PubMed | Rapid Biomedical GmbH and King's College London
Type: | Journal: Magnetic resonance in medicine | Year: 2016
The goal of the Developing Human Connectome Project is to acquire MRI in 1000 neonates to create a dynamic map of human brain connectivity during early development. High-quality imaging in this cohort without sedation presents a number of technical and practical challenges.We designed a neonatal brain imaging system (NBIS) consisting of a dedicated 32-channel receive array coil and a positioning device that allows placement of the infants head deep into the coil for maximum signal-to-noise ratio (SNR). Disturbance to the infant was minimized by using an MRI-compatible trolley to prepare and transport the infant and by employing a slow ramp-up and continuation of gradient noise during scanning. Scan repeats were minimized by using a restart capability for diffusion MRI and retrospective motion correction. We measured the 1) SNR gain, 2) number of infants with a completed scan protocol, and 3) number of anatomical images with no motion artifact using NBIS compared with using an adult 32-channel head coil.The NBIS has 2.4 times the SNR of the adult coil and 90% protocol completion rate.The NBIS allows advanced neonatal brain imaging techniques to be employed in neonatal brain imaging with high protocol completion rates. Magn Reson Med, 2016. 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Resmer F.,University of Aberdeen |
Resmer F.,RAPID Biomedical GmbH |
Seton H.C.,University of Aberdeen |
Hutchison J.M.S.,University of Aberdeen
Journal of Magnetic Resonance | Year: 2010
We have investigated the design and construction of liquid nitrogen cooled surface coils made from stranded (litz) copper wire for low field MRI applications. If designed correctly, cooled litz coils can provide a competitive alternative to high temperature superconducting (HTS) coils without the complications associated with flux trapping. Litz coils can also be produced with a wider range of shapes and sizes, and at lower cost. Existing models were verified experimentally for flat spiral coils wound from solid and litz wires, operated at room temperature and 77 K, and then used to design and optimise a cooled receive coil for MRI at 0.01 T (425 kHz). The Q-factor reached 1022 when the coil was cooled to 77 K, giving a bandwidth of just 0.42 kHz, so a low noise JFET preamplifier was developed to provide active damping of the coil resonance and thus minimise image intensity artefacts. The noise contribution of the preamplifier was determined using a method based on resistive sources and image noise analysis. The voltage and current noise were measured to be 1.25 nV/ Hz1/2 and 51 fA/ Hz1/2, respectively, and these values were used to estimate a noise figure of 0.32 dB at the resonant frequency of the cooled coil. The coil was used to acquire 0.01 T spin echo images, first at room temperature and then cooled to 77 K in a low noise liquid nitrogen cryostat. The measured SNR improvement on cooling, by a factor of 3.0, was found to correspond well with theoretical predictions. © 2009 Elsevier Inc. All rights reserved.
Dregely I.,TU Munich |
Dregely I.,University of California at Los Angeles |
Lanz T.,Rapid Biomedical GmbH |
Metz S.,TU Munich |
And 9 more authors.
European Radiology | Year: 2015
Objectives: To implement and evaluate a dedicated receiver array coil for simultaneous positron emission tomography/magnetic resonance (PET/MR) imaging in breast cancer.Methods: A 16-channel receiver coil design was optimized for simultaneous PET/MR imaging. To assess MR performance, the signal-to-noise ratio, parallel imaging capability and image quality was evaluated in phantoms, volunteers and patients and compared to clinical standard protocols. For PET evaluation, quantitative 18 F-FDG PET images of phantoms and seven patients (14 lesions) were compared to images without the coil. In PET image reconstruction, a CT-based template of the coil was combined with the MR-acquired attenuation correction (AC) map of the phantom/patient.Results: MR image quality was comparable to clinical MR-only examinations. PET evaluation in phantoms showed regionally varying underestimation of the standardised uptake value (SUV; mean 22 %) due to attenuation caused by the coil. This was improved by implementing the CT-based coil template in the AC (<2 % SUV underestimation). Patient data indicated that including the coil in the AC increased the SUV values in the lesions (21 ± 9 %).Conclusions: Using a dedicated PET/MR breast coil, state-of-the-art MRI was possible. In PET, accurate quantification and image homogeneity could be achieved if a CT-template of this coil was included in the AC for PET image reconstruction.Key Points: • State-of-the-art breast MRI using a dedicated PET/MR breast coil is feasible.• A multi-channel design facilitates shorter MR acquisition times via parallel imaging.• An MR coil inside a simultaneous PET/MR system causes PET photon attenuation.• Including a coil CT-template in PET image reconstruction results in recovering accurate quantification. © 2014, European Society of Radiology.
