TRADITIONAL POSTER - ismrm

Poster Sessions
1793. Equivalence of CBV Measurement Methods in DSC-MRI
Matus Straka 1 , Gregory W. Albers 2 , Roland Bammer 1
1 Radiology, Stanford University, Stanford, CA, United States; 2 Stroke Center, Stanford University Medical Center, Stanford, CA,
United States
Two widely used methods exist for computing cerebral blood volume (CBV) in DSC-MRI perfusion, using measured signals as well as deconvolved residue
function. Some authors claim that these methods do not deliver identical results. We explain that the methods must deliver equivalent results and any
difference in obtained values is just caused by signal post-processing errors and wrong interpretation of indicator-dilution theory and convolution theorem.
Identity of the two methods is shown in time- and frequency-domains as well as by means of numerical results. Possible sources of the processing errors are
discussed and solutions how to avoid those are proposed.
1794. Design of a Data Driven Deconvolution Filter for DSC Perfusion
Philipp Emerich 1 , Peter Gall 1 , Birgitte Fuglsang Kjølby 2 , Elias Kellner 1 , Irina Mader 3 , Valerij Kiselev 1
1 Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2 Dept. of Neuroradiology, Arhus University Hospital, Arhus,
Denmark; 3 Dept. of Neuroradiology, University Hospital Freiburg, Freiburg, Germany
Bolus tracking perfusion evaluation relies on the deconvolution of a tracer concentration time-courses in an arterial and a tissue voxel following the tracer
kinetic model. The object of this work is to propose a method to design a data driven Tikhonov regularization filter in the Fourier domain and to compare it
to the singular value decomposition (SVD) based approaches using the mathematical equivalence of Fourier and circular SVD (oSVD).
1795. On the Form of the Residue Function for Brain Tissue
Peter Gall 1 , Valerij Kiselev 1
1 Medical Physics, University Hospital Freiburg, Freiburg, Germany
The residue function, R(t), is fundamental for description of microcirculation. To define this function is one of the aims of DSC perfusion MRI. It is found
by solving an ill-posed problem, the deconvolution, for which one of approaches is to fit a model R(t) to data. Commonly, phenomenological functional
shapes are used to model R(t) respecting only its most general properties. Studies based on ASL indicate insufficiency of this approach. In this work we
present a derivation the residue function from the laws of laminar flow and a model for the architecture of the vascular tree.
MR-Guided Focused Ultrasound
Hall B Tuesday 13:30-15:30
1796. MR-Guided Focused Ultrasound Ablation of the Rat Liver
Randy Lee King 1,2 , Viola Rieke 1 , Kim Butts Pauly 1
1 Department of Radiology, Stanford University, Stanford, CA, United States; 2 Department of Bioengineering, Stanford University,
Stanford, CA, United States
This study investigates the use of a rat model for the MR-guided focused ultrasound treatment of hepatocellular carcinoma. PRF-thermometry, thermal dose
calculation and post-ablation imaging are used to determine the ablated liver area and compared to necropsy. Thermal dose reliably predicts the ablated area
for single sonications, but care has to be taken to avoid overestimation in lesions resulting from multiple sonications.
1797. Non-Invasive Suppression of Animal-Model Chronic Epilepsy Using Image-Guided Focused
Ultrasound
Seung-Schik Yoo 1 , KwangIk Jung 1 , YongZhi Zhang 1 , Nathan McDannold 1 , Alexander Bystritsky, 12 , Ferenc
A. Jolesz 1
1 Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States; 2 Psychiatry, David Geffen School
of Medicine at UCLA, Los Angeles, CA, United States
We showed the evidence of MRI-guided focused ultrasound can suppress the ictal actvity induced by the chemical kindling of rat brain via kainic acid. This
evidence demonstrate that non-invasive suppression of epilepsy may be feasible using pulsed, low-energy focused ultrasound.
1798. Proton Resonance Frequency MRI Shows Focal Spot Shifts Due to Interfaces During MR-HIFU
Treatment
Elizabeth Hipp 1 , Xiaobing Fan 1 , Ari Partanen 2 , Gregory S. Karczmar 1
1 Radiology, University of Chicago, Chicago, IL, United States; 2 Philips Healthcare
MR-HIFU is emerging as a treatment modality for a variety of pathologies. Treatments near tissue interfaces can result in unwanted heating caused by an
impedance mismatch. This research uses the proton resonance frequency measured by MRI to explore the changes in heating pattern and shift in sonication
focus as a result of proximity to an interface in a thermal phantom. Air, acrylic, rubber and a tissue-equivalent gel pad were tested with treatment cells
focused at 1, 2 and 4 cm from the interface material revealing 0.7 to 3 mm shifts depending on focal position and interface material.
1799. An MR-Compatible Hydrophone for Ultrasound Monitoring of MRI-Guided Transcranial Focused
Ultrasound Therapy
Meaghan Anne O'Reilly 1 , Yuexi Huang 1 , Kullervo Hynynen 1,2
1 Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada; 2 Medical Biophysics, University of Toronto, Toronto,
Ontario, Canada
Ultrasound monitoring of MR-guided transcranial ultrasound therapy could help identify control parameters to better deliver therapy to the brain. An MRcompatible
PVDF hydrophone with a high sensitivity was constructed and characterized. The hydrophone was used to monitor microbubble-mediated