To explore the use of five meandering dipole antennas in a multi-transmit setup, combined with a high density receive array for breast imaging at 7 T for improved penetration depth and more ...homogeneous B
field. Five meandering dipole antennas and 30 receiver loops were positioned on two cups around the breasts. Finite difference time domain simulations were performed to evaluate RF safety limits of the transmit setup. Scattering parameters of the transmit setup and coupling between the antennas and the detuned loops were measured. In vivo parallel imaging performance was investigated for various acceleration factors. After RF shimming, a B
map, a T
-weighted image, and a T
-weighted image were acquired to assess B
efficiency, uniformity in contrast weighting, and imaging performance in clinical applications. The maximum achievable local SAR
value was 7.0 W/kg for 5 × 1 W accepted power. The dipoles were tuned and matched to a maximum reflection of -11.8 dB, and a maximum inter-element coupling of -14.2 dB. The maximum coupling between the antennas and the receive loops was -18.2 dB and the mean noise correlation for the 30 receive loops 7.83 ± 8.69%. In vivo measurements showed an increased field of view, which reached to the axilla, and a high transmit efficiency. This coil enabled the acquisition of T
-weighted images with a high spatial resolution of 0.7 mm
isotropic and T
-weighted spin echo images with uniformly weighted contrast.
To explore the use of five meandering dipole antennas in a multi‐transmit setup, combined with a high density receive array for breast imaging at 7 T for improved penetration depth and more ...homogeneous B1 field. Five meandering dipole antennas and 30 receiver loops were positioned on two cups around the breasts. Finite difference time domain simulations were performed to evaluate RF safety limits of the transmit setup. Scattering parameters of the transmit setup and coupling between the antennas and the detuned loops were measured. In vivo parallel imaging performance was investigated for various acceleration factors. After RF shimming, a B1 map, a T1‐weighted image, and a T2‐weighted image were acquired to assess B1 efficiency, uniformity in contrast weighting, and imaging performance in clinical applications. The maximum achievable local SAR10g value was 7.0 W/kg for 5 × 1 W accepted power. The dipoles were tuned and matched to a maximum reflection of −11.8 dB, and a maximum inter‐element coupling of −14.2 dB. The maximum coupling between the antennas and the receive loops was −18.2 dB and the mean noise correlation for the 30 receive loops 7.83 ± 8.69%. In vivo measurements showed an increased field of view, which reached to the axilla, and a high transmit efficiency. This coil enabled the acquisition of T1‐weighted images with a high spatial resolution of 0.7 mm3 isotropic and T2‐weighted spin echo images with uniformly weighted contrast.
The use of a bilateral breast coil with five meandering dipoles and 30 receive loops at 7 T showed uniform B1 field with a large field of view reaching beyond the axilla. This coil enabled the acquisition of T1‐weighted images with a high spatial resolution of 0.7 mm3 isotropic and T2‐weighted spin echo images with uniformly weighted contrast.
Glutamate changes in healthy young adulthood Marsman, Anouk; Mandl, René C.W; van den Heuvel, Martijn P ...
European neuropsychopharmacology,
11/2013, Volume:
23, Issue:
11
Journal Article
Peer reviewed
Open access
Abstract Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and has been associated with several cognitive functions that are known to change with age. In ...rodents and humans age-related glutamate changes have been found in several brain areas. In this cross-sectional study the presence and extent of age-associated glutamate changes in the medial frontal cortex of healthy young adults were measured. Proton magnetic resonance spectroscopy (1 H-MRS) and brain imaging were performed at 7 T in a 2×2×2 cm3 voxel in 33 participants between 18 and 31 years old. Glutamate concentrations and grey and white matter volume could be successfully determined at an ultra-high magnetic field strength. Glutamate concentrations were lower in older individuals (0.33 mM/year). This decline is in line with grey matter thinning in the medial frontal cortex, but could not be explained by cortical thinning alone. Therefore, the decrease in glutamate in young adulthood may be due to physiological changes rather than anatomical changes.
To assess the ability of a polarization transfer (PT) magnetic resonance spectroscopy (MRS) technique to improve the detection of the individual phospholipid metabolites phosphocholine (PC), ...phosphoethanolamine (PE), glycerophosphocholine (GPC), and glycerophosphoethanolamine (GPE) in vivo in breast tumor xenografts.
The adiabatic version of refocused insensitive nuclei enhanced by polarization transfer (BINEPT) MRS was tested at 9.4 Tesla in phantoms and animal models. BINEPT and pulse-acquire (PA) 31P MRS was acquired consecutively from the same orthotopic MCF-7 (n = 10) and MDA-MB-231 (n = 10) breast tumor xenografts. After in vivo MRS measurements, animals were euthanized, tumors were extracted and high resolution (HR)-MRS was performed. Signal to noise ratios (SNRs) and metabolite ratios were compared for BINEPT and PA MRS, and were also measured and compared with that from HR-MRS.
BINEPT exclusively detected metabolites with 1H-31P coupling such as PC, PE, GPC, and GPE, thereby creating a significantly improved, flat baseline because overlapping resonances from immobile and partly mobile phospholipids were removed without loss of sensitivity. GPE and GPC were more accurately detected by BINEPT in vivo, which enabled a reliable quantification of metabolite ratios such as PE/GPE and PC/GPC, which are important markers of tumor aggressiveness and treatment response.
BINEPT is advantageous over PA for detecting and quantifying the individual phospholipid metabolites PC, PE, GPC, and GPE in vivo at high magnetic field strength. As BINEPT can be used clinically, alterations in these phospholipid metabolites can be assessed in vivo for cancer diagnosis and treatment monitoring.
Phosphorus MRS offers a non‐invasive tool for monitoring cell energy and phospholipid metabolism and can be of additional value in diagnosing cancer and monitoring cancer therapy. In this study, we ...determined the transverse relaxation times of a number of phosphorous metabolites in a group of breast cancer patients by adiabatic multi‐echo spectroscopic imaging at 7 T. The transverse relaxation times of phosphoethanolamine, phosphocholine, inorganic phosphate (Pi), glycerophosphocholine and glycerophosphatidylcholine were 184 ± 8 ms, 203 ± 17 ms, 87 ± 8 ms, 240 ± 56 ms and 20 ± 10 ms, respectively. The transverse relaxation time of Pi in breast cancer tissue was less than half that of healthy fibroglandular tissue. This effect is most likely caused by an up‐regulation of glycolysis in breast cancer tissue that leads to interaction of Pi with the GAPDH enzyme, which forms part of the reversible pathway of exchange of Pi with gamma‐adenosine tri‐phosphate, thus shortening its apparent transverse relaxation time. As healthy breast tissue shows very little glycolytic activity, the apparent T2 shortening of Pi due to malignant transformation could possibly be used as a biomarker for cancer.
Transverse relaxation times of phosphorous metabolites were determined in breast cancer tissue at 7 T. The apparent T2 of Pi was less than half that of healthy fibroglandular tissue. This effect is most likely caused by an up‐regulation of glycolysis in breast cancer tissue that leads to increased interaction of Pi with the GADPH enzyme, thus shortening its apparent T2. As healthy breast tissue shows very little glycolytic activity, the observed effect may serve as a biomarker for cancer.
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