CSI Data Research Articles

Restaurant consumer satisfaction research as a basis for ensuring rational consumption patterns

The article is devoted to the study of the degree of satisfaction of consumers of a public catering enterprise as the basis for ensuring rational consumption patterns at the present stage of economic sustainability development and the most important criterion of the company’s performance in order to obtain long-term profit. Customer satisfaction research is one of the main directions in marketing. The provision of rational consumption patterns, according to the authors, in line with the assessment of consumer satisfaction is influenced by many factors such as the environment, consumer behavior patterns, the quality of food and service, the atmosphere, and the company’s image. The main methods we use in assessing satisfaction are SERVQUAL, NPS, and CSI. The CSI index assesses the level of customer satisfaction immediately after interacting with the company. It is based on identifying product properties that are important to the consumer. NPS is one of the best tools for determining the effectiveness of a company in determining the degree of customer loyalty. The concept of “SERVQUAL” reflects in detail the peculiarities of customer perception of service services, allows them to come to an understanding of the standard that will be most in demand among customers.To describe the “Customer Satisfaction” process, the authors used a process passport, which contains the following elements: process name, process definition, process goal, process inputs / outputs, process consumers, process resources, process performance indicators and their criteria, methods of measuring indicators.From the analysis of CSI data obtained from clients, conclusions are drawn about the most important indicators. In this case, it is the quality of the food, the atmosphere, the level of service. Based on the study, recommendations have been developed aimed at increasing the degree of consumer satisfaction and increasing the competitiveness of the catering enterprise.

An Indoor Geolocation Algorithm based on CSI and Affine Propagation Clustering

An indoor geolocation algorithm based on WLAN CSI and affine propagation clustering is proposed in this paper. In this algorithm, the wireless network adaptor Intel 5300 and 802.11n CSI Tools is used to collect the CSI data, and the PCA algorithm is used to reduce the dimension of the CSI data from 30 to 3, based on which the CSI fingerprint database is established. And the affine propagation clustering algorithm is used to group the reference nodes into clusters and then the WKNN is adopted to realize precise indoor geolocation. Experiment results show that the algorithm in this paper has a better performance in the location accuracy, 74% of the testing results has the accuracy of 1m, and 95% of the testing results has the accuracy of 2m.

A robust and accurate indoor localization system using deep auto-encoder combined with multi-feature fusion

Many existing indoor localization systems use RSS as fingerprints, but RSS is a coarse-grained data, which not only fluctuates over time but also is not unique for a specific location due to rich multi-path effects and shadow fading in indoor environments. In order to further improve the localization accuracy, a robust and accurate indoor localization algorithm based on deep auto-encoder network combine with multi-feature fusion. To extract deep features hidden in CSI data and reduce the computational complexity of localization, an improved method is designed to achieve dimension reduction and feature extraction, which can avoid explicit information extraction of available CSI characteristics on the basis of effective representation of CSI fingerprint difference between different locations. Then, the fingerprint database is constructed by combination of RSS and CSI coding. Moreover, the Naive Bayer Classifier is adopted to improve the localization accuracy and stability. In the simulation experiment, the positioning effect of the proposed algorithm under different fingerprint libraries and the positioning effect under different positioning methods are mainly carried out. Experimental results show that the proposed method can effectively perform indoor positioning and has good practicability in the actual production environment.

Modelling, Analysis, and Simulation of the Micro-Doppler Effect in Wideband Indoor Channels with Confirmation Through Pendulum Experiments.

