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Marhabaie S, Labbé A, Quesson B, Poirier-Quinot M. The Minimum Admissible Detuning Efficiency of MRI Receive-Only Surface Coils. J Magn Reson Imaging 2024; 60:777-788. [PMID: 38305462 DOI: 10.1002/jmri.29209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 02/03/2024] Open
Abstract
BACKGROUND The minimum admissible detuning efficiency (DE) of a receive coil is an essential parameter for coil designers. A receive coil with inefficient detuning leads to inhomogeneous B1 during excitation. Previously proposed criteria for quantifying the DE rely on indirect measurements and are difficult to implement. PURPOSE To present an alternative method to quantify the DE of receive-only surface coils. STUDY TYPE Theoretical study supported by simulations and phantom experiments. PHANTOMS Uniform spherical (100 mm diameter) and cylindrical (66 mm diameter) phantoms. FIELD STRENGTH/SEQUENCE Dual repetition time B1 mapping sequence at 1.5T, and Bloch-Siegert shift B1 mapping sequence at 3.0T. ASSESSMENT One non-planar (80 × 43 mm2) and two planar (40 and 57 mm diameter) surface coils were built. Theoretical analysis was performed to determine the minimum DE required to avoid B1 distortions. Experimental B1 maps were acquired for the non-planar and planar surface coils at both 1.5T and 3.0T and visually compared with simulated B1 maps to assess the validity of the theoretical analysis. STATISTICAL TESTS None. RESULTS Based on the theoretical analysis, the proposed minimum admissible DE, defined as DEthr = 20 Log (Q) + 13 dB, depended only on the quality factor (Q) of the coil and was independent of coil area and field strength. Simulations and phantom experiments showed that when the DE was higher than this minimum threshold level, the B1 field generated by the transmission coil was not modified by the receive coil. DATA CONCLUSION The proposed criterion for assessing the DE is simple to measure, and does not depend on the area of the coil or on the magnetic field strength, up to 3T. Experimental and simulated B1 maps confirmed that detuning efficiencies above the theoretically derived minimal admissible DE resulted in a non-distorted B1 field. EVIDENCE LEVEL 2 TECHNICAL EFFICACY: Stage 1.
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Affiliation(s)
- Sina Marhabaie
- Université Paris-Saclay, CNRS, Inserm, Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay, Orsay, France
| | - Aimé Labbé
- Université Paris-Saclay, CNRS, Inserm, Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay, Orsay, France
| | - Bruno Quesson
- University of Bordeaux, CNRS, CRMSB, UMR 5536, IHU Liryc, Bordeaux, France
| | - Marie Poirier-Quinot
- Université Paris-Saclay, CNRS, Inserm, Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay, Orsay, France
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Meissner F, Galbas MC, Szvetics S, von Zur Mühlen C, Heidt T, Maier A, Bock M, Czerny M, Bothe W, Reiss S. Cardioaortic dimensions in German landrace pigs derived from cardiac magnetic resonance imaging. Sci Rep 2024; 14:1869. [PMID: 38253776 PMCID: PMC10803781 DOI: 10.1038/s41598-024-52376-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 01/17/2024] [Indexed: 01/24/2024] Open
Abstract
Pigs are frequently applied as animal models in cardiovascular research due to their anatomical and physiological similarity to humans. For study planning and refinement, precise knowledge of the cardioaortic dimensions is essential. In a retrospective single-center study, the cardioaortic dimensions and left ventricular function of German Landrace pigs were assessed using cardiac MRI. All parameters were compared between male and female pigs and analyzed for correlation with body weight. In total, 15 pigs were included (7 male and 8 female, weight 60.9 ± 7.0 kg). The left ventricle revealed an end-diastolic diameter of 50.5 ± 4.4 mm and an ejection fraction of 51.2 ± 9.8%. The diameters of the ascending and descending aorta were 21.3 ± 2.3 and 16.2 ± 1.4 mm, respectively. There were no significant differences between male and female pigs, except that males had a smaller end-diastolic left ventricular volume (p = 0.041). A moderate correlation was found between body weight and the aortic annulus diameter (R = 0.57, p = 0.027). In conclusion, cardiac MRI allows precise quantification of porcine cardioaortic dimensions. For medical device testing, size differences between pigs and humans should be considered.
