I attended the 5th Annual meeting of Society of Molecular Imaging 2006 held at Kona, in the Big island of Hawaii from 29th August to 2nd September. As well known to all, it is a paradise for anyone choosing it for a vacation. Paradoxically, the travel was for ‘learning’ in the midst of enticing ‘leisure’.
Since I had registered for pre-conference symposium, I reached on 29th August morning. The educating sessions started in the afternoon of that day with Dr. Sam Gambhir delivering the opening lecture on ‘Molecular biology/Reporter genes for imaging scientists’. The talk focused on few molecular biological techniques involving key signal transduction pathways, cell division and systems biological approach that could be applied for imaging. Selected examples include 124I-minibody microPET imaging of CEA, RNA aptamers for SPECT and VEGF promoter activity by TSTA. The lecture given by Martin G. Pomper on Neuroimaging was also interesting. He discussed various PET neuroimaging tracers currently applicable for clinical imaging such as FDG, FLT, and FDOPA and also relative significance of other imaging modalities over PET in neuroimaging. One interesting note also was made that how a drug for prostate specific membrane antigen (PSMA) could be used for brain imaging since PSMA and glutamate carboxypeptidase-2 are same proteins expressed in two different organs. The lecture on new PET agents given by Dr. Eckelman elaborated the target validation methodologies applied for different agents including FLT, Pittsburgh compound B, 64Cu-ATSM and others. Dr. JW Chen of Massachusetts General Hospital gave a talk on Magnetic resonance molecular imaging agents such as MION and its modifications useful for cell tracking and lymph node staging in metastasis. Few other interesting topics were presented by various dignitaries over the two days of symposium which was educative in knowing a battery of probes useful for molecular imaging in multiple ways.
The conference presentations had to be chosen according to the topic of interest, since two or three concurrent sessions run in parallel. Under “Application of nanotechnology in imaging”, J Rao of Stanford University discussed on bioluminescent quantum dot conjugates as nanosensors and imaging probes. He highlighted the principle of Bioluminescence resonance energy transfer (BRET) and discussed on Odot nanosensor for metal ions based on BRET applied to imaging in small animals. Among the new PET/SPECT probes, H Kawashima of Kyoto University presented comparison of two 11C-labeled Benzofuran derivatives for PET imaging of senile plaques in Alzheimer’s disease. He showed how 11C-HMBPF accumulated specifically to Abeta aggregates. In the plenary session 2, Scott M. Lippman of UT M.D. Anderson Cancer center discussed on promising biomarkers for neoplasia detection based on biomarker profile and adaptive randomization-BATTLE program. He also commented the future imaging and treatment will be based on biochemical pathways. Brian D Ross of University of Michigan talked on the usefulness of functional diffusion map as a marker for cancer treatment response assessment. It involves quantification of treatment induced ADC response heterogeneity in various human tumors. The keynote presentation “Seeing beyond the light” given by Alexander Pines focused on major milestones that occurred during development of NMR and MRI techniques and the emerging trends such as microfluidic MRI and NMR with remote detection of flow imaging. As he mentioned at the beginning, it was “Out of the box” technology which was rather difficult to comprehend for the best of my knowledge. However, the complexities involved in its conceptualization could be well appreciated.
One of the futuristic research approach that beckon molecular imaging is “Multimodality Imaging”. A few interesting presentations were made in that session. Different issues regarding combined PET/MRI imaging including image co-registration, development of whole body human PET-MR system and small animal multimodality studies were discussed by Paul Marsden of King’s College London. The last of the plenary sessions focused on use of nanotechnology in imaging. Nanoparticles such as semiconductor quantum dots, FA-Heparin-Taxol and many other multifunctional probes involving various imaging modalities were addressed for their role in pre-symptomatic diagnosis and cancer therapy.
Among the poster sessions, there were few selected posters which interested me. In relation to oncologic imaging, research groups from University of Wisconsin presented posters on NM404, a radioiodinated phospholipid ether (PLE) analog which has a potential to accumulate only in metastatic tumor tissues based on principle of lack of metabolic alkyl cleavage enzyme activity in tumor cells relative to normal cells. The retention of the molecule extended to few days in various animal tumor models. The data evident from different tumor models could make it a major diagnostic agent for tumor imaging in parallel with conventional FDG. In an another study from Massachussets Institute of Technology, M Shapiro and his colleagues presented a novel class of genetically coded MRI contrast agents which can produce signal changes in response to specific molecular interactions. The system took advantage of T1 contrast generated by a ligand interaction with heme domain of cytochrome P450-BM3 which is a soluble bacterial enzyme.
I had my poster presentation on the afternoon session of the last day of the conference. There were few onlookers who stopped by and observed my study. I had opportunity to talk with key researchers working in similar area of research as mine, such as Sam Gambhir of Stanford University and Vijay Sharma of Washington University to name a few. There were various questions raised about the efficiency of our PET-reporter gene system. The signal to background ratio of our system, as evaluated by in vivo autoradiography was considered to be lesser than the existing reporter gene system such as HSV-tk. The viral titer used for in vivo expression was at the higher end of the infecting dose. However, I could convince that considering our system as ligand-receptor interaction without signal amplification, the expression levels were reasonable and also dependent partly on the transduction efficiency of the virus. Dr Gambhir suggested to use SIRES (super IRES which leads to high expression of post-IRES gene sequence) or to flip the hTP and hERL sequence and evaluate the expression efficiency of the system.
Overall, it was a good educative event for me. Though the conference was packed with educating sessions, I could make time to explore the beautiful island of Hawaii. The island is a paradise for vacation with beautiful blue beeches, valleys and must see Hawaii Volcanoes National Park. The picture below shows the crater of one of the most active volcanoes in the world.