This paper is about designing a 3D no n-stationary wideband indoor channel model for radio-frequency sensing. The proposed channel model allows for simulating the time-variant (TV) characteristics of the received signal of indoor channel in the presence of a moving object. The moving object is modelled by a point scatterer which travels along a trajectory. The trajectory is described by the object’s TV speed, TV horizontal angle of motion, and TV vertical angle of motion. An expression of the TV Doppler frequency caused by the moving scatterer is derived. Furthermore, an expression of the TV complex channel transfer function (CTF) of the received signal is provided, which accounts for the influence of a moving object and fixed objects, such as walls, ceiling, and furniture. An approximate analytical solution of the spectrogram of the CTF is derived. The proposed channel model is confirmed by measurements obtained from a pendulum experiment. In the pendulum experiment, the trajectory of the pendulum has been measured by using an inertial-measurement unit (IMU) and simultaneously collecting CSI data. For validation, we have compared the spectrogram of the proposed channel model fed with IMU data with the spectrogram characteristics of the measured CSI data. The proposed channel model paves the way towards designing simulation-based activity recognition systems.

Adversarial WiFi Sensing for Privacy Preservation of Human Behaviors

Recent research on WiFi sensing focuses on the identification of a wide range of human behaviors with high recognition accuracy. However, these well-studied recognition techniques can cause privacy concerns due to the ubiquity of WiFi signal and comprehensive behavior information embedded therein. In this letter, we take the first attempt to develop an adversarial deep network architecture for human behavior preservation. Our goal is to make desirable private behaviors of a human being not recognizable by general classifiers, while the recognition of other ones remaining unaffected. To achieve this, we propose a novel loss function, using which our network is capable of intentionally modifying CSI data extracted from received WiFi signal, constraining the new classification results to match the adversarial requirements. Experimental results demonstrate that, with the proposed adversarial scheme, the recognition rate of the human behaviors needed to be protected can be significantly decreased, while still maintaining the accuracy of other ones desired to be identified. Our source codes are available at https://github.com/siwangzhou/WiFi-ADG.

Mitigation & Identification for Local Aridity, Based of Vegetation Indices Combined with Spatial Statistics & Clustering K Means

This research aims to develop new methods of mapping aridity risk zones and their potential impacts on land fires using a combination of indices to identify land fires such as the CSI and NBR and the indices for NDVI and SAVI. The research location is in Gunung Merapi National Park (TNGM) and Gunung Merbabu National Park (TNGMb), in Central Java Province and Yogyakarta. The data used in this research is Landsat 8 OLI image year 2010-2018, DEM data from ASTER image in TNGM and TNGMb area using landsat 8 OLI image specification. The research was conducted in 3 stages such as pre-processing, image data extraction and post-processing. Global and Local Moran’s Analysis on NDVI, SAVI, CSI and NBR vegetation indices data can be used as an indicator of aridity and potential land fires. The experiments show that the average is in class 4 including the moderate greenish classification. Moderate greenish is interpreted that the study area is overgrown with meadows, shrubs, barren, sandy, rocky areas and a low population of vegetation canopy that shows that the area is on the surrounding mountain peaks. The results of the analysis shows Positive Spatial Autocorrelation, the phenomenon of aridity has spatial connectivity between observed regions. Analysis of K Means on the high vegetation density conditions shows that the weight of the distance between the vegetation data to the centroid is shorter, therefore the data is concentrated on a region. In low vegetation density conditions, the weight of the distance between the data to the centroid is increasingly wide, therefore the data looks more widely distributed.

Dynamic metabolic imaging of copolarized [2-13 C]pyruvate and [1,4-13 C2 ]fumarate using 3D-spiral CSI with alternate spectral band excitation.

