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Tran KA, DeOre BJ, Ikejiani D, Means K, Paone LS, De Marchi L, Suprewicz Ł, Koziol K, Bouyer J, Byfield FJ, Jin Y, Georges P, Fischer I, Janmey PA, Galie PA. Matching mechanical heterogeneity of the native spinal cord augments axon infiltration in 3D-printed scaffolds. Biomaterials 2023; 295:122061. [PMID: 36842339 PMCID: PMC10292106 DOI: 10.1016/j.biomaterials.2023.122061] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/18/2023]
Abstract
Scaffolds delivered to injured spinal cords to stimulate axon connectivity often match the anisotropy of native tissue using guidance cues along the rostral-caudal axis, but current approaches do not mimic the heterogeneity of host tissue mechanics. Although white and gray matter have different mechanical properties, it remains unclear whether tissue mechanics also vary along the length of the cord. Mechanical testing performed in this study indicates that bulk spinal cord mechanics do differ along anatomical level and that these differences are caused by variations in the ratio of white and gray matter. These results suggest that scaffolds recreating the heterogeneity of spinal cord tissue mechanics must account for the disparity between gray and white matter. Digital light processing (DLP) provides a means to mimic spinal cord topology, but has previously been limited to printing homogeneous mechanical properties. We describe a means to modify DLP to print scaffolds that mimic spinal cord mechanical heterogeneity caused by variation in the ratio of white and gray matter, which improves axon infiltration compared to controls exhibiting homogeneous mechanical properties. These results demonstrate that scaffolds matching the mechanical heterogeneity of white and gray matter improve the effectiveness of biomaterials transplanted within the injured spinal cord.
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Affiliation(s)
- Kiet A Tran
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Brandon J DeOre
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - David Ikejiani
- Department of Bioengineering, Rice University, Houston, TX, USA
| | - Kristen Means
- Department of Bioengineering, Rice University, Houston, TX, USA
| | - Louis S Paone
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Laura De Marchi
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Łukasz Suprewicz
- Department of Medical Microbiology and Nanobiomedical Engineering, Medical University of Bialystok, Bialystok, Poland
| | - Katarina Koziol
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA
| | - Julien Bouyer
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Fitzroy J Byfield
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Ying Jin
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Penelope Georges
- Council on Science and Technology, Princeton University, Princeton, NJ, USA
| | - Itzhak Fischer
- Department of Neurobiology and Anatomy, Drexel College of Medicine, Philadelphia, PA, USA
| | - Paul A Janmey
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Peter A Galie
- Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA.
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Abstract
Magnetic resonance elastography (MRE) is an emerging noninvasive technique, an alternative to palpation for quantitative assessment of biomechanical properties of tissue. In MRE, tissue stiffness information is obtained by a 3-step process, propagating mechanical waves in the tissues, measuring the wave propagation using modified magnetic resonance (MR) pulse sequences, and generating the quantitative stiffness maps from the MR images. MRE is clinically used in patients with liver diseases, whereas its applications in other organs are still being investigated. At present, the pediatric studies are in the initial stage and preliminary results promise to provide additional information about tissue characteristics.
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Affiliation(s)
- Manjunathan Nanjappa
- Department of Radiology, The Ohio State University Wexner Medical Center, 460 West 12th Avenue, Room No 333 3rd Floor, Columbus, OH 43210, USA
| | - Arunark Kolipaka
- Department of Radiology, The Ohio State Wexner Medical Center, 395 West 12th Avenue, 4th Floor, Columbus, OH 43210, USA.
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Mazza DF, Boutin RD, Chaudhari AJ. Assessment of Myofascial Trigger Points via Imaging: A Systematic Review. Am J Phys Med Rehabil 2021; 100:1003-1014. [PMID: 33990485 PMCID: PMC8448923 DOI: 10.1097/phm.0000000000001789] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
ABSTRACT This study systematically reviewed the published literature on the objective characterization of myofascial pain syndrome and myofascial trigger points using imaging methods. PubMed, Embase, Ovid, and the Cochrane Library databases were used, whereas citation searching was conducted in Scopus. Citations were restricted to those published in English and in peer-reviewed journals between 2000 and 2021. Of 1762 abstracts screened, 69 articles underwent full-text review, and 33 were included. Imaging data assessing myofascial trigger points or myofascial pain syndrome were extracted, and important qualitative and quantitative information on general study methodologies, study populations, sample sizes, and myofascial trigger point/myofascial pain syndrome evaluation were tabulated. Methodological quality of eligible studies was assessed based on the Quality Assessment of Diagnostic Accuracy Studies criteria. Biomechanical properties and blood flow of active and latent myofascial trigger points assessed via imaging were found to be quantifiably distinct from those of healthy tissue. Although these studies show promise, more studies are needed. Future studies should focus on assessing diagnostic test accuracy and testing the reproducibility of results to establish the best performing methods. Increasing methodological consistency would further motivate implementing imaging methods in larger clinical studies. Considering the evidence on efficacy, cost, ease of use and time constraints, ultrasound-based methods are currently the imaging modalities of choice for myofascial pain syndrome/myofascial trigger point assessment.
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Affiliation(s)
- Dario F. Mazza
- Department of Radiology, University of California, Davis, Sacramento, CA 95817
| | - Robert D. Boutin
- Department of Radiology, Stanford University School of Medicine, Stanford, CA 94305
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Fukui R, Sasaki K, Kawai K, Taira T, Nozawa H, Kaneko M, Murono K, Emoto S, Iida Y, Ishii H, Yokoyama Y, Anzai H, Sonoda H, Ishihara S. Establishing a novel method for assessing elasticity of internal anal sphincter using ultrasonic real-time tissue elastography. ANZ J Surg 2021; 91:E360-E366. [PMID: 33844397 DOI: 10.1111/ans.16760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/07/2021] [Accepted: 03/08/2021] [Indexed: 11/27/2022]
Abstract
BACKGROUND Evaluating anorectal function using real-time tissue elastography (RTE) has not been reported. A previous study reported that in the internal anal sphincter (IAS) of surgical specimens of patients with rectal cancer who underwent abdominoperineal resection, there was an increased fibrosis trend in those who underwent pre-operative chemoradiotherapy (CRT) compared with non-CRT. We speculated that CRT might have induced sclerosis of the IAS because of fibrosis. Therefore, we aimed to establish a method of quantitating the degree of IAS hardness using RTE on endoanal ultrasonography. METHODS RTE was performed with freehand manual compression under a defined pressure at the middle anal canal. Using the most compressive point in the strain graph, we traced the region of interest in the IAS. The strain histogram showed a frequency distribution of colours according to the degree of strain (numeric scan ranging from 0 to 255; smaller number indicated harder tissue). We defined the mean of the strain histogram as 'elasticity'. Ten patients with locally advanced rectal cancer who underwent pre-operative CRT were prospectively enrolled. We statistically evaluated the correlation between IAS elasticity and maximum resting pressure (MRP) values both at pre- and post-CRT. MRP was examined concurrently with the examination of IAS elasticity. RESULTS Representativity of elasticity measurements was demonstrated. It revealed a trend: IAS elasticity had a moderate inverse correlation with MRP (r = 0.41, P = 0.07), regardless of whether measurements were made before or after CRT. CONCLUSION We established a completely novel method for the assessment of elasticity of the IAS, using RTE on endoanal ultrasonography.
