Titus Lanz

Publications of Titus Lanz

• A flexible 32-channel receive array combined with a homogeneous transmit coil for human lung imaging with hyperpolarized 3He at 1.5 T.

  Authors: Martin H Deppe, Juan Parra-Robles, Helen Marshall, Titus Lanz, Jim M Wild

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 05/2011; 66(6):1788-97.

  Parallel imaging presents a promising approach for MRI of hyperpolarized nuclei, as the penalty in signal-to-noise ratio typically encountered with (1)H MRI due to a reduction in acquisition time canParallel imaging presents a promising approach for MRI of hyperpolarized nuclei, as the penalty in signal-to-noise ratio typically encountered with (1)H MRI due to a reduction in acquisition time can be offset by an increase in flip angle. The signal-to-noise ratio of hyperpolarized MRI generally exhibits a strong dependence on flip angle, which makes a homogeneous B(1)(+) transmit field desirable. This paper presents a flexible 32-channel receive array for (3) He human lung imaging at 1.5T designed for insertion into an asymmetric birdcage transmit coil. While the 32-channel array allows parallel imaging at high acceleration factors, the birdcage transmit coil provides a homogeneous B(1)(+) field. Decoupling between array elements is achieved by using a concentric shielding approach together with preamplifier decoupling. Coupling between transmit coil and array elements is low by virtue of a low geometric coupling coefficient, which is reduced further by the concentric shields in the array. The combination of the 32-channel array and birdcage transmit coil provides (3)He ventilation images of excellent quality with similar signal-to-noise ratio at acceleration factors R = 2 and R = 4, while maintaining a homogeneous B(1)(+).

• Accelerated cardiac magnetic resonance imaging in the mouse using an eight-channel array at 9.4 Tesla.

  Authors: Jürgen E Schneider, Titus Lanz, Hannah Barnes, Lee-Anne Stork, Steffen Bohl, Craig A Lygate, Roger J Ordidge, Stefan Neubauer

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 01/2011; 65(1):60-70.

  MRI has become an important tool to noninvasively assess global and regional cardiac function, infarct size, or myocardial blood flow in surgically or genetically modified mouse models of human heartMRI has become an important tool to noninvasively assess global and regional cardiac function, infarct size, or myocardial blood flow in surgically or genetically modified mouse models of human heart disease. Constraints on scan time due to sensitivity to general anesthesia in hemodynamically compromised mice frequently limit the number of parameters available in one imaging session. Parallel imaging techniques to reduce acquisition times require coil arrays, which are technically challenging to design at ultrahigh magnetic field strengths. This work validates the use of an eight-channel volume phased-array coil for cardiac MRI in mice at 9.4 T. Two- and three-dimensional sequences were combined with parallel imaging techniques and used to quantify global cardiac function, T(1)-relaxation times and infarct sizes. Furthermore, the rapid acquisition of functional cine-data allowed for the first time in mice measurement of left-ventricular peak filling and ejection rates under intravenous infusion of dobutamine. The results demonstrate that a threefold accelerated data acquisition is generally feasible without compromising the accuracy of the results. This strategy may eventually pave the way for routine, multiparametric phenotyping of mouse hearts in vivo within one imaging session of tolerable duration.

• A high-throughput eight-channel probe head for murine MRI at 9.4 T.

  Authors: Titus Lanz, Matthias Müller, Hannah Barnes, Stefan Neubauer, Jürgen E Schneider

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 07/2010; 64(1):80-7.

  Murine MRI studies are conducted on dedicated MR systems, typically equipped with ultra-high-field magnets (>or=4.7 T; bore size: approximately 12-25 cm), using a single transmit-receive coil (volumeMurine MRI studies are conducted on dedicated MR systems, typically equipped with ultra-high-field magnets (>or=4.7 T; bore size: approximately 12-25 cm), using a single transmit-receive coil (volume or surface coil in linear or quadrature mode) or a transmit-receive coil combination. Here, we report on the design and characterization of an eight-channel volume receive-coil array for murine MRI at 400 MHz. The array was combined with a volume-transmit coil and integrated into one probe head. Therefore, the animal handling is fully decoupled from the radiofrequency setup. Furthermore, fixed tune and match of the coils and a reduced number of connectors minimized the setup time. Optimized preamplifier design was essential for minimizing the noise coupling between the elements. A comprehensive characterization of transmit volume resonator and receive coil array is provided. The performance of the coil array is compared to a quadrature-driven birdcage coil with identical sensitive volume. It is shown that the miniature size of the elements resulted in coil noise domination and therefore reduced signal-to-noise-ratio performance in the center compared to the quadrature birdcage. However, it allowed for 3-fold accelerated imaging of mice in vivo, reducing scan time requirements and thus increasing the number of mice that can be scanned per unit of time.

