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Made available in DSpace on 2022-04-28T19:41:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Direct detection of Mycoplasma hyopneumoniae through molecular tools is a growing trend for early diagnosis, highlighting the importance of knowing M. hyopneumoniae dynamics in the respiratory tract upon infection. This study focused on monitoring the infection level and its effects in different anatomic sites of the respiratory tract of experimentally infected swine in four time-points post-infection. To this end, 24 pigs were allocated to either non-inoculated group (n = 8) or inoculated group (n = 16). On day 0 post-infection (dpi), animals of the inoculated group were intratracheally inoculated with M. hyopneumoniae. Nasal swabs were collected weekly for qPCR detection of bacterial shedding. At 14, 28, 42, and 56 dpi, four animals from the inoculated group and two from the control group were necropsied. Bronchoalveolar lavage fluid (BALF) and samples from three different anatomical tracheal sections (cranial - CT, medium - MT, lower - LT) were collected for qPCR and histopathology. Bacterial loads (qPCR) in tracheal samples were: 4.47 × 102 copies∕μL (CT), 1.5 × 104- copies∕ μL (MT) and 1.4 × 104 copies∕μL (LT samples). M. hyopneumoniae quantification in BALF showed the highest load at 28 dpi (2.0 × 106 copies∕ μL). Microscopic lesions in LT samples presented the highest scores at 56 dpi and were significantly correlated with the pathogen load on 14 dpi (0.93) and 28 dpi (0.75). The greatest bacterial load of M. hyopneumoniae in CT samples and BALF was registered at 28 dpi, and it remained high in BALF and LT throughout the 56 dpi. The pathogen was able to persist during the whole experimental period, however higher estimated quantification values were registered in the lower parts of the respiratory tract, especially at 56 dpi. These findings are important for improving diagnostics, treatment, and control measures of M. hyopneumoniae infection in swine herds. São Paulo State University (Unesp) School of Agricultural and Veterinarian Sciences, Via de Acesso Prof. Paulo Donato Castellane s/n Faculty of Veterinary Medicine Ghent University São Paulo State University (Unesp) School of Agricultural and Veterinarian Sciences, Via de Acesso Prof. Paulo Donato Castellane s/n FAPESP: #2016∕18698-2 FAPESP: #2019/19710-4 CAPES: 001

In patients with normal left ventricular ejection fraction, it may be difficult to distinguish between the normal and diseased heart. Novel assessments of ventricular function, such as extracellular volume imaging, myocardial perfusion imaging and myocardial contraction fraction are emerging to better assess disease burden in these cases. This study endeavored to determine whether the ratio of myocardial volume in systole to myocardial volume in diastole (MVs/MVd), differs between normal hearts and those with disease states characterized by normal ejection fraction.Consecutive patients from 2008 to 2018 with hypertrophic cardiomyopathy (HCM), cardiac amyloidosis, and heart failure with preserved ejection fraction (HFpEF) who underwent cardiac magnetic resonance imaging (MRI) were selected for inclusion, along with a sex- and age-matched cohort of normal volunteers who also underwent cardiac MRI. Manual tracings were performed on each MRI to calculate MVs/MVd, which was then compared across subgroups.Included were 50 patients with HCM, 50 patients with cardiac amyloidosis, 26 patients with HFpEF, and 30 normal subjects. Age was 54.1 years (SD 16.7); mean MVs/MVd was 0.88 (SD 0.04) in the normal subgroup, 1.03 (SD 0.06) in HCM patients, 1.03 (SD 0.06) in cardiac amyloidosis patients, and 0.97 (SD 0.02) in HFpEF patients, with all pathology subgroups different from the normal subgroup (p .0001 for each). The ratio of MVs/MVd discriminated diseased from normal with c statistic 0.989 (p .001).This study suggests that a novel and easily-captured metric of ventricular function, MVs/MVd, can differentiate normal ventricular function from multiple cardiomyopathies with normal ejection fractions.

Background: Coronavirus disease 2019 (COVID-19) has been implicated in a wide spectrum of cardiac manifestations following the acute phase of the disease. Objectives: To assess the range of cardiac sequelae after COVID-19 recovery. Data sources: PubMed, Embase, Scopus (inception through 17 February 2021) and Google scholar (2019 through 17 February 2021). Study eligibility criteria: Prospective and retrospective studies, case reports and case series. Participants: Adult patients assessed for cardiac manifestations after COVID-19 recovery. Exposure: Severe acute respiratory syndrome coronavirus 2 infection diagnosed by PCR. Methods: Systematic review. Results: Thirty-five studies (fifteen prospective cohort, seven case reports, five cross-sectional, four case series, three retrospective cohort and one ambidirectional cohort) evaluating cardiac sequelae in 52 609 patients were included. Twenty-nine studies used objective cardiac assessments, mostly cardiac magnetic resonance imaging (CMR) in 16 studies, echocardiography in 15, electrocardiography (ECG) in 16 and cardiac biomarkers in 18. Most studies had a fair risk of bias. The median time from diagnosis/recovery to cardiac assessment was 48 days (1–180 days). Common short-term cardiac abnormalities (

Background : Few studies suggest an association between Enterococcal infective endocarditis (EIE) and colorectal disease, including colorectal neoplasia (CRN) and colorectal cancer (CRC). In this study, we analyze differences in prevalence, risk factors and outcome of CRN and CRC between EIE and Streptococcus gallolyticus infective endocarditis (SGIE). Methods : Single center, observational study of 166 patients with definite EIE or SGIE. Clinical data were collected prospectively in a standardized IE protocol. Colonoscopy data were collected retrospectively on 90 patients. Results : 85 patients had EIE, 81 SGIE. EIE patients had a higher rate of prior cancer (20% vs 6%) and health-care associated infection (12% vs 1%), but similar mortality than SGIE. Colonoscopy performed in 90 patients showed intestinal diseases in 30 of 42 (71%) EIE patients vs. 40 of 48 (83%) SGIE patients (p = 0.174), with a predominance of CRN. Among 78 patients who underwent colonoscopy after IE diagnosis, no difference between EIE and SGIE was observed in the rate of non-neoplastic lesions (48% vs 47%), benign (32% vs 40%) or malignant (13% vs 15%) neoplastic lesions. Adverse events during colonoscopy were uncommon, although a careful handling of anticoagulation was required. Conclusions : EIE seems to be associated with colorectal disease, including colorectal neoplasia and colorectal cancer, to the same extent as SGIE. EIE should be considered a marker of colorectal neoplasia, even in patients with a clear health-care related acquisition. Colonoscopy is generally safe in EIE patients, and should be considered to early diagnose and treat colorectal disease.

Obesity-related chronic inflammation contributes to nonalcoholic fatty liver disease (NAFLD) progression in obese patients (body mass index [BMI] >30 kg/m2).1 The early detection of inflammation with noninvasive imaging technology may help identify individuals with a high risk of developing NAFLD.

Brain magnetic resonance elastography (MRE) is an imaging technique capable of accurately and non-invasively measuring the mechanical properties of the living human brain. Recent studies have shown that MRE has potential to provide clinically useful information in patients with intracranial tumors, demyelinating disease, neurodegenerative disease, elevated intracranial pressure, and altered functional states. The objectives of this review are: (1) to give a general overview of the types of measurements that have been obtained with brain MRE in patient populations, (2) to survey the tools currently being used to make these measurements possible, and (3) to highlight brain MRE-based quantitative biomarkers that have the highest potential of being adopted into clinical use within the next 5 to 10 years. The specifics of MRE methodology strategies are described, from wave generation to material parameter estimations. The potential clinical role of MRE for characterizing and planning surgical resection of intracranial tumors and assessing diffuse changes in brain stiffness resulting from diffuse neurological diseases and altered intracranial pressure are described. In addition, the emerging technique of functional MRE, the role of artificial intelligence in MRE, and promising applications of MRE in general neuroscience research are presented.