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Affiliation(s)
- Florian Meissner
- Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany.
| | - Michelle Costa Galbas
- Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Sophie Szvetics
- Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Constantin von Zur Mühlen
- Department of Cardiology and Angiology, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Timo Heidt
- Department of Cardiology and Angiology, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Alexander Maier
- Department of Cardiology and Angiology, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Michael Bock
- Department of Diagnostic and Interventional Radiology, Medical Physics, Faculty of Medicine, University of Freiburg, Killianstrasse 5a, 79106, Freiburg, Germany
| | - Martin Czerny
- Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Wolfgang Bothe
- Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Hugstetter Strasse 55, 79106, Freiburg, Germany
| | - Simon Reiss
- Department of Diagnostic and Interventional Radiology, Medical Physics, Faculty of Medicine, University of Freiburg, Killianstrasse 5a, 79106, Freiburg, Germany
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Marhabaie S, Delcey M, El Hamrani D, Vaillant F, Ginefri JC, Ozenne V, Abell E, Poirier-Quinot M, Quesson B. Remotely detuned receiver coil for high-resolution interventional cardiac magnetic resonance imaging. Front Cardiovasc Med 2023; 10:1249572. [PMID: 38028485 PMCID: PMC10643167 DOI: 10.3389/fcvm.2023.1249572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 10/03/2023] [Indexed: 12/01/2023] Open
Abstract
Introduction Interventional cardiac MRI in the context of the treatment of cardiac arrhythmia requires submillimeter image resolution to precisely characterize the cardiac substrate and guide the catheter-based ablation procedure in real-time. Conventional MRI receiver coils positioned on the thorax provide insufficient signal-to-noise ratio (SNR) and spatial selectivity to satisfy these constraints. Methods A small circular MRI receiver coil was developed and evaluated under different experimental conditions, including high-resolution MRI anatomical and thermometric imaging at 1.5 T. From the perspective of developing a therapeutic MR-compatible catheter equipped with a receiver coil, we also propose alternative remote active detuning techniques of the receiver coil using one or two cables. Theoretical details are presented, as well as simulations and experimental validation. Results Anatomical images of the left ventricle at 170 µm in-plane resolution are provided on ex vivo beating heart from swine using a 2 cm circular receiver coil. Taking advantage of the increase of SNR at its vicinity (up to 35 fold compared to conventional receiver coils), real-time MR-temperature imaging can reach an uncertainty below 0.1°C at the submillimetric spatial resolution. Remote active detuning using two cables has similar decoupling efficiency to conventional on-site decoupling, at the cost of an acceptable decrease in the resulting SNR. Discussion This study shows the potential of small dimension surface coils for minimally invasive therapy of cardiac arrhythmia intraoperatively guided by MRI. The proposed remote decoupling approaches may simplify the construction process and reduce the cost of such single-use devices.
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Affiliation(s)
- Sina Marhabaie
- Laboratoire D'Imagerie Biomédicale Multimodale Paris Saclay, Université Paris-Saclay, CNRS, Inserm, Orsay, France
| | - Marylène Delcey
- Univ. Bordeaux, INSERM, CRCTB, U 1045, IHU Liryc, Bordeaux, France
- Siemens Healthineers, Saint-Denis, France
| | | | - Fanny Vaillant
- Univ. Bordeaux, INSERM, CRCTB, U 1045, IHU Liryc, Bordeaux, France
| | - Jean-Christophe Ginefri
- Laboratoire D'Imagerie Biomédicale Multimodale Paris Saclay, Université Paris-Saclay, CNRS, Inserm, Orsay, France
| | - Valéry Ozenne
- Univ. Bordeaux, CNRS, CRMSB, UMR 5536, IHU Liryc, Bordeaux, France
| | - Emma Abell
- Univ. Bordeaux, INSERM, CRCTB, U 1045, IHU Liryc, Bordeaux, France
| | - Marie Poirier-Quinot
- Laboratoire D'Imagerie Biomédicale Multimodale Paris Saclay, Université Paris-Saclay, CNRS, Inserm, Orsay, France
| | - Bruno Quesson
- Univ. Bordeaux, CNRS, CRMSB, UMR 5536, IHU Liryc, Bordeaux, France
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Abstract
In this review, the roles of detectors in various medical imaging techniques were described. Ultrasound, optical (near-infrared spectroscopy and optical coherence tomography) and thermal imaging, magnetic resonance imaging, computed tomography, single-photon emission tomography, positron emission tomography were the imaging modalities considered. For each methodology, the state of the art of detectors mainly used in the systems was described, emphasizing new technologies applied.
