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Clemens Bos - One of the best experts on this subject based on the ideXlab platform.
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Field drift correction of Proton Resonance frequency shift temperature mapping with multichannel fast alternating nonselective free induction decay readouts.
Magnetic resonance in medicine, 2019Co-Authors: Cyril J. Ferrer, Lambertus W. Bartels, Tijl A. Van Der Velden, Holger Grüll, Edwin Heijman, Chrit T. W. Moonen, Clemens BosAbstract:Purpose: To demonstrate that Proton Resonance frequency shift MR thermometry (PRFS-MRT) acquisition with nonselective free induction decay (FID), combined with coil sensitivity profiles, allows spatially resolved B0 drift-corrected thermometry. Methods: Phantom experiments were performed at 1.5T and 3T. Acquisition of PRFS-MRT and FID were performed during MR-guided high-intensity focused ultrasound heating. The phase of the FIDs was used to estimate the change in angular frequency δωdrift per coil element. Two correction methods were investigated: (1) using the average δωdrift over all coil elements (0th-order) and (2) using coil sensitivity profiles for spatially resolved correction. Optical probes were used for independent temperature verification. In-vivo feasibility of the methods was evaluated in the leg of 1 healthy volunteer at 1.5T. Results: In 30 minutes, B0 drift led to an apparent temperature change of up to –18°C and –98°C at 1.5T and 3T, respectively. In the sonicated area, both corrections had a median error of 0.19°C at 1.5T and –0.54°C at 3T. At 1.5T, the measured median error with respect to the optical probe was –1.28°C with the 0th-order correction and improved to 0.43°C with the spatially resolved correction. In vivo, without correction the spatiotemporal median of the apparent temperature was at –4.3°C and interquartile range (IQR) of 9.31°C. The 0th-order correction had a median of 0.75°C and IQR of 0.96°C. The spatially resolved method had the lowest median at 0.33°C and IQR of 0.80°C. Conclusion: FID phase information from individual receive coil elements allows spatially resolved B0 drift correction in PRFS-based MRT.
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fluid filling of the digestive tract for improved Proton Resonance frequency shift based mr thermometry in the pancreas
Journal of Magnetic Resonance Imaging, 2018Co-Authors: Cyril J. Ferrer, Lambertus W. Bartels, Baudouin Denis De Senneville, Marijn Van Stralen, Chrit Moonen, Clemens BosAbstract:Purpose To demonstrate that fluid filling of the digestive tract improves the performance of respiratory motion-compensated Proton Resonance frequency shift (PRFS)-based magnetic Resonance (MR) thermometry in the pancreas. Materials and Methods In seven volunteers (without heating), we evaluated PRFS thermometry in the pancreas with and without filling of the surrounding digestive tract. All data acquisition was performed at 1.5T, then all datasets were analyzed and compared with three different PRFS respiratory motion-compensated thermometry methods: gating, multibaseline, and referenceless. The temperature precision of the different methods was evaluated by assessing temperature standard deviation over time, while a simulation experiment was used to study the accuracy of the methods. Results Without fluid intake, errors in temperature precision in the pancreas up to 10°C were observed for all evaluated methods. After liquid intake, temperature precision improved to median values between 1.8 and 2.9°C. The simulations showed that gating had the lowest accuracy, with errors up to 7°C. Multibaseline and referenceless thermometry performed better, with a median error in the pancreas between –3 and +3°C after fluid intake, for all volunteers. Conclusion Preparation of the digestive tract near the pancreas by filling it with fluid improved MR thermometry precision and accuracy for all common respiratory motion-compensated methods evaluated. These improvements are attributed to reducing field inhomogeneity in the pancreas. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017.
William A Grissom - One of the best experts on this subject based on the ideXlab platform.
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correcting heat induced chemical shift distortions in Proton Resonance frequency shift thermometry
Magnetic Resonance in Medicine, 2016Co-Authors: Pooja Gaur, Ari Partanen, Beat Werner, Pejman Ghanouni, Rachelle Bitton, Kim Butts Pauly, William A GrissomAbstract:Purpose To reconstruct Proton Resonance frequency-shift temperature maps free of chemical shift distortions. Theory and Methods Tissue heating created by thermal therapies such as focused ultrasound surgery results in a change in Proton Resonance frequency that causes geometric distortions in the image and calculated temperature maps, in the same manner as other chemical shift and off-Resonance distortions if left uncorrected. We propose an online-compatible algorithm to correct these distortions in 2DFT and echo-planar imaging acquisitions, which is based on a k-space signal model that accounts for Proton Resonance frequency change-induced phase shifts both up to and during the readout. The method was evaluated with simulations, gel phantoms, and in vivo temperature maps from brain, soft tissue tumor, and uterine fibroid focused ultrasound surgery treatments. Results Without chemical shift correction, peak temperature and thermal dose measurements were spatially offset by approximately 1 mm in vivo. Spatial shifts increased as readout bandwidth decreased, as shown by up to 4-fold greater temperature hot spot asymmetry in uncorrected temperature maps. In most cases, the computation times to correct maps at peak heat were less than 10 ms, without parallelization. Conclusion Heat-induced Proton Resonance frequency changes create chemical shift distortions in temperature maps resulting from MR-guided focused ultrasound surgery ablations, but the distortions can be corrected using an online-compatible algorithm. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.