International audience; Magnetic resonance elastography (MRE) is a phase contrast-based MRI technique that can measure displacement due to propagating mechanical waves, from which material properties such as shear modulus can be calculated. Magnetic resonance elastography can be thought of as quantitative, noninvasive palpation. It is increasing in clinical importance, has become widespread in the diagnosis and staging of liver fibrosis, and additional clinical applications are being explored. However, publications have reported MRE results using many different parameters, acquisition techniques, processing methods, and varied nomenclature. The diversity of terminology can lead to confusion (particularly among clinicians) about the meaning of and interpretation of MRE results. This paper was written by the MRE Guidelines Committee, a group formalized at the first meeting of the ISMRM MRE Study Group, to clarify and move toward standardization of MRE nomenclature. The purpose of this paper is to (1) explain MRE terminology and concepts to those not familiar with them, (2) define "good practices" for practitioners of MRE, and (3) identify opportunities to standardize terminology, to avoid confusion.

To develop an objective quantitative method to characterize and visualize meningioma-brain adhesion using MR elastography (MRE)-based slip interface imaging (SII). This retrospective study included 47 meningiomas (training dataset: n = 35; testing dataset: n = 12) with MRE/SII examinations. Normalized octahedral shear strain (NOSS) values were calculated from the acquired MRE displacement data. The change in NOSS at the tumor boundary (ΔNOSSbdy) was computed, from which a 3D ΔNOSSbdy map of the tumor surface was created and the probability distribution of ΔNOSSbdy over the entire tumor surface was calculated. Statistical features were calculated from the probability histogram. After eliminating highly correlated features, the capability of the remaining feature for tumor adhesion classification was assessed using a one-way ANOVA and ROC analysis. The magnitude and location of the tumor adhesion can be visualized by the reconstructed 3D ΔNOSSbdy surface map. The entropy of the ΔNOSSbdy histogram was significantly different between adherent tumors and partially/completely non-adherent tumors in both the training (AUC: 0.971) and testing datasets (AUC: 0.900). Based on the cutoff values obtained from the training set, the ΔNOSSbdy entropy in the testing dataset yielded an accuracy of 0.83 for distinguishing adherent versus partially/non-adherent tumors, and 0.67 for distinguishing non-adherent versus completely/partially adherent tumors. SII-derived ΔNOSSbdy values are useful for quantification and classification of meningioma-brain adhesion. The reconstructed 3D ΔNOSSbdy surface map presents the state and location of tumor adhesion in a “clinician-friendly” manner, and can identify meningiomas with a high risk of adhesion to adjacent brain parenchyma. • MR elastography (MRE)–based slip interface imaging shows promise as an objective tool to preoperatively discriminate meningiomas with a high risk of intraoperative adhesion. • Measurement of the change of shear strain at meningioma boundaries can provide quantitative metrics depicting the state of adhesion at the tumor-brain interface. • The surface map of tumor adhesion shows promise in assisting precise adhesion localization, using a comprehensible, “clinician-friendly” 3D visualization.

Background. Oral and maxillofacial bone loss is highly prevalent among populations, and nowadays, increased attention has been focused on dentin derivatives serving as desirable graft materials for bone regeneration. In this study, dentin-derived inorganic mineral (DIM) was fabricated with a high-temperature calcination technique and the effects of DIM on the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMMSCs) and the bone formation were elucidated. Methods. The effects of DIM on BMMSC proliferation and apoptosis capacity were evaluated by CCK-8, flow cytometry, and EdU assays. Alkaline phosphatase (ALP) activity detection, ALP staining, alizarin red staining, and osteogenic marker expression analysis were performed to investigate the influence of DIM on the osteogenic differentiation of BMMSCs, as well as the relevant signal mechanisms. The model of critical-sized defects in the calvarium of rats was constructed for exploring the in vivo efficiency of DIM on bone regeneration. Results. Cell viability assays indicated that DIM had no cytotoxicity. BMMSCs cultured with DIM presented a higher level of osteogenic differentiation ability than those in the control group. The activation in ERK and p38 signals was detected in DIM-treated BMMSCs, and both pathways and osteogenic process were suppressed while using ERK inhibitor U0126 and p38 inhibitor SB203580, respectively. Furthermore, the animal experiments revealed that DIM could dramatically enhance new bone formation compared to the control group. Conclusion. DIM could promote BMMSC osteogenic differentiation via triggering the ERK and p38 MAPK signaling pathways and might be a novel predictable material for facilitating bone formation.

OBJECTIVES Defecation requires relaxation of the internal and external anal sphincters. High anal resting pressure is associated with painful constipation, defecatory disorders, and increased healthcare utilization in constipated patients; the mechanisms are unclear. Perhaps patients with a high anal resting pressure have a less distensible canal, which impedes defecation. METHODS In 50 of 64 participants (33 healthy and 17 constipated women), anal pressures and distensibility were measured, respectively, with manometry and balloon distention combined with magnetic resonance imaging; rectal balloon expulsion time (BET) was also studied. RESULTS The BET (P = .006) was longer, and the mean (SD) rectoanal pressure gradient (-58[40] vs -34[26] mm Hg, P = .03) was more negative in constipated than healthy women; anal resting pressure was not different. During anal distention, the balloon expanded rapidly at an opening pressure of 49 (18) mm Hg, which was lower (P

Purpose To develop a novel magnetic resonance elastography (MRE) acquisition using a hybrid radial EPI readout scheme (TURBINE), and to demonstrate its feasibility to obtain wave images and stiffness maps in a phantom and in vivo brain. Method The proposed 3D TURBINE-MRE is based on a spoiled gradient-echo MRE sequence with the EPI readout radially rotating about the phase-encoding axis to sample a full 3D k-space. A polyvinyl chloride phantom and 6 volunteers were scanned on a compact 3T GE scanner with a 32-channel head coil at 80 Hz and 60 Hz external vibration, respectively. For comparison, a standard 2D, multislice, spin-echo (SE) EPI-MRE acquisition was also performed with the same motion encoding and resolution. The TURBINE-MRE images were off-line reconstructed with iterative SENSE algorithm. The regional ROI analysis was performed on the 6 volunteers, and the median stiffness values were compared between SE-EPI-MRE and TURBINE-MRE. Results The 3D wave-field images and the generated stiffness maps were comparable between TURBINE-MRE and standard SE-EPI-MRE for the phantom and the volunteers. The Bland-Altman plot showed no significant difference in the median regional stiffness values between the two methods. The stiffness measured with the 2 methods had a strong linear relationship with a Pearson correlation coefficient of 0.943. Conclusion We demonstrated the feasibility of the new TURBINE-MRE sequence for acquiring the desired 3D wave-field data and stiffness maps in a phantom and in-vivo brains. This pilot study encourages further exploration of TURBINE-MRE for functional MRE, free-breathing abdominal MRE, and cardiac MRE applications.

Purpose To introduce newly developed MR elastography (MRE)-based dual-saturation imaging and dual-sensitivity motion encoding schemes to directly measure in vivo skull-brain motion, and to study the skull-brain coupling in volunteers with these approaches. Methods Six volunteers were scanned with a high-performance compact 3T-MRI scanner. The skull-brain MRE images were obtained with a dual-saturation imaging where the skull and brain motion were acquired with fat- and water-suppression scans, respectively. A dual-sensitivity motion encoding scheme was applied to estimate the heavily wrapped phase in skull by the simultaneous acquisition of both low- and high-sensitivity phase during a single MRE exam. The low-sensitivity phase was used to guide unwrapping of the high-sensitivity phase. The amplitude and temporal phase delay of the rigid-body motion between the skull and brain was measured, and the skull-brain interface was visualized by slip interface imaging (SII). Results Both skull and brain motion can be successfully acquired and unwrapped. The skull-brain motion analysis demonstrated the motion transmission from the skull to the brain is attenuated in amplitude and delayed. However, this attenuation (%) and delay (rad) were considerably greater with rotation (59 ± 7%, 0.68 ± 0.14 rad) than with translation (92 ± 5%, 0.04 ± 0.02 rad). With SII the skull-brain slip interface was not completely evident, and the slip pattern was spatially heterogeneous. Conclusion This study provides a framework for acquiring in vivo voxel-based skull and brain displacement using MRE that can be used to characterize the skull-brain coupling system for understanding of mechanical brain protection mechanisms, which has potential to facilitate risk management for future injury.

