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Mr thermometry

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https://www.readbyqxmd.com/read/28654336/focal-therapy-for-prostate-cancer-with-in-bore-mr-guided-focused-ultrasound-two-year-follow-up-of-a-phase-i-trial-complications-and-functional-outcomes
#1
Kae Jack Tay, Christopher W S Cheng, Weber K O Lau, James Khoo, Choon Hua Thng, Jin Wei Kwek
Purpose To report the safety profile and 2-year functional outcomes of in-bore magnetic resonance (MR)-guided focused ultrasound on single cancer foci in men with prostate cancer. Materials and Methods Ethics approval was obtained from the centralized institutional review board for this prospective single-arm study, and patients provided informed consent. Patients with untreated low-volume low-grade prostate cancer (clinical stage T2a or lower; Gleason score, 3+3; index tumor ≤10 mm(3)) underwent MR-guided focused ultrasound between July 2011 and February 2013...
June 26, 2017: Radiology
https://www.readbyqxmd.com/read/28646608/fluid-filling-of-the-digestive-tract-for-improved-proton-resonance-frequency-shift-based-mr-thermometry-in-the-pancreas
#2
Cyril J Ferrer, Lambertus W Bartels, Marijn van Stralen, Baudouin Denis de Senneville, Chrit T W Moonen, Clemens Bos
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...
June 24, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28643383/multiecho-pseudo-golden-angle-stack-of-stars-thermometry-with-high-spatial-and-temporal-resolution-using-k-space-weighted-image-contrast
#3
Bryant T Svedin, Allison Payne, Bradley D Bolster, Dennis L Parker
PURPOSE: Implement and evaluate a 3D MRI method to measure temperature changes with high spatial and temporal resolution and large field of view. METHODS: A multiecho pseudo-golden angle stack-of-stars (SOS) sequence with k-space weighted image contrast (KWIC) reconstruction was implemented to simultaneously measure multiple quantities, including temperature, initial signal magnitude M(0), transverse relaxation time ( T2*), and water/fat images. Respiration artifacts were corrected using self-navigation...
June 22, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28643045/validation-of-a-mathematical-model-for-laser-induced-thermotherapy-in-liver-tissue
#4
F Hübner, C Leithäuser, B Bazrafshan, N Siedow, T J Vogl
The purpose of the study was to develop a simulation approach for laser-induced thermotherapy (LITT) that is based on mathematical models for radiation transport, heat transport, and tissue damage. The LITT ablation was applied to ex vivo pig liver tissue. Experiments were repeated with different laser powers, i.e., 22-34 W, and flow rates of the cooling water in the applicator system, i.e., 47-92 ml/min. During the procedure, the temperature was measured in the liver sample at different distances to the applicator as well as in the cooling circuit using a fiber optic thermometer...
June 22, 2017: Lasers in Medical Science
https://www.readbyqxmd.com/read/28598900/interleaved-mapping-of-temperature-and-longitudinal-relaxation-rate-to-monitor-drug-delivery-during-magnetic-resonance-guided-high-intensity-focused-ultrasound-induced-hyperthermia
#5
Esther Kneepkens, Edwin Heijman, Jochen Keupp, Steffen Weiss, Klaas Nicolay, Holger Grüll
OBJECTIVES: Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a method to heat lesions noninvasively to a stable, elevated temperature and a well-suited method to induce local hyperthermia (41°C-43°C) in deep-seated tissues. Magnetic Resonance (MR) imaging provides therapy planning on anatomical images and offers temperature feedback based on near-real-time MR thermometry. Although constant acquisition of MR thermometry data is crucial to ensure prolonged hyperthermia, it limits the freedom to perform measurements of other MR parameters, which are of interest during hyperthermia treatments...