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Stephan S, Reiss S, Lottner T, Özen AC, Bock M. Catheter-based Arterial Input Function Determination for Myocardial Perfusion Measurements. Z Med Phys 2021; 31:65-72. [PMID: 32873440 DOI: 10.1016/j.zemedi.2020.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 07/23/2020] [Accepted: 07/23/2020] [Indexed: 10/23/2022]
Abstract
The quantification of myocardial perfusion with contrast agent (CA) tracers requires the precise knowledge of the arterial input function (AIF). In this study a method for MR-guided vascular interventions is evaluated that determines the AIF via an active tracking catheter during targeted CA injection. A phantom experiment with a dialysis filter was conducted to measure the AIF using an active catheter and a dynamic image series as reference. To compensate for dilution and coil sensitivity effects, correction methods were developed for the catheter-based AIF determination. From the dynamic MR measurements in the perfusion phantom quantitative perfusion maps were calculated by a deconvolution of the measured CA concentration with the AIF, and additional flow measurements were used to normalize the perfusion map. The signal-time-curves of the measured AIF using the catheter-based and imaging-based methods agree while the absolute values differ by a scaling factor of about 9. After normalization to the surrounding flow, both perfusion techniques are in excellent agreement. Catheter-based AIF measurements are feasible but require an additional normalization which can be determined from a flow measurement. The technique might enable faster perfusion measurements during cardiovascular interventions.
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Affiliation(s)
- Simon Stephan
- Department of Radiology - Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Simon Reiss
- Department of Radiology - Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thomas Lottner
- Department of Radiology - Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ali Caglar Özen
- Department of Radiology - Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Bock
- Department of Radiology - Medical Physics, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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Tesfai AS, Fischer J, Özen AC, Eppenberger P, Oehrstroem L, Rühli F, Ludwig U, Bock M. Multi-parameter Analytical Method for B1 and SNR Analysis (MAMBA): An open source RF coil design tool. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 319:106825. [PMID: 32947127 DOI: 10.1016/j.jmr.2020.106825] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/05/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
In Magnetic Resonance Imaging (MRI), radio frequency (RF) coils of different forms and shapes are used to maximize signal-to-noise ratio (SNR). RF coils are designed for clinical applications and have dimensions comparable with the target body part to be imaged, and they perform best when loaded by human tissue majority of which have conductivity values higher than 0.5 S/m. However, they are not properly tuned and matched for samples having low conductivity such as solid samples with low water content. Moreover, for samples with low filling factor and low conductivity, the noise in MRI is dominated by RF coil losses. In this case, RF coil design can be optimized to improve image SNR. Here, a new software tool (Multi-parameter Analytical Method for B1 and SNR Analysis) MAMBA is presented to design and compare volume coils of birdcage, solenoid, and loop-gap design for these samples. The input parameters of the tool are the sample properties, the coil design and the hardware properties, of which a relative SNR is determined. For that, a figure of merit is calculated from the coil sensitivity, applied resonant frequency and the resistive losses of sample, coil and capacitive components. The tool was tested in an ancient Egyptian mummy head which represents an extreme case of MRI with short T2*. Two optimized birdcage coils were designed using MAMBA, constructed and compared to a commercial transmit receive head coil. Calculated relative SNR values are in good agreement with the measurements.