Shear wave elastography methods are able to accurately measure tissue stiffness, allowing these techniques to monitor the progression of hepatic fibrosis. While many methods rely on acoustic radiation force to generate shear waves for 2-D imaging, probe oscillation shear wave elastography (PROSE) provides an alternative approach by generating shear waves through continuous vibration of the ultrasound probe while simultaneously detecting the resulting motion. The generated shear wave field in in vivo liver is complicated, and the amplitude and quality of these shear waves can be influenced by the placement of the vibrating probe. To address these challenges, a real-time shear wave visualization tool was implemented to provide instantaneous visual feedback to optimize probe placement. Even with the real-time display, it was not possible to fully suppress residual motion with established filtering methods. To solve this problem, the shear wave signal in each frame was decoupled from motion and other sources through the use of a parameter-free empirical mode decomposition before calculating shear wave speeds. This method was evaluated in a phantom as well as in in vivo livers from five volunteers. PROSE results in the phantom as well as in vivo liver correlated well with independent measurements using the commercial General Electric Logiq E9 scanner.

PURPOSE To implement a reduced field of view (rFOV) technique for cardiac MR elastography (MRE) and to demonstrate the improvement in image quality of both magnitude images and post-processed MRE stiffness maps compared to the conventional full field of view (full-FOV) acquisition. METHODS With Institutional Review Board approval, 17 healthy volunteers underwent both full-FOV and rFOV cardiac MRE scans using 140-Hz vibrations. Two cardiac radiologists blindly compared the magnitude images and stiffness maps and graded the images based on several image quality attributes using a 5-point ordinal scale. Fisher's combined probability test was performed to assess the overall evaluation. The octahedral shear strain-based signal-to-noise ratio (OSS-SNR) and median stiffness over the left ventricular myocardium were also compared. RESULTS One volunteer was excluded because of an inconsistent imaging resolution during the exam. In the remaining 16 volunteers (9 males, 7 females), the rFOV scans outperformed the full-FOV scans in terms of subjective image quality and ghosting artifacts in the magnitude images and stiffness maps, as well as the overall preference. The quantitative measurements showed that rFOV had significantly higher OSS-SNR (median: 1.4 [95% confidence interval (CI): 1.2-1.5] vs. 2.1 [95% CI: 1.8-2.4]), P

Purpose To investigate the feasibility of using artificial neural networks to estimate stiffness from MR elastography (MRE) data. Methods Artificial neural networks were fit using model-based training patterns to estimate stiffness from images of displacement using a patch size of ∼1 cm in each dimension. These neural network inversions (NNIs) were then evaluated in a set of simulation experiments designed to investigate the effects of wave interference and noise on NNI accuracy. NNI was also tested in vivo, comparing NNI results against currently used methods. Results In 4 simulation experiments, NNI performed as well or better than direct inversion (DI) for predicting the known stiffness of the data. Summary NNI results were also shown to be significantly correlated with DI results in the liver (R2 = 0.974) and in the brain (R2 = 0.915), and also correlated with established biological effects including fibrosis stage in the liver and age in the brain. Finally, repeatability error was lower in the brain using NNI compared to DI, and voxel-wise modeling using NNI stiffness maps detected larger effects than using DI maps with similar levels of smoothing. Conclusion Artificial neural networks represent a new approach to inversion of MRE data. Summary results from NNI and DI are highly correlated and both are capable of detecting biologically relevant signals. Preliminary evidence suggests that NNI stiffness estimates may be more resistant to noise than an algebraic DI approach. Taken together, these results merit future investigation into NNIs to improve the estimation of stiffness in small regions. Magn Reson Med 80:351-360, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose The homeostasis of intracranial pressure (ICP) is of paramount importance for maintaining normal brain function. A noninvasive technique capable of making direct measurements of ICP currently does not exist. MR elastography (MRE) is capable of noninvasively measuring brain tissue stiffness in vivo, and may act as a surrogate to measure ICP. The objective of this study was to investigate the impact of changing ICP on brain stiffness using MRE in a swine model. Methods Baseline MRE measurements were obtained, and then catheters were surgically placed into the left and right lateral ventricles of three animals. ICP was systematically increased over the range of 0 to 55 millimeters mercury (mmHg), and stiffness measurements were made using brain MRE at vibration frequencies of 60 hertz (Hz), 90 Hz, 120 Hz, and 150 Hz. Results A significant linear correlation between stiffness and ICP in the cross-subject comparison was observed for all tested vibrational frequencies (P ≤ 0.01). The 120 Hz (0.030 ± 0.004 kilopascal (kPa)/mmHg, P

Purpose The stiffness of a myocardial infarct affects the left ventricular pump function and remodeling. Magnetic resonance elastography (MRE) is a noninvasive imaging technique for measuring soft-tissue stiffness in vivo. The purpose of this study was to investigate the feasibility of assessing in vivo regional myocardial stiffness with high-frequency 3D cardiac MRE in a porcine model of myocardial infarction, and compare the results with ex vivo uniaxial tensile testing. Methods Myocardial infarct was induced in a porcine model by embolizing the left circumflex artery. Fourteen days postinfarction, MRE imaging was performed in diastole using an echocardiogram-gated spin-echo echo-planar-imaging sequence with 140-Hz vibrations and 3D MRE processing. The MRE stiffness and tensile modulus from uniaxial testing were compared between the remote and infarcted myocardium. Results Myocardial infarcts showed increased in vivo MRE stiffness compared with remote myocardium (4.6 ± 0.7 kPa versus 3.0 ± 0.6 kPa, P = 0.02) within the same pig. Ex vivo uniaxial mechanical testing confirmed the in vivo MRE results, showing that myocardial infarcts were stiffer than remote myocardium (650 ± 80 kPa versus 110 ± 20 kPa, P = 0.01). Conclusions These results demonstrate the feasibility of assessing in vivo regional myocardial stiffness with high-frequency 3D cardiac MRE. Magn Reson Med, 2017. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Quantitative ultrasound elastography is increasingly being used in the assessment of chronic liver disease. Many studies have reported ranges of liver shear wave velocities values for healthy individuals and patients with different stages of liver fibrosis. Nonetheless, ongoing efforts exist to stabilize quantitative ultrasound elastography measurements by assessing factors that influence tissue shear wave velocity values, such as food intake, body mass index (BMI), ultrasound scanners, scanning protocols, ultrasound image quality, etc. Time-to-peak (TTP) methods have been routinely used to measure the shear wave velocity. However, there is still a need for methods that can provide robust shear wave velocity estimation in the presence of noisy motion data. The conventional TTP algorithm is limited to searching for the maximum motion in time profiles at different spatial locations. In this study, two modified shear wave speed estimation algorithms are proposed. The first method searches for the maximum motion in both space and time (spatiotemporal peak, STP); the second method applies an amplitude filter (spatiotemporal thresholding, STTH) to select points with motion amplitude higher than a threshold for shear wave group velocity estimation. The two proposed methods (STP and STTH) showed higher precision in shear wave velocity estimates compared to TTP in phantom. Moreover, in a cohort of 14 healthy subjects STP and STTH methods improved both the shear wave velocity measurement precision and the success rate of the measurement compared to conventional TTP.

