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Purpose This study describes the development and testing of an asymmetrical xenon-129 (129Xe) birdcage radiofrequency (RF) coil for 129Xe lung ventilation imaging at 1.5 Tesla, which allows proton (1H) system body coil transmit–receive functionality. Methods The 129Xe RF coil is a whole-body asymmetrical elliptical birdcage constructed without an outer RF shield to enable 1H imaging. urn:x-wiley:07403194:media:mrm28915:mrm28915-math-0001 field homogeneity and flip angle mapping of the 129Xe birdcage RF coil and 1H system body RF coil with the 129Xe RF coil in situ were evaluated in the MR scanner. The functionality of the 129Xe birdcage RF coil was demonstrated through hyperpolarized 129Xe lung ventilation imaging with the birdcage in both transceiver configuration and transmit-only configuration when combined with an 8-channel 129Xe receive-only RF coil array. The functionality of 1H system body coil with the 129Xe RF coil in situ was demonstrated by acquiring coregistered 1H lung anatomical MR images. Results The asymmetrical birdcage produced a homogeneous urn:x-wiley:07403194:media:mrm28915:mrm28915-math-0002 field (±10%) in agreement with electromagnetic simulations. Simulations indicated an optimal detuning configuration with 4 diodes. The obtained g-factor of 1.4 for acceleration factor of R = 2 indicates optimal array configuration. Coregistered 1H anatomical images from the system body coil along with 129Xe lung images demonstrated concurrent and compatible arrangement of the RF coils. Conclusion A large asymmetrical birdcage for homogenous urn:x-wiley:07403194:media:mrm28915:mrm28915-math-0003 transmission with high sensitivity reception for 129Xe lung MRI at 1.5 Tesla has been demonstrated. The unshielded asymmetrical birdcage design enables 1H structural lung MR imaging in the same exam.

Purpose This study develops a tracer kinetic model of xenon uptake in the human brain to determine the transfer rate of inhaled hyperpolarized 129 Xe from cerebral blood to gray matter that accounts for the effects of cerebral physiology, perfusion and magnetization dynamics. The 129 Xe transfer rate is expressed using a tracer transfer coefficient, which estimates the quantity of hyperpolarized 129 Xe dissolved in cerebral blood under exchange with depolarized 129 Xe dissolved in gray matter under equilibrium of concentration. Theory and methods Time-resolved MR spectra of hyperpolarized 129 Xe dissolved in the human brain were acquired from three healthy volunteers. Acquired spectra were numerically fitted with five Lorentzian peaks in accordance with known 129 Xe brain spectral peaks. The signal dynamics of spectral peaks for gray matter and red blood cells were quantified, and correction for the 129 Xe T1 dependence upon blood oxygenation was applied. 129 Xe transfer dynamics determined from the ratio of the peaks for gray matter and red blood cells was numerically fitted with the developed tracer kinetic model. Results For all the acquired NMR spectra, the developed tracer kinetic model fitted the data with tracer transfer coefficients between 0.1 and 0.14. Conclusion In this study, a tracer kinetic model was developed and validated that estimates the transfer rate of HP 129 Xe from cerebral blood to gray matter in the human brain.

Graphical abstract, Highlights • Review of in vivo methods and applications of 129Xe magnetic resonance in humans. • Focus on polarisation physics, radiofrequency coil and pulse sequence design. • 129Xe MRS/MRI is sensitive to lung ventilation, microstructure and gas exchange. • 129Xe lung MR can detect early disease, disease progression and therapy response. • Dissolved 129Xe MR can monitor blood oxygenation, lung, brain and kidney perfusion., Hyperpolarised gas lung MRI using xenon-129 can provide detailed 3D images of the ventilated lung airspaces, and can be applied to quantify lung microstructure and detailed aspects of lung function such as gas exchange. It is sensitive to functional and structural changes in early lung disease and can be used in longitudinal studies of disease progression and therapy response. The ability of 129Xe to dissolve into the blood stream and its chemical shift sensitivity to its local environment allow monitoring of gas exchange in the lungs, perfusion of the brain and kidneys, and blood oxygenation. This article reviews the methods and applications of in vivo129Xe MR in humans, with a focus on the physics of polarisation by optical pumping, radiofrequency coil and pulse sequence design, and the in vivo applications of 129Xe MRI and MRS to examine lung ventilation, microstructure and gas exchange, blood oxygenation, and perfusion of the brain and kidneys.