June 8, 2017: Investigative Radiology
https://www.readbyqxmd.com/read/28595499/thermal-diffusivity-and-perfusion-constants-from-in-vivo-mr-guided-focused-ultrasound-treatments-a-feasibility-study
#6
Christopher R Dillon, Viola Rieke, Pejman Ghanouni, Allison Payne
PURPOSE: This study investigates the feasibility of non-invasively determining thermal diffusivity (α) and the Pennes perfusion parameter (w) from preclinical and clinical magnetic resonance-guided focused ultrasound (MRgFUS) temperature data. MATERIALS AND METHODS: Pre-clinical MRgFUS experiments were performed in rabbit muscle (N = 3, 28 sonications) using three-dimensional MR thermometry. 8 sonications were made in a clinical QA phantom with two-dimensional thermometry...
June 8, 2017: International Journal of Hyperthermia
https://www.readbyqxmd.com/read/28590938/combined-passive-acoustic-mapping-and-magnetic-resonance-thermometry-for-monitoring-phase-shift-nanoemulsion-enhanced-focused-ultrasound-therapy
#7
Calum Crake, F Can Meral, Mark Burgess, Iason Papademetriou, Nathan McDannold, Tyrone Porter
Focused ultrasound (FUS) has the potential to enable precise, image-guided noninvasive surgery for the treatment of cancer in which tumors are identified and destroyed in a single integrated procedure. However, success of the method in highly vascular organs has been limited due to heat losses to perfusion, requiring development of techniques to locally enhance energy absorption and heating. In addition, FUS procedures are conventionally monitored using MRI, which provides excellent anatomical images and can map temperature, but is not capable of capturing the full gamut of available data such as the acoustic emissions generated during this inherently acoustically-driven procedure...
June 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28580706/mr-techniques-for-guiding-high-intensity-focused-ultrasound-hifu-treatments
#8
REVIEW
Kagayaki Kuroda
To make full use of the ability of magnetic resonance (MR) to guide high-intensity focused ultrasound (HIFU) treatment, effort has been made to improve techniques for thermometry, motion tracking, and sound beam visualization. For monitoring rapid temperature elevation with proton resonance frequency (PRF) shift, data acquisition and processing can be accelerated with parallel imaging and/or sparse sampling in conjunction with appropriate signal processing methods. Thermometry should be robust against tissue motion, motion-induced magnetic field variation, and susceptibility change...
June 5, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28572977/acoustic-and-thermal-characterization-of-agar-based-phantoms-used-for-evaluating-focused-ultrasound-exposures
#9
Georgios Menikou, Christakis Damianou
BACKGROUND: This study describes a series of experimental work completed towards characterizing candidate materials for fabricating brain and muscle tissue mimicking phantoms. METHODS: The acoustic speed, attenuation, impedance, thermal diffusivity, specific heat and thermal conductivity were measured. RESULTS: The resulting brain (2% w/v agar-1.2% w/v Silica Dioxide-25%v/v evaporated milk) and muscle tissue recipe (2% w/v agar-2% w/v Silica Dioxide-40%v/v evaporated milk) introduced a total attenuation coefficient of 0...
2017: Journal of Therapeutic Ultrasound
https://www.readbyqxmd.com/read/28560040/spatially-segmented-undersampled-mri-temperature-reconstruction-for-transcranial-mr-guided-focused-ultrasound
#10
Pooja Gaur, Beat Werner, Xue Feng, Samuel W Fielden, Craig H Meyer, William A Grissom
BACKGROUND: Volumetric thermometry with fine spatiotemporal resolution is desirable to monitor MR-guided focused ultrasound (MRgFUS) procedures in the brain, but requires some form of accelerated imaging. Accelerated MR temperature imaging methods have been developed that undersample k-space and leverage signal correlations over time to suppress the resulting undersampling artifacts. However, in transcranial MRgFUS treatments, the water bath surrounding the skull creates signal variations that do not follow those correlations, leading to temperature errors in the brain due to signal aliasing...
