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Purpose: Mitigating coupling effects between coil elements represents a continuing challenge. Here, we present a 16‐bowtie slot volume coil arranged in eight independent dual‐slot modules without the use of any decoupling circuits. Methods: Two electrically short "bowtie" slot antennas were used to form a "module." A bowtie configuration was chosen because electromagnetic modeling results show that bowtie slots exhibit improved B1+Pin$$ \frac{B_1^{+}}{\sqrt{P_{in}}} $$ efficiency when compared to thin rectangular slots. An eight‐module volume coil was evaluated through electromagnetic modeling, bench tests, and MRI experiments at 4.7 T. Results: Bench tests indicate that worst‐case coupling between modules did not exceed −14.5 dB. MR images demonstrate well‐localized patterns about single excited modules confirming the low coupling between modules. Homogeneous MR images were acquired from a synthesized quadrature birdcage transmit mode. MRI experiments show that the RF power requirements for the proposed coil are 9.2 times more than a birdcage coil. Whereas from simulations performed to assess the proposed coil losses, the total power dissipated in the phantom was 1.1 times more for the birdcage. Simulation results at 7 T reveal an equivalent B1+ homogeneity when compared with an eight‐dipole coil. Conclusion: Although exhibiting higher RF power requirements, as a transmit coil when the power availability is not a restriction, the inherently low coupling between electrically short slots should enable the use of many slot elements around the imaging volume. The slot module described in this paper should be useful in the design of multi‐channel transmit coils. [ABSTRACT FROM AUTHOR] more...

Purpose: The purpose of this work was to design and build a coil for quadri‐nuclear MRI of the human brain at 7 T. Methods: We built a transmit/receive triple‐tuned (45.6 MHz for 2$$ {}^2 $$H, 78.6 MHz for 23$$ {}^{23} $$Na, and 120.3 MHz for 31$$ {}^{31} $$P) quadrature four‐rod birdcage that was geometrically interleaved with a transmit/receive four‐channel dipole array (297.2 MHz for 1$$ {}^1 $$H). The birdcage rods contained passive, two‐pole resonant circuits that emulated capacitors required for single‐tuning at three frequencies. The birdcage assembly also included triple‐tuned matching networks, baluns, and transmit/receive switches. We assessed the performance of the coil with quality factor (Q) and signal‐to‐noise ratio (SNR) measurements, and performed in vivo multinuclear MRI and MR spectroscopic imaging (MRSI). Results: Q measurements showed that the triple‐tuned birdcage efficiency was within 33% of that of single‐tuned baseline birdcages at all three frequencies. The quadri‐tuned coil SNR was 78%, 59%, 44%, and 48% lower than that of single or dual‐tuned reference coils for 1$$ {}^1 $$H, 2$$ {}^2 $$H, 23$$ {}^{23} $$Na, and 31$$ {}^{31} $$P, respectively. Quadri‐nuclear MRI and MRSI was demonstrated in brain in vivo in about 30 min. Conclusion: While the SNR of the quadruple tuned coil was significantly lower than dual‐ and single‐tuned reference coils, it represents a step toward truly simultaneous quadri‐nuclear measurements. [ABSTRACT FROM AUTHOR] more...

Purpose: Development of a novel quadrature inductively driven transceive wireless coil for breast MRI at 1.5 T. Methods: A quadrature wireless coil (HHMM‐coil) design has been developed as a combination of two linearly polarized coils: a pair of 'metasolenoid' coils (MM‐coil) and a pair of Helmholtz‐type coils (HH‐coil). The MM‐coil consisted of an array of split‐loop resonators. The HH‐coil design included two electrically connected flat spirals. All the wireless coils were coupled to a whole‐body birdcage coil. The HHMM‐coil was studied and compared to the linear coils in terms of transmit and SAR efficiencies via numerical simulations. A prototype of HHMM‐coil was built and tested on a 1.5 T scanner in a phantom and healthy volunteer. We also proposed an extended design of the HHMM‐coil and compared its performance to a dedicated breast array. Results: Numerical simulations of the HHMM‐coil with a female voxel model have shown more than a 2.5‐fold increase in transmit efficiency and a 1.7‐fold enhancement of SAR efficiency compared to the linearly polarized coils. Phantom and in vivo imaging showed good agreement with the numerical simulations. Moreover, the HHMM‐coil provided good image quality, visualizing all areas of interest similar to a multichannel breast array with a 32% reduction in signal‐to‐noise ratio. Conclusion: The proposed quadrature HHMM‐coil allows the B1+$$ {\mathrm{B}}_1^{+} $$‐field to be significantly better focused in the region‐of‐interest compared to the linearly polarized coils. Thus, the HHMM‐coil provides high‐quality breast imaging on a 1.5 T scanner using a whole‐body birdcage coil for transmit and receive. [ABSTRACT FROM AUTHOR] more...

