to see reconstructed or even 3D images at the flick of a switch, McClennan said.

OPENING UP NEW OPTIONS

The ER isn't the only place that has seen a rise in CT utilization; CT is the de facto gold standard for patient follow-up in oncology, Fox said. More controversially, it is the default imaging modality for lung cancer screening.

"At this point, CT is the gold standard for most things in the abdomen, from liver to pancreas to kidney to lungs," said Dr. Elliot Fishman, a professor of radiology at Johns Hopkins University.

Some of the growth relates to the early limitations of abdominal and chest imaging. CT has grown in part because it has opened up options that previously did not exist, said Dr. Howard Forman, vice chair of diagnostic radiology at Yale.

"People have evolved over the last 10 years from doing sinus films to doing sinus CTs," he said. "And neuro applications in the emergency room for trauma-five years ago at Yale-New Haven Hospital we would routinely get plain films on most trauma cases. Now we are increasingly doing cervical spine CT studies on most of the same cases."

As the technology has improved and radiologists have become more familiar with it, procedures that were once seen as complex have become routine, Fox said.

"The bulk of the actual growth in CT has come from what used to be the challenging procedures: chest-abdomen-pelvis surveys, triple-phase liver studies looking for mets, thin-slice, dual- or triple-phase evaluations of the pancreas or liver. All this from a single injection, multiple-pass, thin-slice scan," he said.

Abdominal imaging and noncardiac CT have accounted for the lion's share of growth in the modality, but manufacturers and researchers expect cardiac CT to play an increasingly important role, taking over some traditional duties from the cardiac catheterization lab, according to Fox.

"Cardiovascular CT beyond calcium scoring is rapidly being adopted by radiologists and cardiologists alike. We expect that to be responsible for a significant growth curve of the CT market through 2007, starting now," van Elzakker said.

With the most promising applications targeted, the goal has become processing and packaging the data in a radiologist- or cardiologist-friendly format quickly, Fox said. That could ease the burden of growth somewhat, as software is developed to automate reconstructions that now must be done, time-consumingly, by hand.

BACK TO EARTH

The skyrocketing growth should come back to earth a little in coming years, data-watchers suggest, but they vary in their interpretations.

McClennan predicts that growth will slow slightly, not because physicians will stop wanting to perform CT, but because the scanners and technologists available will reach full capacity. At the same time, the resulting images will become more complex.

"The appetite that clinicians have now is for 3D," he said. "They want to see the moving image, to be able to rotate the organ around on their viewing station in the OR, and perform their virtual surgery beforehand, seeing what arteries and veins are attached to it."

Fox believes that growth won't slow much for a few years because the advanced applications haven't completely penetrated the market. Smaller community hospitals and centers that haven't switched to high-end scanners, for example, still have growth in their future.

Van Elzakker is similarly enthusiastic about the modality's prospects, but he sees cardiologists, not radiologists, driving growth as they convert to CT from invasive diagnostic procedures.

Dr. Richard Hausmann, president of the CT division of Siemens, also predicts a slower but still robust growth rate of about 10%.

"With the introduction of 16-slice CT, all CT examinations can be performed in reasonable breath-hold times and with good coverage. Therefore, from the applications point of view, the physiological barrier of breath-holding is overcome," Hausmann said.

Future generations of the technology will refine existing capabilities, but they shouldn't have the quantum-leap effect that the move to multidetector did, he said. Fewer new applications will translate to a slower growth curve.

CT's ability to be used early and often as a patient-care planning tool is a double-edged sword, according to some imagers. Not all experts make such rosy predictions about the continuing growth rate of CT.

"You're going to see a lot more CT being used earlier in patient management as a way of really cutting costs," Fishman said. "We're in this era of cost-containment and cost-efficiency. Every study that's been published shows that we've been able to decrease costs because we're able to aggressively manage the patient earlier."

Forman predicts that those same moves toward cost-containment will dramatically curtail CT's growth rate as insurance companies switch from their current practice of paying for an entire scan to using a copy system.

"Once that starts to change, you're going to see a shift where patients aren't as quick to go for imaging," he said. "I don't think we're going to see a decrease, but I think the double-digit increases will slow to about 3%, 4%, or 5% increases."

The future of CT really depends on how it is treated by the radiologists who provide the service, Fishman said.

"Radiologists have to be careful to make sure they document what can be helpful. If you do a CT correctly, and it replaces three other studies, and the patient is in the hospital for three days instead of five, then CT becomes very cheap," he said. "If it's just done because you can do it, that's a big problem."

MS. JERSILD is a freelance writer based in Chicago.