Ritter C.O.,University of Wurzburg |
Wilke A.,University of Wurzburg |
Wichmann T.,RAPID Biomedical GmbH |
Beer M.,University of Wurzburg |
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.
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.
Pillai D.R.,University of Regensburg |
Pillai D.R.,University of Wurzburg |
Heidemann R.M.,Max Planck Institute for Human Cognitive and Brain Sciences |
Heidemann R.M.,Siemens AG |
And 14 more authors.
PLoS ONE | Year: 2011
Background: Small animal models of human diseases are an indispensable aspect of pre-clinical research. Being dynamic, most pathologies demand extensive longitudinal monitoring to understand disease mechanisms, drug efficacy and side effects. These considerations often demand the concomitant development of monitoring systems with sufficient temporal and spatial resolution. Methodology and Results: This study attempts to configure and optimize a clinical 3 Tesla magnetic resonance scanner to facilitate imaging of small animal central nervous system pathologies. The hardware of the scanner was complemented by a custom-built, 4-channel phased array coil system. Extensive modification of standard sequence protocols was carried out based on tissue relaxometric calculations. Proton density differences between the gray and white matter of the rodent spinal cord along with transverse relaxation due to magnetic susceptibility differences at the cortex and striatum of both rats and mice demonstrated statistically significant differences. The employed parallel imaging reconstruction algorithms had distinct properties dependent on the sequence type and in the presence of the contrast agent. The attempt to morphologically phenotype a normal healthy rat brain in multiple planes delineated a number of anatomical regions, and all the clinically relevant sequels following acute cerebral ischemia could be adequately characterized. Changes in blood-brain-barrier permeability following ischemia-reperfusion were also apparent at a later time. Typical characteristics of intra-cerebral haemorrhage at acute and chronic stages were also visualized up to one month. Two models of rodent spinal cord injury were adequately characterized and closely mimicked the results of histological studies. In the employed rodent animal handling system a mouse model of glioblastoma was also studied with unequivocal results. Conclusions: The implemented customizations including extensive sequence protocol modifications resulted in images of high diagnostic quality. These results prove that lack of dedicated animal scanners shouldn't discourage conventional small animal imaging studies. © 2011 Pillai et al.
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.
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.