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Abbott A, Abe H, Aldous L, Atkin R, Bendová M, Busato M, Canongia Lopes JN, Costa Gomes M, Cross B, Dietz C, Everts J, Firestone M, Gardas R, Gras M, Greaves T, Halstead S, Hardacre C, Harper J, Holbrey J, Jacquemin J, Jessop P, MacFarlane D, Maier F, Medhi H, Mezger M, Pádua A, Perkin S, Reid JESJ, Saha S, Slattery JM, Thomas ML, Tiwari S, Tsuzuki S, Uralcan B, Watanabe M, Wishart J, Youngs T. Phase behaviour and thermodynamics: general discussion. Faraday Discuss 2017; 206:113-139. [PMID: 29185568 DOI: 10.1039/c7fd90091k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Freitag MT, Fenchel M, Bäumer P, Heußer T, Rank CM, Kachelrieß M, Paech D, Kopka K, Bickelhaupt S, Dimitrakopoulou-Strauss A, Maier-Hein K, Floca R, Ladd ME, Schlemmer HP, Maier F. Improved clinical workflow for simultaneous whole-body PET/MRI using high-resolution CAIPIRINHA-accelerated MR-based attenuation correction. Eur J Radiol 2017; 96:12-20. [PMID: 29103469 DOI: 10.1016/j.ejrad.2017.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 08/17/2017] [Accepted: 09/12/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE To explore the value and reproducibility of a novel magnetic resonance based attenuation correction (MRAC) using a CAIPIRINHA-accelerated T1-weighted Dixon 3D-VIBE sequence for whole-body PET/MRI compared to the clinical standard. METHODS The PET raw data of 19 patients from clinical routine were reconstructed with standard MRAC (MRACstd) and the novel MRAC (MRACcaipi), a prototype CAIPIRINHA accelerated Dixon 3D-VIBE sequence, both acquired in 19 s/bed position. Volume of interests (VOIs) for liver, lung and all voxels of the total image stack were created to calculate standardized uptake values (SUVmean) followed by inter-method agreement (Passing-Bablok regression, Bland-Altman analysis). A voxel-wise SUV comparison per patient was performed for intra-individual correlation between MRACstd and MRACcaipi. Difference images (MRACstd-MRACcaipi) of attenuation maps and SUV images were calculated. The image quality of in/opposed-phase water and fat images obtained from MRACcaipi was assessed by two readers on a 5-point Likert-scale including intra-class coefficients for inter-reader agreement. RESULTS SUVmean correlations of VOIs demonstrated high linearity (0.95<Spearman's rho<1, p<0.0001, respectively), substantiated by voxel-wise SUV scatter-plots (1.79×108 pixels). Outliers could be explained by different physiological conditions between the scans such as different segmentation of air-containing tissue, lungs, kidneys, metal implants, diaphragm edge or small air bubbles in the gastrointestinal tracts that moved between MRAC acquisitions. Nasal sinuses and the trachea were better segmented in MRACcaipi. High-resolution T1w Dixon 3D VIBE images were acquired in all cases and could be used for PET/MRI fusion. MRACcaipi images were of high diagnostic quality (4.2±0.8) with 0.92-0.96 intra-class correlation. CONCLUSIONS The novel prototype MRACcaipi extends the value for attenuation correction by providing a high spatial resolution DIXON-based dataset suited for diagnostic assessment towards time-efficient whole-body PET/MRI.