Purpose To evaluate if cardiac magnetic resonance elastography (MRE) can measure increased stiffness in patients with cardiac amyloidosis. Myocardial tissue stiffness plays an important role in cardiac function. A noninvasive quantitative imaging technique capable of measuring myocardial stiffness could aid in disease diagnosis, therapy monitoring, and disease prognostic strategies. We recently developed a high-frequency cardiac MRE technique capable of making noninvasive stiffness measurements. Materials and Methods In all, 16 volunteers and 22 patients with cardiac amyloidosis were enrolled in this study after Institutional Review Board approval and obtaining formal written consent. All subjects were imaged head-first in the supine position in a 1.5T closed-bore MR imager. 3D MRE was performed using 5 mm isotropic resolution oblique short-axis slices and a vibration frequency of 140 Hz to obtain global quantitative in vivo left ventricular stiffness measurements. The median stiffness was compared between the two cohorts. An octahedral shear strain signal-to-noise ratio (OSS-SNR) threshold of 1.17 was used to exclude exams with insufficient motion amplitude. Results Five volunteers and six patients had to be excluded from the study because they fell below the 1.17 OSS-SNR threshold. The myocardial stiffness of cardiac amyloid patients (median: 11.4 kPa, min: 9.2, max: 15.7) was significantly higher (P = 0.0008) than normal controls (median: 8.2 kPa, min: 7.2, max: 11.8). Conclusion This study demonstrates the feasibility of 3D high-frequency cardiac MRE as a contrast-agent-free diagnostic imaging technique for cardiac amyloidosis. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1361–1367.

Purpose To investigate the ability of slip interface imaging (SII), a recently developed magnetic resonance elastography (MRE)-based technique, to predict the degree of meningioma–brain adhesion, using findings at surgery as the reference standard. Materials and Methods With Institutional Review Board approval and written informed consent, 25 patients with meningiomas >2.5 cm in maximal diameter underwent preoperative SII assessment. Intracranial shear motions were introduced using a soft, pillow-like head driver and the resulting displacement field was acquired with an MRE pulse sequence on 3T MR scanners. The displacement data were analyzed to determine tumor–brain adhesion by assessing intensities on shear line images and raw as well as normalized octahedral shear strain (OSS) values along the interface. The SII findings of shear line images, OSS, and normalized OSS were independently and blindly correlated with surgical findings of tumor adhesion by using the Cohen's κ coefficient and chi-squared test. Results Neurosurgeons categorized the surgical plane as extrapial (no adhesion) in 15 patients, mixed in four, and subpial (adhesion) in six. Both shear line images and OSS agreed with the surgical findings in 18 (72%) cases (fair agreement, κ = 0.37, 95% confidence interval [CI]: 0.05–0.69), while normalized OSS was concordant with the surgical findings in 23 (92%) cases (good agreement, κ = 0.86, 95% CI: 0.67–1). The correlation between SII predictions (shear line images, OSS, and normalized OSS) and the surgical findings were statistically significant (chi-squared test, P = 0.02, P = 0.02, and P < 0.0001, respectively). Conclusion SII preoperatively evaluates the degree of meningioma–brain adhesion noninvasively, allowing for improved prediction of surgical risk and tumor resectability. Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1007–1016.

This study presents the first implementation of functional ultrasound (fUS) imaging of the spinal cord to monitor local hemodynamic response to epidural electrical spinal cord stimulation (SCS) on two small and large animal models. SCS has been successfully applied to control chronic refractory pain and recently was evolved to alleviate motor impairment in Parkinson's disease and after spinal cord injury. At present, however, the mechanisms underlying SCS remain unclear, and current methods for monitoring SCS are limited in their capacity to provide the required sensitivity and spatiotemporal resolutions to evaluate functional changes in response to SCS. fUS is an emerging technology that has recently shown promising results in monitoring a variety of neural activities associated with the brain. Here we demonstrated the feasibility of performing fUS on two animal models during SCS. We showed in vivo spinal cord hemodynamic responses measured by fUS evoked by different SCS parameters. We also demonstrated that fUS has a higher sensitivity in monitoring spinal cord response than electromyography. The high spatial and temporal resolutions of fUS were demonstrated by localized measurements of hemodynamic responses at different spinal cord segments, and by reliable tracking of spinal cord responses to patterned electrical stimulations, respectively. Finally, we proposed optimized fUS imaging and post-processing methods for spinal cord. These results support feasibility of fUS imaging of the spinal cord and could pave the way for future systematic studies to investigate spinal cord functional organization and the mechanisms of spinal cord neuromodulation in vivo.

The long-term goal of this study is to assess chemotherapy-induced cardiotoxicity for pediatric cancer patients using cardiac ultrasound shear wave (SW) elastography. This pilot study aimed to systematically investigate the feasibility of using cardiac SW elastography in children and provide myocardial stiffness control data for cancer patients. Twenty healthy volunteers (ages 5-18) were recruited. A novel cardiac SW elastography sequence with pulse-inversion harmonic imaging and time-aligned sequential tracking was developed for this study. Cardiac SW elastography produces and detects transient SWs propagating in the myocardium in late-diastole, which can be used to quantify myocardial stiffness. The parasternal long-axis (L-A) and short-axis (S-A) views of the interventricular septum (IVS) were feasible for pediatric cardiac SW elastography. The L-A and S-A views of the basal and mid IVS provided better success rates than those of the apical IVS. Success rates decreased with increased body mass index (BMI), but did not differ with age or gender. Two-dimensional SW speed measurements were 1.26, 1.22, 1.71 and 1.67 m/s for L-A base, L-A mid, S-A base and S-A mid IVS, respectively. All S-A SW speed values were significantly higher (p

Brain magnetic resonance elastography (MRE) was developed on the basis of a desire to "palpate by imaging" and is becoming a powerful tool in the investigation of neurophysiological and neuropathological states. Measurements are acquired with a specialized MR phase-contrast pulse sequence that can detect tissue motion in response to an applied external or internal excitation. The tissue viscoelasticity is then reconstructed from the measured displacement. Quantitative characterization of brain viscoelastic behaviors provides us an insight into the brain structure and function by assessing the mechanical rigidity, viscosity, friction, and connectivity of brain tissues. Changes in these features are associated with inflammation, demyelination, and neurodegeneration that contribute to brain disease onset and progression. Here, we review the basic principles and limitations of brain MRE and summarize its current neuroanatomical studies and clinical applications to the most common neurosurgical and neurodegenerative disorders, including intracranial tumors, dementia, multiple sclerosis, amyotrophic lateral sclerosis, and traumatic brain injury. Going forward, further improvement in acquisition techniques, stable inverse reconstruction algorithms, and advanced numerical, physical, and preclinical validation models is needed to increase the utility of brain MRE in both research and clinical applications.

To investigate the use of MR elastography (MRE)–derived mechanical properties (shear stiffness (|G*|) and loss modulus (G″)) and MRI-derived fat fraction (FF) to predict the nonalcoholic fatty liver disease (NAFLD) activity score (NAS) in a NAFLD mouse model. Eighty-nine male mice were studied, including 64 training and 25 independent testing animals. An MRI/MRE exam and histologic evaluation were performed. Pairwise, nonparametric comparisons and multivariate analyses were used to evaluate the relationships between the three imaging parameters (FF, |G*|, and G″) and histologic features. A virtual NAS score (vNAS) was generated by combining three imaging parameters with an ordinal logistic model (OLM) and a generalized linear model (GLM). The prediction accuracy was evaluated by ROC analyses. The combination of FF, |G*|, and G″ predicted NAS > 1 with excellent accuracy in both training and testing sets (AUROC > 0.84). OLM and GLM predictive models misclassified 3/54 and 6/54 mice in the training, and 1/25 and 1/25 in the testing cohort respectively, in distinguishing between “not-NASH” and “definite-NASH.” “Borderline-NASH” prediction was poorer in the training set, and no borderline-NASH mice were available in the testing set. This preliminary study shows that multiparametric MRI/MRE can be used to accurately predict the NAS score in a NAFLD animal model, representing a promising alternative to liver biopsy for assessing NASH severity and treatment response. • MRE-derived liver stiffness and loss modulus and MRI-assessed fat fraction can be used to predict NAFLD activity score (NAS) in our preclinical mouse model (AUROC > 0.84 for all NAS levels greater than 1). • The overall agreement between the histological-determined NASH diagnosis and the imaging-predicted NASH diagnosis is 80–92%. • The multiparametric hepatic MRI/MRE has great potential for noninvasively assessing liver disease severity and treatment efficacy.