Developing a method for simultaneous metabolic imaging of copolarized [2-13 C]pyruvate and [1,4-13 C2 ]fumarate without chemical shift displacement artifacts that also permits different excitation flip angles for substrates and their metabolic products. The proposed pulse sequence consists of 2 frequency-selective radiofrequency pulses to alternatingly excite 2 spectral sub-bands each one followed by a fast 3D spiral CSI (3D-spCSI) readout. Spectrally selective radiofrequency pulses were designed to excite differential flip angles on substrates and products in each spectral sub-band. Number of signal averages analysis was used to determine a spectral width suitable to resolve the metabolites of interest in each of the sub-bands. Phantom experiments verified the copolarization strategy and radiofrequency pulse design following differential flip angle used in our method. The signal behavior of the resonances in each sub-band was unaffected by the excitation of the respective alternate frequency band. Dynamic 3D 13 C CSI data demonstrated the ability of the sequence to image metabolites like pyruvate-hydrate, lactate, alanine, fumarate, and malate simultaneously and detect metabolic changes in the liver in a rat model of carbon tetrachloride-induced liver damage. The presented method allows the dynamic CSI of a mixture of [2-13 C]pyruvate and [1,4-13 C2 ]fumarate without chemical shift displacement artifacts while also permitting the use of different flip angles for substrate and product signals. The method is potentially useful for combined in vivo imaging of inflammation and cell necrosis.

MSDFL: a robust minimal hardware low-cost device-free WLAN localization system

The research on fingerprint-based device-free (DF) indoor localization has attracted great interest due to the ubiquitous of radio frequency signals and its accuracy. Most such approaches typically require a large number of transmitters and receivers to achieve acceptable accuracy, and there is another problem that the accuracy is degraded due to the expiration of the fingerprint database over time. In this paper, we present an accurate fingerprint-based device-free localization system using only a single stream over time, termed MSDFL. By analyzing the CSI fingerprint patterns and comparing the matrix similarity between CSI fingerprints and testing CSI samples matrix, the proposed MS algorithm is able to provide accurate DF localization with only a single stream. To cope with the noisy CSI samples and remove the subcarriers greatly affected by multipath, a novel CSI pre-processing scheme is applied on CSI data to reduce the noise and extract the most contributing subcarriers. In addition, to overcome the decrease in positioning accuracy caused by the expiration of the fingerprint database, a rigorously designed update scheme using artificial neural network is utilized for the renewal of fingerprinting database, which further enhance the performance of our system over time. Experimental results are presented to confirm that MSDFL can effectively improve location accuracy, compared with the other existing methods in representative indoor environment.

Unveiling a hidden 31 P signal coresonating with extracellular inorganic phosphate by outer-volume-suppression and localized 31 P MRS in the human brain at 7T.

The study was undertaken to demonstrate that there is more than 1 component in the extracellular Pi31 P signal ( Piex) acquired from human head using nonlocalized 31 P MRS. Outer-volume-suppression (OVS) saturation and 1D/2D 31 P CSI were utilized to reveal the presence of an additional component in the Piex signal. 67% of the head extracellular Pi signal was attenuated upon OVS saturation of the peripheral meningeal tissues, likely reflecting elimination of the Pi signal in the meningeal fluids (the blood and CSF). Localized 1D/2D CSI data provided further support for this assignment. Upon correction for the meningeal contribution, the extracellular Pi concentration was 0.51 ± 0.07 mM, whereas the intracellular Pi was 0.85 ± 0.10 mM. The extracellular pH was measured as 7.32 ± 0.04 when using OVS, as compared to 7.39 ± 0.03 when measured without OVS (N = 7 subjects). The extracellular Pi signal acquired from the human head using nonlocalized 31 P MRS contains a significant component likely contributed by peripheral blood and CSF in meninges that must be removed in order to use this signal as an endogenous probe for measuring extracellular pH and other properties in the brain.