Lack of a body‐sized, bore‐mounted, radiofrequency (RF) body coil for ultrahigh field (UHF) magnetic resonance imaging (MRI) is one of the major drawbacks of UHF, hampering the clinical potential of the technology. Transmit field (B1) nonuniformity and low specific absorption rate (SAR) efficiencies in UHF MRI are two challenges to be overcome. To address these problems, and ultimately provide a pathway for the full clinical potential of the modality, we have designed and simulated two‐dimensional cylindrical high‐pass ladder (2D c‐HPL) architectures for clinical bore‐size dimensions, and demonstrated a simplified proof of concept with a head‐sized prototype at 7 T. A new dispersion relation has been derived and electromagnetic simulations were used to verify coil modes. The coefficient of variation (CV) for brain, cerebellum, heart, and prostate tissues after B1+ shimming in silico is reported and compared with previous works. Three prototypes were designed in simulation: a head‐sized, body‐sized, and long body‐sized coil. The head‐sized coil showed a CV of 12.3%, a B1+ efficiency of 1.33 μT/√W, and a SAR efficiency of 2.14 μT/√(W/kg) for brain simulations. The body‐sized 2D c‐HPL coil was compared with same‐sized transverse electromagnetic (TEM) and birdcage coils in silico with a four‐port circularly polarized mode excitation. Improved B1+ uniformity (26.9%) and SAR efficiency (16% and 50% better than birdcage and TEM coils, respectively) in spherical phantoms was observed. We achieved a CV of 12.3%, 4.9%, 16.7%, and 2.8% for the brain, cerebellum, heart, and prostate, respectively. Preliminary imaging results for the head‐sized coil show good agreement between simulation and experiment. Extending the 1D birdcage coil concept to 2D c‐HPLs provides improved B1+ uniformity and SAR efficiency. [ABSTRACT FROM AUTHOR] more...

Purpose: To evaluate specific absorption rate (SAR) and temperature distributions resulting from pediatric exposure to a 7T head coil. Methods: Exposure from a 297‐MHz birdcage head transmit coil (CP mode single‐channel transmission) was simulated in several child models (ages 3–14, mass 13.9–50.4 kg) and one adult, using time‐domain electromagnetic and thermal solvers. Position variability, age‐related changes in dielectric properties, and differences in thermoregulation were also considered. Results: Age‐adjusted dielectric properties had little effect in this population. Head average SAR (hdSAR) was the limiting factor for all models centered in the coil. The value of hdSAR (normalized to net power) was found to decrease linearly with increasing mass (R2 = 0.86); no equivalent relationship for peak‐spatial 10g averaged SAR (psSAR10g) was identified. Relatively small (< 10%) variability was observed in hdSAR for position shifts of ±25 mm in each orthogonal direction when normalized to net power; accounting for B1+$$ {\mathrm{B}}_1^{+} $$ efficiency can lead to much larger variability. Position sensitivity of psSAR10g was greater, but in most cases hdSAR remained the limiting quantity. For thermal simulations, if blood temperature is fixed (i.e., asserting good thermoregulation), maximum temperatures are compliant with International Electrotechnical Commission limits during 60‐min exposure at the SAR limit. Introducing variable blood temperature leads to core temperature changes proportional to whole‐body averaged SAR, exceeding guideline limits for all child models. Conclusions: Children experienced higher SAR than adults for the 297‐MHz head transmit coil examined in this work. Thermal simulations suggest that core temperature changes could occur in smaller subjects, although experimental data are needed for validation. [ABSTRACT FROM AUTHOR] more...

Purpose: There is increasing use of open‐bore vertical MR systems that consist of two planar RF coils. A recent study showed that the RF‐induced heating of a neuromodulation device was much lower in the open‐bore system at the brain and the chest imaging landmarks. This study focused on the hip and knee implants and compared the specific absorption rate (SAR) distribution in human models in a 1.2T open‐bore coil with that of a 1.5T conventional birdcage coil. Methods: Computational modeling results were compared against the measurement values using a saline phantom. The differences in RF exposure were examined between a 1.2T open‐bore coil and a 1.5T conventional birdcage coil using SAR in an anatomical human model. Results: Modeling setups were validated. The body placed closed to the coil elements led to high SAR values in the birdcage system compared with the open‐bore system. Conclusion: Our computational modeling showed that the 1.2T planar system demonstrated a lower intensity of SAR distribution adjacent to hip and knee implants compared with the 1.5T conventional birdcage system. [ABSTRACT FROM AUTHOR] more...