• 7 Tesla MR imaging of the human eye in vivo.

  Authors: Kathryn Richdale, Peter Wassenaar, Katharine Teal Bluestein, Amir Abduljalil, John A Christoforidis, Titus Lanz, Michael V Knopp, Petra Schmalbrock

  Journal of magnetic resonance imaging : JMRI. 11/2009; 30(5):924-32.

  PURPOSE: To develop a protocol which optimizes contrast, resolution and scan time for three-dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequencyPURPOSE: To develop a protocol which optimizes contrast, resolution and scan time for three-dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequency (RF) coil. MATERIALS AND METHODS: Initial testing was conducted to reduce motion and susceptibility artifacts. Three-dimensional FFE and IR-TFE images were obtained with variable flip angles and TI times. T(1) measurements were made and numerical simulations were performed to determine the ideal contrast of certain ocular structures. Studies were performed to optimize resolution and signal-to-noise ratio (SNR) with scan times from 20 s to 5 min. RESULTS: Motion and susceptibility artifacts were reduced through careful subject preparation. T(1) values of the ocular structures are in line with previous work at 1.5T. A voxel size of 0.15 x 0.25 x 1.0 mm(3) was obtained with a scan time of approximately 35 s for both 3D FFE and IR-TFE sequences. Multiple images were registered in 3D to produce final SNRs over 40. CONCLUSION: Optimization of pulse sequences and avoidance of susceptibility and motion artifacts led to high quality images with spatial resolution and SNR exceeding prior work. Ocular imaging at 7T with a dedicated coil improves the ability to make measurements of the fine structures of the eye.

• Half-fourier-acquisition single-shot turbo spin-echo (HASTE) MRI of the lung at 3 Tesla using parallel imaging with 32-receiver channel technology.

  Authors: Thomas Henzler, Olaf Dietrich, Radko Krissak, Tobias Wichmann, Titus Lanz, Maximilian F Reiser, Stefan O Schoenberg, Christian Fink

  Journal of magnetic resonance imaging : JMRI. 09/2009; 30(3):541-546.

  PURPOSE: To assess the feasibility of half-Fourier-acquisition single-shot turbo spin-echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32-channel torso array coil,PURPOSE: To assess the feasibility of half-Fourier-acquisition single-shot turbo spin-echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32-channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy. MATERIALS AND METHODS: Nine volunteers were examined on a 32-channel 3T MRI system using a prototype 32-channel-torso-array-coil. HASTE-MRI of the lung was acquired at both, end-inspiratory and end-expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal-to-noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements. RESULTS: Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans. CONCLUSION: Using optimized multi-element coil geometry HASTE-MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541-546. (c) 2009 Wiley-Liss, Inc.

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• Ultra-fast and accurate assessment of cardiac function in rats using accelerated MRI at 9.4 Tesla.

  Authors: Jürgen E Schneider, Titus Lanz, Hannah Barnes, Debra Medway, Lee-Anne Stork, Craig A Lygate, Sean Smart, Mark A Griswold, Stefan Neubauer

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 04/2008; 59(3):636-41.

  MRI can accurately and reproducibly assess cardiac function in rodents but requires relatively long imaging times. Therefore, parallel imaging techniques using a 4-element RF-coil array and MRMRI can accurately and reproducibly assess cardiac function in rodents but requires relatively long imaging times. Therefore, parallel imaging techniques using a 4-element RF-coil array and MR sequences for cardiac MRI in rats were implemented at ultra-high magnetic fields (9.4 Tesla [T]). The hypothesis that these developments would result in a major reduction in imaging time without loss of accuracy was tested on female Wistar rats under isoflurane anesthesia. High-resolution, contiguous short-axis slices (thickness 1.5 mm) were acquired covering the entire heart. Two interleaved data sets (i) with the volume coil (eight averages) and (ii) with the four-element coil array (one average) were obtained. In addition, two-, three-, and fourfold accelerated data sets were generated through postprocessing of the coil array data, followed by a TGRAPPA reconstruction, resulting in five data sets per rat (in-plane voxel size 100 x 100 microm). Using a single blinded operator, excellent agreement was obtained between volume coil (acquisition time: 88 min) and the fourfold accelerated (<3 min) data sets (e.g., LV mass 436 +/- 21 mg vs 433 +/- 19 mg; ejection fraction 74 +/- 5% vs 75 +/- 4%). This finding demonstrates that it is possible to complete a rat cine-MRI study under 3 min with low variability and without losing temporal or spatial resolution, making high throughput screening programs feasible.