PURPOSE To measure the transverse relaxation time ( T2∗ ) and apparent diffusion coefficient (ADC) of 19 F-C3 F8 gas in vivo in human lungs at 1.5T and 3T, and to determine the representative distribution of values of these parameters in a cohort of healthy volunteers. METHODS Mapping of ADC at lung inflation levels of functional residual capacity (FRC) and total lung capacity (TLC) was performed with inhaled 19 F-C3 F8 (eight subjects) and 129 Xe (six subjects) at 1.5T. T2∗ mapping with 19 F-C3 F8 was performed at 1.5T (at FRC and TLC) for 8 subjects and at 3T (at TLC for seven subjects). RESULTS At both FRC and TLC, the 19 F-C3 F8 ADC was smaller than the free diffusion coefficient demonstrating airway microstructural diffusion restriction. From FRC to TLC, the mean ADC significantly increased from 1.56 mm2 /s to 1.83 mm2 /s (P = .0017) for 19 F-C3 F8, and from 2.49 mm2 /s to 3.38 mm2 /s (P = .0015) for 129 Xe. The posterior-to-anterior gradient in ADC for FRC versus TLC in the superior half of the lungs was measured as 0.0308 mm2 /s per cm versus 0.0168 mm2 /s per cm for 19 F-C3 F8 and 0.0871 mm2 /s per cm versus 0.0326 mm2 /s per cm for 129 Xe. A consistent distribution of 19 F-C3 F8T2∗ values was observed in the lungs, with low values observed near the diaphragm and large pulmonary vessels. The mean T2∗ across volunteers was 4.48 ms at FRC and 5.33 ms at TLC for 1.5T, and 3.78 ms at TLC for 3T. CONCLUSION In this feasibility study, values of physiologically relevant parameters of lung microstructure measurable by MRI ( T2∗ , and ADC) were established for C3 F8 in vivo lung imaging in healthy volunteers.

PURPOSE To firstly improve the attainable image SNR of 19 F and 1 H C3 F8 lung imaging at 1.5 tesla using an 8-element transmit/receive (Tx/Rx) flexible vest array combined with a 6-element Rx-only array, and to secondly evaluate microelectromechanical systems for switching the array elements between the 2 resonant frequencies. METHODS The Tx efficiency and homogeneity of the 8-element array were measured and simulated for 1 H imaging in a cylindrical phantom and then evaluated for in vivo 19 F/1 H imaging. The added improvement provided by the 6-element Rx-only array was quantified through simulation and measurement and compared to the ultimate SNR. It was verified through the measurement of isolation that microelectromechanical systems switches provided broadband isolation of Tx/Rx circuitry such that the 19 F tuned Tx/Rx array could be effectively used for both 19 F and 1 H nuclei. RESULTS For 1 H imaging, the measured Tx efficiency/homogeneity (mean ± percent SD; 6.79μT/kW±26% ) was comparable to that simulated ( 7.57μT/kW±20% ). The 6 additional Rx-only loops increased the mean Rx sensitivity when compared to the 8-element array by a factor of 1.41× and 1.45× in simulation and measurement, respectively. In regions central to the thorax, the simulated SNR of the 14-element array achieves ≥70% of the ultimate SNR when including noise from the matching circuits and preamplifiers. A measured microelectromechanical systems switching speed of 12 µs and added minimum 22 dB of isolation between Tx and Rx were sufficient for Tx/Rx switching in this application. CONCLUSION The described single-tuned array driven at 19 F and 1 H, utilizing microelectromechanical systems technology, provides excellent results for 19 F and 1 H dual-nuclear lung ventilation imaging.

A capacitive impedance metasurface combined with a transceiver coil to improve the radio frequency magnetic field for 1.5T magnetic resonance imaging applications is presented. The novel transceiver provides localized enhancement in magnetic flux density when compared to a transceiver coil alone by incorporating an electrically small metasurface using an interdigital capacitance approach. Full field simulations employing the metasurface show a significant improvement in magnetic flux density inside a homogeneous dielectric phantom, which is also shown to perform well for a range of depths into the phantom. The concept was experimentally demonstrated through vector network analyzer measurements and images have been taken using a 1.5T MRI scanner. The results show there is a 216% improvement in transmission efficiency, a 133% improvement in receiver signal-to-noise-ratio (SNR), and a 415% improvement in transceiver SNR for a particular transmission power when compared against a surface coil positioned at the same distance from the phantom, where these improvements are the maximum observed during experiments.