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Mikoteit T, Maier F, Miché M, Wersebe H, Imboden C, Hatzinger M, Holsboer-Trachsler E, Lieb R, Gloster A. Impact of irregular sleep patterns on emotion regulation and cognitive flexibility in patients with major depression and in healthy controls. PHARMACOPSYCHIATRY 2017. [DOI: 10.1055/s-0037-1606398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Wagner F, Laun FB, Kuder TA, Mlynarska A, Maier F, Faust J, Demberg K, Lindemann L, Rivkin B, Nagel AM, Ladd ME, Maier-Hein K, Bickelhaupt S, Bach M. Temperature and concentration calibration of aqueous polyvinylpyrrolidone (PVP) solutions for isotropic diffusion MRI phantoms. PLoS One 2017; 12:e0179276. [PMID: 28628638 PMCID: PMC5476261 DOI: 10.1371/journal.pone.0179276] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 05/27/2017] [Indexed: 12/12/2022] Open
Abstract
To use the "apparent diffusion coefficient" (Dapp) as a quantitative imaging parameter, well-suited test fluids are essential. In this study, the previously proposed aqueous solutions of polyvinylpyrrolidone (PVP) were examined and temperature calibrations were obtained. For example, at a temperature of 20°C, Dapp ranged from 1.594 (95% CI: 1.593, 1.595) μm2/ms to 0.3326 (95% CI: 0. 3304, 0.3348) μm2/ms for PVP-concentrations ranging from 10% (w/w) to 50% (w/w) using K30 polymer lengths. The temperature dependence of Dapp was found to be so strong that a negligence seems not advisable. The temperature dependence is descriptively modelled by an exponential function exp(c2 (T - 20°C)) and the determined c2 values are reported, which can be used for temperature calibration. For example, we find the value 0.02952 K-1 for 30% (w/w) PVP-concentration and K30 polymer length. In general, aqueous PVP solutions were found to be suitable to produce easily applicable and reliable Dapp-phantoms.
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Maier F, Niedermaier I, Steinrück HP. Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface. J Chem Phys 2017; 146:170901. [DOI: 10.1063/1.4982355] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Niedermaier I, Kolbeck C, Steinrück HP, Maier F. Erratum: "Dual analyzer system for surface analysis dedicated for angle-resolved photoelectron spectroscopy at liquid surfaces and interfaces" [Rev. Sci. Instrum. 87, 045105 (2016)]. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:059902. [PMID: 28571449 DOI: 10.1063/1.4983571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
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Kaleem B, Maier F, Drissi H, Pierce DM. Low-energy impact of human cartilage: predictors for microcracking the network of collagen. Osteoarthritis Cartilage 2017; 25:544-553. [PMID: 27903450 DOI: 10.1016/j.joca.2016.11.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 11/08/2016] [Accepted: 11/21/2016] [Indexed: 02/02/2023]
Abstract
OBJECTIVE We aimed to determine the minimum mechanical impact to cause microstructural damage in the network of collagen (microcracking) within human cartilage and hypothesized that energies below 0.1 J or 1 mJ/mm3 would suffice. DESIGN We completed 108 low-energy impact tests (0.05, 0.07, or 0.09 J; 0.75 or 1.0 m/s2) using healthy cartilage specimens from six male donors (30.2 ± 8.8 yrs old). Before and after impact we acquired, imaging the second harmonic generation (SHG), ten images from each specimen (50 μm depth, 5 μm step size), resulting in 2160 images. We quantified both the presence and morphology of microcracks. We then correlated test parameters (predictors) impact energy/energy dissipation density, nominal stress/stress rate, and strain/strain rate to microcracking and tested for significance. Where predictors significantly correlated with microstructural outcomes we fitted binary logistic regression plots with 95% confidence intervals (CIs). RESULTS No specimens presented visible damage following impact. We found that impact energy/energy dissipation density and nominal stress/stress rate were significant (P < 0.05) predictors of microcracking while both strain and strain rate were not. In our test configuration, an impact energy density of 2.93 mJ/mm3, an energy dissipation density of 1.68 mJ/mm3, a nominal stress of 4.18 MPa, and a nominal stress rate of 689 MPa/s all corresponded to a 50% probability of microcracking in the network of collagen. CONCLUSIONS An impact energy density of 1.0 mJ/mm3 corresponded to a ∼20% probability of microcracking. Such changes may initiate a degenerative cascade leading to post-traumatic osteoarthritis.