317 Cost-Effectiveness of a Novel Cervical Spine Clearance Protocol

Abstract INTRODUCTION Cervical spine injury (CSI) occurs in 2–4% of trauma patients in the USA causing significant decrements in quality of life and even death. Treatment of CSI is estimated to cost $9.7 billion annually. Computed tomography (CT) has an almost 100% negative predictive value (NPV) for cervical spine (c-spine) clearance, in both alert and obtunded patients. However, MRI can depict occult discoligamentous injury in some patients with negative CT scans. It remains unclear whether MRI findings should preclude c-spine clearance and prolong hospital stay. This review intends to critically assess CT-missed CSI patients and derive a safe, economically sustainable protocol for c-spine clearance. METHODS A retrospective review of prospectively collected CSI data from two, level-1 trauma centers, was conducted from 2015–2016. Primary outcome measures include: NPV and the incremental cost-effectiveness ratio (ICER) of a novel c-spine clearance protocol compared with standard of care. The protocol included thin-cut CT scans with either weight-bearing or flexion-extension films. The ICER was calculated using standard cost-utility analysis techniques in US dollars ($) per quality-adjusted-life-year (QALY), assuming a willingness-to-pay threshold of 50,000$/QALY. RESULTS >A total of 614 patients were reviewed. Mean age was 38.3 years (SD 18.6), 147 (23.9%) had altered mentation, and 12 (2%) had clinically meaningful CT-missed acute discoligamentous disruption. Our c-spine clearance protocol had a NPV of 99.8% (CI 96.5-100%). There was no statistically significant difference between awake and obtunded patients (P = 0.74). Mean time to c-spine clearance improved by 1.3 days (SD 0.9). Duration of c-spine immobilization was reduced by 930 person-days. Mean cost savings was $1230 (SD $242) per patient. Mean change in QALY was 0.02 (SD 0.01). The ICER was 61,500$/QALY. CONCLUSION Our novel CSI clearance protocol is both safe and highly cost-effective. It improves outcomes at less cost, making it a dominant strategy that centers should consider implementing.

An indirect method for in vivo T2 mapping of [1-13 C] pyruvate using hyperpolarized 13 C CSI.

An indirect method for in vivo T2 mapping of 13 C-labeled metabolites using T2 and T2 * information of water protons obtained a priori is proposed. The T2 values of 13 C metabolites are inferred using the relationship to T2 ' of coexisting 1 H and the T2 * of 13 C metabolites, which is measured using routine hyperpolarized 13 C CSI data. The concept is verified with phantom studies. Simulations were performed to evaluate the extent of T2 estimation accuracy due to errors in the other measurements. Also, bias in the 13 C T2 * estimation from the 13 C CSI data was studied. In vivo experiments were performed from the brains of normal rats and a rat with C6 glioma. Simulation results indicate that the proposed method provides accurate and unbiased 13 C T2 values within typical experimental settings. The in vivo studies found that the estimated T2 of [1-13 C] pyruvate using the indirect method was longer in tumor than in normal tissues and gave values similar to previous reports. This method can estimate localized T2 relaxation times from multiple voxels using conventional hyperpolarized 13 C CSI and can potentially be used with time resolved fast CSI.

Speeding up dynamic spiral chemical shift imaging with incoherent sampling and low-rank matrix completion.

To improve the temporal and spatial resolution of dynamic 13 C spiral chemical shift imaging via incoherent sampling and low-rank matrix completion (LRMC). Spiral CSI data were both simulated and acquired in rats, and undersampling was implemented retrospectively and prospectively by pseudorandomly omitting a fraction of the spiral interleaves. Undersampled data were reconstructed with both LRMC and a conventional inverse nonuniform fast Fourier transform (iNUFFT) and compared with fully sampled data. Two-fold undersampling with LRMC reconstruction enabled a two-fold improvement in temporal or spatial resolution without significant artifacts or spatiotemporal distortion. Conversely, undersampling with iNUFFT reconstruction created strong artifacts that obscured the image. LRMC performed better at time points with strong metabolite signal. Incoherent undersampling and LRMC provides a way to increase the spatiotemporal resolution of spiral CSI without degrading data integrity. Magn Reson Med 77:951-960, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

31P CSI of the human brain in healthy subjects and tumor patients at 9.4 T with a three-layered multi-nuclear coil: initial results