Purpose: To test an integrated "AC/DC" array approach at 7T, where B0 inhomogeneity poses an obstacle for functional imaging, diffusion‐weighted MRI, MR spectroscopy, and other applications. Methods: A close‐fitting 7T 31‐channel (31‐ch) brain array was constructed and tested using combined Rx and ΔB0 shim channels driven by a set of rapidly switchable current amplifiers. The coil was compared to a shape‐matched 31‐ch reference receive‐only array for RF safety, signal‐to‐noise ratio (SNR), and inter‐element noise correlation. We characterize the coil array's ability to provide global and dynamic (slice‐optimized) shimming using ΔB0 field maps and echo planar imaging (EPI) acquisitions. Results: The SNR and average noise correlation were similar to the 31‐ch reference array. Global and slice‐optimized shimming provide 11% and 40% improvements respectively compared to baseline second‐order spherical harmonic shimming. Birdcage transmit coil efficiency was similar for the reference and AC/DC array setups. Conclusion: Adding ΔB0 shim capability to a 31‐ch 7T receive array can significantly boost 7T brain B0 homogeneity without sacrificing the array's rdiofrequency performance, potentially improving ultra‐high field neuroimaging applications that are vulnerable to off‐resonance effects. [ABSTRACT FROM AUTHOR] more...

Purpose: To theoretically describe, design, and test the new geometry of the birdcage coil for 7 Tesla anatomical brain imaging, which includes a large window on top, without deliberately jeopardizing its homogeneity and efficiency. This opencage will not only improve patient comfort but also enable the volunteer to follow functional MRI stimuli. This design could also facilitate the tracking of patient compliance and enable better correction of the movement. Methods: Via the transfer matrix approach, a birdcage‐like coil with a nonperiodic distribution of rungs is constructed with optimized currents in the coil rungs. Subsequently, the coil is adjusted in full‐wave simulations. Then, the coil is assembled, fine‐tuned, and matched on the bench. Finally, these results are confirmed experimentally on a phantom and in vivo. Results: Indeed, the computed isolation of −14.9 dB between the feeding ports of the coil and the symmetry of the circular polarized mode pattern transmit RF magnetic field (B1+) showed that the coil was properly optimized. An experimental assessment of the developed coil showed competitive transmit efficiency and coverage compared with the conventional birdcage coil of similar size. Conclusion: The proposed opencage coil can be designed and work without a dramatic drop of performance in terms of the B1+ field homogeneity, transmit efficiency (B1+/Pref), peak local specific absorption rate (SAR10g) and SAR efficiency (B1+/SAR10g). [ABSTRACT FROM AUTHOR] more...

Demand for cage birds is highly prevalent and increasing across Indonesia, as wild bird populations across Asia decline. To find ways to reduce demand, it is important to understand the motivations and psychographic drivers to keep (or not keep) birds, and how demographic characteristics and public attitudes influence such decisions. Based on surveys with over 3,000 people, we found few people citing health, sanitary, or welfare concerns as reasons for not keeping birds, whereas most people started keeping birds to enjoy their beauty or song, or to keep up with peers. Pet‐keepers ("Hobbyists") commonly started doing so opportunistically; song contest participants ("Contestants") and breeders and trainers ("Breeders") did so for financial gain. Bird‐keepers and non‐bird‐keepers disagreed on birds' environmental importance, longevity in captivity, and endangerment by trade. Older respondents were less concerned that keeping birds endangers them and few felt birds to be an important part of the environment. Hobbyists were least likely to consider wild bird population health a major concern. Efforts to dissuade potential bird‐keepers should focus on public concern for the environment and the threat bird‐keeping poses to wild populations. The importance of peer pressure among bird‐keepers presents an opportunity to promote sustainable bird‐keeping activities among key groups. [ABSTRACT FROM AUTHOR] more...

Purpose: An unmet need in carbon‐13 (13C)‐MRI is a transmit system that provides uniform excitation across a large FOV and can accommodate patients of wide‐ranging body habitus. Due to the small difference between the resonant frequencies, sodium‐23 (23Na) coil developments can inform 13C coil design while being simpler to assess due to the higher naturally abundant 23Na signal. Here we present a removable 23Na birdcage, which also allows operation as a 13C abdominal coil. Methods: We demonstrate a quadrature‐driven 4‐rung 23Na birdcage coil of 50 cm in length for both 23Na and 13C abdominal imaging. The coil transmit efficiencies and B1+ maps were compared to a linearly driven 13C Helmholtz‐based (clamshell) coil. SNR was investigated with 23Na and 13C data using an 8‐channel 13C receive array within the 23Na birdcage. Results: The 23Na birdcage longitudinal FOV was > 40 cm, whereas the 13C clamshell was < 32 cm. The transmit efficiency of the birdcage at the 23Na frequency was 0.65 µT/sqrt(W), similar to the clamshell for 13C. However, the coefficient of variation of 23Na‐B1+ was 16%, nearly half that with the 13C clamshell. The 8‐channel 13C receive array combined with the 23Na birdcage coil generated a greater than twofold increase in 23Na‐SNR from the central abdomen compared with the birdcage alone. Discussion: This 23Na birdcage coil has a larger FOV and improved B1+ uniformity when compared to the widely used clamshell coil design while also providing similar transmit efficiency. The coil has the potential to be used for both 23Na and 13C imaging. [ABSTRACT FROM AUTHOR] more...