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Yung JP, Fuentes D, MacLellan CJ, Maier F, Liapis Y, Hazle JD, Stafford RJ. Referenceless magnetic resonance temperature imaging using Gaussian process modeling. Med Phys 2017; 44:3545-3555. [PMID: 28317125 DOI: 10.1002/mp.12231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 12/15/2016] [Accepted: 01/09/2017] [Indexed: 11/12/2022] Open
Abstract
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. The GPM offers a complementary trade-off between data fitting and smoothing and allows prior information to be used. The end result being the GPM provides a full probabilistic prediction and an estimate of the uncertainty. METHODS GPM was employed to estimate the covariance between the spatial position and MR phase measurements. The mean and variance provided by the statistical model extrapolated background phase values from nonheated neighboring voxels used to train the model. MR phase predictions in the heating ROI are computed using the spatial coordinates as the test input. The method is demonstrated in ex vivo rabbit liver tissue during focused ultrasound heating with manually introduced perturbations (n = 6) and in vivo during laser-induced interstitial thermal therapy to treat the human brain (n = 1) and liver (n = 1). RESULTS Temperature maps estimated using the GPM referenceless method demonstrated a RMS error of <0.8°C with artifact-induced reference-based MR thermometry during ex vivo heating using focused ultrasound. Nonheated surrounding areas were <0.5°C from the artifact-free MR measurements. The GPM referenceless MR temperature values and thermally damaged regions were within the 95% confidence interval during in vivo laser ablations. CONCLUSIONS A new approach to estimation for referenceless PRFS temperature imaging is introduced that allows for an accurate probabilistic extrapolation of the background phase. The technique demonstrated reliable temperature estimates in the presence of the background phase changes and was demonstrated useful in the in vivo brain and liver ablation scenarios presented.
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May B, Hönle M, Heller B, Greco F, Bhuin R, Steinrück HP, Maier F. Surface-Induced Changes in the Thermochromic Transformation of an Ionic Liquid Cobalt Thiocyanate Complex. J Phys Chem Lett 2017; 8:1137-1141. [PMID: 28212033 PMCID: PMC5357805 DOI: 10.1021/acs.jpclett.7b00142] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 02/17/2017] [Indexed: 06/06/2023]
Abstract
We demonstrate that a thermodynamic complex equilibrium within an ionic liquid film can be significantly influenced by the presence of the liquid-vacuum interface. Using surface-sensitive X-ray photoelectron spectroscopy, we find that the temperature-driven transition from the blue-colored tetrahedral [Co(II) (NCS)4]2- to the red-colored octahedral [Co(II) (NCS)6]4- complex already occurs within the outermost nanometers at around +4 °C as compared with -25 °C in the bulk. This thermochromic transformation in the near-surface region goes along with a loss in preferential surface orientation of free [SCN]- anions and with a pronounced decrease in the complex density; both effects are attributed to the formation of a weakly bound solvation shell around the [Co(II) (NCS)6]4- anion, leading to an effective complex dilution. Our results are not only relevant for high-surface area thin film systems, such as in sensor and catalysis applications, but also shed light on the role of ionic liquid surfaces in particular and liquid surfaces in general.
