Paul Shreve, MD, a radiologist who has observed the evolution of PET/CT in both academia and private practice, calls the contentiousness surrounding the deployment of PET/CT scanners “a tempest in a teapot.” But for some, the tempest threatens to blow away decades of preeminence, and the teapot could be the size of a whole subspecialty, nuclear medicine, which may be about to fade—although most agree that is an extreme view.

In a nutshell, the problem with the interpretation of PET/CT scans is this: Nuclear medicine physicians have been trained to read PET, but many radiologists have not; radiologists have been trained on CT but to many nuclear medicine specialists, CT is terra infirma .

This simple dichotomy of the subspecialties becomes complex in a hurry. If a hybrid scanner is producing two diagnostic studies that require different expertise to interpret, how is the dual interpretation to be handled? By one expert in both modalities, by two or more who specialize in one or the other imaging system?

Many institutions, especially in academia, try to duck this dual interpretation issue by having their nuclear medicine doctors review the PET scans, but give only a cursory review to the CTs. The rationale is that the CTs produced really are not done for diagnosis. They are done without contrast, and there may be a disclaimer to referring physicians that the CTs are for attenuation and anatomic localization of the PET scans only. The original purpose of combining CT with PET was to make attenuation and anatomic localization of the PET scans quicker and more accurate. PET cannot visualize well when passing through dense, fatty tissue, and the CT helps correct for lost data.

But even if the CT scans are handled only as attenuation scans, there is concern about what may be overlooked if a patient has diseases that a true CT expert might catch, even on an attenuation CT. Noncancerous anomalies might not show up on PET, but a trained interpreter might see them on the CT, even a low-dose CT done only for attenuation.

There is also the reverse of that situation. Most often, radiologists are the ones reading both pieces of the PET/CT. There could be instances where a radiologist trained in CT and narrowly in PET may be looking at both scans and missing things on the PET because the anomalies do not show up on the CT.

Barry Siegel, MD

Barry Siegel, MD, is a radiology professor and director of nuclear medicine at the Mallinckrodt Institute of Radiology (MIR) at Washington University in St Louis. The interpretation procedure at MIR calls for nuclear medicine physicians to interpret the PET and an attenuation CT scan.

“For 2 years, we have not been doing diagnostic CT as a part of PET/CT,” says Siegel, “but the truth is we [the nuclear medicine doctors, some of whom are also radiologists] are looking at the CTs in the subtissue and bone windows, but we’re not billing for that service. We work hard to make sure we don’t miss any tumors or other diseases.”

Siegel says that, if patients have a prescription for a full diagnostic CT, they go to a separate scanner in radiology. Part of the reason for this is because MIR’s PET/CT has only a dual slice CT scanner, which radiologists feel uncomfortable using for diagnostic purposes. Another reason, Siegel adds, is that the scanner requires the CT examination to be done first. If contrast media needed for a diagnostic CT is administered first, it can create artifacts on the PET scan, he asserts.

“It interferes when there is increased density of the blood vessels,” Siegel says. “Where there is very dense contrast in those veins…we end up seeing bright areas on the corrected PET that are artifacts,” Siegel says. “That is one of the arguments for doing the CT after the PET if you’re going to do a diagnostic CT.” (Others interviewed for this story disagreed that CT contrast administered first would interfere with a PET scan.)

But even an attenuation CT must be interpreted for anomalies that would not be caught on PET, Siegel says. “It’s in the PACS, you can’t not look, even though we are not being paid for that. We do see some incidental findings.”

Siegel says that, as MIR upgrades its equipment, it will—soon—start doing full diagnostic CTs as part of its PET/CT process. Those CTs will go to radiology for a separate diagnostic report, he adds.

Like most practitioners interviewed for this story, Siegel thinks that the eventual solution to the PET/CT interpretation dichotomy will be to have the examinations read by one doctor qualified in both PET and CT. In many places this is already happening, although how qualified the interpreters may be is a matter of controversy. Siegel himself is a radiologist, but his expertise is in nuclear medicine. “I’ve been looking at CT every day of my life, but I’ve never personally been responsible for CT,” he says, “but now I am reading the PET/CT with or without what you might call proper training.”