Background Background parenchymal uptake (BPU), which refers to the level of Tc-99m sestamibi uptake within normal fibroglandular tissue on molecular breast imaging (MBI), has been identified as a breast cancer risk factor, independent of mammographic density. Prior analyses have used subjective categories to describe BPU. We evaluate a new quantitative method for assessing BPU by testing its reproducibility, comparing quantitative results with previously established subjective BPU categories, and determining the association of quantitative BPU with breast cancer risk. Methods Two nonradiologist operators independently performed region-of-interest analysis on MBI images viewed in conjunction with corresponding digital mammograms. Quantitative BPU was defined as a unitless ratio of the average pixel intensity (counts/pixel) within the fibroglandular tissue versus the average pixel intensity in fat. Operator agreement and the correlation of quantitative BPU measures with subjective BPU categories assessed by expert radiologists were determined. Percent density on mammograms was estimated using Cumulus. The association of quantitative BPU with breast cancer (per one unit BPU) was examined within an established case-control study of 62 incident breast cancer cases and 177 matched controls. Results Quantitative BPU ranged from 0.4 to 3.2 across all subjects and was on average higher in cases compared to controls (1.4 versus 1.2, p

To test the clinical feasibility and usefulness of slip interface imaging (SII) to identify and quantify the degree of tumor-brain adhesion in patients with vestibular schwannomas.S With institutional review board approval and after obtaining written informed consent, SII examinations were performed in nine patients with vestibular schwannomas. During the SII acquisition, a low-amplitude mechanical vibration is applied to the head with a pillow-like device placed in the head coil and the resulting shear waves are imaged by using a phase-contrast pulse sequence with motion-encoding gradients synchronized with the applied vibration. Imaging was performed with a 3-T magnetic resonance (MR) system in less than 7 minutes. The acquired shear motion data were processed with two different algorithms (shear line analysis and calculation of octahedral shear strain [OSS]) to identify the degree of tumor-brain adhesion. Blinded to the SII results, neurosurgeons qualitatively assessed tumor adhesion at the time of tumor resection. Standard T2-weighted, fast imaging employing steady-state acquisition (FIESTA), and T2-weighted fluid-attenuated inversion recovery (FLAIR) imaging were reviewed to identify the presence of cerebral spinal fluid (CSF) clefts around the tumors. The performance of the use of the CSF cleft and SII to predict the degree of tumor adhesion was evaluated by using the κ coefficient and McNemar test.Among the nine patients, SII agreed with the intraoperative assessment of the degree of tumor adhesion in eight patients (88.9%; 95% confidence interval [CI]: 57%, 98%), with four of four, three of three, and one of two cases correctly predicted as no adhesion, partial adhesion, and complete adhesion, respectively. However, the T2-weighted, FIESTA, and T2-weighted FLAIR images that used the CSF cleft sign to predict adhesion agreed with surgical findings in only four cases (44.4% [four of nine]; 95% CI: 19%, 73%). The κ coefficients indicate good agreement (0.82 [95% CI: 0.5, 1]) for the SII prediction versus surgical findings, but only fair agreement (0.21 [95% CI: -0.21, 0.63]) between the CSF cleft prediction and surgical findings. However, the difference between the SII prediction and the CSF cleft prediction was not significant (P = .103; McNemar test), likely because of the small sample size in this study.SII can be used to predict the degree of tumor-brain adhesion of vestibular schwannomas and may provide a method to improve preoperative planning and determination of surgical risk in these patients.

PURPOSE MR elastography (MRE) is a phase-contrast MRI technique that is used to quantitatively assess liver stiffness for staging hepatic fibrosis. The current approach requires manual selection of a region of interest (ROI) with good wave quality from which to measure stiffness. The purpose of this work was to develop and evaluate a fully automated approach for measuring hepatic stiffness from MRE images to further reduce measurement variability. MATERIALS AND METHODS An automated liver elasticity calculation (ALEC) algorithm was developed to address reader stiffness measurement variability. ALEC has three stages: initial tissue estimation, segmentation, and ROI cleanup. Stiffnesses measured by the algorithm were compared with technicians and an expert radiologist in a set of 121 clinical cases acquired at 1.5 Tesla. Intra-class correlation (ICC), Bland-Altman analysis, and a noninferiority test were performed to evaluate whether the algorithm can be used in place of manual analysis by technicians. RESULTS The stiffness measurement difference with the expert was 1.42% ± 11.17% (mean ± standard deviation) for the algorithm and 1.82% ± 13.65% for the technicians. The ICCs were 0.981 and 0.984, respectively. Both the algorithm and technicians were equivalent to the expert within a 5% significance margin (P

In the last years, a shift from the microsurgical treatment to an endovascular therapy in patients with basilar apex aneurysm has been settled, part of this phenomenon is related to the significant tendency of vital perforators to be involved in the aneurysm dissection and clipping, which can implicate unfavorable outcomes. Nevertheless, microsurgical treatment remains the treatment that can provide the superior rates of stable and durable aneurysm occlusion, which is most important to young patients.In this video, we present the case of a 45-yr-old female patient who complained of a sudden and severe headache and presented with progressive lethargy during the following 3 d.At admission, computed tomography did not show abnormal findings. However, cerebrospinal fluid analysis showed erythrocytes and corroborated the clinical suspicion of spontaneous subarachnoid hemorrhage. The patient signed the Institutional Consent Form, which allows the use of his/her images and videos for any type of medical publications in conferences and/or scientific articles.Angiography and magnetic resonance imaging revealed a saccular basilar apex aneurysm. It showed a wide neck as well as a lobulated dome with upward and slightly left projection. The aneurysm did not involve angiographically visible thalamoperforator arteries, which allowed the microsurgical treatment by the fronto-orbitozygomatic approach. However, during the interpeduncular cistern dissection, an intraoperative rupture of the aneurysm occurred. This video exemplifies the steps required to manage an intraoperative rupture of a basilar apex aneurysm.

Magnetic Resonance Elastography (MRE) is a phase-contrast MRI technique which calculates quantitative stiffness images, called elastograms, by imaging the propagation of acoustic waves in tissues. It is used clinically to diagnose liver fibrosis. Automated analysis of MRE is difficult as the corresponding MRI magnitude images (which contain anatomical information) are affected by intensity inhomogeneity, motion artifact, and poor tissue- and edge-contrast. Additionally, areas with low wave amplitude must be excluded. An automated algorithm has already been successfully developed and validated for clinical 2D MRE. 3D MRE acquires substantially more data and, due to accelerated acquisition, has exacerbated image artifacts. Also, the current 3D MRE processing does not yield a confidence map to indicate MRE wave quality and guide ROI selection, as is the case in 2D. In this study, extension of the 2D automated method, with a simple wave-amplitude metric, was developed and validated against an expert reader in a set of 57 patient exams with both 2D and 3D MRE. The stiffness discrepancy with the expert for 3D MRE was -0.8% ± 9.45% and was better than discrepancy with the same reader for 2D MRE (-3.2% ± 10.43%), and better than the inter-reader discrepancy observed in previous studies. There were no automated processing failures in this dataset. Thus, the automated liver elasticity calculation (ALEC) algorithm is able to calculate stiffness from 3D MRE data with minimal bias and good precision, while enabling stiffness measurements to be fully reproducible and to be easily performed on the large 3D MRE datasets.

Shear wave elastography methods are able to accurately measure tissue stiffness, allowing these techniques to monitor the progression of hepatic fibrosis. While many methods rely on acoustic radiation force (ARF) to generate shear waves for two-dimensional (2D) imaging, probe oscillation shear wave elastography (PROSE) provides an alternative approach by generating shear waves through continuous vibration of the ultrasound probe while simultaneously detecting the resulting motion. The generated shear wave field in in vivo liver is complicated, and the amplitude and quality of these shear waves can be influenced by the placement of the vibrating probe. It was not possible to fully suppress residual motion artifacts with established filtering methods. Instead, the shear wave signal was decoupled from motion from other sources with empirical mode decomposition (EMD). This method was evaluated in a phantom as well as in in vivo livers from five volunteers. PROSE results were well correlated well with independent measurements using the commercial General Electric Logiq E9 scanner.

