1
|
Abstract
We developed a Monte Carlo simulator for diffusion-weighted imaging sequences which displays the motion of water molecules and computes the dynamic phase dispersion due to the applied motion probing gradients. This simulator can be used to validate the analytical equations of diffusion models and understand their limitations due to their approximations. Here, we introduce the software and some specific use cases. The software can be downloaded from the following website: https://www.nirs.qst.go.jp/amr_diag.
Collapse
Affiliation(s)
- Yasuhiko Tachibana
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| | - Tanguy Duval
- NeuroPoly Lab, Institute of Biomedical Engineering
| | - Takayuki Obata
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| |
Collapse
|
2
|
Tachibana Y, Hagiwara A, Hori M, Kershaw J, Nakazawa M, Omatsu T, Kishimoto R, Yokoyama K, Hattori N, Aoki S, Higashi T, Obata T. The Utility of a Convolutional Neural Network for Generating a Myelin Volume Index Map from Rapid Simultaneous Relaxometry Imaging. Magn Reson Med Sci 2020; 19:324-332. [PMID: 31902906 PMCID: PMC7809139 DOI: 10.2463/mrms.mp.2019-0075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Purpose: A current algorithm to obtain a synthetic myelin volume fraction map (SyMVF) from rapid simultaneous relaxometry imaging (RSRI) has a potential problem, that it does not incorporate information from surrounding pixels. The purpose of this study was to develop a method that utilizes a convolutional neural network (CNN) to overcome this problem. Methods: RSRI and magnetization transfer images from 20 healthy volunteers were included. A CNN was trained to reconstruct RSRI-related metric maps into a myelin volume-related index (generated myelin volume index: GenMVI) map using the MVI map calculated from magnetization transfer images (MTMVI) as reference. The SyMVF and GenMVI maps were statistically compared by testing how well they correlated with the MTMVI map. The correlations were evaluated based on: (i) averaged values obtained from 164 atlas-based ROIs, and (ii) pixel-based comparison for ROIs defined in four different tissue types (cortical and subcortical gray matter, white matter, and whole brain). Results: For atlas-based ROIs, the overall correlation with the MTMVI map was higher for the GenMVI map than for the SyMVF map. In the pixel-based comparison, correlation with the MTMVI map was stronger for the GenMVI map than for the SyMVF map, and the difference in the distribution for the volunteers was significant (Wilcoxon sign-rank test, P < 0.001) in all tissue types. Conclusion: The proposed method is useful, as it can incorporate more specific information about local tissue properties than the existing method. However, clinical validation is necessary.
Collapse
Affiliation(s)
- Yasuhiko Tachibana
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences.,Department of Radiology, Juntendo University School of Medicine
| | - Akifumi Hagiwara
- Department of Radiology, Juntendo University School of Medicine.,Department of Radiology, Graduate School of Medicine, The University of Tokyo
| | - Masaaki Hori
- Department of Radiology, Juntendo University School of Medicine
| | - Jeff Kershaw
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| | - Misaki Nakazawa
- Department of Radiology, Juntendo University School of Medicine
| | - Tokuhiko Omatsu
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| | - Riwa Kishimoto
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| | | | | | - Shigeki Aoki
- Department of Radiology, Juntendo University School of Medicine
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| | - Takayuki Obata
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences.,Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences
| |
Collapse
|
3
|
Tachibana Y, Obata T, Kershaw J, Sakaki H, Urushihata T, Omatsu T, Kishimoto R, Higashi T. The Utility of Applying Various Image Preprocessing Strategies to Reduce the Ambiguity in Deep Learning-based Clinical Image Diagnosis. Magn Reson Med Sci 2020; 19:92-98. [PMID: 31080211 PMCID: PMC7232029 DOI: 10.2463/mrms.mp.2019-0021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 03/04/2019] [Indexed: 11/09/2022] Open
Abstract
PURPOSE A general problem of machine-learning algorithms based on the convolutional neural network (CNN) technique is that the reason for the output judgement is unclear. The purpose of this study was to introduce a strategy that may facilitate better understanding of how and why a specific judgement was made by the algorithm. The strategy is to preprocess the input image data in different ways to highlight the most important aspects of the images for reaching the output judgement. MATERIALS AND METHODS T2-weighted brain image series falling into two age-ranges were used. Classifying each series into one of the two age-ranges was the given task for the CNN model. The images from each series were preprocessed in five different ways to generate five different image sets: (1) subimages from the inner area of the brain, (2) subimages from the periphery of the brain, (3-5) subimages of brain parenchyma, gray matter area, and white matter area, respectively, extracted from the subimages of (2). The CNN model was trained and tested in five different ways using one of these image sets. The network architecture and all the parameters for training and testing remained unchanged. RESULTS The judgement accuracy achieved by training was different when the image set used for training was different. Some of the differences was statistically significant. The judgement accuracy decreased significantly when either extra-parenchymal or gray matter area was removed from the periphery of the brain (P < 0.05). CONCLUSION The proposed strategy may help visualize what features of the images were important for the algorithm to reach correct judgement, helping humans to understand how and why a particular judgement was made by a CNN.