Just what is the proper training is at the very heart of the controversy surrounding PET/CT, with nuclear medicine doctors and radiologists calling for different training regimens—not for PET so much as for the diagnostic CT interpretations. The deployment of PET/CT has left both sides feeling threatened.

“I think there are little future job prospects for those who have a background in nuclear medicine and who aren’t radiologists,” Siegel says. “The handwriting is on the wall that anatomical and molecular fusion is here to stay.”

But Siegel says it would be a mistake to think that radiology departments are about to start training nuclear medicine doctors to read CT. “If we [radiologists] give nuclear medicine people training in CT, they’ll go out and start offering diagnostic CT. You don’t have to look far at how radiology’s turf has been eroded by everybody and their brother to understand why radiologists would balk at this.”


Nuclear medicine physicians, who developed PET, probably feel even more threatened than radiologists by the attachment of CT to an imaging system that has essentially been theirs up to now. The consensus of those interviewed for this story is that stand-alone PET scanners will rarely be deployed from now on.

James W. Fletcher, MD

James W. Fletcher, MD, is professor of radiology and director of nuclear medicine PET at the Indiana University School of Medicine in Indianapolis. It is a program run in conjunction with Purdue University.

“Most people aren’t buying stand-alone PET anymore,” he says. “People now see CT as pretty essential. The original thought was that CT would just be an enhancement for attenuation correction. You wouldn’t worry about a real good CT.”

But the latest PET/CT scanners are so good, he says, “that PET/CT is going to replace both PET and CT in oncology.”

At Indiana, full diagnostic CTs are being done on the PET/CT scanner without interference to the PET scan, Fletcher says. While coding and billing practices are lagging behind the technology so that the CTs often cannot be billed as diagnostic procedures in company with a PET scan, dual diagnostic scanning and dual billing for both are the wave of the future, Fletcher insists.

While some routing of CT scans to radiology is being done now in his department, Fletcher says that in the long run, as more PET/CT is deployed, it will not be practical to have separate readers interpret the PET and CT portions. “You must have people trained in both disciplines to determine the findings and generate the [single] report,” he says.

But the single-reader model is difficult to adopt across lines where, traditionally, nuclear medicine and radiology have been separated.

Conrad Nagle, MD, is corporate chief of diagnostic imaging at the William Beaumont Hospitals in Royal Oak and Troy, Mich. Nagle says his background is in nuclear medicine, and he is the rare nuclear medicine physician overseeing a radiology department. At the Beaumont hospitals, he says, there are separate departments of nuclear medicine and radiology, and he coordinates both.

He says Beaumont is now doing PET/CT with nuclear medicine doctors reading the CT for attenuation only. “But there is clearly an underlying expectation that something on the CT should not be missed,” he adds.

Nagle says Beaumont is refining its PET/CT procedure so that the CT scan will somehow be reviewed by radiologists, but he says it is too much to ask of one doctor to diagnostically read both scans.


Model No. 1

The PET is interpreted by nuclear medicine physicians, who also review CT without contrast for anomalies, but do not bill for the CT. This model is common in academic institutions with a strong nuclear medicine department.

Model No. 2

The PET is interpreted by a nuclear medicine physician and the CT is interpreted by a radiologist. This is happening in departments with PET/CT technology featuring a CT scanner considered of diagnostic quality. Both scans are billed for.

Model No. 3

The PET is interpreted by a physician who is comfortable reading both PET and CT. Both are diagnostic quality, and both are billed for if there is not a recent CT on file. This model is common in the private practice setting where turf is not an issue.

“The single-reader model is not a good model currently,” he says. “Even when you have one person trained in both, it’s a different focus. Even if you’re correlating, you’re reviewing huge amounts of data for each patient….Even if a report is not issued on an anatomic localization CT, it’s important to me to have a radiologist expert in CT look over the data.”