Purpose To investigate the utility of magnetic resonance (MR) elastography-derived mechanical properties in the discrimination of hepatic inflammation and fibrosis in the early stages of chronic liver diseases. Materials and Methods All studies were approved by the institutional animal care and use committee. A total of 187 animals were studied, including 182 mice and five pigs. These animals represented five different liver diseases with a varying combination and extent of hepatic inflammation, fibrosis, congestion, and portal hypertension. Multifrequency three-dimensional MR elastography was performed, and shear stiffness, storage modulus, shear loss modulus, and damping ratio were calculated for all animals. Necroinflammation, fibrosis, and portal pressure were either histologically scored or biochemically and physically quantified in all animals. Two-sided Welch t tests were used to evaluate mean differences between disease and control groups. Spearman correlation analyses were used to evaluate the relationships between mechanical parameters and quantitative fibrosis extent (hydroxyproline concentration) and portal pressure. Results Liver stiffness and storage modulus increased with progressively developed fibrosis and portal hypertension (mean stiffness at 80 Hz and 48-week feeding, 0.51 kPa ± 0.12 in the steatohepatitis group vs 0.29 kPa ± 0.01 in the control group; P = .02). Damping ratio and shear loss modulus can be used to distinguish inflammation from fibrosis at early stages of disease, even before the development of histologically detectable necroinflammation and fibrosis (mean damping ratio at 80 Hz and 20-week feeding, 0.044 ± 0.012 in the steatohepatitis group vs 0.014 ± 0.008 in the control group; P < .001). Damping ratio and liver stiffness vary differently with respect to cause of portal hypertension (ie, congestion- or cirrhosis-induced hypertension). These differentiation abilities have frequency-dependent variations. Conclusion Liver stiffness and damping ratio measurements can extend hepatic MR elastography to potentially enable assessment of necroinflammatory, congestive, and fibrotic processes of chronic liver diseases. © RSNA, 2017 Online supplemental material is available for this article.

Background Idiopathic normal pressure hydrocephalus (iNPH) is a ventriculomegaly syndrome characterized by dementia, urinary incontinence, and gait disturbance, which is potentially reversible after ventriculoperitoneal shunting (VPS). Magnetic resonance elastography (MRE) is an evolving imaging technology that noninvasively measures tissue viscoelasticity. We studied iNPH patients using MRE prior to shunting, compared them with normal controls, and analyzed associations between MRE findings and clinical features, as a pilot assessment of MRE in iNPH. Methods Stiffness values were measured on preoperative MRE in 10 iNPH patients scheduled for VPS and compared with those in 20 age- and sex-matched controls. Stiffness results were correlated with clinical iNPH symptoms. Results MRE demonstrated significantly increased stiffness in iNPH in cerebrum ( P = 0.04), occipital ( P = 0.002), and parietal ( P = 0.01) regions of interest (ROIs) and significantly decreased stiffness in periventricular ROIs ( P P = 0.1) and deep gray ROIs ( P = 0.4). Univariate analysis showed associations between preoperative iNPH symptoms and abnormally increased stiffness, including urinary incontinence with cerebrum ( P = 0.005), frontal ( P = 0.04), and cerebellum ( P = 0.03) ROIs, and Parkinsonism with occipital ROI ( P = 0.04). Postoperative improvement was associated with increased deep gray stiffness ( P = 0.01); failure was associated with increased temporal ( P = 0.0002) stiffness. Conclusions Based on the preliminary results of this small, limited analysis, brain stiffness may be altered in iNPH, and these alterations in parenchymal viscoelastic properties may be correlated with clinical symptoms. Increased temporal stiffness may predict surgical failure and potentially suggest an alternative dementing pathology underlying the iNPH-like symptoms. These findings highlight the potential future utility of MRE in iNPH management.

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called External Vibration Multi-directional Ultrasound Shearwave Elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A two-dimensional (2D) shear wave speed map was reconstructed from each individual shear wave field, and a final 2D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver Magnetic Resonance Elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging.

Thoracic aortic diseases (TAD) are relatively frequent conditions associated with high mortality. Recently, several reports have demonstrated the safety and efficacy of endovascular stent-graft (EVG) placement for TAD as an alternative to open surgery. We report our experience in management of thoracic aortic syndrome on 56 consecutive patients with TAD that underwent endovascular stent-graft repair. MDCT angiography was used in all patients to provide preprocedure evaluation and measurements. In particular it is necessary to evaluate the proximal and distal landing zones of the stent-graft. All EVGs in our series were placed successfully. Conversion to open surgery was never required. Six patients (10.7%) died early after the stent-graft deployment. During follow-up four more patients died. The endoleak rate was 16.7% (no. 10 pt). We did not observe any case of paraplegia. The present study shows the efficacy of EVG in the long-term follow-up, with an overall survival of 82.1%, which is comparable to that reported in recent studies. In conclusion this technique is emerging as an alternative approach in the treatment of TAD because this approach offers a less invasive therapeutic option to standard surgical techniques, even in patients who have associated diseases that make them poor surgical candidates. © 2007 Elsevier Ireland Ltd. All rights reserved.

Object The object of this study was to determine the potential of magnetic resonance elastography (MRE) to preoperatively assess the stiffness of meningiomas. Methods Thirteen patients with meningiomas underwent 3D brain MRE examination to measure stiffness in the tumor as well as in surrounding brain tissue. Blinded to the MRE results, neurosurgeons made a qualitative assessment of tumor stiffness at the time of resection. The ability of MRE to predict the surgical assessment of stiffness was tested using a Spearman rank correlation. Results One case was excluded due to a small tumor size. In the remaining 12 cases, both tumor stiffness alone (p = 0.023) and the ratio of tumor stiffness to surrounding brain tissue stiffness (p = 0.0032) significantly correlated with the surgeons' qualitative assessment of tumor stiffness. Results of the MRE examination provided a stronger correlation with the surgical assessment of stiffness compared with traditional T1- and T2-weighted imaging (p = 0.089), particularly when considering meningiomas of intermediate stiffness. Conclusions In this cohort, preoperative MRE predicted tumor consistency at the time of surgery. Tumor stiffness as measured using MRE outperformed conventional MRI because tumor appearance on T1- and T2-weighted images could only accurately predict the softest and hardest meningiomas.

Purpose To investigate the influence of portal pressure on the shear stiffness of the liver and spleen in a well-controlled in vivo porcine model with MR Elastography (MRE). A significant correlation between portal pressure and tissue stiffness could be used to noninvasively assess increased portal venous pressure (portal hypertension), which is a frequent clinical condition caused by cirrhosis of the liver and is responsible for the development of many lethal complications.

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) “push beam” to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a “strain-like” compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio $\geq 19~{\rm dB}$ ) between the target and background.

Magnetic resonance elastography (MRE) is a MR imaging method capable of spatially resolving the intrinsic mechanical properties of normal lung parenchyma. We tested the hypothesis that the mechanical properties of edematous lung exhibit local properties similar to those of a fluid-filled lung at transpulmonary pressures (Ptp) up to 25 cm H2O. Pulmonary edema was induced in anesthetized female adult Sprague-Dawley rats by mechanical ventilation to a pressure of 40 cm H2O for ∼30 min. Prior to imaging the wet weight of each ex vivo lung set was measured. MRE, high-resolution T1-weighted spin echo and T2* gradient echo data were acquired at each Ptpfor both normal and injured ex vivo lungs. At Ptps of 6 cm H2O and greater, the shear stiffness of normal lungs was greater than injured lungs ( P ≤ 0.0003). For Ptps up to 12 cm H2O, shear stiffness was equal to 1.00, 1.07, 1.16, and 1.26 kPa for the injured and 1.31, 1.89, 2.41, and 2.93 kPa for normal lungs at 3, 6, 9, and 12 cm H2O, respectively. For injured lungs MRE magnitude signal and shear stiffness within regions of differing degrees of alveolar flooding were calculated as a function of Ptp. Differences in shear stiffness were statistically significant between groups ( P < 0.001) with regions of lower magnitude signal being stiffer than those of higher signal. These data demonstrate that when the alveolar space filling material is fluid, MRE-derived parenchymal shear stiffness of the lung decreases, and the lung becomes inherently softer compared with normal lung.