Collapse
Affiliation(s)
- Yasuhiko Tachibana
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan
| | - Takayuki Obata
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan
| | - Jeff Kershaw
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan
| | - Hironao Sakaki
- Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Takuya Urushihata
- Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Tokuhiko Omatsu
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan
| | - Riwa Kishimoto
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba 263-8555, Japan
| | - Tatsuya Higashi
- Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| |
Collapse
|
4
|
Tachibana A, Tachibana Y, Kershaw J, Sano H, Fukushi M, Obata T. Comparison of Glass Capillary Plates and Polyethylene Fiber Bundles as Phantoms to Assess the Quality of Diffusion Tensor Imaging. Magn Reson Med Sci 2018; 17:251-258. [PMID: 29212957 PMCID: PMC6039775 DOI: 10.2463/mrms.mp.2017-0079] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Purpose: The purpose of this study was to evaluate the suitability of two phantoms, one made of capillary plates and the other polyethylene fibers, for assessing the quality of diffusion tensor imaging (DTI). Methods: The first phantom was a stack of glass capillary plates with many parallel micropores (CP). The second phantom was a bundle of polyethylene fiber Dyneema held together with a thermal shrinkage tube (Dy). High resolution multi-shot echo planar imaging (EPI) DTI acquisitions were performed at b-values of 0 and 1000 s/mm2 and diffusion-times (Tdiff) of 37.7 and 97.7 ms on a preclinical 7T MRI scanner. Thirty diffusion-encoding directions were used. The data were used to calculate the fractional anisotropy (FA), mean diffusivity (MD), and angular dispersion (AD). Further acquisitions were performed at b-values from 0 to 8000 s/mm2 in 14 steps with the diffusion gradient applied parallel (axial) and perpendicular (radial) to the Z direction. On the other hand, the data acquired with a 3T MRI scanner were used to confirm that measurements on a clinical machine are consistent with the 7T MRI results. Results: The dependence of FA, MD and AD on Tdiff was smaller for the Dy than for the CPs. The b-value-dependent signal attenuations in the axial direction at Tdiff = 37.7 and 97.7 ms were similar for both phantoms. In the radial direction, Dy demonstrated similar b-value attenuation to that of in vivo tissue for both Tdiffs, but the attenuation for the CPs was affected by the change in Tdiff. Parameter estimates were similar for 3T and 7T MRI. Conclusion: The characteristics of the CP indicate that it can be used as a restricted-diffusion dominant phantom, while the characteristics of the Dy suggest that it can be used as a hindered-diffusion dominant phantom. Dy may be more suitable than CP for DTI quality control.