He makes the point that it is equally important to have correlation between the PET and the CT. “What if the PET sees something like a lymph node that’s not enlarged enough so that the CT can see it but is likely a metastatic lymph node?” In this case the referring physician has to be notified even though the CT report would not mention it, he says. “This sort of thing happens very frequently. It’s critical.”

Nagle says in his view the reimbursement for a physician to read a PET scan—and now to correlate it with, at minimum, an attenuation CT—is unfairly low. But the PET/CT technical fee is one of the highest, if not the highest, of “the premier modalities,” he says. So hospitals eying technical fee income and eager to install a PET/CT unit may have to make up some of the reimbursement to interpreters, he suggests.

Marc Seltzer, MD, is a board-certified nuclear medicine physician at the Dartmouth-Hitchcock Medical Center in Lebanon, NH. “I’m the only member of the radiology department not boarded in radiology,” he says.

Seltzer says he is reading both portions of PET/CT scans, but the CT is a noncontrast scan used primarily for attenuation correction, localization, and characterization of PET abnormalities. Diagnostic CTs are ordered separately and interpreted by radiologists separately, he says. Seltzer describes how he handles both data sets from a PET/CT scan:

“The software allows you to look at the two images side by side. As you scroll through the images, you are seeing the PET and the CT and you can view them linked together…. I look at the PET scan in its entirety. I identify abnormalities, then look at the CT to better define those lesions.”

After he has read the PET, he goes back for a closer look at the CT. Things like renal tumors, aortic aneurysms, and small pulmonary nodules may be seen on CT but not on PET. “If we see incidental findings, we will mention them in our PET scan report,” he adds, even though there currently is no billing for separate CT reading. He says even the low radiation dose, noncontrast CTs are of such good quality that “you could make a strong argument that the CT could be interpreted for diagnostic purposes.”

While dual interpretation of CT and PET may be happening slowly in academic settings where nuclear medicine is something of a separate domain, in the private practice world where PET/CTs are proliferating very quickly, dual interpretation is often the norm. And radiologists, since there are so many more of them in private practice than nuclear medicine specialists, are doing PET and CT interpretations much more often than nuclear medicine doctors are also doing full-blown diagnostic CTs.


Paul Shreve is perhaps a prototypical example of a radiologist with training in nuclear medicine who saw the handwriting on the wall and realized it was time to learn CT to go along with his PET skills.

Paul Shreve, MD

Shreve is medical director for the PET center at Advanced Radiology Services PC, a 70-partner radiology group in Grand Rapids, Mich. Prior to joining the group, he was involved in PET/CT imaging early on at the University of Michigan, he says.

“I realized I had to become more proficient at body CT because PET/CT reading is a cointerpretation of PET and diagnostic CT” he says. “You have to be proficient in both modalities. I began to read them, and I read thousands. You have to read a lot.”

Now Shreve is doing full diagnostic interpretations of both PET and CT for the PET/CT patients at his center. He says for body imaging PET/CT is “the only way to go.” As the dual modality proliferates, he foresees the development of “a core group” of dual interpreters “who are really body oncology readers.”

He says both nuclear medicine physicians who know PET and learn CT and radiologists who know CT and learn PET will fill that niche.

“What is important is not academic intradepartmental turf battles, but that PET/CT scans are performed properly and interpreted in an integrated fashion in the best interest of patient care,” Shreve says.


Joseph Busch, MD, is senior radiologist in Diagnostic Radiology Consultants (DRC), a Chattanooga, Tenn, group that has a CON (certificate of need) license to own and operate a PET/CT in its city. Busch says he is a radiologist with nuclear medicine training who has learned to read PET.

Like Shreve, Busch says he thinks CT is harder to learn than PET. Busch says the new wave of PET/CT deployment is going to focus on cancer staging and monitoring the progress of therapy, although he also believes neurological and cardiac applications have a future.

He says the newer CT scanners like the 16-slice unit on his PET/CT are so good and so fast that they can do multi-phasic organ imaging, CT studies that show arterial and venous blood flow cycles.

