MR Elastography

An advanced medical imaging technique that non-invasively quantifies tissue elasticity.

MR Elastography: Diagnostic Innovation Through Tissue Elasticity Imaging

Conventional medical imaging has been able to capture morphological changes in tissues but has faced significant challenges in quantitatively evaluating their physical properties, particularly “stiffness.” This limitation has been especially problematic in assessing the progression of hepatic fibrosis and qualitative diagnosis of brain tumors, where clinicians have had to rely on invasive biopsy procedures.

MR Elastography was developed as an innovative solution to address these challenges (Muthupillai et al., 1995). By applying external mechanical vibrations and capturing their propagation using high-speed MRI, this technology enables non-invasive and quantitative measurement of tissue elasticity. This breakthrough technique has enabled a wide range of clinical applications, including early detection of liver cirrhosis, differentiation between benign and malignant brain tumors, and evaluation of musculoskeletal disorders, simultaneously reducing patient burden while improving diagnostic accuracy.

By augmenting conventional morphological imaging with physical property information, MR Elastography represents a next-generation medical imaging technology that provides more comprehensive and precise diagnostics, with promising prospects for widespread clinical adoption.

MR Elastography Overview The left figure illustrates the basic principle of MRE, while the right figure shows the complete system configuration.

I participated in a comprehensive research and development project at Chiba University and the National Institute of Radiological Sciences (NIRS) aimed at expanding the clinical applications of MRE technology and improving diagnostic accuracy. This research adopted innovative approaches from both hardware and software perspectives to address the technical limitations and clinical application challenges inherent in conventional apporaches.

Effective MRE Measurement

We introduced a novel multi-point convergent external vibration system to replace conventional single-point vibration methods, optimizing vibration propagation characteristics within tissues. Simultaneously, we implemented a transition from conventional differential-type calculation methods to integral-type algorithms for elasticity estimation (Suga et al., 2009), achieving significant improvements in noise tolerance and computational stability. In this project, I served a central role in MRI pulse sequence design and signal processing algorithm development.

Through gradient magnetic field control and RF pulse design in MRI imaging, I implemented selective extraction functionality for specific vibration frequency components (Suga et al., 2009; Suga et al., 2010; Ozawa et al., 2010; Kobayashi et al., 2010; Ozawa et al., 2010; Ozawa et al., 2011). I developed MR pulse sequence to precisely filter target frequency due to diverse biological vibration components and mechanical limitation, achieving substantial improvements in signal-to-noise ratio (SNR). Additionally, I constructed a real-time motion detection and correction system to eliminate artifacts caused by involuntary body movements during imaging, enhancing practical applicability in clinical environments. (Hirano et al., 2008; Arai et al., 2009; Arai et al., 2010; Arai et al., 2011; Suga et al., 2010; Arai et al., 2011; Arai et al., 2011)

Table Resonance Elastography in MR

As one of groundbreaking achievements, I contributed to an external vibration device-free MRE imaging method utilizing the inherent physical characteristics of MR systems (Gallichan et al., 2009). By precisely controlling and utilizing minute vibrations generated during MR scanner coil operations, I developed a revolutionary approach that eliminates the need for conventional large external devices. This technology holds particularly innovative significance in the neurological field. It fundamentally solved the problem of direct vibration application to brain tissue, which was previously difficult due to physical constraints imposed by the skull, achieving the non-invasive brain elasticity measurement. (Arai et al., 2010; Ikeda et al., 2011)

MRE Under Free-Breathing

To overcome respiratory motion artifacts, the major technical challenge in abdominal organ MRE imaging, We developed a system integrating advanced image analysis and machine learning technologies. We constructed proprietary tracking algorithms that monitor diaphragmatic motion in real-time from MR signals and established technology for highly accurate identification of expiratory and inspiratory phases using random forest-based machine learning models. This technology eliminated the constraints of breath-hold imaging previously considered essential, enabling high-quality MRE examinations for patient populations where breath-holding is difficult, including elderly patients and those with chronic respiratory diseases. (Ozaki et al., 2014)

References

2014

ISMRM

MR Elastography Using SS-SE-EPI with Reduced FOV for Kidney: Preliminary Study.

Masanori Ozaki, Ken Arai, Kunihiro Miyoshi, and 5 more authors

In International Society for Magnetic Resonace In Medicine (ISMRM), May 2014

Abs Bib HTML

Current MRE method offers techniques for diagnosis for large organs such as liver. Recent papers report that MRE for kidney could be useful for assessment of renal fibrosis. However, in the renal MRE, high spatial resolution is needed because pathologic evaluation is valid only on the renal cortex which is thin. This study proposes high spatial resolution MRE using Single-Shot Spin Echo Echo Planar Imaging with reduced FOV for kidney.

@inproceedings{ozakiMRElastographyUsing2014,
  title = {{{MR Elastography}} Using {{SS-SE-EPI}} with Reduced {{FOV}} for {{Kidney}}: {{Preliminary Study}}.},
  booktitle = {International {{Society}} for {{Magnetic Resonace In Medicine}} ({{ISMRM}})},
  author = {Ozaki, Masanori and Arai, Ken and Miyoshi, Kunihiro and Worters, Pauline and Banerjee, Suchandrima and Guidon, Arnaud and Ikeda, Hitoshi and Kabasawa, Hiroyuki},
  year = {2014},
  month = may,
  volume = {4234},
  publisher = {The 22th ISMRM Annual Meeting},
  address = {Milan, Italy},
  urldate = {2025-05-30},
  category = {peer-reviewed-abstract},
}