PubMed | Rapid Biomedical GmbH and University of Duisburg - Essen
Type: Journal Article | Journal: Medical physics | Year: 2016
This study aims to develop, implement, and evaluate a 16-channel radiofrequency (RF) coil for integrated positron emission tomography/magnetic resonance (PET/MR) imaging of breast cancer. The RF coil is designed for optimized MR imaging performance and PET transparency and attenuation correction (AC) is applied for accurate PET quantification.A 16-channel breast array RF coil was designed for integrated PET/MR hybrid imaging of breast cancer lesions. The RF coil features a lightweight rigid design and is positioned with a spacer at a defined position on the patient table of an integrated PET/MR system. Attenuation correction is performed by generating and applying a dedicated 3D CT-based template attenuation map. Reposition accuracy of the RF coil on the system patient table while using the positioning frame was tested in repeated measurements using MR-visible markers. The MR, PET, and PET/MR imaging performances were systematically evaluated using modular breast phantoms. Attenuation correction of the RF coil was evaluated with difference measurements of the active breast phantoms filled with radiotracer in the PET detector with and without the RF coil in place, serving as a standard of reference measurement. The overall PET/MR imaging performance and PET quantification accuracy of the new 16-channel RF coil and its AC were then evaluated in first clinical examinations on ten patients with local breast cancer.The RF breast array coil provides excellent signal-to-noise ratio and signal homogeneity across the volume of the breast phantoms in MR imaging and visualizes small structures in the phantoms down to 0.4 mm in plane. Difference measurements with PET revealed a global loss and thus attenuation of counts by 13% (mean value across the whole phantom volume) when the RF coil is placed in the PET detector. Local attenuation ranging from 0% in the middle of the phantoms up to 24% was detected in the peripheral regions of the phantoms at positions closer to attenuating hardware structures of the RF coil. The position accuracy of the RF coil on the patient table when using the positioning frame was determined well below 1 mm for all three spatial dimensions. This ensures perfect position match between the RF coil and its three-dimensional attenuation template during the PET data reconstruction process. When applying the CT-based AC of the RF coil, the global attenuation bias was mostly compensated to 0.5% across the entire breast imaging volume. The patient study revealed high quality MR, PET, and combined PET/MR imaging of breast cancer. Quantitative activity measurements in all 11 breast cancer lesions of the ten patients resulted in increased mean difference values of SUVmax 11.8% (minimum 3.2%; maximum 23.2%) between nonAC images and images when AC of the RF breast coil was applied. This supports the quantitative results of the phantom study as well as successful attenuation correction of the RF coil.A 16-channel breast RF coil was designed for optimized MR imaging performance and PET transparency and was successfully integrated with its dedicated attenuation correction template into a whole-body PET/MR system. Systematic PET/MR imaging evaluation with phantoms and an initial study on patients with breast cancer provided excellent MR and PET image quality and accurate PET quantification.
Ritter C.O.,University of Würzburg |
Wilke A.,University of Würzburg |
Wichmann T.,RAPID Biomedical GmbH |
Beer M.,University of Würzburg |
And 2 more authors.