2017: Journal of Therapeutic Ultrasound
https://www.readbyqxmd.com/read/28557798/thermal-ablation-of-a-confluent-lesion-in-the-porcine-kidney-with-a-clinically-available-mr-hifu-system
#11
J M M van Breugel, M de Greef, J W Wijlemans, G Schubert, M A A J van den Bosch, C T W Moonen, M G Ries
The incidence of small renal masses (SRMs) sized  <4 cm has increased over the decades (as co-findings/or due to introduction of cross sectional imaging). Currently, partial nephrectomy (PN) or watchful waiting is advised in these patients. Ultimately, 80-90% of these SRMs require surgical treatment and PN is associated with a 15% complication rate. In this aging population, with possible comorbidities and poor health condition, both PN and watchful waiting are non-ideal treatment options. This resulted in an increased need for early, non-invasive treatment strategies such as MR-guided high intensity focused ultrasound (MR-HIFU)...
July 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28541897/capacitive-micro-machined-ultrasound-transducers-for-interstitial-high-intensity-ultrasound-therapies
#12
W Apoutou N'Djin, Bjoern Gerold, Jeremy Vion, Michael Canney, An Nguyen-Dinh, Alexandre Carpentier, Jean-Yves Chapelon
Capacitive Micro-machined Ultrasound Transducers (CMUTs) exhibit several potential advantages over conventional piezo technologies for use in therapeutic ultrasound devices, including: ease of miniaturization and integration with electronics, broad bandwidth (>several MHz), and compatibility with magnetic resonance imaging (MRI). In this work, the electro-acoustic performance of CMUTs designed for interstitial high intensity contact ultrasound (HICU) applications was evaluated and the feasibility of generating ultrasound-induced heating and thermal destruction of biological tissues was studied...
May 24, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28540820/theoretical-model-for-laser-ablation-outcome-predictions-in-brain-calibration-and-validation-on-clinical-mr-thermometry-images
#13
Samuel John Fahrenholtz, Reza Madankan, Shabbar Danish, John D Hazle, R Jason Stafford, David Fuentes
PURPOSE: Neurosurgical laser ablation is experiencing a renaissance. Computational tools for ablation planning aim to further improve the intervention. Here, global optimisation and inverse problems are demonstrated to train a model that predicts maximum laser ablation extent. METHODS: A closed-form steady state model is trained on and then subsequently compared to N = 20 retrospective clinical MR thermometry datasets. Dice similarity coefficient (DSC) is calculated to provide a measure of region overlap between the 57 °C isotherms of the thermometry data and the model-predicted ablation regions; 57 °C is a tissue death surrogate at thermal steady state...
May 19, 2017: International Journal of Hyperthermia
https://www.readbyqxmd.com/read/28516051/evaluation-of-mr-thermometry-with-proton-resonance-frequency-method-at-7t
#14
Ping Wang
Quantitative and non-invasive temperature mapping using magnetic resonance imaging (MRI) provides a unique way to measure temperature evolution inside biological tissues. The method is widely used in thermal ablation procedures with magnetic fields at or below 3T. In this paper, the sensitivity of the MRI thermometry at 7T was studied using a proton resonance frequency (PRF)-based technique. We first used an agarose gel phantom with MR-compatible thermometry to calibrate the temperature coefficient, and then this temperature coefficient was employed to measure the internal temperature in both ex vivo (beef muscle) and in vivo (rat) experiments using focused ultrasound heating...
April 2017: Quantitative Imaging in Medicine and Surgery
https://www.readbyqxmd.com/read/28513855/technical-note-system-for-evaluating-local-hypothermia-as-a-radioprotector-of-the-rectum-in-a-small-animal-model
#15
Brian A Hrycushko, Chenchen Bing, Cecil Futch, Michelle Wodzak, Strahinja Stojadinovic, Paul M Medin, Rajiv Chopra
PURPOSE: The protective effects of induced or even accidental hypothermia on the human body are widespread with several medical uses currently under active research. In vitro experiments using human cell lines have shown hypothermia provides a radioprotective effect that becomes more pronounced at large, single-fraction doses common to stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) treatments. This work describes the development of a system to evaluate local hypothermia for a radioprotive effect of the rat rectum during a large dose of radiation relevant to prostate SBRT...