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Polak D, Setsompop K, Cauley SF, Gagoski BA, Bhat H, Maier F, Bachert P, Wald LL, Bilgic B. Wave-CAIPI for highly accelerated MP-RAGE imaging. Magn Reson Med 2017; 79:401-406. [PMID: 28220617 DOI: 10.1002/mrm.26649] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 01/24/2017] [Accepted: 01/26/2017] [Indexed: 11/10/2022]
Abstract
PURPOSE To introduce a highly accelerated T1-weighted magnetization-prepared rapid gradient echo (MP-RAGE) acquisition that uses wave-controlled aliasing in parallel imaging (wave-CAIPI) encoding to retain high image quality. METHODS Significant acceleration of the MP-RAGE sequence is demonstrated using the wave-CAIPI technique. Here, sinusoidal waveforms are used to spread aliasing in all three directions to improve the g-factor. Combined with a rapid (2 s) coil sensitivity acquisition and data-driven trajectory calibration, we propose an online integrated acquisition-reconstruction pipeline for highly efficient MP-RAGE imaging. RESULTS The 9-fold accelerated MP-RAGE acquisition can be performed in 71 s, with a maximum and average g-factor of gmax = 1.27 and gavg = 1.06 at 3T. Compared with the state-of-the-art method controlled aliasing in parallel imaging results in higher acceleration (2D-CAIPIRINHA), this is a factor of 4.6/1.4 improvement in gmax /gavg . In addition, we demonstrate a 57 s acquisition at 7T with 12-fold acceleration. This acquisition has a g-factor performance of gmax = 1.15 and gavg = 1.04. CONCLUSION Wave encoding overcomes the g-factor noise amplification penalty and allows for an order of magnitude acceleration of MP-RAGE acquisitions. Magn Reson Med 79:401-406, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Rietzler F, May B, Steinrück HP, Maier F. Switching adsorption and growth behavior of ultrathin [C 2C 1Im][OTf] films on Au(111) by Pd deposition. Phys Chem Chem Phys 2016; 18:25143-25150. [PMID: 27711556 DOI: 10.1039/c6cp04938a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Combining in vacuo deposition of ultrathin ionic liquid (UTIL) films with angle-resolved X-ray photoelectron spectroscopy (ARXPS), we demonstrate that by deposition of submonolayer amounts of Pd onto Au(111) the initial growth mode of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2C1Im][OTf]) can be switched from three-dimensional (3D) to two-dimensional (2D) growth, that is, from non-wetting to wetting. On clean Au(111), pronounced 3D growth occurs on top of an initially formed 2D wetting layer with cations and anions next to each other in a checkerboard arrangement. After pre- or postdeposition of only 0.7 ML Pd, two-dimensional layer-by-layer growth is found, which is attributed to strong attractive interactions between [C2C1Im][OTf] and surface Pd. For Pd post deposition onto the IL, the ARXPS data revealed particularly strong interactions between the dialkylimidazolium cation and Pd atoms, which considerably reduce the regular surface alloying of Pd with the Au substrate stabilizing Pd at the metal surface. In the context of heterogeneous catalysis using the SCILL (solid catalyst coated with ionic liquid layer) concept, these results directly provide a possible explanation on the molecular level for the beneficial influence of the IL layer in case of heterogeneous metal alloy catalysts.
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Schweifer A, Maier F, Ehrlichmann W, Lamparter D, Kneilling M, Pichler BJ, Hammerschmidt F, Reischl G. [ 18F]Fluoro-azomycin-2´-deoxy-β-d-ribofuranoside - A new imaging agent for tumor hypoxia in comparison with [ 18F]FAZA. Nucl Med Biol 2016; 43:759-769. [PMID: 27693670 DOI: 10.1016/j.nucmedbio.2016.08.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 07/25/2016] [Accepted: 08/07/2016] [Indexed: 01/30/2023]
Abstract
