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APPLICATION SHEET: NeuroCam

fMRI:
EXPLORE CUTTING-EDGE MRI ACQUISITION METHODS FOR fMRI

FOR A WIDENED SCOPE OF FUNCTIONAL MRI IN NEUROSCIENCE

Freedom to explore and use novel acquisition techniques - single-shot spiral imageFreedom to explore and use novel acquisition techniques
The prevalent single-shot EPI acquisition is limited in the type and range of physiological effects it can capture: E.g., its inherently long echo time needed for a high resolution prohibits the detection of BOLD activations at short T2*. This leads to a failure in identifying the full constellation of neural responses involved in a task. The NeuroCam allows the use of MR acquisitions such as spirals which can be optimized for sensitivity to the full range of BOLD responses. This freedom in sequence design also benefits the exploration of other physiological effects (e.g. perfusion).

Geometrical congruence for multi-modal imagingGeometrical congruence for multi-modal imaging
Fast MRI methods are plagued by distortions that arise from deviations of the encoding fields. The resulting geometrical misalignment between individuals in an fMRI study leads to erroneous anatomical allocation of the group-level BOLD signal or even a failure to detect a population effect. Moreover, multi-modal imaging studies can fail due to anatomical inconsistency between different contrasts (e.g., fMRI and DWI). Measuring the imperfect encoding fields, the geometrical congruence can be recovered, thus enabling reliable group-level analyses and multi-modal imaging studies.

Optimized temporal SNROptimized temporal SNR
Functional MRI exploits changes in MR signal intensity that are small in comparison to temporal signal variation from perturbing sources: e.g., changing gradient delays or magnetic field drifts cause temporally varying signal levels in the images. The result is a reduced sensitivity towards detecting the BOLD signal. The NeuroCam in combination with skope-i removes noise contributions related to perturbations in image encoding. The gained temporal SNR provides the basis for a more reliable detection of the true BOLD response, for a heightended sensitivity when testing neuroscience hypotheses.


NeuroCam and skope-i

Detecting functional signal from the brain with high anatomical consistency is hindered by perturbations of encoding magnetic fields. This often results in a failure of detecting functional neurophysiological effects.

Picture of the NeuroCam

By concurrently measuring the field dynamics with the NeuroCam, one can correct for systematic and physiologic artifacts and achieve more accurate and consistent diffusion imaging. Based on the acquired MRI data the skope-i, image production software, produces consistent diffusion images for repeatable and reproducible diffusion MR studies.


NeuroCam for 3T

Physical dimensions
Housing (w x d x h), incl. base 60 cm x 46 cm x 30 cm
Head fit > 95% of adult population
Full face access open view and possibility to use eye tracking tools
Dynamic field measurement
Measurable variable Magnetic field magnitude
Temporal resolution 1 μs
intrinsic kmax ± 9580 rad/m
Spatial field expansion
Basis Real-valued spherical harmonics up to 3rd order
Output terms for image correction Generalized k-space (16 terms: k0 – k15)

  • 3D k-space (k1– k3)
  • Dynamic B0 perturbation (k0)
  • 2nd order perturbations (k4 – k8)
  • 3rd order perturbations (k9 – k15)
Camera Acquisition System

Skope Camera Acquisition SystemThe field sensor signals of the NeuroCam are acquired by the 16-channel Skope Camera Acquisition System and automatically processed to provide the actual magnetic field dynamics. The field dynamics can be conveniently displayed in the user interface or piped directly into the skope-i, image production software.

skope-i, image production software

The image production software complements the NeuroCam and takes into account

  • Measured/simulated gradient encoding
  • Coil sensitivity information (SENSE)
  • Static B0 maps
  • Higher order field evolution

Technical illustration

NeuroCam - Technical illustrationNeuroCam - Technical illustration


Integration into MRI set-up

Integration Skope System graphic


skope-i – Reconstruction pipeline

Publications related to initial research and employed MR images:

[1] Diffusion MRI with concurrent magnetic field monitoring. MRM: 2015.

[2] Single-shot spiral imaging enabled by an expanded encoding model. Demonstration in diffusion MRI. MRM: 2016.


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