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Affiliation(s)
- Agazi Samuel Tesfai
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| | - Johannes Fischer
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ali Caglar Özen
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany; German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Patrick Eppenberger
- Institute of Evolutionary Medicine, Faculty of Medicine, University of Zurich, Switzerland
| | - Lena Oehrstroem
- Institute of Evolutionary Medicine, Faculty of Medicine, University of Zurich, Switzerland
| | - Frank Rühli
- Institute of Evolutionary Medicine, Faculty of Medicine, University of Zurich, Switzerland
| | - Ute Ludwig
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Bock
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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7
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Shen S, Xu Z, Koonjoo N, Rosen MS. Optimization of a Close-Fitting Volume RF Coil for Brain Imaging at 6.5 mT Using Linear Programming. IEEE Trans Biomed Eng 2020; 68:1106-1114. [PMID: 32746026 DOI: 10.1109/tbme.2020.3002077] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE The use of a close-fitting roughly head-shaped volume coil for MRI (magnetic resonance imaging) has the merit of improving the filling factor and thus the SNR (signal-to-noise ratio) from the brain. However, the surface of the RF coil follows that of the head which makes it difficult to determine an optimal coil winding pattern. We describe here a new method to optimize a head-shaped RF coil with the objective of maximizing its SNR and RF-magnetic-field homogeneity for operation at ultra-low magnetic field (6.5 mT, 276 kHz). METHODS The approach consists of FEM (finite-element-method) simulation and linear programing based optimization. RESULTS We have implemented the optimization and further studied the relationship between the design requirements and the performance of the RF coil. Finally, we constructed an optimal RF coil and scanned both a head-shaped phantom and a human subject. CONCLUSION The method we outline here provide new insight into the conductor layout needed for magnetic optimization of structurally complex coils, especially when tradeoffs between competing attributes (SNR and homogeneity in this case) must be made.
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8
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Özen AC, Lottner T, Bock M. Safety of active catheters in MRI: Termination impedance versus RF‐induced heating. Magn Reson Med 2018; 81:1412-1423. [DOI: 10.1002/mrm.27481] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 06/08/2018] [Accepted: 07/15/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Ali Caglar Özen
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
- German Cancer Consortium Partner Site Freiburg, German Cancer Research Center (DKFZ) Heidelberg Germany
| | - Thomas Lottner
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
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Kaiser M, Detert M, Rube MA, El-Tahir A, Elle OJ, Melzer A, Schmidt B, Rose GH. Resonant marker design and fabrication techniques for device visualization during interventional magnetic resonance imaging. ACTA ACUST UNITED AC 2016; 60:89-103. [PMID: 25460277 DOI: 10.1515/bmt-2013-0097] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 10/24/2014] [Indexed: 11/15/2022]
Abstract
Magnetic resonance imaging (MRI) has great potential as an imaging modality for guiding minimally invasive interventions because of its superior soft tissue contrast and the possibility of arbitrary slice positioning while avoiding ionizing radiation and nephrotoxic iodine contrast agents. The major constraints are: limited patient access, the insufficient assortment of compatible instruments and the difficult device visualization compared to X-ray based techniques. For the latter, resonant MRI markers, fabricated by using the wire-winding technique, have been developed. This fabrication technique serves as a functional model but has no clinical use. Thus, the aim of this study is to illustrate a four-phase design process of resonant markers involving microsystems technologies. The planning phase comprises the definition of requirements and the simulation of electromagnetic performance of the MRI markers. The following technologies were considered for the realization phase: aerosol-deposition process, hot embossing technology and thin film technology. The subsequent evaluation phase involves several test methods regarding electrical and mechanical characterization as well as MRI visibility aspects. The degree of fulfillment of the predefined requirements is determined within the analysis phase. Furthermore, an exemplary evaluation of four realized MRI markers was conducted, focusing on the performance within the MRI environment.