INTRODUCTION Radiolabeled 2-nitroimidazoles (azomycins) are a prominent class of biomarkers for PET imaging of hypoxia. [18F]Fluoro-azomycin-α-arabinoside ([18F]FAZA) - already in clinical use - may be seen as α-configuration nucleoside, but enters cells only via diffusion and is not transported by cellular nucleoside transporters. To enhance image contrast in comparison to [18F]FAZA our objective was to 18F-radiolabel an azomycin-2´-deoxyriboside with β-configuration ([18F]FAZDR, [18F]-β-8) to mimic nucleosides more closely and comparatively evaluate it versus [18F]FAZA. METHODS Precursor and cold standards for [18F]FAZDR were synthesized from methyl 2-deoxy-d-ribofuranosides α- and β-1 in 6 steps yielding precursors α- and β-5. β-5 was radiolabeled in a GE TRACERlab FXF-N synthesizer in DMSO and deprotected with NH4OH to give [18F]FAZDR ([18F]-β-8). [18F]FAZA or [18F]FAZDR was injected in BALB/c mice bearing CT26 colon carcinoma xenografts, PET scans (10min) were performed after 1, 2 and 3h post injection (p.i.). On a subset of mice injected with [18F]FAZDR, we analyzed biodistribution. RESULTS [18F]FAZDR was obtained in non-corrected yields of 10.9±2.4% (9.1±2.2GBq, n=4) 60min EOB, with radiochemical purity >98% and specific activity >50GBq/μmol. Small animal PET imaging showed a decrease in uptake over time for both [18F]FAZDR (1h p.i.: 0.56±0.22% ID/cc, 3h: 0.17±0.08% ID/cc, n=9) and [18F]FAZA (1h: 1.95±0.59% ID/cc, 3h: 0.87±0.55% ID/cc), whereas T/M ratios were significantly higher for [18F]FAZDR at 1h (2.76) compared to [18F]FAZA (1.69, P<0.001), 3h p.i. ratios showed no significant difference. Moreover, [18F]FAZDR showed an inverse correlation between tracer uptake in carcinomas and oxygen breathing, while muscle tissue uptake was not affected by switching from air to oxygen. CONCLUSIONS First PET imaging results with [18F]FAZDR showed advantages over [18F]FAZA regarding higher tumor contrast at earlier time points p.i. Availability of precursor and cold fluoro standard together with high output radiosynthesis will allow for a more detailed quantitative evaluation of [18F]FAZDR, especially with regard to mechanistic studies whether active transport processes are involved, compared to passive diffusion as observed for [18F]FAZA.
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Stahl V, Maier F, Freitag MT, Floca RO, Berger MC, Umathum R, Berriel Diaz M, Herzig S, Weber MA, Dimitrakopoulou-Strauss A, Rink K, Bachert P, Ladd ME, Nagel AM. In vivoassessment of cold stimulation effects on the fat fraction of brown adipose tissue using DIXON MRI. J Magn Reson Imaging 2016; 45:369-380. [DOI: 10.1002/jmri.25364] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 06/15/2016] [Indexed: 12/13/2022] Open
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Akhgar G, Klochan O, Willems van Beveren LH, Edmonds MT, Maier F, Spencer BJ, McCallum JC, Ley L, Hamilton AR, Pakes CI. Strong and Tunable Spin-Orbit Coupling in a Two-Dimensional Hole Gas in Ionic-Liquid Gated Diamond Devices. NANO LETTERS 2016; 16:3768-3773. [PMID: 27186800 DOI: 10.1021/acs.nanolett.6b01155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Hydrogen-terminated diamond possesses due to transfer doping a quasi-two-dimensional (2D) hole accumulation layer at the surface with a strong, Rashba-type spin-orbit coupling that arises from the highly asymmetric confinement potential. By modulating the hole concentration and thus the potential using an electrostatic gate with an ionic-liquid dielectric architecture the spin-orbit splitting can be tuned from 4.6-24.5 meV with a concurrent spin relaxation length of 33-16 nm and hole sheet densities of up to 7.23 × 10(13) cm(-2). This demonstrates a spin-orbit interaction of unprecedented strength and tunability for a 2D hole system at the surface of a wide band gap semiconductor. With a spin relaxation length that is experimentally accessible using existing nanofabrication techniques, this result suggests that hydrogen-terminated diamond has great potential for the study and application of spin transport phenomena.