The anal sphincters and pelvic floor muscles preserve fecal continence and participate in defecation (1). By visualizing structural (e.g., rectocele) and functional (e.g., impaired anal relaxation) disturbances, barium defecography and magnetic resonance imaging (MRI) facilitate the diagnosis of defecatory disorders, particularly when anal manometry and a rectal balloon expulsion test are inconclusive (2-6). MRI also reveals puborectalis atrophy and impaired pelvic floor contraction in some women with fecal incontinence (FI) (7-9). However, the clinical utility of barium defecography and MRI is limited by variable reproducibility of these assessments. For example, in one study, inter-observer agreement was good for identifying enteroceles and rectoceles but suboptimal for identifying intussusception, anismus, or the puborectalis impression by barium defecography (10). Moreover, for some measurements, agreement was much better for experienced observers (10). The American Gastroenterological Association technical review concluded that “there is poor agreement between independent observers in the measurement of the anorectal angle, a parameter thought to be critical to the interpretation of defecography results” (11). This is partly attributable to lack of a standardized definition for the rectal axis, which forms one aspect of the anorectal angle and can be drawn through the anterior, middle or posterior rectal wall. Moreover, the rectum is curvilinear, and the puborectalis indentation on the posterior rectal wall is variable. Hence, even minor differences in the orientation of the rectal axis can profoundly affect the anorectal angle. Lastly, the bony landmarks (e.g., pubic symphysis, coccyx) which are used to measure perineal descent may not be visible during barium defecography but are distinctly visualized on MR images (12). Nonetheless, and despite centralized training, a NIH-sponsored multi-institutional study concluded that “measurement variability adversely affects the utility of many MRI measurements for multicenter pelvic floor disorder research,” although agreement was better for bony than pelvic soft-tissue measurements during dynamic pelvic MRI (13). By contrast, we documented substantial inter-observer agreement for anorectal angles and the anorectal location at rest, during squeeze and evacuation measured by MRI in asymptomatic women and women with defecatory disorders; however, differences between observers were statistically significant (12). While most attention has focused on anorectal motion and the puborectalis, the coccyx also moves during pelvic floor contraction and rectal evacuation (14). The coccygei, which have a variable proportion of muscle and fibrous tissue, may pull forward and support the coccyx, after it has been pressed backwards, during defecation or parturition (14-16). With the levatores ani and piriforms, they close the posterior part of the pelvic outlet. Previous studies have evaluated the relationship of coccygeal mobility to age, sex, parity, and minor trauma but not to fecal incontinence. It is conceivable that coccygeal weakness may contribute to pelvic weakness in FI. Hence, the aims of this study were to (i) to develop a user-friendly semi-automated program to measure anorectal motion by defecography; (ii) evaluate the within-subject reproducibility of anorectal motion measured by this semi-automated program; (iii) to compare measurements of anorectal motion by a radiologist and a semi-automated program; and (iv) compare anorectal motion disturbances in women with and without FI. A more robust and refined approach to measure pelvic floor motion by MR defecography may enhance the utility of this technique in clinical practice and research studies.

Purpose: To develop a novel MR-based method for visualizing the elastic properties of human lung parenchyma in vivo and to evaluate the ability of this method to resolve differences in parenchymal stiffness at different respiration states in healthy volunteers. Materials and Methods: A spin-echo MR Elastography (MRE) pulse sequence was developed to provide both high shear wave motion sensitivity and short TE for improved visualization of lung parenchyma. The improved motion sensitivity of this approach was modeled and tested with phantom experiments. In vivo testing was then performed on 10 healthy volunteers at the respiratory states of residual volume (RV) and total lung capacity (TLC). Results: Shear wave propagation was visualized within the lungs of all volunteers and was processed to provide parenchymal shear stiffness maps for all 10 subjects. Density corrected stiffness values at TLC (1.83 ± 0.22 kPa) were higher than those at the RV (1.14 ± 0.14 kPa) with the difference being statistically significant (P < 0.0001). Conclusion: 1H-based MR elastography can noninvasively measure the shear stiffness of human lung parenchyma in vivo and can quantitate the change in shear stiffness due to respiration. The values obtained were consistent with previously reported in vitro assessments of cadaver lungs. Further work is required to increase the flexibility of the current acquisition and to investigate the clinical potential of lung MRE. J. Magn. Reson. Imaging 2011;33:1351–1361. © 2011 Wiley-Liss, Inc.

MR elastography (MRE) is a noninvasive technique in which images of externally generated waves propagating in tissue are used to measure stiffness. The first aim is to determine, from a range of driver configurations, the optimal driver for the purpose of generating waves within the heart in vivo. The second aim is to quantify the shear stiffness of normal myocardium throughout the cardiac cycle using MRE and to compare MRE stiffness to left ventricular chamber pressure in an in vivo pig model. MRE was performed in six pigs with six different driver setups, including no motion, three noninvasive drivers, and two invasive drivers. MRE wave displacement amplitudes were calculated for each driver. During the same MRI examination, left ventricular pressure and MRI-measured left ventricular volume were obtained, and MRE myocardial stiffness was calculated for 20 phases of the cardiac cycle. No discernible waves were imaged when no external motion was applied, and a single pneumatic drum driver produced higher amplitude waves than the other noninvasive drivers (P < 0.05). Pressure-volume loops overlaid onto stiffness-volume loops showed good visual agreement. Pressure and MRE-measured effective stiffness showed good correlation (R(2) = 0.84). MRE shows potential as a noninvasive method for estimating effective myocardial stiffness throughout the cardiac cycle.

Purpose To develop and test a magnetic resonance imaging-based method for assessing the mechanical shear connectivity across tissue interfaces with phantom experiments and in vivo feasibility studies. Materials and Methods External vibrations were applied to phantoms and tissue and the differential motion on either side of interfaces within the media was mapped onto the phase of the MR images using cyclic motion encoding gradients. The phase variations within the voxels of functional slip interfaces reduced the net magnitude signal in those regions, thus enhancing their visualization. A simple two-compartment model was developed to relate this signal loss to the intravoxel phase variations. In vivo studies of the abdomen and forearm were performed to visualize slip interfaces in healthy volunteers. Results The phantom experiments demonstrated that the proposed technique can assess the functionality of shear slip interfaces and they provided experimental validation for the theoretical model developed. Studies of the abdomen showed that the slip interface between the small bowel and the peritoneal wall can be visualized. In the forearm, this technique was able to depict the slip interfaces between the functional compartments of the extrinsic forearm muscles. Conclusion Functional shear slip interfaces can be visualized sensitively using cyclic motion encoding of externally applied tissue vibrations. J. Magn. Reson. Imaging 2009;30:855–863. © 2009 Wiley-Liss, Inc.