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reweighted l1 referenceless prf shift thermometry
Magnetic Resonance in Medicine, 2010Co-Authors: William A Grissom, John M Pauly, Andrew B Holbrook, Michael Lustig, Viola Rieke, Kim ButtspaulyAbstract:Temperature estimation in Proton Resonance frequency (PRF) shift MR thermometry requires a reference, or pretreatment, phase image that is subtracted from image phase during thermal treatment to yield a phase difference image proportional to temperature change. Referenceless thermometry methods derive a reference phase image from the treatment image itself by assuming that in the absence of a hot spot, the image phase can be accurately represented in a smooth (usually low order polynomial) basis. By masking the hot spot out of a least squares (l2) regression, the reference phase image's coefficients on the polynomial basis are estimated and a reference image is derived by evaluating the polynomial inside the hot spot area. Referenceless methods are therefore insensitive to motion and bulk main field shifts, however, currently these methods require user interaction or sophisticated tracking to ensure that the hot spot is masked out of the polynomial regression. This article introduces an approach to reference PRF shift thermometry that uses reweighted l1 regression, a form of robust regression, to obtain background phase coefficients without hot spot tracking and masking. The method is compared to conventional referenceless thermometry, and demonstrated experimentally in monitoring HIFU heating in a phantom and canine prostate, as well as in a healthy human liver. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.
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maximum linear phase spectral spatial radiofrequency pulses for fat suppressed Proton Resonance frequency shift mr thermometry
Magnetic Resonance in Medicine, 2009Co-Authors: William A Grissom, John M Pauly, Adam B Kerr, Andrew B Holbrook, Kim ButtspaulyAbstract:Conventional spectral-spatial pulses used for water-selective excitation in Proton Resonance frequency–shift MR thermometry require increased sequence length compared to shorter wideband pulses. This is because spectral-spatial pulses are longer than wideband pulses, and the echo time period starts midway through them. Therefore, for a fixed echo time, one must increase sequence length to accommodate conventional spectral-spatial pulses in Proton Resonance frequency–shift thermometry. We introduce improved water-selective spectral-spatial pulses for which the echo time period starts near the beginning of excitation. Instead of requiring increased sequence length, these pulses extend into the long echo time periods common to PRF sequences. The new pulses therefore alleviate the traditional tradeoff between sequence length and fat suppression. We experimentally demonstrate an 11% improvement in frame rate in a Proton Resonance frequency imaging sequence compared to conventional spectral-spatial excitation. We also introduce a novel spectral-spatial pulse design technique that is a hybrid of previous model- and filter-based techniques and that inherits advantages from both. We experimentally validate the pulses' performance in suppressing lipid signal and in reducing sequence length compared to conventional spectral-spatial pulses. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.
Holger Grüll - One of the best experts on this subject based on the ideXlab platform.
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Field drift correction of Proton Resonance frequency shift temperature mapping with multichannel fast alternating nonselective free induction decay readouts.
Magnetic resonance in medicine, 2019Co-Authors: Cyril J. Ferrer, Lambertus W. Bartels, Tijl A. Van Der Velden, Holger Grüll, Edwin Heijman, Chrit T. W. Moonen, Clemens BosAbstract:Purpose: To demonstrate that Proton Resonance frequency shift MR thermometry (PRFS-MRT) acquisition with nonselective free induction decay (FID), combined with coil sensitivity profiles, allows spatially resolved B0 drift-corrected thermometry. Methods: Phantom experiments were performed at 1.5T and 3T. Acquisition of PRFS-MRT and FID were performed during MR-guided high-intensity focused ultrasound heating. The phase of the FIDs was used to estimate the change in angular frequency δωdrift per coil element. Two correction methods were investigated: (1) using the average δωdrift over all coil elements (0th-order) and (2) using coil sensitivity profiles for spatially resolved correction. Optical probes were used for independent temperature verification. In-vivo feasibility of the methods was evaluated in the leg of 1 healthy volunteer at 1.5T. Results: In 30 minutes, B0 drift led to an apparent temperature change of up to –18°C and –98°C at 1.5T and 3T, respectively. In the sonicated area, both corrections had a median error of 0.19°C at 1.5T and –0.54°C at 3T. At 1.5T, the measured median error with respect to the optical probe was –1.28°C with the 0th-order correction and improved to 0.43°C with the spatially resolved correction. In vivo, without correction the spatiotemporal median of the apparent temperature was at –4.3°C and interquartile range (IQR) of 9.31°C. The 0th-order correction had a median of 0.75°C and IQR of 0.96°C. The spatially resolved method had the lowest median at 0.33°C and IQR of 0.80°C. Conclusion: FID phase information from individual receive coil elements allows spatially resolved B0 drift correction in PRFS-based MRT.