In this work a 21 MHz radiofrequency (RF) exposure system was designed, constructed and evaluated as a testing platform for MRI device safety. The exposure system consisted of a birdcage coil powered in quadrature by a power system consisting of a hybrid coupler, a power splitter, a phase shifter and two baluns. The birdcage coil was designed as a low‐pass 16 rung coil. Both the coil and the power system were fabricated as printed circuit boards with a copper thickness of 205.7 μm and a G10 substrate thickness of 581.7 μm. The birdcage was assembled by wrapping the copper clad G10 inside of an acrylic tube. A shield for the coil was created as a cylindrical ground plane with a diameter of 39.7 cm. The birdcage and the power system were simulated in ADS and EMPro, Keysight Technologies Inc. both as lumped elements and using full wave 3D simulations. Simulation results were compared to measurements of the produced components to validate each component and entire system. In addition, a 3D magnetic field probe was developed to measure and compare the fields to analytical and numerical calculations. [ABSTRACT FROM AUTHOR] more...

Purpose: Multichannel transcranial magnetic stimulation (TMS)1 is an emerging technology that allows multiple sites to be stimulated simultaneously or sequentially under electronic control without movement of the coils. A multichannel TMS/MRI head coil array for 3 Tesla is currently under development to mitigate challenges of concurrent TMS/fMRI as well as enable potential new applications. The influence of the multichannel TMS system on the MR image quality and safety must be carefully investigated. Methods: A standard birdcage volume coil for 3 Tesla systems was simulated using a commercial numerical electromagnetic solver. Two setups, consisting of 1) a MR‐compatible TMS coil, and 2) a 3‐axis TMS coil array, were simulated to quantify changes in the transmit field B1+ and the SAR. A realistically shaped homogeneous head model was used in the computations. Results: The stimulation coils produced enhancements and attenuations on the transmit field with effects greater than 5% up to 2.4 cm and 3.3 cm under the scalp for the MR‐compatible TMS coil and 3‐axis TMS coil array, respectively. The 10 g‐SAR distribution did not change significantly in either of the cases; however, the nominal SAR maximum locus was shifted between existing hot spots. Conclusion: The simulated B1+ variations found near the TMS coils indicate the possibility of inducing sequence‐dependent image artefacts predominatly limited to the vicinity of the coil(s). However, we conclude that neither the MR‐compatible commercial TMS coil nor the 3‐axis TMS coil array siginificantly elevate SAR in the head or neck beyond accepted safety limits. [ABSTRACT FROM AUTHOR] more...

This article explores a historic rural craft tradition as the focus of economic development through the valorisation of the local cultural heritage, or culture economy. The case‐study traces the revival of bamboo birdcage making in Da'ou village in Shandong Province, where the craft knowledge of making birdcages once prized by the Chinese imperial court has been passed on through generations and protected from outsiders. Since economic reforms in the 1980s, the birdcage craft has again become the major activity in Da'ou village, responding to new urban market demands, and bringing prosperity. Yet, through a conceptualisation of cultural heritage as a 'prosaic third space', the article reveals the dynamics and tensions involved in the incorporation of the birdcage tradition in local economic development strategies and the promotion of e‐commerce and tourism, and the processes of abstraction initiated. As such, it raises questions about the relationship between craft, knowledge and place that resonate beyond China. The research is based on semi‐structured interviews conducted in 2016 with respondents including local leaders, craftspeople, suppliers, and sellers. [ABSTRACT FROM AUTHOR] more...

Feather samples of 80 birds, representing 18 breeds and six groups of fancy pigeons, racing and feral population of pigeons, were investigated with consent of the Polish Association of Pedigree Pigeons and Small Livestock Breeders. In the European Association of Poultry, Pigeon, Cage Bird, Rabbit and Cavy Breeders, more than 1100 fancy pigeon breeds are recognized and grouped to eight Groups (Table 1, Fig. Breeding of fancy pigeons is a popular hobby all over the world. [Extracted from the article] more...

Invited for the cover of this issue is the group of Atsushi Shimojima and Kazuyuki Kuroda at Waseda University. The image depicts the functionalization of a cubic cage germanoxane (birdcage) containing a fluoride ion (blue bird) inside the cage. Read the full text of the article at10.1002/chem.201900439. [ABSTRACT FROM AUTHOR] more...