Purpose\ud \ud To assess the feasibility of using dissolved hyperpolarized xenon‐129 (129Xe) MRI to study renal physiology in humans at 3 T.\ud \ud \ud \ud Methods\ud \ud Using a flexible transceiver RF coil, dynamic and spatially resolved 129Xe spectroscopy was performed in the abdomen after inhalation of hyperpolarized 129Xe gas with 3 healthy male volunteers. A transmit‐only receive‐only RF coil array was purpose‐built to focus RF excitation and enhance sensitivity for dynamic imaging of 129Xe uptake in the kidneys using spoiled gradient echo and balanced steady‐state sequences.\ud \ud \ud \ud Results\ud \ud Using spatially resolved spectroscopy, different magnitudes of signal from 129Xe dissolved in red blood cells and tissue/plasma could be identified in the kidneys and the aorta. The spectra from both kidneys showed peaks with similar amplitudes and chemical shift values. Imaging with the purpose‐built coil array was shown to provide more than a 3‐fold higher SNR in the kidneys when compared with surrounding tissues, while further physiological information from the dissolved 129Xe in the lungs and in transit to the kidneys was provided with the transceiver coil. The signal of dissolved hyperpolarized 129Xe could be imaged with both tested sequences for about 40 seconds after inhalation.\ud \ud \ud \ud Conclusion\ud \ud The uptake of 129Xe dissolved in the human kidneys was measured with spectroscopic and imaging experiments, demonstrating the potential of hyperpolarized 129Xe MR as a novel, noninvasive technique to image human kidney tissue perfusion.

To measure the transverse relaxation time (Mapping of ADC at lung inflation levels of functional residual capacity (FRC) and total lung capacity (TLC) was performed with inhaledAt both FRC and TLC, theIn this feasibility study, values of physiologically relevant parameters of lung microstructure measurable by MRI (

Two magnetic resonance specific ventilation imaging (SVI) techniques, namely, oxygen-enhanced proton (OE-1H) and hyperpolarized 3He (HP-3He), were compared in eight healthy supine subjects [age 32 (6) yr]. An in-house radio frequency coil array for 1H configured with the 3He transmit-receive coil in situ enabled acquisition of SVI data from two nuclei from the same slice without repositioning the subjects. After 3 × 3 voxel downsampling to account for spatial registration errors between the two SV images, the voxel-by-voxel correlation coefficient of two SV maps ranged from 0.11 to 0.63 [0.46 mean (0.17 SD); P < 0.05]. Several indexes were analyzed and compared from the tidal volume-matched SV maps: the mean of SV log-normal distribution (SVmean), the standard deviation of the distribution as a measure of SV heterogeneity (SVwidth), and the gravitational gradient (SVslope). There were no significant differences in SVmean [OE-1H: 0.28 (0.08) and HP-3He: 0.32 (0.14)], SVwidths [OE-1H: 0.28 (0.08) and HP-3He: 0.27 (0.10)], and SVslopes [OE-1H: −0.016 (0.006) cm−1 and HP-3He: −0.013 (0.007) cm−1]. Despite the statistical similarities of the population averages, Bland-Altman analysis demonstrated large individual intertechnique variability. SDs of differences in these indexes were 42% (SVmean), 46% (SVwidths), and 62% (SVslopes) of their corresponding overall mean values. The present study showed that two independent, spatially coregistered, SVI techniques presented a moderate positive voxel-by-voxel correlation. Population averages of SVmean, SVwidth, and SVslope were in close agreement. However, the lack of agreement when the data sets were analyzed individually might indicate some fundamental mechanistic differences between the techniques. NEW & NOTEWORTHY To the best of our knowledge, this is the first cross-comparison of two different specific ventilation (SV) MRI techniques in the human lung (i.e., oxygen-enhanced proton and hyperpolarized 3He). The present study showed that two types of spatially coregistered SV images presented a modest positive correlation. The two techniques also yielded similar population averages of SV indexes such as log-normal mean, SV heterogeneity, and the gravitational slope, albeit with some intersubject variability.

