A thermometry software tool for monitoring laser-induced interstitial thermotherapy

2019 ◽  
Vol 64 (4) ◽  
pp. 449-457 ◽  
Author(s):  
Babak Bazrafshan ◽  
Ahmad Koujan ◽  
Frank Hübner ◽  
Christian Leithäuser ◽  
Norbert Siedow ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Software Tool ◽  
Biological Tissues ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Mri Thermometry ◽  
Visualization Toolkit ◽  
Magnetic Resonance Imaging Mri ◽  
Echo Planar ◽  
Interstitial Thermotherapy

Abstract The purpose of this study was to develop a thermometry software tool for temperature monitoring during laser-induced interstitial thermotherapy (LITT). C++ programming language and several libraries including DICOM Toolkit, Grassroots DICOM library, Insight Segmentation and Registration Toolkit, Visualization Toolkit and Quasar Toolkit were used. The software’s graphical user interface creates windows displaying the temperature map and the coagulation extent in the tissue, determined by the magnetic resonance imaging (MRI) thermometry with the echo planar imaging sequence and a numerical simulation based on the radiation and heat transfer in biological tissues, respectively. The software was evaluated applying the MRI-guided LITT to ex vivo pig liver and simultaneously measuring the temperature through a fiber-optic thermometer as reference. Using the software, the temperature distribution determined by the MRI method was compared with the coagulation extent simulation. An agreement was shown between the MRI temperature map and the simulated coagulation extent. Furthermore, the MRI-based and simulated temperatures agreed with the measured one – a correlation coefficient of 0.9993 and 0.9996 was obtained, respectively. The precision of the MRI temperature amounted to 2.4°C. In conclusion, the software tool developed in the present study can be applied for monitoring and controlling the LITT procedure in ex vivo tissues.

scholarly journals MRI Powered and Triggered Current Stimulator for Concurrent Stimulation and MRI

2019 ◽  
Author(s):  
Ranajay Mandal ◽  
Nishant Babaria ◽  
Jiayue Cao ◽  
Kun-Han Lu ◽  
Zhongming Liu
Keyword(s):  
Scale Up ◽  
Small Animal ◽  
7 Tesla ◽  
Planar Imaging ◽  
Novel Device ◽  
Peripheral Muscle ◽  
Gradient Fields ◽  
Magnetic Resonance Imaging Mri ◽  
Small Animal Mri ◽  
Echo Planar

AbstractBioelectric stimulation during concurrent magnetic resonance imaging (MRI) is of interest to basic and translational studies. However, existing stimulation systems often interfere with MRI, are difficult to use or scale up, have limited efficacy, or cause safety concerns. To address these issues, we present a novel device capable of supplying current stimulation synchronized with MRI while being wirelessly powered by the MRI gradient fields. Results from testing it with phantoms and live animals in a 7 Tesla small-animal MRI system suggest that the device is able to harvest up to 72 (or 18) mW power during typical echo-planar imaging (or fast low angle shot imaging) and usable for stimulating peripheral muscle or nerve to modulate the brain or the gut, with minimal effects on MRI image quality. As a compact and standalone system, the plug-and-play device is suitable for animal research and merits further development for human applications.

scholarly journals Simultaneous Perfusion and Permeability Measurements Using Combined Spin- and Gradient-Echo MRI

2013 ◽  
Vol 33 (5) ◽  
pp. 732-743 ◽  
Author(s):  
Heiko Schmiedeskamp ◽  
Jalal B Andre ◽  
Matus Straka ◽  
Thomas Christen ◽  
Seema Nagpal ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Spin Echo ◽  
Mean Transit Time ◽  
Brain Perfusion ◽  
Gradient Echo ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Tissue Characteristics ◽  
Echo Planar ◽  
Good Agreement