“Different cancers are positive in different phases,” he says. “I guess what I’m trying to say is that this machine [PET/CT] is a complicated device. It’s more than a PET scan with attenuation correction. It’s capable of a lot of diagnosis. Now, we can put out a data set to make a 3-D treatment plan for the radiation oncologist.”

DRC is doing diagnostic PET and CT interpretations from a single scan using contrast for the CT. Busch says the contrast does not interfere with the PET scan.

Because its PET/CT machine is owned by a private diagnostic radiology practice, DRC is also doing stand-alone CT and CTA on the machine where there is no PET involved. There may not be enough patients to keep the PET busy, Busch says, so the CT is used alone to help pay for the machine.

“I can’t understand why anyone would pay over $2 million for a scanner and just do PET,” Busch says. “We average only six or seven PETs, so we have lots of other hours to do CT diagnoses. The other day we did seven PETs, 21 CTs, and two radiation therapy treatment plans. That was a busy day and we still finished before 4 PM.”

Busch says in this type of an entrepreneurial environment he would not hire someone trained only in nuclear medicine just to read PET, even though he credits nuclear medicine for developing PET. “I think there’s a great place for a nuclear medicine fellowship following a diagnostic radiology residency,” he says. “Those people will find good jobs. But it’s going to be difficult for the pure nuclear medicine specialist.”


Dartmouth-Hitchcock’s Seltzer for one thinks that the rapid proliferation of PET/CT and the differing practice models for interpreting both scans have raised questions about the quality of those interpretations.

“The quality is not uniform,” he says, “and it’s highly dependent on the training and experience of the interpreting physicianthat goes for either nuclear medicine or radiology.”

Seltzer says he now spends some of his time training radiologists in his and other radiology groups around the country to read PET. In the future, he says, a lot more cross-training is needed to get nuclear medicine and radiology up to speed on both sets of images.

Some nuclear medicine experts think PET/CT deployment has happened so quickly that it is jeopardizing nuclear medicine as a subspecialty. One prominent nuclear medicine expert is calling for research to determine when stand-alone PET might suffice (see sidebar below), although that appears to be an uphill battle since device manufacturers have found PET/CTs to be more lucrative to sell and get maintenance contracts for, and today’s PET customers want the dual application.

But both sides—radiology and nuclear medicine—are working to resolve their conflicts so that neither side is locked out or loses out in the PET/CT interpretation equation.

Next month both the American College of Radiology (ACR) and the Society of Nuclear Medicine (SNM) will publish the same white paper in the July editions of their respective journals to help clarify the issues involved in how PET/CT should be handled and lay the groundwork for a second step—the development of training guidelines that would define both PET and CT interpretative competence. Both the ACR and the SNM have also started training programs to prepare interpreters to read both examinations.

R. Edward Coleman, MD

R. Edward Coleman, MD, and Dominique Delbeke, MD, PhD, are the co-authors of the white paper. Coleman, a professor of radiology and director of nuclear medicine at Duke University, participated on behalf of the ACR; Delbeke, a professor of radiology and director of nuclear medicine at Vanderbilt University, wrote on behalf of the SNM.

Coleman calls the white paper “a discussion of the experience and background an individual interpreting PET/CT should have.” He says both sides’ recommendations were reasonable, but no consensus emerged.

“One group may have said we think you need X, whereas the other may have said you need Y amount of training,” he adds. “We have a good idea of the physicians who are interpreting PET scans and the physicians who are interpreting CT scans, but who is interpreting both PET and CT? We don’t have a good handle on how those arrangements are being made throughout the United States.”

Coleman says he is concerned that the “tremendous” growth in PET/CT in radiology practices has resulted in radiologists interpreting PET “without adequate training.”

He says it is more difficult to determine “the exact amount of training that is needed for a nonradiologist to interpret a CT scan.” But he adds that many more PET/CTs are being interpreted by radiologists than by nuclear medicine doctors.

Delbeke calls the white paper a prelude to guidelines. “PET belongs to nuclear medicine and CT belongs to radiology, and we have to work on ways of looking at the studies,” she says. “This is what the white paper is about. The paper just summarizes the issues to be resolved. The next step will be practice guidelines.”