Collapse
Affiliation(s)
- Atsushi Tachibana
- Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University.,Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Yasuhiko Tachibana
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Jeff Kershaw
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Hiromi Sano
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Masahiro Fukushi
- Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University
| | - Takayuki Obata
- Applied MRI Research, Department of Molecular Imaging and Theranostics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| |
Collapse
|
5
|
Favaretto A, Lazzarotto A, Riccardi A, Pravato S, Margoni M, Causin F, Anglani MG, Seppi D, Poggiali D, Gallo P. Enlarged Virchow Robin spaces associate with cognitive decline in multiple sclerosis. PLoS One 2017; 12:e0185626. [PMID: 29045421 PMCID: PMC5646763 DOI: 10.1371/journal.pone.0185626] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 09/15/2017] [Indexed: 11/19/2022] Open
Abstract
The clinical significance of Virchow Robin spaces (VRS) in inflammatory brain disorders, especially in multiple sclerosis (MS), is still undefined. We analysed enlarged VRS (eVRS) by means of phase sensitive inversion recovery (PSIR) MRI sequence and investigated their association with inflammation or brain atrophy, and to clinical or physical disability. Forty-three MS patients (21 clinically isolated syndrome suggestive of MS [CIS], 15 RRMS, 7 progressive [PMS]) and 10 healthy controls (HC) were studied. 3DT1, 3DFLAIR and 2DPSIR images were obtained with a 3T MRI scanner. eVRS number and volume were calculated by manual segmentation (ITK-SNAP). Freesurfer was used to assess brain parenchymal fraction (BPF). All patients underwent clinical (EDSS) and cognitive (Rao’s BRB and DKEFS) evaluation. eVRS number and volume resulted significantly higher on 2D-PSIR compared to both 3D-T1 (p<0.001) and 3D-FLAIR (p<0.001) and were significantly increased in CIS compared to HC (p<0.05), in PMS and RRMS compared to CIS (p<0.001) and in male versus female patients (p<0.05). eVRS volume increased significantly with disease duration (r = 0.6) but did not correlate with EDSS. eVRS significantly correlated with SPARTd (r = -0.47) and DKEFSfs (r = -0.46), especially when RRMS and PMS were merged in a single group (r = 0.89, p = 0.002 and r = 0.66, p = 0.009 respectively), while no correlation was found with BPF (r = 0.3), gadolinium-enhancing lesions (r = 0.2) and WMT2 lesion volume (r = 0.2). 2DPSIR allowed the detection of an impressive higher number of eVRS compared to 3DT1 and 3DFLAIR. eVRS associate with SPARTd and DKEFSfs failure in relapse-onset MS, suggesting they may contribute to cognitive decline in MS.
Collapse
Affiliation(s)
- Alice Favaretto
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Andrea Lazzarotto
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Alice Riccardi
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Stefano Pravato
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Monica Margoni
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Francesco Causin
- Neuroradiology Unit, Azienda Ospedaliera di Padova, Padova, Italy
| | | | - Dario Seppi
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Davide Poggiali
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
| | - Paolo Gallo
- Multiple Sclerosis Centre of the Veneto Region, Department of Neurosciences, University Hospital of Padova–Medical School, Padova, Italy
- * E-mail:
| |
Collapse
|
6
|
Connor M, Karunamuni R, McDonald C, White N, Pettersson N, Moiseenko V, Seibert T, Marshall D, Cervino L, Bartsch H, Kuperman J, Murzin V, Krishnan A, Farid N, Dale A, Hattangadi-Gluth J. Dose-dependent white matter damage after brain radiotherapy. Radiother Oncol 2016; 121:209-216. [PMID: 27776747 PMCID: PMC5136508 DOI: 10.1016/j.radonc.2016.10.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 09/16/2016] [Accepted: 10/02/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND PURPOSE Brain radiotherapy is limited in part by damage to white matter, contributing to neurocognitive decline. We utilized diffusion tensor imaging (DTI) with multiple b-values (diffusion weightings) to model the dose-dependency and time course of radiation effects on white matter. MATERIALS AND METHODS Fifteen patients with high-grade gliomas treated with radiotherapy and chemotherapy underwent MRI with DTI prior to radiotherapy, and after months 1, 4-6, and 9-11. Diffusion tensors were calculated using three weightings (high, standard, and low b-values) and maps of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ∥), and radial diffusivity (λ⊥) were generated. The region of interest was all white matter. RESULTS MD, λ∥, and λ⊥ increased significantly with time and dose, with corresponding decrease in FA. Greater changes were seen at lower b-values, except for FA. Time-dose interactions were highly significant at 4-6months and beyond (p<.001), and the difference in dose response between high and low b-values reached statistical significance at 9-11months for MD, λ∥, and λ⊥ (p<.001, p<.001, p=.005 respectively) as well as at 4-6months for λ∥ (p=.04). CONCLUSIONS We detected dose-dependent changes across all doses, even <10Gy. Greater changes were observed at low b-values, suggesting prominent extracellular changes possibly due to vascular permeability and neuroinflammation.