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simultaneous t1 measurements and Proton Resonance frequency shift based thermometry using variable flip angles
Magnetic Resonance in Medicine, 2012Co-Authors: S Hey, Holger Grüll, De Mariska M Smet, Christian Stehning, Jochen Keupp, C T W Moonen, M RiesAbstract:A method is presented which allows precise temperature and longitudinal (T1) relaxation time measurements with high spatial and temporal resolution. This is achieved by combining dynamic variable flip angle based T1 relaxation mapping with Proton Resonance frequency shift based thermometry. Herein, dynamic T1 mapping is either used as a complementary measure of temperature or for the detection of T1 contrast agent release. For the first application, the temperature evolution during a high-intensity focused ultrasound tissue ablation experiment was measured in both, porcine fat and muscle, simultaneously. In this application, temperature accuracies of 2.5 K for T1-based thermometry in fat and 1.2 K for Proton Resonance frequency shift-based thermometry in muscle were observed. The second application relates to MR-guidance of high-intensity focused ultrasound-induced local drug delivery by means of thermo-sensitive liposomes labeled with a T1 contrast agent (Gd-HPDO3A). When the measured temperature exceeded the phase transition temperature of the liposomes, T1 was observed to decrease with a good temporal and spatial correlation due to the release of Gd-HPDO3A. The presented results demonstrate the feasibility of the proposed method for two important applications in MR-guided noninvasive therapy. It offers a high temporal resolution when compared with interleaved Look-Locker based T1 mapping techniques and thus represents an interesting candidate for simultaneous real-time monitoring of T1 and temperature changes. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
U Modder - One of the best experts on this subject based on the ideXlab platform.
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invited in vivo mri thermometry using a phase sensitive sequence preliminary experience during mri guided laser induced interstitial thermotherapy of brain tumors
Journal of Magnetic Resonance Imaging, 1998Co-Authors: T Kahn, Thorsten Harth, J C W Kiwit, Hansjoachim Schwarzmaier, Christoph Wald, U ModderAbstract:The purpose of this study was the application of the Proton-Resonance-frequency method to monitor laser-induced interstitial thermotherapy (LITT) in a patient with an astrocytoma WHO II. A phase-sensitive two-dimensional (2D) fast low-angle shot (FLASH) sequence was used to determine the temperature-related phase shifts during LITT. Temperature maps were displayed during therapy with a temporal resolution of 20 seconds. Irradiation was discontinued as soon as the 60 to 65°C isotherm reached the margin of the tumor. A contrast-enhanced MRI study performed immediately after therapy showed a good correlation of the size of an enhancing rim around the lesion with the 60 to 65°C isotherm. The preliminary results of our study indicate that MRI guidance of LITT may be improved by temperature quantification based on the Proton-Resonance-frequency method.
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invited in vivo mri thermometry using a phase sensitive sequence preliminary experience during mri guided laser induced interstitial thermotherapy of brain tumors
Journal of Magnetic Resonance Imaging, 1998Co-Authors: T Kahn, Thorsten Harth, J C W Kiwit, Hansjoachim Schwarzmaier, Christoph Wald, U ModderAbstract:The purpose of this study was the application of the Proton-Resonance-frequency method to monitor laser-induced interstitial thermotherapy (LITT) in a patient with an astrocytoma WHO II. A phase-sensitive two-dimensional (2D) fast low-angle shot (FLASH) sequence was used to determine the temperature-related phase shifts during LITT. Temperature maps were displayed during therapy with a temporal resolution of 20 seconds. Irradiation was discontinued as soon as the 60 to 65 degrees C isotherm reached the margin of the tumor. A contrast-enhanced MRI study performed immediately after therapy showed a good correlation of the size of an enhancing rim around the lesion with the 60 to 65 degrees C isotherm. The preliminary results of our study indicate that MRI guidance of LITT may be improved by temperature quantification based on the Proton-Resonance-frequency method.