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Affiliation(s)
- Risa Fukui
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kazuhito Sasaki
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kazushige Kawai
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tetsuro Taira
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroaki Nozawa
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Manabu Kaneko
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Koji Murono
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Shigenobu Emoto
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yuuki Iida
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroaki Ishii
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yuichiro Yokoyama
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroyuki Anzai
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hirofumi Sonoda
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Soichiro Ishihara
- Department of Surgical Oncology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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Garcés Iñigo E, Llorens Salvador R, Escrig R, Hervás D, Vento M, Martí-Bonmatí L. Quantitative Evaluation of Neonatal Brain Elasticity Using Shear Wave Elastography. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2021; 40:795-804. [PMID: 32876366 DOI: 10.1002/jum.15464] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 07/09/2020] [Accepted: 07/12/2020] [Indexed: 06/11/2023]
Abstract
OBJECTIVES To demonstrate the feasibility of 2-dimensional brain ultrasound shear wave elastography (SWE) and to define the average elasticity values of the gray and white matter in term neonates. METHODS This work was a prospective observational single-center study including 55 healthy term neonates consecutively recruited in the maternity ward between the second and third postnatal days. All were successfully evaluated with a cerebral SWE examination performed with a multifrequency 4-9-MHz transducer. Bilateral sagittal planes of the thalamus and corona radiata were used to measure stiffness using a quantitative SWE method. Several elastograms with 5 to 15 nonoverlapping areas were obtained from the 2 different anatomic locations. The 5 most central measurements were averaged as representative values. RESULTS The 55 neonates ranged from 37 to 40 weeks' gestation. The estimated mean velocity values of the thalamus (1.17 m/s; 95% confidence interval, 1.13, 1.22 m/s) and corona radiata (1.60 m/s; 95% confidence interval, 1.57, 1.64 m/s) were statistically different (P < .001). There was no significant influence of laterality, gestational age, cephalic perimeter, sex, length, or type of delivery on the stiffness measurements. CONCLUSIONS Brain ultrasound SWE is feasible and allows measurements of neonatal brain elasticity. The elasticity of the thalamus and corona radiata at the frontal white matter in healthy term neonates is different. The knowledge of normal SWE ranges in term neonates allows comparative studies under pathologic conditions.
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Affiliation(s)
| | | | - Raquel Escrig
- Department of Pediatrics, Neonatal Research Unit, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - David Hervás
- Data Science, Biostatistics, and Bioinformatics Platform, Instituto de Investigación Sanitaria La Fe, Valencia, Spain
| | - Máximo Vento
- Department of Pediatrics, Neonatal Research Unit, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - Luis Martí-Bonmatí
- Department of Radiology, Hospital Universitario y Politécnico La Fe, Valencia, Spain
- Research Group on Biomedical Imaging, Instituto de Investigación Sanitaria La Fe, Valencia, Spain
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Arani A, Manduca A, Ehman RL, Huston Iii J. Harnessing brain waves: a review of brain magnetic resonance elastography for clinicians and scientists entering the field. Br J Radiol 2021; 94:20200265. [PMID: 33605783 PMCID: PMC8011257 DOI: 10.1259/bjr.20200265] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
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.
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Affiliation(s)
- Arvin Arani
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Armando Manduca
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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MR elastography frequency-dependent and independent parameters demonstrate accelerated decrease of brain stiffness in elder subjects. Eur Radiol 2020; 30:6614-6623. [PMID: 32683552 DOI: 10.1007/s00330-020-07054-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 05/10/2020] [Accepted: 06/30/2020] [Indexed: 01/22/2023]
Abstract
OBJECTIVES To analyze the mechanical properties in different regions of the brain in healthy adults in a wide age range: 26 to 76 years old. METHODS We used a multifrequency magnetic resonance elastography (MRE) protocol to analyze the effect of age on frequency-dependent (storage and loss moduli, G' and G″, respectively) and frequency-independent parameters (μ1, μ2, and η, as determined by a standard linear solid model) of the cerebral parenchyma, cortical gray matter (GM), white matter (WM), and subcortical GM structures of 46 healthy male and female subjects. The multifrequency behavior of the brain and frequency-independent parameters were analyzed across different age groups. RESULTS The annual change rate ranged from - 0.32 to - 0.36% for G' and - 0.43 to - 0.55% for G″ for the cerebral parenchyma, cortical GM, and WM. For the subcortical GM, changes in G' ranged from - 0.18 to - 0.23%, and G″ changed - 0.43%. Interestingly, males exhibited decreased elasticity, while females exhibited decreased viscosity with respect to age in some regions of subcortical GM. Significantly decreased values were also found in subjects over 60 years old. CONCLUSION Values of G' and G″ at 60 Hz and the frequency-independent μ2 of the caudate, putamen, and thalamus may serve as parameters that characterize the aging effect on the brain. The decrease in brain stiffness accelerates in elderly subjects. KEY POINTS • We used a multifrequency MRE protocol to assess changes in the mechanical properties of the brain with age. • Frequency-dependent (storage moduli G' and loss moduli G″) and frequency-independent (μ1, μ2, and η) parameters can bequantitatively measured by our protocol. • The decreased value of viscoelastic properties due to aging varies in different regions of subcortical GM in males and females, and the decrease in brain stiffness is accelerated in elderly subjects over 60 years old.
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Numano T, Habe T, Ito D, Onishi T, Takamoto K, Mizuhara K, Nishijo H, Igarashi K, Ueki T. A new technique for motion encoding gradient-less MR elastography of the psoas major muscle: A gradient-echo type multi-echo sequence. Magn Reson Imaging 2019; 63:85-92. [PMID: 31425804 DOI: 10.1016/j.mri.2019.08.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 07/29/2019] [Accepted: 08/15/2019] [Indexed: 11/29/2022]
Abstract
The present study aimed to develop vibration techniques for magnetic resonance (MR) elastography (MRE) of the psoas major muscle (PM). Seven healthy volunteers were included. MRE was performed with motion-encoding gradient (MEG)-less multi-echo MRE sequence, which allows clinicians to perform MRE using conventional MR imaging. In order to transmit mechanical vibration of the pneumatic type to the PM, a long narrow vibration pad was designed using a 3D printer, and the optimum vibration techniques were verified. The vibration pad was placed under the lower back, with the volunteers in the supine position. The results indicated that the PM vibrated well through the transmitted vibration from the lumbar spine, which suggests that the placement of a narrow vibration pad under the supine body, along the lumbar spine, allows the vibration of the PM. The shear modulus of the PM (n = 7) was 1.23 ± 0.09 kPa (mean ± SEM) on the right side and 1.22 ± 0.15 kPa on the left side, with no significant difference (t-test, P > 0.05). Increased stiffness of the muscle due to continuous local contraction may be an important cause of non-specific low back pain (LBP). The present vibration techniques for MRE of the PM provide a quantitative diagnostic tool for changes in muscle stiffness associated with non-specific LBP.