May 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28415147/neurosurgical-laser-ablation-and-mr-thermometry-risks-of-multisite-workflow-pattern
#16
Paul S Larson, Sudhakar Vadivelu, Hooman Azmi-Ghadimi, Amy Nichols, Loretta Fauerbach, Helen Boehm Johnson
Neurosurgical laser ablation is a relatively new but rapidly growing application of stereotactic neurosurgery that allows neurosurgeons to treat many previously untreatable conditions with the added benefit of shorter hospitalizations and recovery times. The vast majority of these procedures, however, are performed using a multisite workflow pattern involving transport of the patient between the operating room (OR), the computed tomography (CT) suite, and the magnetic resonance imaging (MRI) suite, often necessitating patient transfer through public pathways and requiring multiple trips if laser fiber placement is not accurate...
April 2017: Journal of Healthcare Risk Management: the Journal of the American Society for Healthcare Risk Management
https://www.readbyqxmd.com/read/28413682/multi-focal-hifu-reduces-cavitation-in-mild-hyperthermia
#17
Vandiver Chaplin, Charles F Caskey
BACKGROUND: Mild-hyperthermia therapy (40-45 °C) with high-intensity focused ultrasound (HIFU) is a technique being considered in a number of different treatments such as thermally activated drug delivery, immune-stimulation, and as a chemotherapy adjuvant. Mechanical damage and loss of cell viability associated with HIFU-induced acoustic cavitation may pose a risk during these treatments or may hinder their success. Here we present a method that achieves mild heating and reduces cavitation by using a multi-focused HIFU beam...
2017: Journal of Therapeutic Ultrasound
https://www.readbyqxmd.com/read/28324929/hyperthermia-by-electromagnetic-fields-to-enhanced-clinical-results-in-oncology
#18
Gerard C van Rhoon, Maarten M Paulides, Jeannette M L van Holthe, Martine Franckena
Confining treatment to the tumor to improve therapeutic outcome and reduce toxicity, is a hot issue in cancer research. Hyperthermia is recognized as a strong sensitizer for radiotherapy and chemotherapy enhancing tumor control without increasing toxicity. Today's electromagnetic hyperthermia systems heat large tissue volumes with limited ability to selectively heat the tumor. Fortunately, tremendous improvements in 3-dimensional electromagnetic & temperature modelling provide an exciting opportunity to design advanced multi-element electromagnetic applicator systems...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28317125/referenceless-magnetic-resonance-temperature-imaging-using-gaussian-process-modeling
#19
Joshua P Yung, David Fuentes, Christopher J MacLellan, Florian Maier, Yannis Liapis, John D Hazle, R Jason Stafford
PURPOSE: During magnetic resonance (MR)-guided thermal therapies, water proton resonance frequency shift (PRFS) based MR temperature imaging can quantitatively monitor tissue temperature changes. It is widely known that the PRFS technique is easily perturbed by tissue motion, tissue susceptibility changes, magnetic field drift, and modality-dependent applicator induced artifacts. Here a referenceless Gaussian process modeling (GPM) based estimation of the PRFS is investigated as a methodology to mitigate unwanted background field changes...
March 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28237922/an-adaptive-non-local-means-filter-for-real-time-mr-thermometry
#20
Cornel Zachiu, Mario Ries, Chrit Moonen, Baudouin Denis de Senneville
Proton resonance frequency shift-based magnetic resonance thermometry is a currently used technique for monitoring temperature during targeted thermal therapies. However, in order to provide temperature updates with very short latency times, fast MR acquisition schemes are usually employed, which in turn might lead to noisy temperature measurements. This will, in general, have a direct impact on therapy control and endpoint detection. In this paper, we address this problem through an improved non-local filtering technique applied on the temperature images...
April 2017: IEEE Transactions on Medical Imaging
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