She says many radiologists in private practice will not hire nuclear medicine specialists to read the PET portion of PET/CT scans, preferring to keep the PET interpretations for themselves. “Often these radiologists are not optimally trained [in PET],” she says, “but the training guidelines will put the pressure on for appropriate training.”

She says she is not worried about the disappearance of nuclear medicine as a subspecialty. “Nuclear medicine will retain its autonomy, but we need to collaborate. There needs to be more collaboration and exchange.”

Neither Coleman nor Delbeke will reveal the content of the white paper. The mystery seems appropriate, since there is a larger sense of mystery about how exactly PET/CT is going to be utilized from here on out and what controls are going to be placed on the dual interpretation of both its data sets—if any.

Those answers could be years away. Milton Guiberteau, MD, is immediate past chairman of the ACR’s Commission on Nuclear Medicine. He calls PET/CT a classic example of “disruptive technology” that blurs old borders.

“Occam’s razor would tell us that the dual interpretation will have to be handled by one person,” he says. “We don’t have enough nuclear medicine doctors and radiologists to go around as it is. We’re not at the stage where we know how this is going to play out ultimately….We are hoping to do this development of guidelines in 2006, but it will take more consensus type meetings before we’ll be able to do it. This may be evolving for the next 5 or 6 years.”


The thought that a proliferation of PET/CTs in radiology imaging centers will suck up all the PET business and take it out of the hands of nuclear medicine specialists is anathema to a veteran nuclear medicine (NM) doctor like Abass Alavi, MD.

Future generations of nuclear medicine doctors can be trained in CT so that they can earn a living on the dual scanner, but what about the 5,000 to 6,000 NM specialists that Alavi estimates are out there practicing now? How will they earn a living without a career-interrupting hiatus to learn CT? Even Alavi agrees that learning CT is the answer for NM in the long run, and at the University of Pennsylvania Hospital, where he is chief of nuclear medicine, programs are under way to provide this training. “We are starting to learn more and more about CT, because we have to,” he says.

But Alavi, who is also a professor of radiology and neurology at UPENN, says another part of the solution is to rethink the deployment of stand-alone PET scanners.

“The implications will be enormous for us in nuclear medicine if there is only PET/CT,” he says. He is calling for a study or studies to “define where we need PET alone and where we need PET/CT…. That has to happen.

Abass Alavi, MD

“Almost every disease we can imagine can be looked at by PET,” he says. “In my view for a large segment of these maladies, you may not need to use PET/CT.” He says many brain and cardiac disorders and lesions such as lung nodules and lymphomas do not call for PET/CT; neither do certain metastatic cancers. “Is there disease that can be checked by PET alone? I want a study to prove these points before we write off PET alone as an unviable option.”

Alavi contends that PET/CT is being oversold and overhyped. “The vendors are in the business to make money. They want to give the impression that you don’t need training in PET, you look at the CT for an abnormality and then use the FDG as a contrast agent. Currently, more PET/CTs are being sold in the US than any other major imaging modality. The reimbursement is terrific for PET, and that’s why there is the strong interest.”

Alavi wants a study to determine when stand-alone PET can be used so that referring doctors know what to order. “You can’t say PET/CT is the only way to do PET,” he says. “That is a disservice to cost containment in medicine, which is an enormous concern to health care providers in our country and elsewhere around the globe.”

Alavi is not just anyone talking. He was one of three researchers at Penn to introduce the use of FDG (fluorodeoxyglucose) as a PET imaging agent in the early 1970s. He was the first doctor ever to inject FDG into a human subject.

He thinks researchers in nuclear medicine like him will be discouraged from continuing their innovative investigation into the future, if the focus shifts completely over to combined PET/CT as the only option. “Nuclear medicine has been unbelievably good to me. I hate to see money and turf battles destroy the possibility of individuals like myself who truly enjoy contributing to the growth of the field to choose this specialty as a career. This will be a disaster and every effort should be made to avoid it. I truly love practicing this specialty.”

—G. Wiley

George Wiley is a contributing writer for Decisions in Axis Imaging News.