TRADITIONAL POSTER - ismrm

Poster Sessions
1805. Does Proton Resonance Frequency Linearly Change with Temperature?
Donghoon Lee 1 , Kenneth Marro 1 , Bryan Cunitz 1 , Michael Bailey 1
1 University of Washington, Seattle, WA, United States
To improve the accuracy in temperature measurements over a wide temperature region (20 – 95 C), we designed and fabricated a test sample holder and
conducted temperature measurements over the temperature range. The test sample holder comprised a reference chamber for temperature reference and a
heating chamber. Both chambers, filled with water, were in well thermal insulation. Nonlinear relationship between proton resonance frequency shift and
temperature was observed for the wide temperature region. Accurate information of temperature variations over a wide temperature region would be
valuable to thermal therapy for a temperature region that could reach the water boiling temperature.
1806. Temperature Sensitive Liposomes for Drug Delivery with MRI-HIFU
Mariska de Smet 1 , Sander Langereis 2 , Roland van de Molengraaf 2 , Edwin Heijman 2 , Nicole Hijnen 1 ,
Holger Gruell 1,2
1 Biomedical NMR, Eindhoven University of Technology, Eindhoven, Netherlands; 2 Biomolecular Engineering, Philips Research
Eindhoven, Eindhoven, Netherlands
Temperature sensitive liposomes (TSL) incorporating both a chemotherapeutic drug, i.e. doxorubicin, and a clinically approved MRI contrast agent,
[Gd(HPDO3A)(H2O)] were prepared and evaluated for MR image guided drug delivery. A gel phantom was prepared containing spots of agarose gel mixed
with the liposomes. Before and after heating with High Intensity Focused Ultrasound (HIFU), a T1 map was obtained with a Look-Locker EPI-sequence.
When heated above the phase transition temperature, the TSLs showed a rapid release of both the drug and contrast agent. The spots with liposomes which
were heated with HIFU clearly showed a lower T1 after ultrasound application.
1807. Latency Compensation for Real-Time 3D HIFU Beam-Steering on Moving Targets
Mario Ries 1 , Baudouin Denis de Senneville 1 , Sébastien Roujol 1 , Chrit Moonen 1
1 laboratory for molecular and functional imaging: from physiology to therapy, CNRS/ University Bordeaux 2, Bordeaux, Aquitaine,
France
Dynamic beam-steering of high intensity focused ultrasound (HIFU) based on MR-guidance is a promising technology for the non-invasive ablation of
pathological tissue in abdominal organs such as liver and kidney. A particular problem of this technique remains the intrinsic latency between the position
measurement and the beam update, which leads to undesired energy dispersion and potentially to the destruction of non-pathological tissue. In this study,
dynamic beam-steering using a robust Kalman-predictor for 3D motion anticipation is evaluated experimentally.
1808. Retrospective Reconstruction of High Spatial and Temporal Resolution Temperature Maps for Tissue
Property Determination
Nick Todd 1 , Josh De Bever 2 , Urvi Vyas 3 , Allison Payne 4 , Dennis L. Parker 5
1 Physics, University of Utah, Salt Lake City, UT, United States; 2 Robotics, University of Utah, Salt Lake City, UT, United States;
3 Bioengineering, University of Utah, Salt Lake City, UT, United States; 4 Mechanical Engineering, University of Utah, Salt Lake City,
UT, United States; 5 Radiology, University of Utah, Salt Lake City, UT, United States
For certain MR thermometry applications, such as tissue property determination or total accumulated thermal dose calculations, retrospectively reconstructed
temperature maps are acceptable. For such purposes, we have implemented a temporally constrained reconstruction method. The technique uses the entire
dynamic imaging data set and an iterative cost function minimization algorithm to create 3-D temperature maps with high spatial resolution (~1 - 2mm3),
high temporal resolution (~1 sec), and large field of view coverage (~26x16x3cm3). We present the TCR method and applications to retrospective
determination of tissue thermal conductivity, ultrasound power deposition, and total accumulated thermal dose.
1809. Three-Slice MR Pre-Treatment Temperature Mapping and Spherical Model Estimation for Accurate
Localization of the Heating Focus Before High-Intensity Focused Ultrasound Treatment
Hsu-Hsia Peng 1 , Teng-Yi Huang 2 , Hsiao-Wen Chung 3 , Po-Cheng Chen 4 , Yu-Hui Ding 4 , Shiun-Ying Ju 2 ,
Yao-Hao Yang 2 , Wen-Yih Isaac Tseng 5,6 , Wen-Shiang Chen 4,7
1 Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan; 2 Department
of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan; 3 Department of Electrical
Engineering, National Taiwan University, Taipei, Taiwan; 4 Department of Physical Medicine and Rehabilitation, National Taiwan
University Hospital, Taipei, Taiwan; 5 Center for Optoelectronic Biomedicine, Medical College of National Taiwan University, Taipei,
Taiwan; 6 Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan; 7 Division of Medical Engineering
Research, National Health Research Institutes, Miaoli, Taiwan
During HIFU treatment, the focus of ultrasound (US) is arranged to the targeting region determined in advance. In practical treatments, however, the focus
might be deviated due to the complex path (tissue-bone interface or tissue-air interface) of US beams. For safety considerations, accurate localization of
heating focus is important before performing HIFU treatment. In this study, a spherical model is proposed to estimate the real position of US focus. A low
power pre-treatment experiment was performed on ex vivo porcine muscle. The estimated focus position was verified via magnetization transfer ratio images
after a high power HIFU transmission.
1810. Tissue Acoustic Properties Using MRI Temperature Measurements of Low Powered Ultrasound
Heating Pulse.
Urvi Vyas 1 , Nick Todd 2 , Allison Payne 3 , Douglas Christensen, Dennis L. Parker 4
1 Bioengineering, University of Utah, Salt Lake City, UT, United States; 2 Physics, University of Utah; 3 Mechanical Engineering,
University of Utah; 4 Radiology, University of Utah
An inverse parameter estimation technique that non-invasively determines ultrasound tissue properties ( speed of sound, attenuation) using MRI temperature
maps of low level ultrasound heating pulses is presented. The properties determined by the new technique are compared to ultrasound tissue properties
measured using the transmission-substitution technique.