Hybrid & Unconventional Systems
Thursday 23 April 2009
Room 316A 10:30-12:30


Steven M. Conolly and Timothy J. Scholl

10:30 589. Evaluation of a Clinical PET/MR System
    Hans F. Wehrl1, Armin Kolb1, Martin S. Judenhofer1, Matthias P. Lichy, Claus D. Claussen, Bernd J. Pichler1
Laboratory for Preclinical Imaging of the Werner Siemens-Foundation, Department of Radiology, University of Tuebingen, Tuebingen, BW, Germany
    Clinical PET/MR is a new, emerging imaging approach. An evaluation of the MR and PET image performance without and with the PET-Insert installed in a 3 T MR scanner was conducted. MR and PET imaging quality are not fundamentally influenced in this hybrid imaging device. Patient studies show the potential of simultaneous PET/MR imaging.
10:42 590. First Hybrid Images from a Combined PET and Field-Cycled MRI System
    Geron Andre Bindseil1, William B. Handler1, Timothy J. Scholl1, Kyle M. Gilbert2, Blaine A. Chronik1
Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada; 2Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
    The first fully interleaved hybrid images from a combined positron emission tomography (PET) and field-cycled MRI (FCMRI) system are presented. In FCMRI, it is possible to rapidly turn all magnetic fields off, enabling the use of conventional photomultiplier-tube-based PET detectors. PET data were acquired during MRI sequences in an interleaved manner with a period of several seconds.
10:54 591. Simultaneous MRI/PET Image Acquisition from an MRI Compatible Positron Emission Tomography System
    Sri Harsha Maramraju1, Bosky Ravindranath1, Sachin Junnarkar2, Dardo Tomasi2, S. David Smith2, Sudeepti Southekal1, Sean Stoll2, Sergio Rescia2, Jean-Francois Pratte2, Martin Purschke2, Xiaole Hong3, David Bennett3, Ken Cheng3, Aiping Jiang3, William Lenz2, Srilalan Krishnamoorthy2, Craig Woody2, Paul Vaska2, David Schlyer2
Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA; 2Brookhaven National Laboratory, Upton, NY, USA; 3Aurora Imaging Technology, North Andover, MA, USA
    We have developed MRI compatible PET scanners based on RatCAP for truly simultaneous acquisition of MRI and PET images by integrating PET in 1.5T, 4T and 9.4T MRI facilities, respectively. The main objective is to obtain structural and functional information simultaneously, retaining MRI and PET functionalities. Simultaneous rat brain and striatum phantom MRI/PET images were acquired with RatCAP in 4T and 9.4T MRI facilities, respectively. MR image quality tests were performed in 1.5T MRI, with our prototype breast MRI/PET scanner based on RatCAP. Our initial results demonstrate the feasibility of performing quantitative MRI/PET studies, with minimal interference between both modalities.
11:06 592. Is Accurate Bone Segmentation Required for MR-Based PET Attenuation Correction?
    Ciprian Catana1, Andre van der Kouwe1, Thomas Benner1, Michael Hamm2, Christian Michel3, Bruce Fischl1, Matthias Schmand3, Bruce R. Rosen1, A. Gregory Sorensen1
MGH, Radiology, A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA; 2Siemens Medical Solutions USA Inc., Charlestown, MA, USA; 3Siemens Medical Solutions USA Inc., Knoxville, TN, USA
    Combined PET and MRI systems have recently been developed. Attenuation correction is one of the most important and difficult correction that have to be applied to the PET data. In an integrated scanner, we have to rely on the MR data for obtaining attenuation correction maps. The challenge is that the MR images are not typically directly related to tissue linear attenuation and tissues with very different attenuation properties cannot be easily distinguished using conventional MR sequences. In this work, we studied the effects of misclassifying the bone on PET data quantification in structures of interest using segmented MR images.
11:18 593.