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Affiliation(s)
- Tomokazu Numano
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan; Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan.
| | - Tetsushi Habe
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan
| | - Daiki Ito
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan; Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan; Office of Radiation Technology, Keio University Hospital, Japan
| | - Takaaki Onishi
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan
| | - Koichi Takamoto
- System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Japan
| | | | - Hisao Nishijo
- System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Japan
| | - Keisuke Igarashi
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan
| | - Takamichi Ueki
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Japan
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Takamura T, Motosugi U, Sasaki Y, Kakegawa T, Sato K, Glaser KJ, Ehman RL, Onishi H. Influence of Age on Global and Regional Brain Stiffness in Young and Middle-Aged Adults. J Magn Reson Imaging 2019; 51:727-733. [PMID: 31373136 DOI: 10.1002/jmri.26881] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/12/2019] [Accepted: 07/12/2019] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND An understanding of potential age-related changes in brain stiffness and its regional variation is important for further clinical application of MR elastography. PURPOSE To investigate the effect of age on global and regional brain stiffness in young and middle-aged adults. STUDY TYPE Prospective. SUBJECTS Fifty subjects with normal brains and aged in their 20s, 30s, 40s, 50s, or 60s (five men, five women per decade). FIELD STRENGTH/SEQUENCE 3.0T MRI and elastography with a vibration frequency of 60 Hz. ASSESSMENT Stiffness was measured in nine brain regions (cerebrum, temporal lobes, sensorimotor areas, frontotemporal composite region, deep gray matter and white matter (deep GM/WM), parietal lobes, occipital lobes, frontal lobes, and cerebellum) using an atlas-based region-of-interest approach. The influence of age on regional brain stiffness was evaluated. STATISTICAL TESTS Multiple linear regression analysis, followed by Dunnett's multiple comparisons test, using subjects in their 20s as controls. RESULTS Following adjustment for sex, multiple linear regression revealed a significant negative correlation between age and stiffness of the cerebrum (P < 0.0001), temporal lobes (P < 0.0001), sensorimotor areas (P < 0.0001), frontotemporal composite region (P < 0.0001), deep GM/WM (P = 0.0028), parietal lobes (P < 0.0001), occipital lobes (P = 0.0055), and frontal lobes (P < 0.0001). Dunnett's multiple comparison test showed that the stiffness of the sensorimotor areas, frontotemporal composite region, and frontal lobes was significantly decreased in subjects in their 40s (P < 0.0367), 50s (P < 0.0001), and 60s (P < 0.0001), while that of the cerebrum, temporal lobes, and parietal lobes was significantly decreased only in subjects in their 50s (P < 0.0012) and 60s (P < 0.0031) when compared with the controls. DATA CONCLUSION There is an age-related decrease in brain stiffness that varies across the different regions. LEVEL OF EVIDENCE 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:727-733.
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Affiliation(s)
- Tomohiro Takamura
- The Department of Radiology, University of Yamanashi, Yamanashi, Japan
| | - Utaroh Motosugi
- The Department of Radiology, University of Yamanashi, Yamanashi, Japan
| | - Yu Sasaki
- Department of Radiology, Shizuoka General Hospital, Shizuoka, Japan
| | - Takashi Kakegawa
- Division of Radiology, University of Yamanashi Hospital, Yamanashi, Japan
| | - Kazuyuki Sato
- Division of Radiology, University of Yamanashi Hospital, Yamanashi, Japan
| | - Kevin J Glaser
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Richard L Ehman
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Hiroshi Onishi
- The Department of Radiology, University of Yamanashi, Yamanashi, Japan
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Huang X, Chafi H, Matthews KL, Carmichael O, Li T, Miao Q, Wang S, Jia G. Magnetic resonance elastography of the brain: A study of feasibility and reproducibility using an ergonomic pillow-like passive driver. Magn Reson Imaging 2019; 59:68-76. [PMID: 30858002 DOI: 10.1016/j.mri.2019.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 03/08/2019] [Accepted: 03/08/2019] [Indexed: 01/12/2023]
Abstract
Magnetic resonance elastography (MRE) can be used to noninvasively resolve the displacement pattern of induced mechanical waves propagating in tissue. The goal of this study is to establish an ergonomically flexible passive-driver design for brain MRE, to evaluate the reproducibility of MRE tissue-stiffness measurements, and to investigate the relationship between tissue-stiffness measurements and driver frequencies. An ergonomically flexible passive pillow-like driver was designed to induce mechanical waves in the brain. Two-dimensional finite-element simulation was used to evaluate mechanical wave propagation patterns in brain tissues. MRE scans were performed on 10 healthy volunteers at mechanical frequencies of 60, 50, and 40 Hz. An axial mid-brain slice was acquired using an echo-planar imaging sequence to map the displacement pattern with the motion-encoding gradient along the through-plane (z) direction. All subjects were scanned and rescanned within 1 h. The Wilcoxon signed-rank test was used to test for differences between white matter and gray matter shear-stiffness values. One-way analysis of variance (ANOVA) was used to test for differences between shear-stiffness measurements made at different frequencies. Scan-rescan reproducibility was evaluated by calculating the within-subject coefficient of variation (CV) for each subject. The finite-element simulation showed that a pillow-like passive driver is capable of efficient shear-wave propagation through brain tissue. No subjects complained about discomfort during MRE acquisitions using the ergonomically designed driver. The white-matter elastic modulus (mean ± standard deviation) across all subjects was 3.85 ± 0.12 kPa, 3.78 ± 0.15 kPa, and 3.36 ± 0.11 kPa at frequencies of 60, 50, and 40 Hz, respectively. The gray-matter elastic modulus across all subjects was 3.33 ± 0.14 kPa, 2.82 ± 0.16 kPa, and 2.24 ± 0.14 kPa at frequencies of 60, 50, and 40 Hz, respectively. The Wilcoxon signed-rank test confirmed that the shear stiffness was significantly higher in white matter than gray matter at all three frequencies. The ranges of within-subject coefficients of variation for white matter, gray matter, and whole-brain shear-stiffness measurements for the three frequencies were 1.8-3.5% (60 Hz), 4.7-6.0% (50 Hz), and 3.7-4.1% (40 Hz). An ergonomic pneumatic pillow-like driver is feasible for highly reproducible in vivo evaluation of brain-tissue shear stiffness. Brain-tissue shear-stiffness values were frequency-dependent, thus emphasizing the importance of standardizing MRE acquisition protocols in multi-center studies.
