Thermal Therapy & Focused Ultrasound
Wednesday 22 April 2009
Room 323ABC 10:30-12:30

Moderators:

 Kagayaki Kuroda and Nathan J. McDannold
 
10:30 439. Bio-Functional Magnetic Nanoparticles for MR Monitoring and Localized Hyperthermic Treatment of Cancer
    Panagiotis G. Kyrtatos*1,2, Michael R. Loebinger*3, Anthony N. Price1, Mathew Kallumadil4,5, Paul Southern4,6, Quentin A. Pankhurst4,6, Sam M. Janes3, Mark F. Lythgoe2,7
1Centre for Advanced Biomedical Imaging , UCL Institute of Child Health and UCL Department of Medicine, London, UK; 2RCS Unit of Biophysics, UCL Institute of Child Health, London, UK; 3Centre for Respiratory Research, University College London; 4London Centre for Nanotechnology; 5Davy-Faraday Research Laboratories, The Royal Institution  of Great Britain, London, UK, *equal contribution to this work; 6Davy-Faraday Research Laboratories, The Royal Institution of Great Britain, London, UK, *equal contribution to this work; 7Centre for Advanced Biomedical Imaging, UCL Institute of Child Health and UCL Department of Medicine, London, UK
    Lung cancer is the biggest cancer killer. Recent evidence suggests that stromal tissue within cancers can be mesenchymal stem cell (MSC) derived. Superparamagnetic iron oxide nanoparticles (SPIO) offer attractive possibilities in biomedicine as they can be utilized for MR imaging and targeted localized hyperthermia by application of RF magnetic field. The long term aim of our study is to utilize the tumor-homing capacity of MSCs to deliver a payload of nanoparticles for targeted hyperthermia and non-invasive MR monitoring of therapy. Here we present preliminary data on particle heating using a custom-made RF applicator, MSC labeling and tumor imaging.
     
10:42 440. Endocavitary Phased Array Applicator of Therapeutic Ultrasound with an Integrated Opposed-Solenoid Coil for High Resolution MRI-Guided Thermotherapy: An in Vivo Study
    Mihaela Rata1,2, Francois Cotton3,4, Christian Paquet5, Vlad Birlea1, Michael Bock6, Rares Salomir1
1INSERM U556, Lyon, France; 2UCBL Lyon 1, Lyon, France; 3UCBL  Lyon 1, Lyon, France; 4CHU Lyon Sud, Radiology Department , Lyon, France; 5National Veterinary School, Lyon, France; 6DKFZ, Heidelberg, Germany
    High intensity contact ultrasound (HICU) under MRI guidance may provide minimally invasive treatment of endocavitary digestive tumors (colon/rectum). In this study, opposed-solenoid receiver-only coils were integrated into an endoscopic phased array ultrasound probe to offer high resolution MRI guidance of thermotherapy. The improvement of the image quality and temperature monitoring and control using this device has been investigated in- vivo, on a clinical 1.5T. The comparison endocavitary/external standard coils (voxel: 0.88 x 0.88 x 8 mm3) showed a sensitivity gain up to a factor 4, at the limit of the cooling balloon. Infra-millimeter resolution became feasible for fast MR thermometry while providing an excellent SDT. The endoscopic device was actively operated under automatic temperature control, demonstrating accurate performance.
     
10:54 441. Fast Imaging Sequence for Temperature Monitoring in Moving Objects
    Bruno Madore1, Jing Yuan1, Chang-Sheng Mei1, Lawrence P. Panych1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, USA
    A novel approach to monitor both motion and temperature in moving organs is presented. The technique is based on an SSFP sequence modified to be tolerant but yet sensitive to resonance frequency variations, such as those created by temperature. A phantom moving over a 2-cm range with a period of about 5 s, typical of the motion expected in the liver during free breathing, was imaged with a temporal resolution of 500 ms to resolve the motion. After registration, temperature curves and images comparable (although visibly degraded) to the static case were obtained.
     
11:06 442. Three Dimensional Motion Compensation for Real-Time MRI Guided Focused Ultrasound Treatment of Abdominal Organs
    Mario Ries1, Baudouin Dennis De Senneville1, Gregory Maclair1, Max O. Köhler2, Bruno Quesson1, Chrit Moonen1
1UMR 5231, CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France; 2Philips Healthcare, Vantaa, Finland
    A method for real-time 3D positioning of a High Intensity Focused Ultrasound (HIFU) beam onto a moving target with simultaneous temperature monitoring is presented as a step towards MR-guided HIFU for the ablation of tumors in abdominal organs under free-breathing conditions. The feasibility of the proposed method is demonstrated with phantom experiments and an in-vivo ablation of a pig kidney.
     
11:18 443. Advances in Real-Time MR Temperature Mapping of the Human Heart
    Sebastien Roujol1, Baudouin denis de Senneville1, Gregory Maclair1, Silke Hey1, Pierre Jais1, Chrit Moonen1, Bruno Quesson1
1CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France
    A method for monitoring the temperature evolution in the heart muscle at each cardiac cycle is presented. Cardiac triggering and navigator-based slice tracking for respiratory compensation were combined with image registration and with modeling of motion-related susceptibility changes. With this approach, temperature images were updated approximately each cardiac cycle (1 second) and the resulting median value of the temperature standard deviation in the septum ranged between 1  and 5 C for all volunteers (N=19). This rapid temperature imaging could be used for monitoring radiofrequency catheter ablations.
     