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Hegde SS, Zhang Y, Bottomley PA. Acceleration and motion-correction techniques for high-resolution intravascular MRI. Magn Reson Med 2014; 74:452-61. [PMID: 25163750 DOI: 10.1002/mrm.25436] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 08/06/2014] [Accepted: 08/11/2014] [Indexed: 11/07/2022]
Abstract
PURPOSE High-resolution intravascular (IV) MRI is susceptible to degradation from physiological motion and requires high frame-rates for true endoscopy. Traditional cardiac-gating techniques compromise efficiency by reducing the effective scan rate. Here we test whether compressed sensing (CS) reconstruction and ungated motion-compensation using projection shifting, could provide faster motion-suppressed, IVMRI. THEORY AND METHODS CS reconstruction is developed for undersampled Cartesian and radial imaging using a new IVMRI-specific cost function to effectively increase imaging speed. A new motion correction method is presented wherein individual IVMRI projections are shifted based on the IVMRI detector's intrinsic amplitude and phase properties. The methods are tested at 3 Tesla (T) in fruit, human vessel specimens, and a rabbit aorta in vivo. Images are compared using structural-similarity and "spokal variation" indices. RESULTS Although some residual artifacts persisted, CS acceleration and radial motion compensation strategies reduced motion artifact in vitro and in vivo, allowing effective accelerations of up to eight-fold at 200-300 µm resolution. CONCLUSION The 3T IVMRI detectors are well-suited to CS and motion correction strategies based on their intrinsic radially-sparse sensitivity profiles and high signal-to-noise ratios.
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Affiliation(s)
- Shashank Sathyanarayana Hegde
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yi Zhang
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Paul A Bottomley
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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Wech T, Shea SM, Barbot J, Vij K, Pan L, Lorenz CH, Patil S. Measurement accuracy of different active tracking sequences for interventional MRI. J Magn Reson Imaging 2014; 40:490-5. [PMID: 24677517 DOI: 10.1002/jmri.24374] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 07/22/2013] [Indexed: 01/19/2023] Open
Abstract
PURPOSE To compare the spatial accuracy of three typical active tracking sequences using a new, unique phantom design. MATERIALS AND METHODS Three different tracking sequences (Single Echo, Dual Echo and Hadamard Multiplexed) were compared with each other in a phantom study with respect to their positional accuracy. A custom-built phantom was constructed to conduct the experiments with precise framework conditions which facilitated sufficient measurement accuracy. An electrophysiology catheter incorporating four micro-coils was used as an interventional device. Tracking profiles were acquired in all three spatial dimensions and validated against the distances that were measured by a Vernier caliper in combination with a three-dimensional reference scan. RESULTS The Bland-Altman plots demonstrated that all three sequences show < 1.5 mm positional error. The measurement accuracy of Single Echo and Double Echo are prone to off-resonances, whereas Hadamard Encoding is immune to it. CONCLUSION The developed phantom enabled the performance of objective measurements of the accuracy of different active tracking sequences. The proposed setup allows for objectively contrasting different methods for interventional procedures.
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Affiliation(s)
- Tobias Wech
- Center for Applied Medical Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Baltimore, Maryland, USA; Institute of Radiology, University of Würzburg, Würzburg, Germany; Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
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12
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Celik H, Mahcicek DI, Senel OK, Wright GA, Atalar E. Tracking the position and rotational orientation of a catheter using a transmit array system. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:809-817. [PMID: 23412592 DOI: 10.1109/tmi.2013.2247047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A new method for detecting the rotational orientation and tracking the position of an inductively coupled radio frequency (ICRF) coil using a transmit array system is proposed. The method employs a conventional body birdcage coil, but the quadrature hybrid is eliminated so that the two excitation channels can be used separately. The transmit array system provides RF excitations such that the body birdcage coil creates linearly polarized and changing RF pulses instead of a conventional rotational forward-polarized excitation. The receive coils and their operations are not modified. Inductively coupled RF coils are constructed on catheters for detecting rotational orientation and for tracking purposes. Signals from the anatomy and from tissue close to the ICRF coil are different due to the new RF excitation scheme: the ICRF coil can be separated from the anatomy in real time, and after doing so, a color-coded image is reconstructed. More importantly, this novel method enables a real-time calculation of the absolute rotational orientation of an ICRF coil constructed on a catheter. Modified FLASH and TrueFISP sequences are used for the experiments. The acquired images from this technique show the feasibility of different applications, such as catheter tracking. Furthermore, applications where knowledge of the rotational orientation of the catheter is important, such as magnetic resonance-guided endoluminal-focused ultrasound, RF ablation, side-looking optical imaging, and catheters with side ports for needles, become feasible with this method.
