13 research outputs found
Multi-sensor system for simultaneous ultra-low-field MRI and MEG
Magnetoencephalography (MEG) and magnetic resonance imaging at ultra-low
fields (ULF MRI) are two methods based on the ability of SQUID (superconducting
quantum interference device) sensors to detect femtotesla magnetic fields.
Combination of these methods will allow simultaneous functional (MEG) and
structural (ULF MRI) imaging of the human brain. In this paper, we report the
first implementation of a multi-sensor SQUID system designed for both MEG and
ULF MRI. We present a multi-channel image of a human hand obtained at 46
microtesla field, as well as results of auditory MEG measurements with the new
system.Comment: To appear in Proceedings of 15th International Conference on
Biomagnetis
Microtesla MRI of the human brain combined with MEG
One of the challenges in functional brain imaging is integration of
complementary imaging modalities, such as magnetoencephalography (MEG) and
functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive
superconducting quantum interference devices (SQUIDs) to directly measure
magnetic fields of neuronal currents, cannot be combined with conventional
high-field MRI in a single instrument. Indirect matching of MEG and MRI data
leads to significant co-registration errors. A recently proposed imaging method
- SQUID-based microtesla MRI - can be naturally combined with MEG in the same
system to directly provide structural maps for MEG-localized sources. It
enables easy and accurate integration of MEG and MRI/fMRI, because microtesla
MR images can be precisely matched to structural images provided by high-field
MRI and other techniques. Here we report the first images of the human brain by
microtesla MRI, together with auditory MEG (functional) data, recorded using
the same seven-channel SQUID system during the same imaging session. The images
were acquired at 46 microtesla measurement field with pre-polarization at 30
mT. We also estimated transverse relaxation times for different tissues at
microtesla fields. Our results demonstrate feasibility and potential of human
brain imaging by microtesla MRI. They also show that two new types of imaging
equipment - low-cost systems for anatomical MRI of the human brain at
microtesla fields, and more advanced instruments for combined functional (MEG)
and structural (microtesla MRI) brain imaging - are practical.Comment: 8 pages, 5 figures - accepted by JM
Multi-Channel SQUID System for MEG and Ultra-Low-Field MRI
A seven-channel system capable of performing both magnetoencephalography
(MEG) and ultra-low-field magnetic resonance imaging (ULF MRI) is described.
The system consists of seven second-order SQUID gradiometers with 37 mm
diameter and 60 mm baseline, having magnetic field resolution of 1.2-2.8
fT/rtHz. It also includes four sets of coils for 2-D Fourier imaging with
pre-polarization. The system's MEG performance was demonstrated by measurements
of auditory evoked response. The system was also used to obtain a multi-channel
2-D image of a whole human hand at the measurement field of 46 microtesla with
3 by 3 mm resolution.Comment: To appear in Proceedings of 2006 Applied Superconductivity Conferenc
SQUIDs in biomagnetism : A roadmap towards improved healthcare
This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686865.Peer reviewedPublisher PD
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING (IN SUBMISSION) 1 Blind Source Separation for the Superconducting
AbstractâMagnetic signals from brain responses are very weak compared to those from its surroundings. A system based on SQUIDs (Superconducting Quantum Interference Devices) was constructed to detect these fields. This system is novel in that it contains a superconducting lead (Pb) surface which shields the sensors from external magnetic fields. Since the signals of interest still have a low signal to noise (S/N) ratio, and each sensor receives a mixture of signals from different parts of the brain, we used a blind source separation (BSS) algorithm to separate the various sources. This increased the S/N ratio sufficiently to allow us to perform single-trial analysis of the data, including wavelet denoising
First downscattered neutron images from Inertial Confinement Fusion experiments at the National Ignition Facility
Inertial Confinement Fusion experiments at the National Ignition Facility (NIF) are designed to understand and test the basic principles of self-sustaining fusion reactions by laser driven compression of deuterium-tritium (DT) filled cryogenic plastic (CH) capsules. The experimental campaign is ongoing to tune the implosions and characterize the burning plasma conditions. Nuclear diagnostics play an important role in measuring the characteristics of these burning plasmas, providing feedback to improve the implosion dynamics. The Neutron Imaging (NI) diagnostic provides information on the distribution of the central fusion reaction region and the surrounding DT fuel by collecting images at two different energy bands for primary (13â15 MeV) and downscattered (10â12 MeV) neutrons. From these distributions, the final shape and size of the compressed capsule can be estimated and the symmetry of the compression can be inferred. The first downscattered neutron images from imploding ICF capsules are shown in this paper