Investigation of the feasibility and performance of phosphorus ((31)P) magnetic resonance spectroscopic imaging (MRSI) at 9.4 T with a three-layered phosphorus/proton coil in human normal brain tissue and tumor. A multi-channel (31)P coil was designed to enable MRSI of the entire human brain. The performance of the coil was evaluated by means of electromagnetic field simulations and actual measurements. A 3D chemical shift imaging approach with a variable repetition time and flip angle was used to increase the achievable signal-to-noise ratio of the acquired (31)P spectra. The impact of the resulting k-space modulation was investigated by simulations. Three tumor patients and three healthy volunteers were scanned and differences between spectra from healthy and cancerous tissue were evaluated qualitatively. The high sensitivity provided by the 27-channel (31)P coil allowed acquiring CSI data in 22min with a nominal voxel size of 15×15×15mm(3). Shimming and anatomical localization could be performed with the integrated four-channel proton dipole array. The amplitudes of the phosphodiesters and phosphoethanolamine appeared reduced in tumorous tissue for all three patients. A neutral or slightly alkaline pH was measured within the brain lesions. These initial results demonstrate that (31)P 3D CSI is feasible at 9.4T and could be performed successfully in healthy subjects and tumor patients in under 30min.

Abstract 18663: Myocardial Heterogeneity in Heart With Postinfarction LV Remodeling and its Response to Cell Therapy

Rationale and Objective: Human induced pluripotent stem cells (hiPSCs) hold promise for myocardial repair following injury. Here, we investigated the functional impact and myocardial heterogeneity of bioenergetics using a porcine model of post infarction LV remodeling, and 2 dimensional chemical shift imaging (2D CSI) P-31 MR spectroscopy. Methods and Results: Ischemia-reperfusion (I/R) injury was surgically induced by occlusion distal LAD (OCCL) for 60 minutes in female Yorkshire farm swine (≈15kg), then randomly assigned to experimental groups: 1) 16 million human induced pluripotent stem cells (hiPSC) derived cardio myocytes (CMs), smooth muscle cells (SMC) and Endothelia cells (ECs) were directly myocardial injected through an epicardial fibrin patch (P+Cell, n= 4), 2) open patch (fibrin patch with no cell) were placed over the injury site (P w/o Cell, n=4). Size matched normal (n=9) and OCCL only (n=5) pigs were also studied. Four weeks after I/R, 2D CSI MRS studies were performed in a 9.4T/ 65 cm bore magnet. In vivo myocardial energetic mapping was achieved using 31 P 2D CSI. To measure the forward flux rate PCr to ATP, 2D CSI data were acquired with or without saturation on ATPγ resonance. I/R injury has a heterogeneous effect on LV myocardial bioenergetics. Myocardial creatine phosphate (PCr)/ATP ratio is significantly decreased in border zone (BZ) of the infarction than the myocardial areas remote from the scar (RZ) in cell treated and patch only groups (1.54+/- 0.05 vs 2.25 +/- 0.10, 1.49+/-0.07 vs 2.34 +/- 0.07, BZ vs RZ, p<0.05). The BZ PCr/ATP ratio is improved in the cell treated group compared with open patch group (1.71 +/- 0.05 vs. 1.54 +/- 0.05, p<0.05). The forward flux rate constant of PCr/ATP (k pcr→ATP ) in the border zone is slightly increased in cell treated group compared with patch only group (0.29 +/- 0.02 vs 0.22 +/- 0.04 , p<0.05) Conclusion: The approach of 2D CSI 31 P MRS can effectively map the heterogeneity of myocardial ATP flux rate via CK In Vivo porcine hearts. Postinfarction LV remodeling heart manifests pronounced heterogeneity in myocardial bioenergetics with most severe alterations in BZ. Cell therapy may effectively improve BZ myocardial bioenergetics.