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Affiliation(s)
- Haydar Celik
- Electrical and Electronics Engineering Department, Bilkent University, TR-06800 Ankara, Turkey.
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Qin L, Schmidt EJ, Tse ZTH, Santos J, Hoge WS, Tempany-Afdhal C, Butts-Pauly K, Dumoulin CL. Prospective motion correction using tracking coils. Magn Reson Med 2013; 69:749-59. [PMID: 22565377 PMCID: PMC3416927 DOI: 10.1002/mrm.24310] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 03/31/2012] [Accepted: 04/04/2012] [Indexed: 11/10/2022]
Abstract
Intracavity imaging coils provide higher signal-to-noise than surface coils and have the potential to provide higher spatial resolution in shorter acquisition times. However, images from these coils suffer from physiologically induced motion artifacts, as both the anatomy and the coils move during image acquisition. We developed prospective motion-correction techniques for intracavity imaging using an array of tracking coils. The system had <50 ms latency between tracking and imaging, so that the images from the intracavity coil were acquired in a frame of reference defined by the tracking array rather than by the system's gradient coils. Two-dimensional gradient-recalled and three-dimensional electrocardiogram-gated inversion-recovery-fast-gradient-echo sequences were tested with prospective motion correction using ex vivo hearts placed on a moving platform simulating both respiratory and cardiac motion. Human abdominal tests were subsequently conducted. The tracking array provided a positional accuracy of 0.7 ± 0.5 mm, 0.6 ± 0.4 mm, and 0.1 ± 0.1 mm along the X, Y, and Z directions at a rate of 20 frames-per-second. The ex vivo and human experiments showed significant image quality improvements for both in-plane and through-plane motion correction, which although not performed in intracavity imaging, demonstrates the feasibility of implementing such a motion-correction system in a future design of combined tracking and intracavity coil.
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Affiliation(s)
- Lei Qin
- Department of Radiology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
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14
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Volland NA, Kholmovski EG, Parker DL, Hadley JR. Initial feasibility testing of limited field of view magnetic resonance thermometry using a local cardiac radiofrequency coil. Magn Reson Med 2012; 70:994-1004. [PMID: 23165722 DOI: 10.1002/mrm.24534] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 09/27/2012] [Accepted: 09/27/2012] [Indexed: 01/28/2023]
Abstract
The visualization of lesion formation in real time is one potential benefit of carrying out radiofrequency ablation under magnetic resonance (MR) guidance in the treatment of atrial fibrillation. MR thermometry has the potential to detect such lesions. However, performing MR thermometry during cardiac radiofrequency ablation requires high temporal and spatial resolution and a high signal-to-noise ratio. In this study, a local MR coil (2-cm diameter) was developed to investigate the feasibility of performing limited field of view MR thermometry with high accuracy and speed. The local MR coil allowed high-resolution (1 × 1 × 3 mm(3)) image acquisitions in 76.3 ms with a field of view 64 × 32 mm(2) during an open-chest animal experiment. This represents a 4-fold image acquisition acceleration and an 18-fold field of view reduction compared to that achieved using external MR coils. The signal sensitivity achieved using the local coil was over 20 times greater than that achievable using external coils with the same scan parameters. The local coil configuration provided fewer artifacts and sharper and more stable images. These results demonstrate that MR thermometry can be performed in the heart wall and that lesion formation can be observed during radiofrequency ablation procedures in a canine model.
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Affiliation(s)
- Nelly A Volland
- Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, Utah, USA; Comprehensive Arrhythmia Research and Management Center, University of Utah, Salt Lake City, Utah, USA
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Real-time MR navigation and localization of an intravascular catheter with ferromagnetic components. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2010; 23:153-63. [DOI: 10.1007/s10334-010-0214-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 03/26/2010] [Accepted: 04/20/2010] [Indexed: 11/25/2022]
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