The PET debate is a hot topic. Below are two of the comments we received about Wayne Webster's article in last week's DOTmed News, "Is There Life After PET?" The first response is from Scott A. Welpe, CNMT. The second is from Douglas J. Wagenaar, PhD.

From: Scott A. Welpe, CNMT --
In response to the Wayne Webster article published January 25, 2007, Is there life After PET? I ask has plain film been replaced by CT? Has MR been run out of town by the more cost effective CT? Has nuclear medicine been abolished by PET? Obviously the answer is no to all of the above and the reply will be the same in 60 months for the proposition that SPECT/CT will replace PET/CT. As each modality emerges or expands it creates a stir, inevitably it encroaches on territory of another, and eventually finds its place and acceptance in the physicians arsenal of diagnostic abilities to accurately stage and treat their patients.

Access to PET Radiopharmaceuticals:
PETNET Pharmaceuticals is the largest of all vendors supplying FDG through a network of radiopharmacies that is capable of supplying PET isotopes to 98% of all the hospital beds in the United States. Add to the mix two other large pharmaceutical companies and the host of independent pharmacies, I feel justified dismissing the notion that there is an issue with accessibility to FDG. Additionally the Bracco Rb82 generator can be supplied to the most remote of regions and enables 24/7 access to PET cardiac imaging. These two radiopharmaceuticals cover 99% of the Oncology, Neurology and Cardiology clinical imaging done in PET/CT today. As market leaders, PETNET, Bracco and others certainly "participate and support the market with product, distribution, education and regulatory" at clinical through congressional levels. Development and FDA approval of the PET pharmaceuticals is not inexpensive, and I believe there is not one pharmaceutical manufacturer that will disagree with the statement, though we see the introduction of dozens of new drugs every year. It is the NIH grants and the large corporations within the industry that use their revenue to fund the innovators that bring about the next generation.

Life Cycles:
The life cycle of PET did not occur over just the last 6 years. The first commercial PET scanner was offered in 1976 resulting in the first life cycle being two decades old before the introduction of CT, which offered a cleaner and faster form of attenuation correction as well as superior anatomical correlation. This adaptation came on the heels of multi-slice CT and the ensuing CT slice war. Why would PET not take advantages of multi-slice? The ability to utilize the system as an efficient PET scanner as well to perform the most advanced CT functions. Cardiac CTA, radiation therapy integration and respiratory gating open new avenues of revenue generation, clinical efficiency and diagnostic use.

Current Market State:
The effect of the Deficit Reduction Act (DRA) is significantly more responsible for the very recent flattening of the PET/CT market than the suggestion that the rapid development of PET/CT technology has any impact whatsoever. The January 1 enactment of the DRA slashed PET reimbursement by 25-75% causing an understandable hesitation in the market's willingness to purchase new systems until the effects are fully understood. Technology has become more affordable with a health care provider now able to purchase as much as a 40 slice PET/CT for what they would have paid for a capable dedicated PET system five years ago. A system which now offers significantly more utilization in both PET/CT and diagnostic CT, the model for PET has changed with the ability to utilize the PET/CT as a dual modality imaging device. Over 1.1 million PET scans were performed in 2005 and experts estimate over 2 million exams to be performed in the year 2010. PET/CT continues its acceptance with its well established history of tumor imaging while growth in Radiation Oncology and Cardiology secure its future for more broad utilization.

What's Next?
Yes, SPECT/CT is next. As PET had done over 7 years ago, nuclear medicine is enjoying all of the benefits that the integration of CT offers in the way of efficient and effective attenuation correction and accurate anatomical correlation. The increased ability to accurately detect disease presence and localization enable accurate diagnosis and staging and offer more effective treatment decisions in SPETC/CT over SPECT alone. MR/PET is next, integration of PET imaging for neurology and body imaging is on the roadmap for further utilization of the benefits brought about by positron imaging.

Why SPECT/CT can not replace PET:
PET/CT's superior sensitivity and specificity and the significantly better resolution make it the obvious choice for tumor imaging. The ability to quantitate PET data which is as critical clinically as it is in research for the evaluation of response to therapy, coronary flow, tumor thresholding and so on is unmatched. SPECT is functional, not metabolic as there is no FDA approved drug for metabolic SPECT. Clinical efficiency plays an important factor, count for count it would take hours to accomplish the same exam with SPECT as in an eleven minute whole body PET exam which coincidentally is directly related to the wonderfully short half-life pharmaceuticals used in PET. Compare the image quality of an F-18 ion bone scan with that of a SPECT with MDP. SPECT/CT works at a body system level where PET/CT works at a cellular level. And of course, PET/CT will not replace many of the effective functional exams that only SPECT and SPECT/CT currently provide.

What does the future hold for PET/CT?
I won't go as far as proclaiming the world is round, but will firmly stand my belief that PET/CT will survive the growth of SPECT/CT, the DRA, and all of the future technological advances that come. Each of these modalities will continue to advance in coexistence of one another and the cross modality integrations will bring further enhancements . To debate the future of SPECT/CT and PET/CT is to look with blinders on. The road to the future in molecular medicine will be the growth of personalized medicine. Advancements in micro fluidics, in-vitro diagnostics and the integration of IT will forge the growth of molecular imaging and the important role it plays in the world of medicine. I am certainly a proponent of SPECT/CT and am optimistic about its growth and future as it follows the trail blazed by PET/CT and offers greater diagnostic capability over SPECT alone.
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From Douglas J. Wagenaar, PhD --
Please pass along my compliments to Wayne, perhaps he remembers me from my Medical Physicist days at Beth Israel Hospital, Boston, in the office next to Tony Parker. One thought that has been with me since I first saw the 5-headed PET monstrosity proposed by CTI a few years ago at an IEEE meeting, and that is: PET is a mainframe.

Optical and, more importantly, SPECT are PCs. There is no conceivable way to make a mainframe into a PC. There is no conceivable way to make PET a small, handheld device. I believe this analogy will carry forward as PET diminishes and SPECT rises. Why use a mainframe to write a word document? Why use $1.5 M worth of LSO to image a hot spot in the chest? This is a separate argument from Wayne's, but perhaps it can strengthen his radionuclide angle. Thanks for the enlightening article.
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