Collapse
Affiliation(s)
- Michael Connor
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Roshan Karunamuni
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Carrie McDonald
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States; Department of Psychiatry, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Nathan White
- Department of Radiology, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Niclas Pettersson
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Vitali Moiseenko
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Tyler Seibert
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Deborah Marshall
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Laura Cervino
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Hauke Bartsch
- Department of Radiology, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Joshua Kuperman
- Department of Radiology, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Vyacheslav Murzin
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States
| | - Anitha Krishnan
- Department of Radiology, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Nikdokht Farid
- Department of Radiology, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Anders Dale
- Department of Radiology, University of California San Diego, United States; Department of Psychiatry, University of California San Diego, United States; Department of Neurosciences, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States
| | - Jona Hattangadi-Gluth
- Department of Radiation Medicine and Applied Sciences, University of California San Diego, United States; Multimodal Imaging Laboratory, University of California San Diego, United States.
| |
Collapse
|
7
|
Diffusion-tensor-based method for robust and practical estimation of axial and radial diffusional kurtosis. Eur Radiol 2015; 26:2559-66. [PMID: 26443602 PMCID: PMC4927605 DOI: 10.1007/s00330-015-4038-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/23/2015] [Accepted: 09/18/2015] [Indexed: 12/15/2022]
Abstract
Objectives A new method that can estimate diffusional kurtosis image (DKI), estimated DKI (eDKI), parallel and perpendicular to neuronal fibres from greatly limited image data was designed to enable quick and practical assessment of DKI in clinics. The purpose of this study was to discuss the potential of this method for clinical use. Methods Fourteen healthy volunteers were examined with a 3-Tesla MRI. The diffusion-weighting parameters included five different b-values (0, 500, 1,500, 2,000 and 2,500 s/mm2) with 64 different encoding directions for each of the b-values. K values were calculated by both conventional DKI (convDKI) and eDKI from these complete data, and also from the data that the encoding directions were abstracted to 32, 21, 15, 12 and 6. Error-pixel ratio and the root mean square error (RMSE) compared with the standard were compared between the methods (Wilcoxon signed-rank test: P < 0.05 was considered significant). Results Error-pixel ratio was smaller in eDKI than in convDKI and the difference was significant. In addition, RMSE was significantly smaller in eDKI than in convDKI, or otherwise the differences were not significant when they were obtained from the same data set. Conclusion eDKI might be useful for assessing DKI in clinical settings. Key Points • A method to practically estimate axial/radial DKI from limited data was developed. • The high robustness of the proposed method can greatly improve map images. • The accuracy of the proposed method was high. • Axial/radial K maps can be calculated from limited diffusion-encoding directions. • The proposed method might be useful for assessing DKI in clinical settings.
Collapse
|
8
|
Dadalti Fragoso Y. Why some of us do not like the expression "no evidence of disease activity" (NEDA) in multiple sclerosis. Mult Scler Relat Disord 2015. [PMID: 26195061 DOI: 10.1016/j.msard.2015.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Yara Dadalti Fragoso
- Multiple Sclerosis Reference Center, Universidade Metropolitana de Santos, SP, Brazil.
| |
Collapse
|