Purpose To evaluate the performance of micro‐electromechanical systems (MEMS) switches against PIN diodes for switching a dual‐tuned RF coil between 19F and 1H resonant frequencies for multi‐nuclear lung imaging. Methods A four‐element fixed‐phase and amplitude transmit–receive RF coil was constructed to provide homogeneous excitation across the lungs, and to serve as a test system for various switching methods. The MR imaging and RF performance of the coil when switched between the 19F and 1H frequencies using MEMS switches, PIN diodes and hardwired configurations were compared. Results The performance of the coil with MEMS or PIN diode switching was comparable in terms of RF measurements, transmit efficiency and image SNR on both 19F and 1H nuclei. When the coil was not switched to the resonance frequency of the respective nucleus being imaged, reductions in the transmit efficiency were observed of 32% at the 19F frequency and 12% at the 1H frequency. The coil provides transmit field homogeneity of ±12.9% at the 1H frequency and ±14.4% at the 19F frequency in phantoms representing the thorax with the air space of the lungs filled with perfluoropropane gas. Conclusion MEMS and PIN diodes were found to provide comparable performance in on‐state configuration, while MEMS were more robust in off‐state high‐powered operation (>1 kW), providing higher isolation and requiring a lower DC switching voltage than is needed for reverse biasing of PIN diodes. In addition, clear benefits of switching between the 19F and 1H resonances were demonstrated, despite the proximity of their Larmor frequencies.

The feasibility of directly imaging the uptake of xenon by the human brain following perfusion and gas transfer across the blood-brain barrier has been demonstrated by using inhaled hyperpolarized xenon 129 MR imaging.

Prognosticating idiopathic pulmonary fibrosis (IPF) is challenging, in part due to a lack of sensitive biomarkers. A recent article in Thorax described how hyperpolarised xenon magnetic resonance spectroscopy may quantify regional gas exchange in IPF lungs. In a population of patients with IPF, we find that the xenon signal from red blood cells diminishes relative to the tissue/plasma signal over a 12-month time period, even when the diffusion factor for carbon monoxide is static over the same time period. We conclude that hyperpolarised 129Xe MR spectroscopy may be sensitive to short-term changes in interstitial gas diffusion in IPF.

To firstly improve the attainable image SNR ofThe Tx efficiency and homogeneity of the 8-element array were measured and simulated forForThe described single-tuned array driven at

PURPOSE: To optimize 19 F imaging pulse sequences for perfluoropropane (C3 F8 ) gas human lung ventilation MRI considering intrinsic in vivo relaxation parameters at both 1.5T and 3T. METHODS: Optimization of the imaging parameters for both 3D spoiled gradient (SPGR) and steady-state free precession (SSFP) 19 F imaging sequences with inhaled 79% C3 F8% and 21% oxygen was performed. Phantom measurements were used to validate simulations of SNR. In vivo parameter mapping and sequence optimization and comparison was performed by imaging the lungs of a healthy adult volunteer. T1 and T2* mapping was performed in vivo to optimize sequence parameters for in vivo lung MRI. The performance of SSFP and SPGR was then evaluated in vivo at 1.5T and 3T. RESULTS: The in vivo T2* of C3 F8 was shown to be dependent upon lung inflation level (2.04 ms ± 36% for residual volume and 3.14 ms ± 28% for total lung capacity measured at 3T), with lower T2* observed near the susceptibility interfaces of the diaphragm and around pulmonary blood vessels. Simulation and phantom measurements indicate that a factor of ~2-3 higher SNR can be achieved with SSFP when compared with optimized SPGR. In vivo lung imaging showed a 1.7 factor of improvement in SNR achieved at 1.5T, while the theoretical improvement at 3T was not attained due to experimental SAR constraints, shorter in vivo T1 , and B0 inhomogeneity. CONCLUSION: SSFP imaging provides increased SNR in lung ventilation imaging of C3 F8 demonstrated at 1.5T with optimized SSFP similar to the SNR that can be obtained at 3T with optimized SPGR.