Fast whole brain quantitative proton density mapping to quantify metabolites in tumors

Introduction Gliomas are the most common primary brain tumors, whose aggressive forms are glioblastomas (high grade gliomas). Common treatment of glioblastomas is concomitant chemotherapy and radiotherapy (RT). Volumes considered for RT are defined from T1 weighted images to which security (but not optimal) margins are added to cover possible tumoral infiltration. In this context, metabolite quantification could be a precious marker to obtain a better delineation of the tumor invasion and a characterization of RT adverse effects in normal brain tissue and in tumor. Metabolic information is brought by spectroscopy imaging. However, intra and inter-subjects comparison could only be achieved with normalized signal CSI maps. The aim of this study is validate a fast method of normalization and to determine quantification in tumors based on CSI normalization for water content. Material and methods 3 sequences (T2*, XEP[1] and DESPOT1 [2]) for the water content determination and CSI sequence were acquired at 3T (Siemens Verio system), on a phantom containing NAA and different concentrations of deuterium and on five healthy volunteers, using a 32-channel receiver head coil. CSI data normalization was realized using the method [3] correcting non-water suppressed CSI by proton-density ( ρ ) MRI. Results Phantom: T1, ρ and absolute concentration of NAA were found similar to theoretical calculations. Volunteers A good agreement was achieved between T1, ρ and absolute concentration of metabolites between published values and mean values found on volunteers in different regions. A patient analysis is in work-in-progress. Conclusion This combination yields to a real benefit for water spectrum correction and could be applied in clinical protocol to obtain signal normalization of metabolites (acquisition time = 9 mn) even in the presence of brain disorder which water content cannot be directly known.

Applying of PAW for Standarization of CsI(Tl) Light Output

The basis of a new method of automatic particle identification for CsI(Tl) scintillators is described and discussed. A useful tool for this purpose is PAW (Physics Analysis Workstation). PAW is an interactive and object-oriented utility for visualizing data, statistical analysis and some other tasks, which combines different CERN packages. A special procedure for CsI(Tl) data analysis, running under PAW in a batch mode, has been written and tested. The recent paper presents the main idea of the method and results obtained for simulated data. As the first step of the test, a relatively simple case of data has been examined. Obtained results indicate that for more complicated cases the procedure should work effectively as well.

Comparison of oxidative capacity among leg muscles in humans using gated 31P 2‐D chemical shift imaging

In many small animals there are distinct differences in fiber-type composition among limb muscles, and these differences typically correspond to marked disparities in the oxidative capacities. However, whether there are similar differences in the oxidative capacity among leg muscles in humans is less clear. The purpose of this study was to compare the rate of phosphocreatine (PCr) recovery, a functional in vivo marker of oxidative capacity, in the lateral and medial gastrocnemius, soleus, and the anterior compartment of the leg (primarily the tibialis anterior) of humans. Subjects performed plantar flexion and dorsiflexion gated exercise protocols consisting of 70 sets of three rapid dynamic contractions (<2.86 s) at 20 s intervals (total: 23.3 min). Starting after the sixth set of contractions, (31)P 2-D CSI (8 x 8 matrix, 14-16 cm FOV, 3 cm slice, TR 2.86 s) were acquired via a linear transmit/receive surface coil using a GE 3T Excite System. The CSI data were zero-filled (32 x 32) and a single FID was produced for each time point in the lateral and medial gastrocnemius, soleus, and anterior compartment. The time constant for PCr recovery was calculated from tau = -Deltat/ln[D/(D + Q)], where Q is the percentage change in PCr due to contraction during the steady-state portion of the protocol, D the additional drop in PCr from rest, and Deltat is the interval between contractions. The tau of PCr recovery was longer (p < 0.05) in the anterior compartment (32 +/- 3 s) than in the lateral (23 +/- 2 s) and medial gastrocnemius muscles (24 +/- 3 s) and the soleus (22 +/- 3 s) muscles. These findings suggest that the oxidative capacity is lower in the anterior compartment than in the triceps surae muscles and is consistent with the notion that fiber-type phenotypes vary among the leg muscles of humans.