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in vivo mri thermometry using a phase sensitive sequence preliminary experience during mri guided laser induced interstitial thermotherapy of brain tumors
Journal of Magnetic Resonance Imaging, 1998Co-Authors: T Kahn, Thorsten Harth, J C W Kiwit, Hansjoachim Schwarzmaier, Christoph Wald, U ModderAbstract:The purpose of this study was the application of the Proton-Resonance-frequency method to monitor laser-induced interstitial thermotherapy (LITT) in a patient with an astrocytoma WHO II. A phase-sensitive two-dimensional (2D) fast low-angle shot (FLASH) sequence was used to determine the temperature-related phase shifts during LITT. Temperature maps were displayed during therapy with a temporal resolution of 20 seconds. Irradiation was discontinued as soon as the 60 to 65 degrees C isotherm reached the margin of the tumor. A contrast-enhanced MRI study performed immediately after therapy showed a good correlation of the size of an enhancing rim around the lesion with the 60 to 65 degrees C isotherm. The preliminary results of our study indicate that MRI guidance of LITT may be improved by temperature quantification based on the Proton-Resonance-frequency method.
Cyril J. Ferrer - One of the best experts on this subject based on the ideXlab platform.
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Field drift correction of Proton Resonance frequency shift temperature mapping with multichannel fast alternating nonselective free induction decay readouts.
Magnetic resonance in medicine, 2019Co-Authors: Cyril J. Ferrer, Lambertus W. Bartels, Tijl A. Van Der Velden, Holger Grüll, Edwin Heijman, Chrit T. W. Moonen, Clemens BosAbstract:Purpose: To demonstrate that Proton Resonance frequency shift MR thermometry (PRFS-MRT) acquisition with nonselective free induction decay (FID), combined with coil sensitivity profiles, allows spatially resolved B0 drift-corrected thermometry. Methods: Phantom experiments were performed at 1.5T and 3T. Acquisition of PRFS-MRT and FID were performed during MR-guided high-intensity focused ultrasound heating. The phase of the FIDs was used to estimate the change in angular frequency δωdrift per coil element. Two correction methods were investigated: (1) using the average δωdrift over all coil elements (0th-order) and (2) using coil sensitivity profiles for spatially resolved correction. Optical probes were used for independent temperature verification. In-vivo feasibility of the methods was evaluated in the leg of 1 healthy volunteer at 1.5T. Results: In 30 minutes, B0 drift led to an apparent temperature change of up to –18°C and –98°C at 1.5T and 3T, respectively. In the sonicated area, both corrections had a median error of 0.19°C at 1.5T and –0.54°C at 3T. At 1.5T, the measured median error with respect to the optical probe was –1.28°C with the 0th-order correction and improved to 0.43°C with the spatially resolved correction. In vivo, without correction the spatiotemporal median of the apparent temperature was at –4.3°C and interquartile range (IQR) of 9.31°C. The 0th-order correction had a median of 0.75°C and IQR of 0.96°C. The spatially resolved method had the lowest median at 0.33°C and IQR of 0.80°C. Conclusion: FID phase information from individual receive coil elements allows spatially resolved B0 drift correction in PRFS-based MRT.
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fluid filling of the digestive tract for improved Proton Resonance frequency shift based mr thermometry in the pancreas
Journal of Magnetic Resonance Imaging, 2018Co-Authors: Cyril J. Ferrer, Lambertus W. Bartels, Baudouin Denis De Senneville, Marijn Van Stralen, Chrit Moonen, Clemens BosAbstract:Purpose To demonstrate that fluid filling of the digestive tract improves the performance of respiratory motion-compensated Proton Resonance frequency shift (PRFS)-based magnetic Resonance (MR) thermometry in the pancreas. Materials and Methods In seven volunteers (without heating), we evaluated PRFS thermometry in the pancreas with and without filling of the surrounding digestive tract. All data acquisition was performed at 1.5T, then all datasets were analyzed and compared with three different PRFS respiratory motion-compensated thermometry methods: gating, multibaseline, and referenceless. The temperature precision of the different methods was evaluated by assessing temperature standard deviation over time, while a simulation experiment was used to study the accuracy of the methods. Results Without fluid intake, errors in temperature precision in the pancreas up to 10°C were observed for all evaluated methods. After liquid intake, temperature precision improved to median values between 1.8 and 2.9°C. The simulations showed that gating had the lowest accuracy, with errors up to 7°C. Multibaseline and referenceless thermometry performed better, with a median error in the pancreas between –3 and +3°C after fluid intake, for all volunteers. Conclusion Preparation of the digestive tract near the pancreas by filling it with fluid improved MR thermometry precision and accuracy for all common respiratory motion-compensated methods evaluated. These improvements are attributed to reducing field inhomogeneity in the pancreas. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017.