Liver stiffness is associated with portal hypertension in patients with chronic liver disease. However, the relation between spleen stiffness and clinically significant portal hypertension remains unknown. The purposes of this study were to determine the feasibility of measuring spleen stiffness with MR elastography and to prospectively test the technique in healthy volunteers and in patients with compensated liver disease.Spleen stiffness was measured with MR elastography in 12 healthy volunteers (mean age, 37 years; range, 25-82 years) and 38 patients (mean age, 56 years; range, 36-60 years) with chronic liver disease of various causes. For patients with liver disease, laboratory findings, spleen size, presence and size of esophageal varices, and liver histologic results were recorded. Statistical analyses were performed to assess all measurements.MR elastography of the spleen was successfully performed on all volunteers and patients. The mean spleen stiffness was significantly lower in the volunteers (mean, 3.6 +/- 0.3 kPa) than in the patients with liver fibrosis (mean, 5.6 +/- 5.0 kPa; range, 2.7-19.2 kPa; p0.001). In addition, a significant correlation was observed between liver stiffness and spleen stiffness for the entire cohort (r(2) = 0.75; p0.001). Predictors of spleen stiffness were splenomegaly, spleen volume, and platelet count. A mean spleen stiffness of 10.5 kPa or greater was identified in all patients with esophageal varices.MR elastography of the spleen is feasible and shows promise as a quantitative method for predicting the presence of esophageal varices in patients with advanced hepatic fibrosis.

Magnetic resonance elastography (MRE) measurements of shear stiffness (mu) in a spherical phantom experiencing both static and cyclic pressure variations were compared to those derived from an established pressure-volume (P-V)-based model. A spherical phantom was constructed using a silicone rubber composite of 10 cm inner diameter and 1.3 cm thickness. A gradient echo MRE sequence was used to determine mu within the phantom at static and cyclic pressures ranging from 55 to 90 mmHg. Average values of mu using MRE were obtained within a region of interest and were compared to the P-V-derived estimates. Under both static and cyclic pressure conditions, the P-V- and MRE-based estimates of mu ranged from 98.2 to 155.1 kPa and 96.2 to 150.8 kPa, respectively. Correlation coefficients (R(2)) of 0.98 and 0.97 between the P-V and MRE-based estimates of shear stiffness measurements were obtained. For both static and cyclic pressures, MRE-based measures of mu agree with those derived from a P-V model, suggesting that MRE can be used as a new, noninvasive method of assessing mu in sphere-like fluid-filled organs such as the heart.

The purpose of our study was to evaluate the performance of noncathartic, dietary unrestricted CT colonography, without and with the aid of electronic stool subtraction, for detecting colorectal neoplasia in a high-prevalence referral population.Patients with known or suspected colorectal neoplasms were potentially eligible for participation, regardless of the presence or absence of gastrointestinal symptoms. Subjects ingested 21.6 g of barium in nine divided doses. CT colonography was performed in the standard fashion. Data sets were randomly evaluated by two of three experienced radiologists, with subsequent reanalysis of each data set after electronic stool subtraction at least 6 weeks later. Optical colonoscopy was performed after purgation and served as the reference standard.One hundred thirty-one adenomatous neoplasms were identified among 114 subjects. On a per subject basis, the sensitivity for detecting adenomas 6-9 oror = 10 mm in diameter ranged from 53% to 88% and 84% to 93% without stool subtraction, respectively. By including stool subtraction, these sensitivity estimates improved to 68% to 92% and 93% to 94%, respectively. Specificity ranged from 71% to 91% and 88% to 100% for lesions 6-9 andor = 10 mm in size, respectively. Double reading resulted in detection of 27 (87%) of 31 and 65 (96%) of 68 patients with 6-9 andor = 10 mm adenomas, respectively. With double reading, the area under the receiver operating characteristic curve for large adenomas was 0.97.In this increased-risk referral population, CT colonography in the non-cathartic-tagged colon without dietary restrictions compared favorably with optical colonoscopy.

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) to: [a] obtain estimates of the shear modulus of human cerebral tissue in vivo, and [b] assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy adult volunteers. The data were analyzed using spatio-temporal filters and a local frequency estimating algorithm. Statistical analysis was performed using a paired t-test. The mean shear stiffness of cerebral white matter was 13.6 kPa (95% CI 12.3 to 14.8 kPa); while that of gray matter was lower at 5.22 kPa (95% CI 4.76 to 5.66 kPa). The difference was statistically significant (p < 0.0001).

The purpose of our study was to develop a method to subtract barium-labeled stool from the colon using a phantom and to evaluate the performance of the technique in a pilot human population.A phantom containing 6-mm flat polyps and three types of simulated stool (homogeneous, moderately heterogeneous, and severely heterogeneous) mixed with barium was created, scanned, and tested using three stool subtraction algorithms but no cathartic. Thirty patients with suspected colorectal polyps were studied using stool tagging to determine which was the most effective stool subtraction algorithm. Colonoscopy was the reference standard. Examinations were evaluated blindly using the unsubtracted and 6 weeks later both the unsubtracted and subtracted data sets.A threshold of 200 H and expansion and convolution techniques were the most effective tools for subtracting stool and minimizing artifacts. When applied to the human population, sensitivities using the unsubtracted data sets were 90% (18/20) and 68% (26/38) for polypsor = 1 cm andor = 5 mm, respectively. Specificities were 100% (4/4) and 75% (3/4) for polypsor = 1 cm andor = 5 mm. For the stool-subtracted data sets, sensitivities were 90% (18/20) and 71% (27/38) for polypsor = 1 cm andor = 5 mm. Per patient sensitivities were 88% (15/17) and 77% (20/26) foror = 1 cm andor = 5 mm polyps. Specificities were 100% (4/4) for large polyps and 25% (1/4) for smaller polyps.Image processing tools combining thresholding, expansion, and convolution were the most useful for stool subtraction. Laxative-free colon examinations using barium for stool labeling can be performed at CT colonography with or without stool subtraction with high accuracy. Further study is warranted.

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) push beam to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity, by generating shear waves using a continuous mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a compression strain artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed (SWS) images were obtained by applying a local frequency estimation (LFE) method, capable of generating a 2D map from a single frame of shear wave motion, allowing for an imaging frame rate comparable to the vibration frequency. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥19 dB) between the target and background.

Dynamic contrast-enhanced (DCE) MRI is an important tool for the detection and characterization of primary and recurring prostate cancer. Advanced reconstruction strategies (e.g., sparse or low-rank regression) provide improved depiction of contrast dynamics and pharmacokinetic parameters; however, the high computation cost of reconstructing 4D (3D+time, 50+ frames) datasets typically inhibits their routine clinical use. Here, a novel alternating direction method-of-multipliers (ADMM) optimization strategy is described that enables these methods to be executed in ∠5 minutes, and thus within the standard clinical workflow. After overviewing the mechanics of this approach, high-performance implementation strategies will be discussed and demonstrated through clinical cases.

To assess the technical success rate and diagnostic performance of liver magnetic resonance (MR) elastography.This retrospective study was approved by the institutional review board with patient informed consent. A total of 1377 consecutive MR elastography examinations performed between 2007 and 2010 in 1287 patients for clinical indications were included. Medical records were used to retrieve liver stiffness as assessed with MR elastography, histologic analysis, blood work, and other liver disease-related information. Nonparametric Kruskal-Wallis tests and analysis of covariance methods were used to evaluate the diagnostic values and relationships of the collected data.Hepatic MR elastography had a success rate of 94.4% (1300 of 1377 cases) and yielded reproducible measurements (r = 0.9716, P.0001) in the study cohort, with a complex patient profile and multiple interpreters. Body mass index had no significant effect on success rate (P = .2). In 289 patients who underwent liver biopsy within 1 year of the MR elastography date, mean liver stiffness as assessed with MR elastography was significantly higher in patients with advanced fibrosis (stages F3, F4) than in those with mild to moderate fibrosis (stages F0, F1, F2) (5.93 kPa ± 2.31 [standard deviation] vs 3.35 kPa ± 1.44, P.0001). Liver stiffness is associated with many factors other than fibrosis extent, including cause of fibrosis (viral hepatitis C vs nonalcoholic fatty liver disease, P = .025), inflammation (severe vs mild to moderate, P = .03), and hepatic metabolic and synthetic function (no fibrosis vs intermediate fibrosis, P ≤ .01).In a general clinical practice environment, hepatic MR elastography is a robust imaging method with a high success rate in a broad spectrum of patients. It also shows the complex association between liver stiffness and hepatic pathophysiology.