Introduction In spite of recent advances in our understanding of the pathophysiology and treatment of idiopathic pulmonary fibrosis (IPF), clinical assessment remains challenging due to a paucity of clinically sensitive biomarkers. We present a longitudinal pilot study to assess the potential role of magnetic resonance imaging (MRI) techniques in assessing gas diffusion and perfusion in IPF. Methods Nineteen patients with IPF, but without echocardiographic evidence of pulmonary hypertension, were recruited from a tertiary centre (mean age 71.4 years). All underwent magnetic resonance spectroscopy with inhaled hyperpolarised xenon (129Xe) MRI. During breath-hold maneuvers, a high-resolution MR spectroscopy sequence acquired MR spectra of 129Xe dissolved in the pulmonary tissue and plasma (TP) and red blood cell (RBC) compartments. Integrals of RBC and TP spectral peaks were expressed as the ratio RBC:TP. Fifteen participants returned at six months, and twelve returned at 12 months. Five participants died before completing follow-up. In addition, twelve participants agreed to undergo Dynamic Contrast-Enhanced MRI (DCE-MRI) with gadolinium at baseline. Eight returned at 12 months. Parametric maps of bolus transit time across the lungs were produced and a mean transit time across all pixels is reported (MTT). Pulmonary function tests were performed at each visit, including forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO). Results 129Xe RBC:TP correlated with both DLCO (r=0.65; p=0.003) and MTT (r=−0.70; 0.008). This relationship with DLCO was preserved at six (r=0.77; p=0.001) and twelve months (r=0.67; p=0.018). However, while DLCO did not significantly change over 12 months (−0.5% median change; p=0.791) both RBC:TP (−0.08 change; p=0.002) and MTT (1.69 s change; p=0.031) demonstrated whole-lung changes. RBC:TP and MTT changes were not significantly correlated (p=0.091) On parametric maps, transit time was increased in basal and peripheral regions of lung tissue (figure 1) and progressed in these areas over time. Conclusion Hyperpolarised 129Xe spectroscopy and DCE-MRI have potential to probe diffusion and perfusion pathophysiology in IPF and are potentially more sensitive to change than existing whole-lung markers of gas exchange. Regional lung mapping is likely to yield highly sensitive metrics, possibly for patient enrichment or detection of treatment response in early intervention studies.

This paper presents a novel design of a High Impedance Surface (HIS) to improve the magnetic field strength of a Radio Frequency (RF) coil at 63.8 MHz, suitable for 1.5T magnetic resonance imaging (MRI) systems. The HIS is miniaturized using distributed interdigital capacitors. A HIS with an electrically small unit cell (λ/94) and is positioned between a RF transmit-receive (TR) coil and an RF shield. The magnitude of the magnetic field from an RF coil when coupled to a dielectric phantom load (mimicking a biological sample) was estimated using numerical simulation (finite integral methods) and corroborated with measurements. Simulated median improvements in magnetic field inside a dielectric phantom range from approximately 18% to 32% depending on the area of the HIS.

Here we present a Rb−129Xe spin-exchange optical pumping polarizer capable of rapid generation of large volumes of highly polarized 129Xe gas. Through modeling and measurements we maximize the 129Xe nuclear spin polarization output to enable the generation of polarized 129Xe gas imaging volumes (300 cm3) every 5 min within a clinical setting. Our model is verified by experiment to correctly predict the optimum Rb vapor density for maximum 129Xe nuclear polarization for a flux 3.4 W/cm2 of circularly polarized Rb D1 photons incident on an 80 cm long cylindrical optical cell. We measure a 129Xe magnetization production efficiency of ηpr=1.8%, which approaches the photon efficiency limit ηγ=3.3% of this system and enables the polarization of 2.72×1022 129Xe spins per hour, corresponding to 1013 cm3 of 100% polarized 129Xe at STP. This magnetization production rate is threefold higher than the highest previously published 129Xe magnetization production rate and has enabled routine clinical lung magnetic resonance imaging (MRI) with hyperpolarized 129Xe doses available on demand at run time, as well as high-SNR 129Xe MRI of the human brain and kidneys.

This paper describes a method for designing a non-periodic metasurface for use in 1.5T magnetic resonance imaging applications. The use of an inter-digitated capacitive surface combined with a circular radio frequency transceiver coil is shown to improve the magnetic flux density whilst being compact in cross section and thickness. By using a single unit cell structure the magnetic flux density, which is proportional to signal to noise ratio (SNR), was improved by a maximum of 120%. The single unit cell design also offers a more uniform magnetic flux density distribution when compared to periodic metamaterial approaches.