The N Terminus of Connexin37 Contains an α-Helix That Is Required for Channel Function

The cytoplasmic N-terminal domain of connexins has been implicated in multiple aspects of gap junction function, including connexin trafficking/assembly and channel gating. A synthetic peptide corresponding to the first 23 amino acids of human connexin37 was prepared, and circular dichroism and nuclear magnetic resonance studies showed that this N-terminal peptide was predominantly alpha-helical between glycine 5 and glutamate 16. The importance of this structure for localization of the protein at appositional membranes and channel function was tested by expression of site-directed mutants of connexin37 in which amino acids leucine 10 and glutamine 15 were replaced with prolines or alanines. Wild type connexin37 and both substitution mutants localized to appositional membranes between transfected HeLa cells. The proline mutant did not allow intercellular transfer of microinjected neurobiotin; the alanine mutant allowed transfer, but less extensively than wild type connexin37. When expressed alone in Xenopus oocytes, wild type connexin37 produced hemichannel currents, but neither of the double substitution mutants produced detectable currents. The proline mutant (but not the alanine mutant) inhibited co-expressed wild type connexin37. Taken together, our data suggest that the alpha-helical structure of the connexin37 N terminus may be dispensable for protein localization, but it is required for channel and hemichannel function.

NMR Assignment of 2H, 13C and 15N Labeled Amino-Terminal Domain of Apo-Pantothenate Synthetase from E. coli

Pantothenate (vitamin $b_5$) is an essential precursor for the biosynthesis of coenzyme A (CoA), an essential metabolite for many important cellular processes (Brown et al., 1987). Pantothenate Synthetase (PS) catalyzes the ATP dependent condensation of D-pantoate with $_\beta$-alanine to give rise to pantothenate. Our interest lies in studying the solution-state inter-domain interactions in E. coli PS that results in formation of the catalytic site. As a first step we have cloned and over-expressed an isotopically enriched sample of the dimeric amino-terminal domain (residues 1–176) of E. coli PS. Here we report the backbone and side-chain assignments for HN, $^{13}C (C^a, C^\beta & CO)$ and $^{15}N$ nuclei of the protein, obtained using triple resonance NMR experiments (Yamazaki et al., 1994). CSI and NOE data indicates that the protein is well folded containing both \alpha-helices and $_\beta$-sheet. Assignment for \sim 95% of backbone and side-chain resonances for the catalytic domain has been obtained and deposited in BMRB (accession # 6940).

Evaluation of the RF field uniformity of a double‐tuned 31P/1H birdcage RF coil for spin‐echo MRI/MRS of the diabetic foot

To evaluate the B1 field uniformity of a double-tuned birdcage coil designed for (31)P/(1)H MRI/MRS spin-echo (SE) imaging of the metatarsal head region of the foot in neuropathic diabetic patients. A low-pass double-tuned (31)P/(1)H RF birdcage coil was constructed to fit over the adult forefoot. Flip angle (FA) maps were created from B1 data acquired at the 3T (31)P (four normal subjects) and (1)H (five normal subjects) frequencies. T2-weighted (T2-W) (1)H images, (31)P rapid acquisition with relaxation enhancement (RARE) images, and composite SE pulse CSI data were acquired to demonstrate the uniformity of the resulting images and data. The means and standard deviations (SDs) of the range of FAs across the feet of the volunteer subjects indicated good uniformity (the maximum coefficients of variation (CVs) for all of the (31)P and (1)H FA maps were 7.6% and 7.3%, respectively). The FA values across the metatarsal head region indicated a maximum signal intensity variation of +/-3% in a RARE image acquired using an echo train length of 32. A (31)P/(1)H birdcage coil constructed for MRI/MRS studies of the human forefoot provided sufficient signal uniformity of SE data to facilitate accurate (31)P concentration measurements in muscle.