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Affiliation(s)
- Xunan Huang
- School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China
| | - Hatim Chafi
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kenneth L Matthews
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Owen Carmichael
- Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA
| | - Tanping Li
- School of Physics and Optoelectronic Engineering, Xidian University, Xi'an, Shaanxi 710071, China
| | - Qiguang Miao
- School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China
| | - Shuzhen Wang
- School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China.
| | - Guang Jia
- School of Computer Science and Technology, Xidian University, Xi'an, Shaanxi, 710071, China.
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Zaki F, Wang Y, Wang C, Liu X. Adaptive Doppler analysis for robust handheld optical coherence elastography. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2019; 10880. [PMID: 31333279 DOI: 10.1117/12.2503809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Optical coherence tomography (OCT) allows structural and functional imaging of biological tissue with high resolution and high speed. Optical coherence elastography (OCE), a functional extension of OCT, has been used to perform mechanical characterization. A handheld fiber-optic OCE instrument allows high sensitivity virtual palpation of tissue with great convenience and flexibility and can be used in a wide range of clinical settings. Moreover, fiber-optic OCE instruments can be integrated into a needle device to access deep tissue. However, the major challenge in the development of handheld OCE instrument is non-constant motion within the tissue. In this study, a simple and effective method for temporally and spatially adaptive Doppler analysis is investigated. The adaptive Doppler analysis method strategically chooses the time interval (δt) between signals involved in Doppler analysis, to track the motion speed v(z,t) that varies as time (t) and depth (z) in a deformed sample volume under manual compression. The aim is to use an optimal time interval to achieve a large yet artifact free Doppler phase shift for motion tracking.
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Affiliation(s)
- Farzana Zaki
- Dept. of Electrical and Computer Engineering, New Jersey Institute of Technology, University Heights, Newark, New Jersey, USA, 07102
| | - Yahui Wang
- Dept. of Electrical and Computer Engineering, New Jersey Institute of Technology, University Heights, Newark, New Jersey, USA, 07102
| | - Chizhong Wang
- Dept. of Electrical and Computer Engineering, New Jersey Institute of Technology, University Heights, Newark, New Jersey, USA, 07102
| | - Xuan Liu
- Dept. of Electrical and Computer Engineering, New Jersey Institute of Technology, University Heights, Newark, New Jersey, USA, 07102
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12
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Feng Y, Zhu M, Qiu S, Shen P, Ma S, Zhao X, Hu CH, Guo L. A multi-purpose electromagnetic actuator for magnetic resonance elastography. Magn Reson Imaging 2018; 51:29-34. [DOI: 10.1016/j.mri.2018.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 04/15/2018] [Indexed: 01/17/2023]
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Simon EG, Callé S, Perrotin F, Remenieras JP. Measurement of shear wave speed dispersion in the placenta by transient elastography: A preliminary ex vivo study. PLoS One 2018; 13:e0194309. [PMID: 29621270 PMCID: PMC5886409 DOI: 10.1371/journal.pone.0194309] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 02/28/2018] [Indexed: 12/31/2022] Open
Abstract
Background Placental elasticity may be modified in women with placental insufficiency. Shear wave elastography (SWE) can measure this, using acoustic radiation force, but the safety of its use in pregnant women has not yet been demonstrated. Transient elastography (TE) is a safer alternative, but has not yet been applied to the placenta. Moreover, the dispersion of shear wave speed (SWS) as a function of frequency has received relatively little study for placental tissue, although it might improve the accuracy of biomechanical assessment. Objective To explore the feasibility and reproducibility of TE for placental analysis, to compare the values of SWS and Young’s modulus (YM) from TE and SWE, and to analyze SWS dispersion as a function of frequency ex vivo in normal placentas. Materials and methods Ten normal placentas were analyzed ex vivo by an Aixplorer ultrasound system as shear waves were generated by a vibrating plate and by using an Aixplorer system. The frequency analysis provided the value of the exponent n from a fractional rheological model applied to the TE method. We calculated intra- and interobserver agreement for SWS and YM with 95% prediction intervals, created Bland-Altman plots with 95% limits of agreement, and estimated the intraclass correlation coefficient (ICC). Main results The mean SWS was 1.80 m/s +/- 0.28 (standard deviation) with the TE method at 50 Hz and 1.82 m/s +/-0.13 with SWE (P = 0.912). No differences were observed between the central and peripheral regions of placentas with either TE or SWE. With TE, the intraobserver ICC for SWS was 0.68 (0.50–0.82), and the interobserver ICC for SWS 0.65 (0.37–0.85). The mean parameter n obtained from the fractional rheological model was 1.21 +/- 0.12, with variable values of n for any given SWS. Conclusions TE is feasible and reproducible on placentas ex vivo. The frequency analysis of SWS provides additional information about placental elasticity and appears to be able to distinguish differences between placental structures.
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Affiliation(s)
- Emmanuel G. Simon
- UMR 1253, iBrain, University of Tours, Inserm, Tours, France
- Department of Obstetrics, Gynecology and Fetal Medicine, University Hospital Center of Tours, Tours, France
- * E-mail:
| | - Samuel Callé
- UMR 1253, iBrain, University of Tours, Inserm, Tours, France
- GREMAN, UMR CNRS 7347, University of Tours, Tours, France
| | - Franck Perrotin
- UMR 1253, iBrain, University of Tours, Inserm, Tours, France
- Department of Obstetrics, Gynecology and Fetal Medicine, University Hospital Center of Tours, Tours, France
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Zhao W, Choate B, Ji S. Material properties of the brain in injury-relevant conditions - Experiments and computational modeling. J Mech Behav Biomed Mater 2018; 80:222-234. [PMID: 29453025 DOI: 10.1016/j.jmbbm.2018.02.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/16/2018] [Accepted: 02/03/2018] [Indexed: 10/18/2022]
Abstract
Material properties of the brain have been extensively studied but remain poorly characterized. The vast variations in constitutive models and material constants are well documented. However, no study exists to translate the variations into disparities in impact-induced brain strains most relevant to brain injury. Here, we reviewed a subset of injury-relevant brain material properties either characterized in experiments or adopted in recent head injury models. To highlight how variations in measured brain material properties manifested in simulated brain strains, we selected six experiments that have provided a complete set of brain material model and constants to implement a common head injury model. Responses resulting from two extreme events representing a high-rate cadaveric head impact and a low-rate in vivo head rotation, respectively, varied substantially. We hypothesized, and further confirmed, that the time-varying shear moduli at the appropriate time scales (e.g., ~5 ms and ~40 ms corresponding to the impulse durations of the major acceleration peaks for the two impacts, respectively), rather than the initial or long-term shear moduli, were the most indicative of impact-induced brain strains. These results underscored the need to implement measured brain material properties into an actual head injury model for evaluation. They may also provide guidelines to better characterize brain material properties in future experiments and head injury models. Finally, our finding provided a practical solution to satisfy head injury model validation requirements at both ends of the impact severity spectrum. This would improve the confidence in model simulation performance across a range of time scales relevant to concussion and sub-concussion in the real-world.