Background To support translational lung MRI research with hyperpolarized 129Xe gas, comprehensive evaluation of derived quantitative lung function measures against established measures from 3He MRI is required. Few comparative studies have been performed to date, only at 3T, and multisession repeatability of 129Xe functional metrics have not been reported. Purpose/Hypothesis To compare hyperpolarized 129Xe and 3He MRI‐derived quantitative metrics of lung ventilation and microstructure, and their repeatability, at 1.5T. Study Type Retrospective. Population Fourteen healthy nonsmokers (HN), five exsmokers (ES), five patients with chronic obstructive pulmonary disease (COPD), and 16 patients with nonsmall‐cell lung cancer (NSCLC). Field Strength/Sequence 1.5T. NSCLC, COPD patients and selected HN subjects underwent 3D balanced steady‐state free‐precession lung ventilation MRI using both 3He and 129Xe. Selected HN, all ES, and COPD patients underwent 2D multislice spoiled gradient‐echo diffusion‐weighted lung MRI using both hyperpolarized gas nuclei. Assessment Ventilated volume percentages (VV%) and mean apparent diffusion coefficients (ADC) were derived from imaging. COPD patients performed the whole MR protocol in four separate scan sessions to assess repeatability. Same‐day pulmonary function tests were performed. Statistical Tests Intermetric correlations: Spearman's coefficient. Intergroup/internuclei differences: analysis of variance / Wilcoxon's signed rank. Repeatability: coefficient of variation (CV), intraclass correlation (ICC) coefficient. Results A significant positive correlation between 3He and 129Xe VV% was observed (r = 0.860, P

Recently, dynamic MRI of hyperpolarized3He during inhalation revealed an alternation of the image intensity between left and right lungs with a cardiac origin (Sun Y, Butler JP, Ferrigno M, Albert MS, Loring SH. Respir Physiol Neurobiol 185: 468–471, 2013). This effect is investigated further using dynamic and phase-contrast flow MRI with inhaled3He during slow inhalations (flow rate ∼100 ml/s) to elucidate airflow dynamics in the main lobes in six healthy subjects. The ventilation MR signal and gas inflow in the left lower lobe (LLL) of the lungs were found to oscillate clearly at the cardiac frequency in all subjects, whereas the MR signals in the other parts of the lungs had a similar oscillatory behavior but were smaller in magnitude and in anti-phase to the signal in the left lower lung. The airflow in the main bronchi showed periodic oscillations at the frequency of the cardiac cycle. In four of the subjects, backflows were observed for a short period of time of the cardiac cycle, demonstrating a pendelluft effect at the carina bifurcation between the left and right lungs. Additional1H structural MR images of the lung volume and synchronized ECG recording revealed that maximum inspiratory flow rates in the LLL of the lungs occurred during systole when the corresponding left lung volume increased, whereas the opposite effect was observed during diastole, with gas flow redirected to the other parts of the lung. In conclusion, cardiogenic flow oscillations have a significant effect on regional gas flow and distribution within the lungs.

Introduction: Assessment of lung disease in primary ciliary dyskinesia (PCD) is challenging. As lung disease is progressive, early detection would inform early intervention and treatment. Hyperpolarised gas ventilation MRI (HP-MRI) has been shown to be more sensitive than FEV 1 , HRCT and LCI at detecting early lung disease in cystic fibrosis and may have a similar role in PCD. Aim: To assess HP-MRI as a modality to detect early lung disease in PCD. Methods: Children with confirmed PCD were assessed using HP-MRI, LCI calculated using 0.2% SF 6 and spirometry during a single visit. The quantitative HP-MRI metrics of ventilated defect % (VD) and coefficient of variation (CV) (a measure of ventilation heterogeneity) were calculated. Results: 5 children of median (range) age=12.2 (10.1-17.0) years were assessed. All subjects had ventilation defects visible on HP-MRI (VD=2.9 (2.1-13.2)%, CV=13.4 (10.8-19.1)%) but only 1 child had abnormal lung function (FEV 1 z-score=-2.11, LCI=8.08). 4/5 children had normal FEV 1 (z-score >-1.64) and LCI ( Conclusion: HP-MRI has the sensitivity to detect early lung ventilation heterogeneity in PCD when both FEV 1 and LCI are normal. HP-MRI in 2 subjects with PCD. Subject A has clear ventilation heterogeneity with multiple defects present and abnormal FEV1 and LCI. Ventilation defects are also present in Subject B (white arrows), with normal FEV1 and LCI.