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Niedermaier I, Kolbeck C, Steinrück HP, Maier F. Dual analyzer system for surface analysis dedicated for angle-resolved photoelectron spectroscopy at liquid surfaces and interfaces. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:045105. [PMID: 27131705 DOI: 10.1063/1.4942943] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The investigation of liquid surfaces and interfaces with the powerful toolbox of ultra-high vacuum (UHV)-based surface science techniques generally has to overcome the issue of liquid evaporation within the vacuum system. In the last decade, however, new classes of liquids with negligible vapor pressure at room temperature-in particular, ionic liquids (ILs)-have emerged for surface science studies. It has been demonstrated that particularly angle-resolved X-ray Photoelectron Spectroscopy (ARXPS) allows for investigating phenomena that occur at gas-liquid and liquid-solid interfaces on the molecular level. The results are not only relevant for IL systems but also for liquids in general. In all of these previous ARXPS studies, the sample holder had to be tilted in order to change the polar detection angle of emitted photoelectrons, which restricted the liquid systems to very thin viscous IL films coating a flat solid support. We now report on the concept and realization of a new and unique laboratory "Dual Analyzer System for Surface Analysis (DASSA)" which enables fast ARXPS, UV photoelectron spectroscopy, imaging XPS, and low-energy ion scattering at the horizontal surface plane of macroscopically thick non-volatile liquid samples. It comprises a UHV chamber equipped with two electron analyzers mounted for simultaneous measurements in 0° and 80° emission relative to the surface normal. The performance of DASSA on a first macroscopic liquid system will be demonstrated.
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Scheuermeyer M, Kusche M, Agel F, Schreiber P, Maier F, Steinrück HP, Davis JH, Heym F, Jess A, Wasserscheid P. Thermally stable bis(trifluoromethylsulfonyl)imide salts and their mixtures. NEW J CHEM 2016. [DOI: 10.1039/c6nj00579a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The investigated salts form a eutectic mixture which melts below 100 °C, and surface analysis shows the depletion of phosphonium cations.
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Fahrenholtz SJ, Moon TY, Franco M, Medina D, Danish S, Gowda A, Shetty A, Maier F, Hazle JD, Stafford RJ, Warburton T, Fuentes D. A model evaluation study for treatment planning of laser-induced thermal therapy. Int J Hyperthermia 2015; 31:705-14. [PMID: 26368014 DOI: 10.3109/02656736.2015.1055831] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A cross-validation analysis evaluating computer model prediction accuracy for a priori planning magnetic resonance-guided laser-induced thermal therapy (MRgLITT) procedures in treating focal diseased brain tissue is presented. Two mathematical models are considered. (1) A spectral element discretisation of the transient Pennes bioheat transfer equation is implemented to predict the laser-induced heating in perfused tissue. (2) A closed-form algorithm for predicting the steady-state heat transfer from a linear superposition of analytic point source heating functions is also considered. Prediction accuracy is retrospectively evaluated via leave-one-out cross-validation (LOOCV). Modelling predictions are quantitatively evaluated in terms of a Dice similarity coefficient (DSC) between the simulated thermal dose and thermal dose information contained within N = 22 MR thermometry datasets. During LOOCV analysis, the transient model's DSC mean and median are 0.7323 and 0.8001 respectively, with 15 of 22 DSC values exceeding the success criterion of DSC ≥ 0.7. The steady-state model's DSC mean and median are 0.6431 and 0.6770 respectively, with 10 of 22 passing. A one-sample, one-sided Wilcoxon signed-rank test indicates that the transient finite element method model achieves the prediction success criteria, DSC ≥ 0.7, at a statistically significant level.