11:30 444. Reference-Less MR Thermometry Using Iteratively-Reweighted L1 Regression
    William Allyn Grissom1, Michael Lustig2, Viola Rieke, Andrew B. Holbrook3, John B. Pauly2, Kim B. Butts-Pauly
1Electrical Engineering and Radiology, Stanford University, Stanford, CA, USA; 2Electrical Engineering, Stanford University, Stanford, CA, USA; 3Bioengineering, Stanford University, Stanford, CA, USA
    Conventional reference-less thermometry techniques derive baseline phase images using least-squares polynomial regression performed on image phase during thermotherapy. Because least-squares regression is sensitive to outliers, i.e., the phase within the hot spot, the hot spot must be masked out of this regression, so its location must be known or tracked. We propose a new thermometry method that uses reweighted-L1 polynomial regression to prevent hot spot bias, obviating the need for masking or tracking. The method is therefore more robust to motion than conventional reference-less thermometry, and requires less user interaction.
     
11:42 445. 3-D MR Temperature Imaging with Model Predictive Filtering Reconstruction
    Nick Todd1, Allison Payne2, Dennis Parker3
1Physics, University of Utah, Salt Lake City, UT, USA; 2Mechanical Engineering, University of Utah, Salt Lake City, UT, USA; 3Radiology, University of Utah, Salt Lake City, UT, USA
    We present MRI temperature imaging using a 3-D gradient echo sequence that undersamples k-space and is reconstructed using a model predictive filtering (MPF) algorithm. The MPF algorithm combines information from an identified thermal model of the tissue with undersampled k-space data. The 3-D imaging was chosen for its superior spatial resolution and coverage. The technique provides temperature maps with 2mm3 isotropic spatial resolution and 6 second temporal resolution. The 3-D MPF technique was compared to the traditional 2-D PRF technique over 8 HIFU heating experiments. The standard deviation of the temperature difference between the 2 methods was 0.57 degrees C.
     
11:54 446. Transcranial MRI-Guided Focused Ultrasound Surgery of Brain Tumors: Initial Findings in Patients
    Nathan McDannold1, Greg Clement1, Eyal Zadicario2, Peter Black1, Ferenc Jolesz1, Kullervo Hynynen1,3
1Brigham & Women's Hospital, Boston, MA, USA; 2InSightec, Haifa, Israel; 3University of Toronto, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
    In initial trials in three glioblastoma patients, we found that it was possible to focus an ultrasound beam transcranially into the brain and to visualize the heating with MR temperature imaging. While we were limited by the power available at the time with the device and thus appeared to not achieve thermal coagulation, analysis of the temperature measurements suggests that thermal ablation will be possible with this device without overheating the brain surface, with some possible limitation on the treatment envelope. These findings are a major step forward in producing a completely noninvasive alternative to surgical resection for brain disorders.
     
12:06 447. Determination of Pulse Sequence and Timing of Contrast-Enhanced MRI for Assessing Blood-Brain Barrier Disruption Following Transcranial Focused Ultrasound
    Jun-Cheng Weng1, Sheng-Kai Wu2, Feng-Yi Yang3,4, Win-Li Lin2,5, Wen-Yih I. Tseng1,6
1Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan; 2Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan; 3Institute of Biomedical Engineering, College of Medicine and College of Engineering,, National Taiwan University, Taipei, Taiwan; 4Department of Biomedical Imaging and Radiological Science, National Yang-Ming University, Taipei, Taiwan; 5Medical Engineering Research Division, National Health Research Institutes, Miaoli, Taiwan; 6Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan
    The purpose of this study was to find the optimum pulse sequence and timing of contrast-enhanced MRI that best indicate the BBB disruption in the presence of hemorrhage. Twelve rat brains were sonicated with center frequency of 1 MHz at four different doses of ultrasound contrast agent (0, 150, 300, and 450 μl/kg, three rats for each dose). T1WI spin echo and T1WI gradient echo sequences were performed at three time points, baseline, 10 min and 45 min after Gd-chelate T1-shortening administration. The degree of enhancement was quantified and correlated with the Evans blue staining. Our results showed that contrast-enhanced T1W spin echo sequence acquired at 10 min post contrast enhancement can reliably indicate the degree and location of the BBB disruption despite in the presence of hemorrhage.
     
12:18 448. PRF Shift in Frozen Tissue at 3T
    Elena Kaye1,2, Aiming Lu3, Marcus Alley2, Kim Butts Pauly2
1Electrical Engineering, Stanford University, Palo Alto, CA, USA; 2Radiology, Stanford University, Palo Alto, CA, USA; 3University of Chicago
    In clinical cryoablation temperature monitoring is typically done with temperature sensors built into cryoprobes or inserted in addition to cryoprobes. Placement of temperature sensors is invasive, time consuming, and doesn’t provide continuous temperature feedback throughout the region of treatment. The following MRI parameters have been shown to be sensitivity to temperature: signal intensity, R2*, and phase shift. The phase shift is a parameter that is usually used for MRI-based thermometry in tissue at T>0 C. In frozen tissue, there is still little known about the phase and proton resonance frequency (PRF) shift dependence on temperature. In a previous 7T spectroscopy study, PRF shift as a function of temperature was found to go from a linear temperature dependence at T>0 C to an exponential dependence at T<0 C. In this work, for the first time, we measure frequency shift in frozen tissue on a clinical 3T MRI scanner.