• Mouse MRI using phased-array coils.

  Authors: Daniel Gareis, Tobias Wichmann, Titus Lanz, Gerd Melkus, Michael Horn, Peter M Jakob

  NMR in biomedicine. 06/2007; 20(3):326-34.

  The advantages of array coil imaging in human whole-body MR systems are well known and have gained relevance in many applications and MR techniques. In the field of small-animal studies, this conceptThe advantages of array coil imaging in human whole-body MR systems are well known and have gained relevance in many applications and MR techniques. In the field of small-animal studies, this concept has become increasingly important. In this work, three different phased-array coils for performing MRI on mice are presented. For imaging at 300 MHz, a four-channel receive-only phased-array coil is introduced. One two-channel and a four-channel transmit/receive setup operating at 750 MHz show the feasibility of array coil imaging at 17.6 T. All of these coils show excellent performance and deliver high-quality MR images of mice.

• Cardiac CINE MR imaging with a 32-channel cardiac coil and parallel imaging: impact of acceleration factors on image quality and volumetric accuracy.

  Authors: Bernd J Wintersperger, Scott B Reeder, Konstantin Nikolaou, Olaf Dietrich, Armin Huber, Andreas Greiser, Titus Lanz, Maximilian F Reiser, Stefan O Schoenberg

  Journal of magnetic resonance imaging : JMRI. 03/2006; 23(2):222-7.

  PURPOSE: To assess the impact of parallel imaging algorithms on image quality and volumetric accuracy of CINE magnetic resonance imaging (MRI) with high temporal and spatial resolution using a newPURPOSE: To assess the impact of parallel imaging algorithms on image quality and volumetric accuracy of CINE magnetic resonance imaging (MRI) with high temporal and spatial resolution using a new 32-channel dedicated cardiac phased array coil. MATERIALS AND METHODS: Fourteen individuals underwent steady-state free precession (SSFP) CINE MRI using a 32-element phased-array coil and parallel imaging acceleration using spatiotemporal sensitivity encoding (TSENSE). Acquisition acceleration ranged from R = 2 to 7. In conjunction with data extracted from phantom measurements, contrast-to-noise ratio (CNR) performance was evaluated for each acceleration factor and subjective image quality was evaluated by two independent readers. In addition, volumetric assessment was performed for each acceleration factor based on a single breath-hold multi-slice data acquisition. Results were compared to nonTSENSE measurements. RESULTS: CNR for non-accelerated CINE (R = 1) was 45.7 +/- 12.8 and showed a constant decrease with increase in acceleration of 51% at R = 4 and 86% at R = 7. CNR losses accompanied reductions in subjective image quality. Volumetric evaluation was accurate for R <or= 4, with significant underestimation of ejection fraction (EF) at higher accelerations. CONCLUSION: This study shows that one-dimensional acceleration factors up to R = 4 allow accurate SSFP CINE MRI even though CNR is significantly reduced. This allows for a marked reduction in scan time and allows for multi-slice CINE imaging with high spatial and temporal resolution.

• Practical approaches to the evaluation of signal-to-noise ratio performance with parallel imaging: application with cardiac imaging and a 32-channel cardiac coil.

  Authors: Scott B Reeder, Bernd J Wintersperger, Olaf Dietrich, Titus Lanz, Andreas Greiser, Maximilian F Reiser, Gary M Glazer, Stefan O Schoenberg

  Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine. 10/2005; 54(3):748-54.

  In this work, two practical methods for the measurement of signal-to-noise-ratio (SNR) performance in parallel imaging are described. Phantoms and human studies were performed with a 32-channelIn this work, two practical methods for the measurement of signal-to-noise-ratio (SNR) performance in parallel imaging are described. Phantoms and human studies were performed with a 32-channel cardiac coil in the context of ultrafast cardiac CINE imaging at 1.5 T using steady-state free precession (SSFP) and TSENSE. SNR and g-factor phantom measurements using a "multiple acquisition" method were compared to measurements from a "difference method". Excellent agreement was seen between the two methods, and the g-factor shows qualitative agreement with theoretical predictions from the literature. Examples of high temporal (42.6 ms) and spatial (2.1x2.1x8 mm3) resolution cardiac CINE SSFP images acquired from human volunteers using TSENSE are shown for acceleration factors up to 7. Image quality agrees qualitatively with phantom SNR measurements, suggesting an optimum acceleration of 4. With this acceleration, a cardiac function study consisting of 6 image planes (3 short-axis views, 3 long-axis views) was obtained in an 18-heartbeat breath-hold.