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Affiliation(s)
- Wei Zhao
- Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA 01605, USA
| | - Bryan Choate
- Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA 01605, USA
| | - Songbai Ji
- Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA 01605, USA; Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
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Chartrain AG, Kurt M, Yao A, Feng R, Nael K, Mocco J, Bederson JB, Balchandani P, Shrivastava RK. Utility of preoperative meningioma consistency measurement with magnetic resonance elastography (MRE): a review. Neurosurg Rev 2017; 42:1-7. [DOI: 10.1007/s10143-017-0862-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 04/06/2017] [Accepted: 05/10/2017] [Indexed: 10/19/2022]
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McGrath DM, Ravikumar N, Beltrachini L, Wilkinson ID, Frangi AF, Taylor ZA. Evaluation of wave delivery methodology for brain MRE: Insights from computational simulations. Magn Reson Med 2016; 78:341-356. [PMID: 27416890 DOI: 10.1002/mrm.26333] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Revised: 06/10/2016] [Accepted: 06/17/2016] [Indexed: 01/22/2023]
Abstract
PURPOSE MR elastography (MRE) of the brain is being explored as a biomarker of neurodegenerative disease such as dementia. However, MRE measures for healthy brain have varied widely. Differing wave delivery methodologies may have influenced this, hence finite element-based simulations were performed to explore this possibility. METHODS The natural frequencies of a series of cranial models were calculated, and MRE-associated vibration was simulated for different wave delivery methods at varying frequency, using simple isotropic viscoelastic material models for the brain. Displacement fields and the corresponding brain constitutive properties estimated by standard inversion techniques were compared across delivery methods and frequencies. RESULTS The delivery methods produced widely different MRE displacement fields and inversions. Furthermore, resonances at natural frequencies influenced the displacement patterns. Consequently, some delivery methods led to lower inversion errors than others, and the error on the storage modulus varied by up to 11% between methods. CONCLUSION Wave delivery has a considerable impact on brain MRE reliability. Assuming small variations in brain biomechanics, as recently reported to accompany neurodegenerative disease (e.g., 7% for Alzheimer's disease), the effect of wave delivery is important. Hence, a consensus should be established on a consistent methodology to ensure diagnostic and prognostic consistency. Magn Reson Med 78:341-356, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Deirdre M McGrath
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, United Kingdom
- Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, University of Sheffield, Sheffield, United Kingdom
| | - Nishant Ravikumar
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, University of Sheffield, Sheffield, United Kingdom
| | - Leandro Beltrachini
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, United Kingdom
| | - Iain D Wilkinson
- Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, University of Sheffield, Sheffield, United Kingdom
- INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Alejandro F Frangi
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, United Kingdom
- INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Zeike A Taylor
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, University of Sheffield, Sheffield, United Kingdom
- INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sheffield, United Kingdom
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Koser DE, Moeendarbary E, Hanne J, Kuerten S, Franze K. CNS cell distribution and axon orientation determine local spinal cord mechanical properties. Biophys J 2016; 108:2137-47. [PMID: 25954872 PMCID: PMC4423070 DOI: 10.1016/j.bpj.2015.03.039] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 02/03/2015] [Accepted: 03/10/2015] [Indexed: 11/10/2022] Open
Abstract
Mechanical signaling plays an important role in cell physiology and pathology. Many cell types, including neurons and glial cells, respond to the mechanical properties of their environment. Yet, for spinal cord tissue, data on tissue stiffness are sparse. To investigate the regional and direction-dependent mechanical properties of spinal cord tissue at a spatial resolution relevant to individual cells, we conducted atomic force microscopy (AFM) indentation and tensile measurements on acutely isolated mouse spinal cord tissue sectioned along the three major anatomical planes, and correlated local mechanical properties with the underlying cellular structures. Stiffness maps revealed that gray matter is significantly stiffer than white matter irrespective of directionality (transverse, coronal, and sagittal planes) and force direction (compression or tension) (Kg= ∼130 Pa vs. Kw= ∼70 Pa); both matters stiffened with increasing strain. When all data were pooled for each plane, gray matter behaved like an isotropic material under compression; however, subregions of the gray matter were rather heterogeneous and anisotropic. For example, in sagittal sections the dorsal horn was significantly stiffer than the ventral horn. In contrast, white matter behaved transversely isotropic, with the elastic stiffness along the craniocaudal (i.e., longitudinal) axis being lower than perpendicular to it. The stiffness distributions we found under compression strongly correlated with the orientation of axons, the areas of cell nuclei, and cellular in plane proximity. Based on these morphological parameters, we developed a phenomenological model to estimate local mechanical properties of central nervous system (CNS) tissue. Our study may thus ultimately help predicting local tissue stiffness, and hence cell behavior in response to mechanical signaling under physiological and pathological conditions, purely based on histological data.
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Affiliation(s)
- David E Koser
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom; Department of Anatomy I, University of Cologne, Cologne, Germany
| | - Emad Moeendarbary
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Janina Hanne
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Stefanie Kuerten
- Department of Anatomy I, University of Cologne, Cologne, Germany; Department of Anatomy and Cell Biology, University of Wuerzburg, Wuerzburg, Germany
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
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Low G, Kruse SA, Lomas DJ. General review of magnetic resonance elastography. World J Radiol 2016; 8:59-72. [PMID: 26834944 PMCID: PMC4731349 DOI: 10.4329/wjr.v8.i1.59] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/14/2015] [Accepted: 12/04/2015] [Indexed: 02/06/2023] Open
Abstract
Magnetic resonance elastography (MRE) is an innovative imaging technique for the non-invasive quantification of the biomechanical properties of soft tissues via the direct visualization of propagating shear waves in vivo using a modified phase-contrast magnetic resonance imaging (MRI) sequence. Fundamentally, MRE employs the same physical property that physicians utilize when performing manual palpation - that healthy and diseased tissues can be differentiated on the basis of widely differing mechanical stiffness. By performing “virtual palpation”, MRE is able to provide information that is beyond the capabilities of conventional morphologic imaging modalities. In an era of increasing adoption of multi-parametric imaging approaches for solving complex problems, MRE can be seamlessly incorporated into a standard MRI examination to provide a rapid, reliable and comprehensive imaging evaluation at a single patient appointment. Originally described by the Mayo Clinic in 1995, the technique represents the most accurate non-invasive method for the detection and staging of liver fibrosis and is currently performed in more than 100 centers worldwide. In this general review, the mechanical properties of soft tissues, principles of MRE, clinical applications of MRE in the liver and beyond, and limitations and future directions of this discipline -are discussed. Selected diagrams and images are provided for illustration.