The purpose of this study was to estimate magnetic resonance imaging-based brain perfusion parameters from combined multiecho spin-echo and gradient-echo acquisitions, to correct them for T1-, T2-, and T∗2-related contrast agent (CA) extravasation effects, and to simultaneously determine vascular permeability. Perfusion data were acquired using a combined multiecho spin- and gradient-echo (SAGE) echo-planar imaging sequence, which was corrected for CA extravasation effects using pharmacokinetic modeling. The presented method was validated in simulations and brain tumor patients, and compared with uncorrected single-echo and multiecho data. In the presence of CA extravasation, uncorrected single-echo data resulted in underestimated CA concentrations, leading to underestimated single-echo cerebral blood volume ( CBV) and mean transit time ( MTT). In contrast, uncorrected multiecho data resulted in overestimations of CA concentrations, CBV, and MTT. The correction of CA extravasation effects resulted in CBV and MTT estimates that were more consistent with the underlying tissue characteristics. Spin-echo perfusion data showed reduced large-vessel blooming effects, facilitating better distinction between increased CBV due to active tumor progression and elevated CBV due to the presence of cortical vessels in tumor proximity. Furthermore, extracted permeability parameters were in good agreement with elevated T1-weighted postcontrast signal values.

scholarly journals Diffusion in Sephadex Gel Structures: Time Dependency Revealed by Multi-Sequence Acquisition over a Broad Diffusion Time Range

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1688
Author(s):  
Guangyu Dan ◽  
Weiguo Li ◽  
Zheng Zhong ◽  
Kaibao Sun ◽  
Qingfei Luo ◽  
...  
Keyword(s):  
Fractional Order ◽  
Spin Echo ◽  
Time Derivative ◽  
Biological Tissues ◽  
Diffusion Time ◽  
Time Range ◽  
Time Dependency ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Non Gaussian

It has been increasingly reported that in biological tissues diffusion-weighted MRI signal attenuation deviates from mono-exponential decay, especially at high b-values. A number of diffusion models have been proposed to characterize this non-Gaussian diffusion behavior. One of these models is the continuous-time random-walk (CTRW) model, which introduces two new parameters: a fractional order time derivative α and a fractional order spatial derivative β. These new parameters have been linked to intravoxel diffusion heterogeneities in time and space, respectively, and are believed to depend on diffusion times. Studies on this time dependency are limited, largely because the diffusion time cannot vary over a board range in a conventional spin-echo echo-planar imaging sequence due to the accompanying T2 decays. In this study, we investigated the time-dependency of the CTRW model in Sephadex gel phantoms across a broad diffusion time range by employing oscillating-gradient spin-echo, pulsed-gradient spin-echo, and pulsed-gradient stimulated echo sequences. We also performed Monte Carlo simulations to help understand our experimental results. It was observed that the diffusion process fell into the Gaussian regime at extremely short diffusion times whereas it exhibited a strong time dependency in the CTRW parameters at longer diffusion times.

scholarly journals Mapping of Absolute Host Concentration and Exchange Kinetics of Xenon Hyper-CEST MRI Agents

2021 ◽  
Vol 14 (2) ◽  
pp. 79 ◽  
Author(s):  
Martin Kunth ◽  
Christopher Witte ◽  
Leif Schröder
Keyword(s):  
Spin Exchange ◽  
Chemical Exchange ◽  
Chemical Exchange Saturation Transfer ◽  
Planar Imaging ◽  
Internal Reference ◽  
Cest Mri ◽  
Exchange Kinetics ◽  
Magnetic Resonance Imaging Mri ◽  
Echo Planar

Xenon magnetic resonance imaging (MRI) provides excellent sensitivity through the combination of spin hyperpolarization and chemical exchange saturation transfer (CEST). To this end, molecular hosts such as cryptophane-A or cucurbit[n]urils provide unique opportunities to design switchable MRI reporters. The concentration determination of such xenon binding sites in samples of unknown dilution remains, however, challenging. Contrary to 1H CEST agents, an internal reference of a certain host (in this case, cryptophane-A) at micromolar concentration is already sufficient to resolve the entire exchange kinetics information, including an unknown host concentration and the xenon spin exchange rate. Fast echo planar imaging (EPI)-based Hyper-CEST MRI in combination with Bloch–McConnell analysis thus allows quantitative insights to compare the performance of different emerging ultra-sensitive MRI reporters.

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