• Preamplified planar microcoil on GaAs substrates for microspectroscopy

  Authors: Jorn Dechow, Titus Lanz, Michael Stumber, Alfred Forchel, Axel Haase

  Review of Scientific Instruments. 12/2003;

  In the course of the publication the design, fabrication, and experimental evaluation of a planar microcoil for nuclear magnetic resonance (NMR) spectroscopy with a 360 μm inner diameter integratedIn the course of the publication the design, fabrication, and experimental evaluation of a planar microcoil for nuclear magnetic resonance (NMR) spectroscopy with a 360 μm inner diameter integrated to a low-noise metal–semiconductor field-effect transistor is presented. The impedance matching of the coil and transistor was achieved by adjusted coil geometry, while an appropriate microfabrication process including air bridge contacts and a multilayer metal stack was developed for the necessary susceptibility matching of the coil metallization. The NMR spectra of experiments in an 11.75 T magnet (corresponding to 500 MHz) show the amplification of the signal by the integrated transistor. Due to previous experiments, we wanted to ensure that the whole signal emerged from the sensitive volume of the microcoil. © 2003 American Institute of Physics.

• Mitochondrial creatine kinase is critically necessary for normal myocardial high-energy phosphate metabolism.

  Authors: Matthias Spindler, Reinhard Niebler, Helga Remkes, Michael Horn, Titus Lanz, Stefan Neubauer

  American journal of physiology. Heart and circulatory physiology. 09/2002; 283(2):H680-7.

  The individual functional significance of the various creatine kinase (CK) isoenzymes for myocardial energy homeostasis is poorly understood. Whereas transgenic hearts lacking the M subunit of CKThe individual functional significance of the various creatine kinase (CK) isoenzymes for myocardial energy homeostasis is poorly understood. Whereas transgenic hearts lacking the M subunit of CK (M-CK) show unaltered cardiac energetics and left ventricular (LV) performance, deletion of M-CK in combination with loss of sarcomeric mitochondrial CK (ScCKmit) leads to significant alterations in myocardial high-energy phosphate metabolites. To address the question as to whether this alteration is due to a decrease in total CK activity below a critical threshold or due to the specific loss of ScCKmit, we studied isolated perfused hearts with selective loss of ScCKmit (ScCKmit(-/-), remaining total CK activity approximately 70%) using (31)P NMR spectroscopy at two different workloads. LV performance in ScCKmit(-/-) hearts (n = 11) was similar compared with wild-type hearts (n = 9). Phosphocreatine/ATP, however, was significantly reduced in ScCKmit(-/-) compared with wild-type hearts (1.02 +/- 0.05 vs. 1.54 +/- 0.07, P < 0.05). In parallel, free [ADP] was higher (144 +/- 11 vs. 67 +/- 7 microM, P < 0.01) and free energy release for ATP hydrolysis (DeltaG(ATP)) was lower (-55.8 +/- 0.5 vs. -58.5 +/- 0.5 kJ/mol, P < 0.01) in ScCKmit(-/-) compared with wild-type hearts. These results demonstrate that M- and B-CK containing isoenzymes are unable to fully substitute for the loss of ScCKmit. We conclude that ScCKmit, in contrast to M-CK, is critically necessary to maintain normal high-energy phosphate metabolite levels in the heart.

• Three-Dimensional 13C-Spectroscopic Imaging in the Isolated Infarcted Rat Heart

  Authors: Claudia Weidensteiner, Titus Lanz, Michael Horn, Stefan Neubauer, Axel Haase, Markus von Kienlin

  Journal of Magnetic Resonance.

  Acquisition weighted 13C-spectroscopic imaging with three spatial dimensions is demonstrated in the isolated, perfused rat heart. Experiments were performed at 11.75 T with a homebuilt doubleAcquisition weighted 13C-spectroscopic imaging with three spatial dimensions is demonstrated in the isolated, perfused rat heart. Experiments were performed at 11.75 T with a homebuilt double resonant 13C–1H probehead. Three-dimensional chemical shift imaging was used to obtain 1H-decoupled 13C-spectra in 96-μl voxels in about 58 min. Acquisition weighting significantly reduced signal contamination and improved image quality, with no penalty in sensitivity. As a first application, infarcted hearts were studied during perfusion with [2-13C]-sodium acetate. The extent of the incorporation of the 13C-label into glutamate allows us to distinguish intact and infarcted myocardium. Chemical shift images show a homogeneous glutamate distribution in intact tissue, but a neglible amount in the infarction scar.