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McGrath DM, Ravikumar N, Wilkinson ID, Frangi AF, Taylor ZA. Magnetic resonance elastography of the brain: An in silico study to determine the influence of cranial anatomy. Magn Reson Med 2015; 76:645-62. [PMID: 26417988 DOI: 10.1002/mrm.25881] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 07/11/2015] [Accepted: 07/19/2015] [Indexed: 12/15/2022]
Abstract
PURPOSE Magnetic resonance elastography (MRE) of the brain has demonstrated potential as a biomarker of neurodegenerative disease such as dementia but requires further evaluation. Cranial anatomical features such as the falx cerebri and tentorium cerebelli membranes may influence MRE measurements through wave reflection and interference and tissue heterogeneity at their boundaries. We sought to determine the influence of these effects via simulation. METHODS MRE-associated mechanical stimulation of the brain was simulated using steady state harmonic finite element analysis. Simulations of geometrical models and anthropomorphic brain models derived from anatomical MRI data of healthy individuals were compared. Constitutive parameters were taken from MRE measurements for healthy brain. Viscoelastic moduli were reconstructed from the simulated displacement fields and compared with ground truth. RESULTS Interference patterns from reflections and heterogeneity resulted in artifacts in the reconstructions of viscoelastic moduli. Artifacts typically occurred in the vicinity of boundaries between different tissues within the cranium, with a magnitude of 10%-20%. CONCLUSION Given that MRE studies for neurodegenerative disease have reported only marginal variations in brain elasticity between controls and patients (e.g., 7% for Alzheimer's disease), the predicted errors are a potential confound to the development of MRE as a biomarker of dementia and other neurodegenerative diseases. Magn Reson Med 76:645-662, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Deirdre M McGrath
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.,Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, The University of Sheffield, Sheffield, UK
| | - Nishant Ravikumar
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, The University of Sheffield, Sheffield, UK
| | - Iain D Wilkinson
- Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
| | - Alejandro F Frangi
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
| | - Zeike A Taylor
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
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20
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Numano T, Mizuhara K, Hata J, Washio T, Homma K. A simple method for MR elastography: a gradient-echo type multi-echo sequence. Magn Reson Imaging 2015; 33:31-7. [DOI: 10.1016/j.mri.2014.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/27/2014] [Accepted: 10/05/2014] [Indexed: 12/20/2022]
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Petrov AY, Sellier M, Docherty PD, Chase JG. Parametric-based brain Magnetic Resonance Elastography using a Rayleigh damping material model. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2014; 116:328-339. [PMID: 24986109 DOI: 10.1016/j.cmpb.2014.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 05/28/2014] [Accepted: 05/29/2014] [Indexed: 06/03/2023]
Abstract
The three-parameter Rayleigh damping (RD) model applied to time-harmonic Magnetic Resonance Elastography (MRE) has potential to better characterise fluid-saturated tissue systems. However, it is not uniquely identifiable at a single frequency. One solution to this problem involves simultaneous inverse problem solution of multiple input frequencies over a broad range. As data is often limited, an alternative elegant solution is a parametric RD reconstruction, where one of the RD parameters (μI or ρI) is globally constrained allowing accurate identification of the remaining two RD parameters. This research examines this parametric inversion approach as applied to in vivo brain imaging. Overall, success was achieved in reconstruction of the real shear modulus (μR) that showed good correlation with brain anatomical structures. The mean and standard deviation shear stiffness values of the white and gray matter were found to be 3±0.11kPa and 2.2±0.11kPa, respectively, which are in good agreement with values established in the literature or measured by mechanical testing. Parametric results with globally constrained μI indicate that selecting a reasonable value for the μI distribution has a major effect on the reconstructed ρI image and concomitant damping ratio (ξd). More specifically, the reconstructed ρI image using a realistic μI=333Pa value representative of a greater portion of the brain tissue showed more accurate differentiation of the ventricles within the intracranial matter compared to μI=1000Pa, and ξd reconstruction with μI=333Pa accurately captured the higher damping levels expected within the vicinity of the ventricles. Parametric RD reconstruction shows potential for accurate recovery of the stiffness characteristics and overall damping profile of the in vivo living brain despite its underlying limitations. Hence, a parametric approach could be valuable with RD models for diagnostic MRE imaging with single frequency data.
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Affiliation(s)
- Andrii Y Petrov
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
| | - Mathieu Sellier
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
| | - Paul D Docherty
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
| | - J Geoffrey Chase
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
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22
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Mousavi SR, Fehlner A, Streitberger KJ, Braun J, Samani A, Sack I. Measurement of in vivo cerebral volumetric strain induced by the Valsalva maneuver. J Biomech 2014; 47:1652-7. [DOI: 10.1016/j.jbiomech.2014.02.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 02/25/2014] [Accepted: 02/25/2014] [Indexed: 10/25/2022]
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Fu J, Li F. An elastography method based on the scanning contact resonance of a piezoelectric cantilever. Med Phys 2013; 40:123502. [PMID: 24320542 DOI: 10.1118/1.4829502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Most tissues may become significantly stiffer than their normal states when there are lesions inside. The tissue's modulus can then act as an identification parameter for clinic diagnosis of tumors or fibrosis, which leads to elastography. This study introduces a novel elastography method that can be used for modulus imaging of superficial organs. METHODS This method is based on the scanning contact-resonance of a unimorph piezoelectric cantilever. The cantilever vibrates in its bending mode with the tip pressed tightly on the sample. The contact resonance frequency of the cantilever-sample system is tracked at each scanning point, from which the sample's modulus can be derived based on a beam dynamic model and a contact mechanics model. Scanning is performed by a three-dimensional motorized stage and the whole system is controlled by a homemade software program based on LabVIEW. RESULTS Testing on in vitro beef tissues indicates that the fat and the muscle can be easily distinguished using this system, and the accuracy of the modulus measurement can be comparable with that of nanoindentation. Imaging on homemade gelatin phantoms shows that the depth information of the abnormalities can be qualitatively obtained by varying the pressing force. The detection limit of this elastography method is specially examined both experimentally and numerically. Results show that it can detect the typical lesions in superficial organs with the depth of several centimeters. The lateral resolution of this elastography method∕system is better than 0.5 mm, and could be further enhanced by using more scanning points. CONCLUSIONS The proposed elastography system can be regarded as a sensitive palpation robot, which may be very promising in early diagnosis of tumors in superficial organs such as breast and thyroid.
