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Physics helps medicine gain a sharper view

1 November 2003

The ITBS meeting in Greece showed significant progress in the collaboration between physicists and physicians, as Paul Lecoq and Patrick Le Du describe.

The second International Conference on Imaging Technologies in Biomedical Sciences (ITBS) was held on 26-30 May in Athens and on the island of Milos, Greece. The conference was organized by the Greek Institute of Accelerating Systems and Applications (IASA) and the University of Athens, and was supported by CERN, CEA/DAPNIA and IN2P3 in France. It focused on the recent advances in detectors and techniques for clinical and experimental nuclear imaging.

The main aim of this particular conference is to attract medical doctors, medical physicists and physics detector experts, as well as industrial partners, to the same location to discuss needs and improvements in areas of clinical nuclear medical imaging such as single-photon computed tomography (SPECT) and positron emission tomography (PET). As an illustration of the multidisciplinary spirit of the meeting, it was co-chaired by a particle physicist, Paul Lecoq from CERN, and a medical doctor, Jean Maublant from the Jean Perrin anti-cancer centre in Clermont-Ferrand, France. This year there were nearly 80 participants, from Canada, Japan and the US, as well as from Europe.

During the first day, which was held at the University of Athens, various tutorials were given with the aim of mutually educating the medical and physics communities. After an introductory talk on “Medicine and economy”, the first tutorial session on “Medicine for the physicist” was devoted to various medical topics, including oncology, neurotransmitters, the development of radio pharmaceuticals and a review of the technical requirements and clinical impact of PET. The second tutorial session, “Physics for the physician”, was oriented towards experimental physics with didactical reviews of detectors and techniques for medical imaging, including scintillation mechanisms and new crystals, semiconductor sensors, photodetectors, electronics and data acquisition.

The remainder of the conference was held at the George Eliopoulos Conference Centre on the scenic island of Milos in the Cyclades Islands. Here, several sessions reported new hardware developments, revealing, for example, the advance in real-time and high-resolution beta imaging for applications in molecular imaging and dosimetry. Results on new crystals such as LuAP (lutetium aluminate perovskite), novel techniques to optimize light collection on tiny crystals, and experience with flat-panel photomultiplier tubes for PET, provided convincing evidence that progress is underway in this field. A specific session on “Small animal PET imaging” reported on the latest technical developments and challenges in this very active domain, particularly in the area of new drug developments and animal modelling of human diseases. The “RatCAP” developed at the Brookhaven National Laboratory offered the most memorable image of the conference. This portable PET scanner allows in vivo neurophysiological studies of rat brain functions without anaesthesia.

Several reports on breast-cancer detection, diagnostics and treatment follow-up aroused much interest in instrumentation for functional breast imaging using positron emission mammography techniques (PEM). The low sensitivity of X-ray mammography in dense breast tissue leads to a very large number of unnecessary biopsies, which have a high cost implication for health services, not to mention their psychological impact. Figure 1 clearly illustrates the much higher sensitivity of PEM. New developments in PEM, SPECT and a dedicated camera show that this field is now moving towards clinical applications.

The conference also heard about new developments in per-operative probes. This very active field involves dedicated, state-of-the-art “small” detectors, which are used in many different applications for diagnostics, staging and surgery of cancer (for example in prostate cancer or the procedure of sentinel lymph node staging for breast cancer), as well as for genomics and proteomics studies. The possible uses of new devices such as micropattern chambers (MICROMEGAS) and silicon strip detectors were also presented.

The conference included a round-table discussion session on the theme of “Multimodality”. Since the remarkable demonstration a few years ago by Dave Townsend, a former physicist at CERN, that merging PET and computer tomography (CT) could greatly enhance the diagnostic power of each of these imaging modalities, there is a growing trend to study different combinations of scanners, in particular to combine morphologic and functional imaging techniques. Beside the combination of PET and CT, which is now becoming commercially available, PET and nuclear magnetic resonance imaging can offer considerable improvements, specifically in studies of the brain. More generally, multimodality could be the way to address the very challenging problem of the molecular signature of cancers. The co-registration of different metabolic functions in which tumour cells are involved could provide a non-invasive way to identify precisely the type of cancer under investigation, so as to guide the medical team to the best treatment strategy, in particular when determining the type of chemotherapy to be applied.

The final session of the conference was devoted to Monte Carlo simulations. Many groups are using GEANT4 libraries to simulate and optimize imaging detectors. The success of GATE (GEANT4 Application for Tomographic Emission) and its first results has clearly demonstrated that the transfer of high-energy physics techniques to the field of medical imaging is now real.

After the success of this conference, all the participants have agreed to reconvene in May 2005, again on the island of Milos, to measure the progress of this fruitful collaboration between physicists and medical doctors.

Further reading

More information can be found on the conference website at http://itbs2003.web.cern.ch/itbs2003. The proceedings will be published in Nuclear Instruments and Methods A.

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