System for MRI Guided Radiotherapy

    Johan Overweg1, Bas Raaymakers2, Jan Lagendijk2, Kevin Brown3
Philips Research Europe, Hamburg, Germany; 2University Medical Center Utrecht, Utrecht, Netherlands; 3Elekta, Crawley, UK
    The abstract presents key features of an MRI system for MRI guided radiotherapy. The Linac-based radiation source is located on the outside of a cylindrical high-field MR scanner, radiating through the magnet's cryostat. The coil designs of main magnet and gradient coil provide a gap in the midplane of sufficient width to allow the beam to pass through. Magnetic interaction with the Linac is minimized by modification of the magnetís active shielding configuration so that a ring-shaped low field ring is obtained at the location of the field-sensitive parts of the accelerator.
11:30 594. The Application of MRI Pulse Sequences in the Verification of Proton Beam Radiotherapy
    Joao Seco1, Ravi Teja Seethamraju2, George Phil Broussard3, Hanne Kooy1, Mukesh Harisinghani4
Radiation Oncology, Harvard Medical School and Massachusetts General Hospital, Boston, MA, USA; 2Siemens Medical Solutions, USA Inc., Charlestown, MA, USA; 3Francis H Burr Proton Center, Massachusetts General Hospital, Boston, MA, USA; 4Radiology, Harvard Medical School and Massachusetts General Hospital, Boston, MA, USA
    The purpose of this study is to assess the clinical feasibility and effectiveness of magnetic resonance imaging (MRI) for quality assurance in proton beam therapy. The hypothesis is that as MRI relies on the relaxation times of protons within the patient and proton beam therapy delivers protons to the tumor volume, the extra protons delivered to the cancer tumor volume will produce an additional magnetic signal that can be observed by MRI. Therefore, MRI is assessed as a tool to give functional information of proton beam therapy of cancerous tumor volume.
11:42 595. Lorentz Force Effects in Multimodality MR-SPECT Imaging
    Mark Jason Hamamura1, Seung-Hoon Ha1, Werner W. Roeck1, Orhan Nalcioglu1, Douglas J. Wagenaar2, Dirk Meier2, Bradley E. Patt2
Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, USA; 2Gamma Medica-Ideas Inc., Northridge, CA, USA
    In a multimodality MR-SPECT system, a SPECT detector system is placed within the high magnetic field of an MRI system. In this study, we investigated the effects of the Lorentz force on the SPECT measurements. The results revealed a shift in the position of the SPECT projection data that must be taken into account for more accurate image reconstruction. Proper acquisition of the flood field image for sensitivity correction was also found to be critical for accurate image reconstruction.
11:54 596. Direct Imaging of SPIOs in Mice Using Magnetic Particle Imaging:  Instrument Construction and 3D Imaging
    Patrick Goodwill1, Greig Scott2, Pascal Stang2, Gary Chiray Lee1, Doug Morris3, Steve Conolly4
Joint Graduate Group in Bioengineering, UC Berkeley / UCSF, Berkeley, CA, USA; 2Electrical Engineering, Stanford University; 3National Institutes of Health, Bethesda, MD, USA; 4Bioengineering, University of California, Berkeley, Berkeley, CA, USA
    We have developed the first Magnetic Particle Imaging (MPI) scanner capable of imaging a whole mouse. The system directly detects the magnetization of Super-Paramagnetic Iron Oxide (SPIO) particles commonly used as MRI contrast agents with remarkable sensitivity and resolution over a 3cm field of view without requiring sample movement. Our system incorporates technical advances that enable small receive bandwidths at high frequencies, with a clear path towards body noise dominance.
12:06 597. A Novel Single-Sided Imaging Device for MR Elastography
    Daniel V. Litwiller1, Eric A. Borisch1, Roger C. Grimm1, Joel P. Felmlee1, Richard L. Ehman1
Radiology, Mayo Clinic, Rochester, MN, USA
    Recent years have seen the development of small, single-sided NMR systems suitable for a variety of applications in biomedicine. These novel imaging systems are typified by their small size, single-sided nature and nonuniform polarizing fields. Another emerging field of research is non-invasive imaging of material properties of tissues and biomaterials with the clinical application of techniques like MR elastography. The goal of this work was to develop a low cost single-sided NMR device, capable of MR elastography, which would be potentially useful for applications such as evaluation of normal and pathological skin, benchtop pathology, and evaluating engineered tissue constructs.
12:18 598. Development of Cryogen-Free Ultra-Low Field MRI Instrument
    Byeong Ho Eom1, Konstantin Penanen1, Peter K. Day1, Inseob Hahn1, Mark S. Cohen2
Jet Propulsion Lab/Caltech, Pasadena, CA, USA; 2Center for Cognitive Neuroscience, UCLA School of Medicine, Los Angeles, CA, USA
    In-vivo MR imaging at very low fields using superconducting quantum interference device (SQUID) magnetometry and pre-polarizing field cycling technique has been demonstrated recently and many advantages have been noted. Although the expensive superconducting magnet can be essentially eliminated in a pre-polarizing low field SQUID MRI system, expendable cryogens and its maintenance service, required to cool the low temperature detector, are still placing increasing burden on the operational cost. We have built a prototype cryogen-free SQUID MRI system. Here we present its design, noise characterizations and the first phantom image.