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Affiliation(s)
- Ji Fu
- State Key Lab for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871, China and HEDPS, Center for Applied Physics and Technologies, Peking University, Beijing 100871, China
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Non-identifiability of the Rayleigh damping material model in magnetic resonance elastography. Math Biosci 2013; 246:191-201. [PMID: 24018294 DOI: 10.1016/j.mbs.2013.08.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/24/2013] [Accepted: 08/23/2013] [Indexed: 01/31/2023]
Abstract
Magnetic Resonance Elastography (MRE) is an emerging imaging modality for quantifying soft tissue elasticity deduced from displacement measurements within the tissue obtained by phase sensitive Magnetic Resonance Imaging (MRI) techniques. MRE has potential to detect a range of pathologies, diseases and cancer formations, especially tumors. The mechanical model commonly used in MRE is linear viscoelasticity (VE). An alternative Rayleigh damping (RD) model for soft tissue attenuation is used with a subspace-based nonlinear inversion (SNLI) algorithm to reconstruct viscoelastic properties, energy attenuation mechanisms and concomitant damping behavior of the tissue-simulating phantoms. This research performs a thorough evaluation of the RD model in MRE focusing on unique identification of RD parameters, μI and ρI. Results show the non-identifiability of the RD model at a single input frequency based on a structural analysis with a series of supporting experimental phantom results. The estimated real shear modulus values (μR) were substantially correct in characterising various material types and correlated well with the expected stiffness contrast of the physical phantoms. However, estimated RD parameters displayed consistent poor reconstruction accuracy leading to unpredictable trends in parameter behaviour. To overcome this issue, two alternative approaches were developed: (1) simultaneous multi-frequency inversion; and (2) parametric-based reconstruction. Overall, the RD model estimates the real shear shear modulus (μR) well, but identifying damping parameters (μI and ρI) is not possible without an alternative approach.
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Feng Y, Clayton EH, Chang Y, Okamoto RJ, Bayly PV. Viscoelastic properties of the ferret brain measured in vivo at multiple frequencies by magnetic resonance elastography. J Biomech 2013; 46:863-70. [PMID: 23352648 DOI: 10.1016/j.jbiomech.2012.12.024] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 12/03/2012] [Accepted: 12/21/2012] [Indexed: 11/16/2022]
Abstract
Characterization of the dynamic mechanical behavior of brain tissue is essential for understanding and simulating the mechanisms of traumatic brain injury (TBI). Changes in mechanical properties may also reflect changes in the brain due to aging or disease. In this study, we used magnetic resonance elastography (MRE) to measure the viscoelastic properties of ferret brain tissue in vivo. Three-dimensional (3D) displacement fields were acquired during wave propagation in the brain induced by harmonic excitation of the skull at 400 Hz, 600 Hz and 800 Hz. Shear waves with wavelengths in the order of millimeters were clearly visible in the displacement field, in strain fields, and in the curl of displacement field (which contains no contributions from longitudinal waves). Viscoelastic parameters (storage and loss moduli) governing dynamic shear deformation were estimated in gray and white matter for these excitation frequencies. To characterize the reproducibility of measurements, two ferrets were studied on three different dates each. Estimated viscoelastic properties of white matter in the ferret brain were generally similar to those of gray matter and consistent between animals and scan dates. In both tissue types G' increased from approximately 3 kPa at 400 Hz to 7 kPa at 800 Hz and G″ increased from approximately 1 kPa at 400 Hz to 2 kPa at 800 Hz. These measurements of shear wave propagation in the ferret brain can be used to both parameterize and validate finite element models of brain biomechanics.
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Affiliation(s)
- Y Feng
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO 63130, USA
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26
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Minton JA, Iravani A, Azizeh-Mitra Yousefi. Improving the homogeneity of tissue-mimicking cryogel phantoms for medical imaging. Med Phys 2012; 39:6796-807. [DOI: 10.1118/1.4757617] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Glaser KJ, Manduca A, Ehman RL. Review of MR elastography applications and recent developments. J Magn Reson Imaging 2012; 36:757-74. [PMID: 22987755 PMCID: PMC3462370 DOI: 10.1002/jmri.23597] [Citation(s) in RCA: 160] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The technique of MR elastography (MRE) has emerged as a useful modality for quantitatively imaging the mechanical properties of soft tissues in vivo. Recently, MRE has been introduced as a clinical tool for evaluating chronic liver disease, but many other potential applications are being explored. These applications include measuring tissue changes associated with diseases of the liver, breast, brain, heart, and skeletal muscle including both focal lesions (e.g., hepatic, breast, and brain tumors) and diffuse diseases (e.g., fibrosis and multiple sclerosis). The purpose of this review article is to summarize some of the recent developments of MRE and to highlight some emerging applications.
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Affiliation(s)
| | - Armando Manduca
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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Johnson CL, McGarry MDJ, Van Houten EEW, Weaver JB, Paulsen KD, Sutton BP, Georgiadis JG. Magnetic resonance elastography of the brain using multishot spiral readouts with self-navigated motion correction. Magn Reson Med 2012; 70:404-12. [PMID: 23001771 DOI: 10.1002/mrm.24473] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Revised: 07/20/2012] [Accepted: 08/06/2012] [Indexed: 12/17/2022]
Abstract
Magnetic resonance elastography (MRE) has been introduced in clinical practice as a possible surrogate for mechanical palpation, but its application to study the human brain in vivo has been limited by low spatial resolution and the complexity of the inverse problem associated with biomechanical property estimation. Here, we report significant improvements in brain MRE data acquisition by reporting images with high spatial resolution and signal-to-noise ratio as quantified by octahedral shear strain metrics. Specifically, we have developed a sequence for brain MRE based on multishot, variable-density spiral imaging, and three-dimensional displacement acquisition and implemented a correction scheme for any resulting phase errors. A Rayleigh damped model of brain tissue mechanics was adopted to represent the parenchyma and was integrated via a finite element-based iterative inversion algorithm. A multiresolution phantom study demonstrates the need for obtaining high-resolution MRE data when estimating focal mechanical properties. Measurements on three healthy volunteers demonstrate satisfactory resolution of gray and white matter, and mechanical heterogeneities correspond well with white matter histoarchitecture. Together, these advances enable MRE scans that result in high-fidelity, spatially resolved estimates of in vivo brain tissue mechanical properties, improving upon lower resolution MRE brain studies that only report volume averaged stiffness values.
