Since 1991, I have been involved in the development of technology for combined PET/CT scanning. In the beginning, as we explored how this combined imaging modality could be designed, built and delivered to the clinical setting, we recognized the benefits of combining physiological and anatomical imaging. Such dual-modality imaging yields comprehensive and unique diagnostic information.
Since the commercial introduction of this combined modality in 2001, there have been rapid advances in both the CT and PET components. It is my belief that it is important to have a clear understanding of CT and PET physics, as well as the performance of the combined devices, in order to establish a comprehensive PET practice.
As the WebMedEd Course Instructor for PET and PET/CT Physics and Instrumentation, it is my goal to provide the medical professional with an understanding of the basic physics of the imaging techniques and an appreciation of the performance of the available hardware and software which ultimately, will assist the professional in reaching appropriate decisions when both acquiring and using such devices.
The educational content in this Section is designed to provide an overview of the physical principles of CT and PET scanning, including the different sources of radioactivity, the various detectors and detector systems used to capture the radiation passing through, or emitted from, the patient, the collection and sorting of the data, the corrections for processes such as attenuation, scatter and randoms, and then finally reconstruction of the images. Once the basic principles of anatomical (CT) and functional (PET) imaging have been discussed, we will explore the rationale for combining the two modalities into a single device, the combined PET/CT scanner. We will describe the historical development of the first PET/CT scanner and the impact of the PET/CT scans on medical imaging.
A major advantage of the PET/CT scanner is the use of the CT images to generate the attenuation correction factors to apply to the PET emission data. We will describe the algorithms for CT-based attenuation correction and outline some of the problems and pitfalls associated with this approach. We will review the status of current instrumentation and imaging technology for PET/CT, and the established imaging protocols.
Finally, we will compare PET-only imaging with the combined modality, and explore future developments. It is anticipated that in oncology, PET/CT will replace PET-only scanning sooner rather than later. Should you desire to learn more about PET and PET/CT Physics and Instrumentation, or if you find that the content in this section could benefit you in making an informed decision about the purchase of the appropriate equipment for your practice, I invite you to participate in this educational experience offered by WebMedEd.com.
Sincerely,
David Townsend, PhD
David W. Townsend, PhD, joined the University of Tennessee in Knoxville in February 2003 as Professor of Medicine and Radiology, and Director of the Cancer Imaging and Tracer Development Program. He obtained his Ph.D. in Particle Physics from the University of London and worked for eight years at the European Centre for Nuclear Research in Geneva, Switzerland. In 1980, Dr. Townsend held a position at Geneva University Hospital, Geneva, Switzerland as a physicist in the Department of Nuclear Medicine. He has worked on PET instrumentation development since the early eighties, and has been a senior consultant for CPS Innovations, Knoxville, Tennessee since 1992. He initially participated in the development of 3D reconstruction and methodology for PET in collaboration with Hammersmith Hospital, London, and later designed and built the first rotating partial ring PET scanner using BGO block detectors. The design was commercialized as the ECAT ART scanner by CPS in 1994.
In 1993, Dr. Townsend moved to the University of Pittsburgh as an Associate Professor of Radiology and Senior PET Physicist. He was Co-Director of the Pittsburgh PET Facility from 1996-2002, and became Professor of Radiology in 2000. In 1995, Dr. Townsend was Principal Investigator on the first proposal to design and build a combined PET/CT scanner, and subsequently on the competing continuation grant that was active until 2003 to further develop PET/CT methodology.
The PET/CT scanner, attributed to Dr. Townsend and Dr. Ron Nutt, President of CTI Molecular Imaging, Inc., was named by TIME Magazine as the "Medical Invention of the Year" in 2000. From 1999-2001, Dr. Townsend collaborated with CPS Innovations on the development of the commercial PET/CT scanner, a design based on experience with the successful clinical operation of the first prototype at the University of Pittsburgh PET Facility. Dr. Townsend and Dr. Nutt also hold a patent on the PET/CT concept that is based on their work performed in 1992 and 1993, prior to Dr. Townsend joining the faculty at the University of Pittsburgh.
Since 2002, Dr. Townsend has been funded by the National Cancer Institute to collaborate with, among others, CPS Innovations to design and build the next generation of high performance, combined PET/CT scanners using LSO detectors. The new, $3 million NCI grant covers the period 2002-2005, representing a decade of NCI funding for the PET/CT program.