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Gray JP, Dana N, Dextraze KL, Maier F, Emelianov S, Bouchard RR. Multi-Wavelength Photoacoustic Visualization of High Intensity Focused Ultrasound Lesions. ULTRASONIC IMAGING 2015; 38:96-112. [PMID: 26149314 DOI: 10.1177/0161734615593747] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
High intensity focused ultrasound (HIFU) thermal therapies are limited by deficiencies in existing image-guidance techniques. Previous studies using single-wavelength photoacoustic (PA) imaging have demonstrated that HIFU lesions generate contrast with respect to native tissues but have not sufficiently assessed lesion extent. The purpose of this study is to demonstrate feasibility of characterization of in vitro HIFU ablation lesion dimensions using 3D multi-wavelength PA imaging. Fresh porcine cardiac and liver tissue samples were embedded in agar phantoms and ablated using a 2.5 MHz small-animal HIFU system. Both 2D and 3D multi-wavelength photoacoustic-ultrasonic (PAUS) scans were performed in the near-infrared (NIR) range to characterize the change in the absorption spectrum of tissues following ablation and were compared to stained gross pathology to assess treatment margins and lesion extent. Comprehensive 2D multi-wavelength PA imaging yielded a spectrum in ablated tissue that did not display the characteristic local maximum in the optical absorption spectrum of deoxy-hemoglobin (Hb) near 760 nm. Two-dimensional tissue characterization map (TCM) images reconstructed from 3D TCM volumes reliably characterized lesion area and showed >70% area agreement with stained gross pathology. In addition, tissue samples were heated via water bath and concurrently interrogated with 2D PAUS imaging. PA signal exhibited an initial amplitude increase across all wavelengths, corresponding to an initial temperature increase, before then exhibiting a spectral change. This study suggests that multi-wavelength PA imaging has potential to obtain accurate characterization of HIFU lesion extent and may be better suited to guide HIFU ablation therapies during clinical treatments than single-wavelength methods.
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Matsuda T, Taccardi N, Schwegler J, Wasserscheid P, Steinrück HP, Maier F. Inside Cover: Vacuum Surface Science Meets Heterogeneous Catalysis: Dehydrogenation of a Liquid Organic Hydrogen Carrier in the Liquid State (ChemPhysChem 9/2015). Chemphyschem 2015. [DOI: 10.1002/cphc.201590047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Matsuda T, Taccardi N, Schwegler J, Wasserscheid P, Steinrück HP, Maier F. Vacuum Surface Science Meets Heterogeneous Catalysis: Dehydrogenation of a Liquid Organic Hydrogen Carrier in the Liquid State. Chemphyschem 2015; 16:1873-9. [DOI: 10.1002/cphc.201500236] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Indexed: 11/08/2022]
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Maier F, Fuentes D, Weinberg JS, Hazle JD, Stafford RJ. Robust phase unwrapping for MR temperature imaging using a magnitude-sorted list, multi-clustering algorithm. Magn Reson Med 2015; 73:1662-8. [PMID: 24809984 PMCID: PMC4224999 DOI: 10.1002/mrm.25279] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 11/09/2022]
Abstract
PURPOSE Several methods in MRI use the phase information of the complex signal and require phase unwrapping (e.g., B0 field mapping, chemical shift imaging, and velocity measurements). In this work, an algorithm was developed focusing on the needs and requirements of MR temperature imaging applications. METHODS The proposed method performs fully automatic unwrapping using a list of all pixels sorted by magnitude in descending order and creates and merges clusters of unwrapped pixels until the entire image is unwrapped. The algorithm was evaluated using simulated phantom data and in vivo clinical temperature imaging data. RESULTS The evaluation of the phantom data demonstrated no errors in regions with signal-to-noise ratios of at least 4.5. For the in vivo data, the algorithm did not fail at an average of more than one pixel for signal-to-noise ratios greater than 6.3. Processing times less than 30 ms per image were achieved by unwrapping pixels inside a region of interest (53 × 53 pixels) used for referenceless MR temperature imaging. CONCLUSIONS The algorithm has been demonstrated to operate robustly with clinical in vivo data in this study. The processing time for common regions of interest in referenceless MR temperature imaging allows for online updates of temperature maps without noticeable delay.