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Affiliation(s)
- Curtis L Johnson
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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Othman SF, Curtis ET, Plautz SA, Pannier AK, Butler SD, Xu H. MR elastography monitoring of tissue-engineered constructs. NMR IN BIOMEDICINE 2012; 25:452-463. [PMID: 21387443 DOI: 10.1002/nbm.1663] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2010] [Revised: 11/15/2010] [Accepted: 12/03/2010] [Indexed: 05/30/2023]
Abstract
The objective of tissue engineering (TE) is to create functional replacements for various tissues; the mechanical properties of these engineered constructs are critical to their function. Several techniques have been developed for the measurement of the mechanical properties of tissues and organs; however, current methods are destructive. The field of TE will benefit immensely if biomechanical models developed by these techniques could be combined with existing imaging modalities to enable noninvasive, dynamic assessment of mechanical properties during tissue growth. Specifically, MR elastography (MRE), which is based on the synchronization of a mechanical actuator with a phase contrast imaging pulse sequence, has the capacity to measure tissue strain generated by sonic cyclic displacement. The captured displacement is presented in shear wave images from which the complex shear moduli can be extracted or simplified by a direct measure, termed the shear stiffness. MRE has been extended to the microscopic scale, combining clinical MRE with high-field magnets, stronger magnetic field gradients and smaller, more sensitive, radiofrequency coils, enabling the interrogation of smaller samples, such as tissue-engineered constructs. The following topics are presented in this article: (i) current mechanical measurement techniques and their limitations in TE; (ii) a description of the MRE system, MRE theory and how it can be applied for the measurement of mechanical properties of tissue-engineered constructs; (iii) a summary of in vitro MRE work for the monitoring of osteogenic and adipogenic tissues originating from human adult mesenchymal stem cells (MSCs); (iv) preliminary in vivo studies of MRE of tissues originating from mouse MSCs implanted subcutaneously in immunodeficient mice with an emphasis on in vivo MRE challenges; (v) future directions to resolve current issues with in vivo MRE in the context of how to improve the future role of MRE in TE.
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Affiliation(s)
- Shadi F Othman
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA.
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Johnson CL, Chen DD, Olivero WC, Sutton BP, Georgiadis JG. Effect of off-frequency sampling in magnetic resonance elastography. Magn Reson Imaging 2011; 30:205-12. [PMID: 22055750 DOI: 10.1016/j.mri.2011.09.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 09/22/2011] [Accepted: 09/23/2011] [Indexed: 01/22/2023]
Abstract
In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results were compared with numerical simulations to quantify these effects. It is known that off-frequency encoding alone results in a scaling of wave amplitude, and it is shown here that off-frequency sampling can result in two main effects: (1) errors in the overall shear stiffness estimate of the material on the global scale and (2) local variations appearing as stiffer and softer structures in the material. For small differences in frequency, it was found that measured global stiffness of the brain could theoretically vary by up to 12.5% relative to actual stiffness with local variations of up to 3.7% of the mean stiffness. It was demonstrated that performing MRE experiments at a frequency other than that of tissue vibration can lead to artifacts in the MRE stiffness images, and this mismatch could explain some of the large-scale scatter of stiffness data or lack of repeatability reported in the brain MRE literature.
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Affiliation(s)
- Curtis L Johnson
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Palmeri ML, Nightingale KR. What challenges must be overcome before ultrasound elasticity imaging is ready for the clinic? IMAGING IN MEDICINE 2011; 3:433-444. [PMID: 22171226 PMCID: PMC3235674 DOI: 10.2217/iim.11.41] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ultrasound elasticity imaging has been a research interest for the past 20 years with the goal of generating novel images of soft tissues based on their material properties (i.e., stiffness and viscosity). The motivation for such an imaging modality lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have very different mechanical properties that can be used to clearly visualize normal anatomy and delineate diseased tissues and masses. Recently, elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric and commercial implementations of ultrasonic elasticity imaging are beginning to appear on the market. This article provides a foundation for elasticity imaging, an overview of current research and commercial realizations of elasticity imaging technology and a perspective on the current successes, limitations and potential for improvement of these imaging technologies.
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Affiliation(s)
- Mark L Palmeri
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
- Department of Anesthesiology, Duke University, Durham, NC 27708, USA
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Tse ZTH, Chan YJ, Janssen H, Hamed A, Young I, Lamperth M. Piezoelectric actuator design for MR elastography: implementation and vibration issues. Int J Med Robot 2011; 7:353-60. [PMID: 21793149 DOI: 10.1002/rcs.405] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2011] [Indexed: 11/08/2022]
Abstract
BACKGROUND MR elastography (MRE) is an emerging technique for tumor diagnosis. MRE actuation devices require precise mechanical design and radiofrequency engineering to achieve the required mechanical vibration performance and MR compatibility. METHOD A method of designing a general-purpose, compact and inexpensive MRE actuator is presented. It comprises piezoelectric bimorphs arranged in a resonant structure designed to operate at its resonant frequency for maximum vibration amplitude. An analytical model was established to understand the device vibration characteristics. RESULTS The model-predicted performance was validated in experiments, showing its accuracy in predicting the actuator resonant frequency with an error < 4%. The device MRI compatibility was shown to cause minimal interference to a 1.5 tesla MRI scanner, with maximum signal-to-noise ratio reduction of 7.8% and generated artefact of 7.9 mm in MR images. CONCLUSIONS A piezoelectric MRE actuator is proposed, and its implementation, vibration issues and future work are discussed.
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Affiliation(s)
- Zion Tsz Ho Tse
- Harvard Medical School, Radiology Department, Brigham and Women's Hospital, 221 Longwood Avenue, LM-010, Boston, MA 02115, USA.
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Sun C, Standish B, Yang VXD. Optical coherence elastography: current status and future applications. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:043001. [PMID: 21529067 DOI: 10.1117/1.3560294] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Optical coherence tomography (OCT) has several advantages over other imaging modalities, such as angiography and ultrasound, due to its inherently high in vivo resolution, which allows for the identification of morphological tissue structures. Optical coherence elastography (OCE) benefits from the superior spatial resolution of OCT and has promising applications, including cancer diagnosis and the detailed characterization of arterial wall biomechanics, both of which are based on the elastic properties of the tissue under investigation. We present OCE principles based on techniques associated with static and dynamic tissue excitation, and their corresponding elastogram image-reconstruction algorithms are reviewed. OCE techniques, including the development of intravascular- or catheter-based OCE, are in their early stages of development but show great promise for surgical oncology or intravascular cardiology applications.
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Affiliation(s)
- Cuiru Sun
- Department of Electrical and Computer Engineering, Biophotonics and Bioengineering Laboratory, Ryerson University, Toronto, Ontario M5B 2K3, Canada
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Convertible pneumatic actuator for magnetic resonance elastography of the brain. Magn Reson Imaging 2010; 29:147-52. [PMID: 20833495 DOI: 10.1016/j.mri.2010.07.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 07/06/2010] [Accepted: 07/13/2010] [Indexed: 12/12/2022]
Abstract
Here we present a novel pneumatic actuator design for brain magnetic resonance elastography (MRE). Magnetic resonance elastography is a phase contrast technique capable of tracing strain wave propagation and utilizing this information for the calculation of mechanical properties of materials and living tissues. In MRE experiments, the acoustic waves are generated in a synchronized way with respect to image acquisition, using various types of mechanical actuators. The unique feature of the design is its simplicity and flexibility, which allows reconfiguration of the actuator for different applications ranging from in vivo brain MRE to experiments with phantoms. Phantom and in vivo data are presented to demonstrate actuator performance.
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