Prognostication in idiopathic pulmonary fibrosis (IPF) is challenging and drug testing expensive due to insensitivity of existing biomarkers. 18 IPF subjects underwent hyperpolarised gas magnetic resonance imaging (MRI). 12 returned at six months. Diffusion-weighted MRI generated apparent diffusion coefficient of 3-Helium gas (3He-ADC), to quantify intra-acinar gas diffusivity. 129-Xenon spectroscopy generated red blood cells (RBC) and tissue plasma (T/P) signals. The ratio (RBC:TP), is taken as a metric of gas exchange. Same-day carbon monoxide gas diffusion (DLCO) was measured. Baseline mean 3He-ADC and RBC:TP correlate with DLCO (r=-0.538 p=0.021; r=0.677 p=0.002, respectively). At six months, no individual exhibited a decline in DLCO ≥15%, nor was the population change statistically significant, whereas RBC:TP declined significantly (Figure 1). Mean 3He-ADC did not change overall, but ADC maps qualitatively demonstrate increased gas diffusivity in several subjects (Figure 2). MRI metrics of microstructural assessment and gas exchange are regionally quantifiable. These may provide early warning of functional deterioration before it is detectable by DLCO.

Hyperpolarized (HP) gas magnetic resonance imaging (MRI) is an imaging modality that exploits the ability of stable spin ½ noble gases, such as 129 Xe and 3 He to be polarized, allowing an increase in their nuclear magnetic resonance signal-to-noise ratio of up to five orders of magnitude over their thermal equilibrium polarization. This allows for the detection and imaging of these gases at concentrations of up to four orders of magnitude lower than the tissue water proton concentration used for conventional 1 H imaging. In this chapter, we review the state-of-the-art of HP 129 Xe MRI when used for brain imaging. We briefly cover existing brain imaging techniques and their relative advantages and disadvantages. The relevant properties of 129 Xe as applied to MR are discussed. A major focus of this chapter is on the potential medical applications of HP 129 Xe MRI, including stroke and functional brain imaging.

Purpose Same-breath acquisition of 1H and hyperpolarized gases (3He and 129Xe) in the lungs provides complementary information on pulmonary structure and function with inherent spatial-temporal registration of the images from the different nuclei. To date 1H images have been acquired using the MR system's body coil, which has low SNR when compared with dedicated receiver-array coils. This study demonstrates the design and application of a dedicated 1H receiver array to improve the 1H lung SNR for use in same-breath acquisition with hyperpolarized gas 3He or 129Xe at 1.5 Tesla. Theory and Methods A four-loop dedicated receiver-array was developed in-house for 1H lung MRI to work in compatibility with existing 3He/129Xe transmit–receive coils. As part of the design process, a new generalized circuit formalism was developed for trap circuits for such a dedicated 1H receiver array at 63.8 MHz with traps for 3He 48.6 MHz and 129Xe 17.7 MHz. Results The 1H lung image SNR from the novel 1H array was twice that observed with the 1H body coil when used in same-breath acquisition with the 3He or 129Xe T–R coil in situ. Conclusion An array coil to improve 1H SNR of the lung in same-breath acquisition with hyperpolarized gases has been demonstrated. Magn Reson Med 74:291–299, 2015. © 2014 Wiley Periodicals, Inc.

This paper presents a reflective capacitive impedance surface combined with a radio frequency loop coil to improve the radio frequency magnetic field for 1.5 Tesla magnetic resonance imaging applications. The proposed structure is based on a miniaturized surface unit cell using an inter digital capacitance approach. Full field simulations employing an inter digital frequency selective surface shows a maximum improvement in magnetic field inside a homogeneous dielectric phantom of 170% as compared to a loop coil alone.

Background Diffusion-weighted magnetic resonance imaging (DW-MRI) of the lung with hyperpolarised helium ( 3 He) demonstrates increased intra-acinar Brownian gas diffusivity, related to micro-structural changes in emphysematous lungs (Swift AJ et al. Eur Radiol 2005;54:352-8.), but is relatively unexplored in idiopathic pulmonary fibrosis (IPF). Aims To investigate baseline reproducibility and clinical significance of 3 He DW-MRI metrics in patients with IPF. Methods Seven participants with IPF underwent PFTs and two identical MRI protocols on the same day. 3-Dimensional 3 He DW-MRI yielded coronal apparent diffusion coefficient (ADC) maps of the lungs and mean ADC for each participant. Results 3 He ADC maps showed elevated diffusivity in basal and peripheral lung regions, particularly in posterior coronal slices, which was in qualitative agreement with the distribution of fibrosis on CT. Mean ADC correlated with PFTs, in particular KCO (r = -0.954; p Conclusions 3 He ADC MRI demonstrates reproducibility and correlation with anatomical and functional IPF features. These results indicate that alveolar microstructural changes accompany interstitial thickening in IPF and that ADC may be a useful non-ionizing non-invasive regional marker of disease severity.