Journal of Magnetic Resonance Imaging | Year: 2011
Purpose: To use the contrast agent gadofosveset for absolute quantification of myocardial perfusion and compare it with gadobenate dimeglumine (Gd-BOPTA) using a high-resolution generalized autocalibrating partially parallel acquisition (GRAPPA) sequence. Materials and Methods: Ten healthy volunteers were examined twice at two different dates with a first-pass perfusion examination at rest using prebolus technique. We used a 1.5 T scanner and a 32 channel heart-array coil with a steady-state free precession (SSFP) true fast imaging with steady state precession (trueFISP) GRAPPA sequence (acceleration-factor 3). Manual delineation of the myocardial contours was performed and absolute quantification was performed after baseline and contamination correction. At the first appointment, 1cc/4cc of the extracellular contrast agent Gd-BOPTA were administered, on the second date, 1cc/4cc of the blood pool contrast agent (CA) gadofosveset. At each date the examination was repeated after a 15-minute time interval. Results: Using gadofosveset perfusion the value (in cc/g/min) at rest was 0.66 ± 0.25 (mean ± standard deviation) for the first, and 0.55 ± 0.24 for the second CA application; for Gd-BOPTA it was 0.62 ± 0.25 and 0.45 ± 0.23. No significant difference was found between the acquired perfusion values. The apparent mean residence time in the myocardium was 23 seconds for gadofosveset and 19.5 seconds for Gd-BOPTA. Neither signal-to-noise ratio (SNR) nor subjectively rated image contrast showed a significant difference. Conclusion: The application of gadofosveset for an absolute quantification of myocardial perfusion is possible. Yet the acquired perfusion values show no significant differences to those determined with Gd-BOPTA, maintained the same SNR and comparable perfusion values, and did not picture the expected concentration time-course for an intravasal CA in the first pass. Copyright © 2011 Wiley-Liss, Inc.
Lanz T.,RAPID Biomedical GmbH |
Muller M.,RAPID Biomedical GmbH |
Barnes H.,University of Oxford |
Neubauer S.,University of Oxford |
Schneider J.E.,University of Oxford
Magnetic Resonance in Medicine | Year: 2010
Murine MRI studies are conducted on dedicated MR systems, typically equipped with ultra-high-field magnets (≤4.7 T; bore size: ∼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. © 2010 Wiley-Liss, Inc.
RAPID Biomedical GmbH | Date: 2012-08-21
An imaging device for imaging an anaesthetized animal such as a rodent (rats or mice or other animals), with the device having a split array coil capable of providing at least two channels for use in a restraining assembly with animal bed for magnetic resonance imaging (MRI) the animal in real-time in a non-destructive manner.
RAPID Biomedical GmbH | Date: 2012-05-04
A flexible coil device for supporting imaging experiments on subjects, such as small animals. The device has a rigid part where electronics are accommodated and a flexible loop acting as a receiving coil that picks up the imaging signal. The flexible loop allows its shape to be adapted to the particular shape of the imaged subject at the point of placement. This provides a better filling factor and hence better SNR of the region of interest (ROI). This has the advantage that various imaging applications pose less of a compromise than with rigid coils. The flexible loop can be positioned right against the region of interest (ROI) and so maximises the filling factor and the image SNR.
Rapid Biomedical Gmbh | Date: 2012-05-04
An imaging device for imaging an anaesthetized animal such as a rodent (rats or mice or other), with the device having a split array coil providing at least two channels for use in a restraining assembly and animal bed for magnetic resonance imaging (MRI) the animal in real-time in a non-destructive manner.
PubMed | University of Eastern Finland, RAPID Biomedical GmbH and Kuopio University Hospital
Type: | Journal: Journal of neuroscience methods | Year: 2016
Simultaneous EEG-fMRI is a valuable tool in the clinic as it provides excellent temporal and spatial information about normal and diseased brain function. In pre-clinical research with small rodents, obtaining simultaneous EEG-fMRI in longitudinal studies faces a number of challenges, including issues related to magnetic susceptibility artifacts.Here, we demonstrate a method for permanent MRI RF-coil and EEG electrode implantation in rats that is suitable for long-term chronic follow-up studies in both stimulus and resting-state fMRI paradigms.Our findings showed that the screw-free implantation method is well suited for long-term follow-up studies in both freely moving video-EEG settings and fMRI without causing MRI susceptibility artifacts. Furthermore, the results demonstrated that a multimodal approach can be used to track the progression of structural and functional changes.The quality of both MRI and EEG data were comparable to those obtained with traditional methods with the benefit of combining them into artifact-free simultaneous recordings. The signal-to-noise ratios of the MRI images obtained with the implanted RF-coil were similar to those using a quadrature coil and were therefore suitable for resting-state fMRI experiments. Similarly, EEG data collected with the RF-coil/electrode set-up were comparable to EEG recorded with traditional epidural screw electrodes.This new multimodal EEG-fMRI approach provides a novel tool for concomitant analysis and follow-up of anatomic and functional MRI, as well as electrographic changes in a preclinical research.