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Lewis CJ, Maier F, Horstkötter N, Zywczok A, Witt K, Eggers C, Meyer TD, Dembek TA, Maarouf M, Moro E, Zurowski M, Woopen C, Kuhn J, Timmermann L. Subjectively perceived personality and mood changes associated with subthalamic stimulation in patients with Parkinson's disease. Psychol Med 2015; 45:73-85. [PMID: 25066623 DOI: 10.1017/s0033291714001081] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Clinical and ethical implications of personality and mood changes in Parkinson's disease (PD) patients treated with subthalamic deep brain stimulation (STN-DBS) are under debate. Although subjectively perceived personality changes are often mentioned by patients and caregivers, few empirical studies concerning these changes exist. Therefore, we analysed subjectively perceived personality and mood changes in STN-DBS PD patients. METHOD In this prospective study of the ELSA-DBS group, 27 PD patients were assessed preoperatively and 1 year after STN-DBS surgery. Two categories, personality and mood changes, were analysed with semi-structured interviews. Patients were grouped into personality change yes/no, as well as positive/negative mood change groups. Caregivers were additionally interviewed about patients' personality changes. Characteristics of each group were assessed with standard neurological and psychiatric measurements. Predictors for changes were analysed. RESULTS Personality changes were perceived by six of 27 (22%) patients and by 10 of 23 caregivers (44%). The preoperative hypomania trait was a significant predictor for personality change perceived by patients. Of 21 patients, 12 (57%) perceived mood as positively changed. Higher apathy and anxiety ratings were found in the negative change group. CONCLUSIONS Our results show that a high proportion of PD patients and caregivers perceived personality changes under STN-DBS, emphasizing the relevance of this topic. Mood changed in positive and negative directions. Standard measurement scales failed to adequately reflect personality or mood changes subjectively perceived by patients. A more individualized preoperative screening and preparation for patients and caregivers, as well as postoperative support, could therefore be useful.
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Zamecnik P, Schouten MG, Krafft AJ, Maier F, Schlemmer HP, Barentsz JO, Bock M, Fütterer JJ. Automated real-time needle-guide tracking for fast 3-T MR-guided transrectal prostate biopsy: a feasibility study. Radiology 2014; 273:879-86. [PMID: 25061830 DOI: 10.1148/radiol.14132067] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE To assess the feasibility of automatic needle-guide tracking by using a real-time phase-only cross correlation ( POCC phase-only cross correlation ) algorithm-based sequence for transrectal 3-T in-bore magnetic resonance (MR)-guided prostate biopsies. MATERIALS AND METHODS This study was approved by the ethics review board, and written informed consent was obtained from all patients. Eleven patients with a prostate-specific antigen level of at least 4 ng/mL (4 μg/L) and at least one transrectal ultrasonography-guided biopsy session with negative findings were enrolled. Regions suspicious for cancer were identified on 3-T multiparametric MR images. During a subsequent MR-guided biopsy, the regions suspicious for cancer were reidentified and targeted by using the POCC phase-only cross correlation -based tracking sequence. Besides testing a general technical feasibility of the biopsy procedure by using the POCC phase-only cross correlation -based tracking sequence, the procedure times were measured, and a pathologic analysis of the biopsy cores was performed. RESULTS Thirty-eight core samples were obtained from 25 regions suspicious for cancer. It was technically feasible to perform the POCC phase-only cross correlation -based biopsies in all regions suspicious for cancer in each patient, with adequate biopsy samples obtained with each biopsy attempt. The median size of the region suspicious for cancer was 8 mm (range, 4-13 mm). In each region suspicious for cancer (median number per patient, two; range, 1-4), a median of one core sample per region was obtained (range, 1-3). The median time for guidance per target was 1.5 minutes (range, 0.7-5 minutes). Nineteen of 38 core biopsy samples contained cancer. CONCLUSION This study shows that it is feasible to perform transrectal 3-T MR-guided biopsies by using a POCC phase-only cross correlation algorithm-based real-time tracking sequence.
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MacLellan C, Maier F, Cressman E, Stafford R. SU-E-J-180: Monitoring Thermochemical Ablation Using Fast Chemical Shift Magnetic Resonance Imaging. Med Phys 2014. [DOI: 10.1118/1.4888233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Kolbeck C, Taccardi N, Paape N, Schulz PS, Wasserscheid P, Steinrück HP, Maier F. Redox chemistry, solubility, and surface distribution of Pt(II) and Pt(IV) complexes dissolved in ionic liquids. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2013.07.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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