This paper investigates the use of High Impedance Surfaces (HIS) to enhance the magnetic near-field within a dielectric phantom stimulated by a surface coil antenna resonating at 63.8 MHz for use in Magnetic Resonance Imaging (MRI) systems. Specifically, the optimization of the space between the surface of the coil and the HIS is presented here. The HIS incorporates interdigitated capacitive elements that produce an electrically small unit cell size. The magnetic field strength is shown to be improved by 42% as compared to a system which uses only an RF shield The associated Specific Absorption Rate (SAR) for the optimum design is simulated and compared to international standards. The work is aimed at 1.5T MRI applications.

Introduction: Multiple breath washout (MBW) is a sensitive marker of early-stage lung disease. MBW imaging (MBWI) has recently been developed using hyperpolarised (HP) 3He MRI to regionally quantify ventilation heterogeneity (fractional ventilation) (Horn et al., J Appl Physiol,116(2):129-39,2014). 3He and 129Xe gases provide unique and complementary information about lung function due to their intrinsically different physicochemical properties (e.g. diffusion coefficient). Objective: To demonstrate MBWI with 129Xe and 3He using an optimised magnetic resonance imaging sequence and a novel dual-tuned radiofrequency coil. Methods: MBWI was performed on 5 healthy volunteers with an isotropic resolution of 1.2 cm3. Subjects remained stationary during the

Purpose The hyperpolarized gases 3He and 129Xe have distinct properties and provide unique and complementary functional information from the lungs. A triple‐nuclear, same‐breath imaging examination of the lungs with 1H, 3He, and 129Xe can therefore provide exclusive functional information from the gas images. In addition, the 1H images provide complementary co‐registered structural information in the same physiological time frame. The goal of this study was to design an RF system for triple nuclear lung MRI at 1.5T, consisting of a dual‐tuned transceiver coil for 3He and 129Xe, RF switches and a nested 1H receiver array. Methods A dual‐tuned transmit‐receive dual‐Helmholtz RF coil for 3He and 129Xe was designed and constructed to work in unison with a nested 1H receiver array. Results Triple‐nuclear imaging (structural and ventilation) and apparent diffusion coefficient mapping of the human lungs was performed in the same breath‐hold using the integrated RF system. B1 maps and volumetric ventilation imaging using a three‐dimensional, balanced steady‐state free precession pulse sequence performed with both hyperpolarized 3He and 129Xe indicate good stand‐alone performance of the coil for the respective nucleus. Conclusion Triple‐nuclear same‐breath lung imaging with a dual‐tuned coil (3He and 129Xe) and a nested 1H array has been demonstrated with a custom RF system. Magn Reson Med 75:1841–1848, 2016. © © The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Same-breath acquisition ofA four-loop dedicated receiver-array was developed in-house forTheAn array coil to improve

Introduction Despite the excellent functional sensitivity of hyperpolarised gas MRI to early lung disease, clinical uptake of the technique has to date been hindered by patents, regulatory classification, availability of 3 He and access to polariser technology. However, many of these constraints have been alleviated in recent years, and 129 Xe MRI is now providing high quality lung images at relatively low cost. In January 2015 UK regulatory approval for the manufacture of hyperpolarised gases for routine clinical lung imaging was obtained in Sheffield. Here we present a case series as an overview of the clinical questions that this technology can help resolve in various respiratory indications. Methods More than 20 patients (aged 13 to 74) have been clinically referred to date with HP gas MRI in Sheffield to date from NHS hospitals across the UK. Clinical histories include non-CF bronchiectasis (scanned before and after a 2 week course of IV antibiotics), COPD for consideration for LVRS/EB valves, complex asthma (scanned before and after bronchodilator inhalation), CF, patients with poor gas transfer but well-preserved lung parenchyma on CT, IPF overlapping with emphysema. Results Figure 1 shows example images from a cross-section of patients scanned, details of the individual cases will be expanded upon. No adverse events related to imaging were reported. In terms of imaging workflow, scan time average was between 30 min and 1 h 30 min. Patients have been referred from clinics within a 100 km radius and we are also active in enabling novice sites further afield with the technology. Conclusion Hyperpolarised gas MR provides sensitive, regional images of lung function which can be used to aid in clinical decision making on an individual patient basis. With improvements in gas polarisation, MR hardware and image acquisition techniques routine clinical lung imaging with the cheaper gas isotope 129 Xe is also now possible and large scale clinical evaluation of these methods in patient populations are now underway as part of clinical work up.