Gustav K. Von Schulthess, MD, PhD

The number of PET/CT systems in Europe is limited but growing rapidly. The world market was estimated at around $1.2 billion in 2004, which translates into 600 to 700 systems sold. Approxi-mately 90% of European PET sales, whether new installations or replacement, now involve PET/CT scanners. This figure shows the tremendous need for education in PET/CT.

FDG-PET is very sensitive in detecting lesions, but it has limitations as an anatomical reference for complex cases. PET/CT places lesions in an anatomic framework, which makes localization of lesions far easier and is sometimes key to a proper diagnosis. Although viewing PET and CT scans next to each other provides a more sensitive and specific diagnosis than either modality on its own, separate reading of PET and CT scans is often difficult and time-consuming. Some reports suggest that fusing data further increases sensitivity and specificity.

Combining PET with CT in a single unit also offers technological advantages. All PET scanners require some form of attenuation correction to account for absorption differences be-tween deep-seated and surface lesions. Integrating CT with a PET scanner means that manufacturers no longer have to fit this correction element into the PET scanner, which provides cost savings and makes PET/ CT substantially faster than PET alone.

Most PET/CT scanners sold to European hospitals and clinics end up in nuclear medicine departments or in units shared by nuclear physicians and radiologists. "Turf battles" in-evitably surface. I dislike the word "turf," which im-plies strict divisions: This is yours, and that is mine. Such a view does not recognize that technologies are changing rapidly. It is key that the most competent people, whoever they are, do the work. Nuclear physicians are clearly most competent to read PET, and radiologists are most competent to read CT.

But PET/CT is a new kind of modality for which specific skills have to be developed. If you want to make the most of PET/CT, you need staff with skills in both areas. It will not be cost-effective to have two different doctors look at the scans and then have a case conference for every patient.

Perhaps 50% of all oncological staging will be done with PET/CT-not CT-five years from now. This concerns some radiologists, who worry that they may lose this imaging field to nuclear physicians. One strategy radiologists use to remain involved in PET/CT is to overemphasize the CT portion, that is, their "turf." They claim that a contrast-enhanced CT study is essential for the best diagnosis, but there are no data to support this argument. It may also be more cost- effective to do the PET/CT first and then decide whether a tailored CT examination is needed.

The key question is, How do we efficiently train our young doctors? Reading a PET study requires considerable expertise to distinguish normal FDG accumulations from the abnormal. A CT study requires significant experience in cross-sectional anatomical interpretation. I would not trust anyone to read a PET/CT study who had not reported at least 500 to 1000 PET/CT scans under the supervision of a colleague with the necessary credentials in both fields.

I hope that in Switzerland we will find an efficient and amicable way to train our young doctors. To qualify both in radiology and nuclear medicine takes eight years. If the Swiss radiology board accepts one year of PET/CT or SPECT/CT as a year of radiological training, dual board certification would take only seven years. The penalty of obtaining double board certification would be only one extra year for a radiologist and two years for a nuclear physician.

I see a trend toward "fused" departments of imaging, rather than separate departments of radiology and nuclear medicine. The PET/CT "fusion ma-chine" may well be a catalyst. There is no reason that the person who specializes in abdominal imaging could not also understand the most about nuclear medicine technology, or that the person responsible for musculoskeletal imaging could not be the MRI technology expert as well.

PROF. VON SCHULTHESS is director of nuclear medicine and codirector of the MR center at University Hospital Zurich, Switzerland.

Editor's Note: The views expressed in this column are those of Prof. von Schulthess and not necessarily those of DI Europe.

Gustav K. Von Schulthess, MD, PhD

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PET/CT need not become a medical battleground