TRADITIONAL POSTER - ismrm

Poster Sessions
1821. Optimal Multi-Echo Water-Fat Separated Imaging Parameters for Temperature Change
Measurement Using Cramer-Rao Bounds
Cory Robert Wyatt 1 , Brian J. Soher 2 , Kavitha Arunachalam 3 , James R. MacFall 2
1 Department of Biomedical Engineering, Duke University, Durham, NC, United States; 2 Department of Radiology, Duke University
Medical Center, Durham, NC, United States; 3 Department of Radiation Oncology, Duke University Medical Center, Durham, NC,
United States
Multi-echo fat-water fitting techniques that separate the fat and water effects have been shown to be useful in measuring temperature in fat-water phantoms.
In this study we explore optimization of echo time selection by minimizing the temperature noise using Cramer-Rao Lower Bound (CRLB) analysis.
Accuracy of fitting is improved by including multiple fat peaks and T2* effects. Our approach finds the minimum temperature noise that has the minimum
sensitivity to the values of nominally fixed parameters. The CRLB results were then confirmed in experiments with fat-water gelatin phantoms.
1822. Measurement of Human Brain Temperature Changes During Cooling
Jan Weis 1 , Lucian Covaciu 2 , Sten Rubertsson 2 , Mats Allers 3 , Anders Lunderquist 4 , Francisco Ortiz-Nieto 1 ,
Håkan Ahlström 1
1 Department of Radiology, University Hospital, Uppsala, Sweden; 2 Department of Surgical Sciences, Anesthesiology and Intensive
Care, University Hospital, Uppsala, Sweden; 3 Department of Clinical Sciencies, University Hospital, Lund, Sweden; 4 Department of
Clinical Sciences, University Hospital, Lund, Sweden
Decrease of the human brain temperature (1-2 oC in 15 minutes) was induced by intranasal cooling. The purpose of this study was to verify the cooling
technique on the volunteers and to compare two methods for noninvasive monitoring of the relative brain temperature: MRSI with high spatial and reduced
spectral resolution and PRF shift technique. Ability of the proposed brain cooling technique to induce moderate hypothermia was confirmed. Good
agreement was found between relative temperatures measured by MRSI and PRF method. Both temperature mapping techniques can be used for monitoring
the brain temperature changes during hypothermia.
1823. Measurement of the Temperature Dependence of the Susceptibility of Human Breast Fat Tissue
Sara Maria Sprinkhuizen 1 , Chris J. Bakker 1 , Johannes H. Ippel 2 , Rolf Boelens 2 , Lambertus Wilhelmus
Bartels 1
1 Radiology, Image Sciences Institute, Utrecht, Netherlands; 2 Bijvoet Center for Biomolecular Research, NMR Spectroscopy Research
Group, Utrecht, Netherlands
In fat tissue, large susceptibility-related PRFS-based temperature errors can be expected, due to temporal changes in tissue susceptibility (χ) which lead to
non-local magnetic field changes. This affects the PRF (hence, the measured temperature) of all water protons that experience this magnetic field change,
leading to temperature errors. In order to conclusively assess the impact of temperature-induced χ changes on PRFS-based MRT, accurate and precise
susceptibility measurements in human tissue are a prerequisite. We therefore measured dχ/dT of fat tissue of the human breast on a 14 T NMR spectrometer.
A dependence of 0.0051 ppm/°C was found.
1824. PRFS-Based MR Thermometry Is Hampered by Susceptibility Changes Caused by the Heating of Fat:
Experimental Demonstration
Sara Maria Sprinkhuizen 1 , Chris J. Bakker 1 , Lambertus Wilhelmus Bartels 1
1 Radiology, Image Sciences Institute, Utrecht, Netherlands
Susceptibility (χ) related field changes are commonly ignored in the application of proton resonance frequency shift (PRFS)-based MR thermometry (MRT)
during thermal interventions, even though the temperature dependence of the χ of fat is in the same order of magnitude as the temperature dependence of the
chemical shift of water. Its influence on PRFS-based MRT maps was investigated experimentally. The results showed that changes in χ fat hamper the PRFSbased
MRT method nonlocally. The measured errors were ranging between -4.6 °C and +4.1 °C. Important to stress is the fact that fat suppression is not a
solution for this effect.
1825. Modified Balanced SSFP Sequence for Better Temperature Sensitivity
Mahamadou Diakite 1 , Nick Todd 1 , Dennis L. Parker 2
1 Physics, University of Utah, Salt lake, UT, United States; 2 Radiology, Utah Center for Advanced Imaging Research (UCAIR), Salt
lake, UT, United States
Safety and efficacy of tumor treatment using high intensity focus ultrasound requires accurate temperature measurement throughout the thermal procedure.
In this work, we investigate how the noise in temperature measurements can be reduced by variations to this new ub-SSFP sequence.
1826. Hyperthermia Induced Gadodiamide Release from Thermosensitive Liposomes in Solid Tumors and
Muscle Tissue
Michael Peller 1 , Martin Hossann 2 , Tungte Wang 2,3 , Steven Sourbron 1 , Lars H. Lindner 2,3
1 Institute of Clinical Radiology, University Hospital of Munich, Munich, Germany; 2 Department of Internal Medicine III, University
Hospital Munich; 3 CCG-Hyperthermia, Helmholtz Zentrum München, German Research Center for Environmental Health, Germany
Purpose was to investigate the dynamics of mild temperature induced contrast agent release from phosphatidylglyc-eroglycerol containing thermosensitive
liposomes with encapsulated Gd-DTPA-BMA (Gd-TSL) in tumor tissue. Tumor bearing mice were investigated at 1.5T after intravenous injection. The
temperature induced release of contrast agent at 42°C caused a fast and strong increase of T1-weighted signal. Immediately after i.v. injection heated tumor
tissue was distinguishable from unheated tumor and muscle tissue. Unheated muscle tissue may thus be less affected by a potential anti tumor therapy based
on TSL.