2011

Evaluation of the Effectiveness of a Multipoint Vibration System for MRE on a Living Body

Shinya Ozawa, Mikio Suga, Yusuke Takei, and 5 more authors

In The 60th National Congress of Theoretical and Applied Mechanics, Mar 2011
Investigation of Imaging Methods in MR Elastography of the Human Abdomen - Comparison of Echo-planar and Gradient Echo Methods -

Ken Arai, Mikio Suga, Shinya Ozawa, and 3 more authors

In The 60th National Congress of Theoretical and Applied Mechanics, Mar 2011
Preliminary study of in-vivo liver measurement by optimized pulse sequence for MR elastography

Ken Arai, Mikio Suga, Shinya Ozawa, and 4 more authors

IEICE Technical Report; IEICE Tech. Rep., Jan 2011

Abs Bib HTML

Magnetic resonance elastography (MRE) is a technique for quantitative and noninvasive assessment of tissue elasticity. MRE is often described as image-based palpation that can be used to characterize disease because the mechanical properties of tissues are often dramatically affected by the presence of disease processes. MRE pulse sequences obtain shear wave images by synchronizing motion sensitized gradients (MSG) with an external vibrator. A quantitative shear modulus map is calculated from the shear wave images. However, the magnitude property of the external vibrator and nonlinearity of the imaged object often induce unwanted higher harmonics that distort the shear wave images and impair the estimation of the elastic modulus. Additionally, bulk motion can induce signal loss, ghosting and unwanted phase accumulation. In this study, we apply the MSGs to gradient moment nulling (GMN) technique for reducing bulk motion effect and optimize them to minimize the contribution of higher harmonics to the shear wave images and therefore improve the accuracy of shear modulus estimation. Phantom and in-vivo study was performed to confirm the performance of the proposed MRE pulse sequence. The results show that the optimized MSG is able to acquire single frequency shear wave images even when large amplitude harmonic waves are present in the imaged object. Additionally, the proposed MRE pulse sequence reduced cardiac motion artifact. These results suggest that the proposed pulse sequence might be useful for in-vivo MRE studies.
@article{araiPreliminaryStudyInvivo2011, title = {{Preliminary study of in-vivo liver measurement by optimized pulse sequence for MR elastography}}, author = {Arai, Ken and Suga, Mikio and Ozawa, Shinya and Ikeda, Hajime and Hirano, Masaya and Kobayashi, Etsuko and Obata, Takayuki}, year = {2011}, month = jan, journal = {IEICE Technical Report; IEICE Tech. Rep.}, volume = {110}, number = {364}, pages = {47--50}, publisher = {IEICE}, issn = {0913-5685; 2432-6380}, urldate = {2025-05-30}, langid = {japanese}, category = {peer-reviewed}, }
Reduction of harmonic distortion on shear wave images by pulse sequence optimization for MR elastography

Ken Arai, Mikio Suga, Shinya Ozawa, and 3 more authors

Transactions of Japanese Society for Medical and Biological Engineering, Feb 2011

Abs Bib HTML

Magnetic Resonance Elastography (MRE) is a technique for quantitative and noninvasive assessment of tissue elasticity. MRE is often described as image-based palpation that can be used to characterize disease because the mechanical properties of tissues are often dramatically affected by the presence of disease processes. MRE pulse sequences obtain shear wave images by synchronizing motion sensitized gradients (MSG) with an external vibrator. A quantitative shear modulus map is calculated from the shear wave images. However, the magnitude property of the external vibrator and nonlinearity of the imaged object often induce unwanted higher harmonics that distort the shear wave images and impair the estimation of the elastic modulus. In this study, we optimize the MSGs to minimize the contribution of higher harmonics to the shear wave images and therefore improve the accuracy of shear modulus estimation. Simulation and phantom studies were performed to confirm the performance of the proposed MRE pulse sequence. The results show that the optimized MSG is able to acquire single frequency shear wave images even when large amplitude harmonic waves are present in the imaged object. (author)
@article{araiReductionHarmonicDistortion2011, title = {{Reduction of harmonic distortion on shear wave images by pulse sequence optimization for MR elastography}}, author = {Arai, Ken and Suga, Mikio and Ozawa, Shinya and Hirano, Masaya and Kobayashi, Etsuko and Obata, Takayuki}, year = {2011}, month = feb, journal = {Transactions of Japanese Society for Medical and Biological Engineering}, volume = {49}, number = {1}, pages = {200--206}, issn = {1347-443X}, urldate = {2025-05-30}, langid = {japanese}, category = {peer-reviewed}, }
Preliminary Study of MR Elastography Using Gantry Vibration - Estimation of Optimum Imaging Parameters by Measuring Amplitude Characteristics -

Hajime Ikeda, Mikio Suga, Yusuke Takei, and 5 more authors

In The 60th National Congress of Theoretical and Applied Mechanics, Mar 2011

2010

ISMRM
Focused Acoustic Driver to Generate High-Frequency Shear Waves in Deep Regions for Magnetic Resonance Elastography

M Suga, T Obata, M Sekine, and 5 more authors

In International Society for Magnetic Resonace In Medicine (ISMRM), May 2010

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Magnetic resonance elastography (MRE) can noninvasively visualize shear waves patterns within tissue. To acquire an accurate shear modulus map in high spatial resolution in deep regions, external drivers must generate a precisely controlled high frequency and a large amplitude vibration. In this study, we develop a simple and robustly designed focused acoustic driver to enhance shear wave amplitude in deep regions by high frequency using a piezoelectric actuator. From the results of the experimental studies, it was shown that the focused acoustic driver increases the SNR of the shear wave image in the deep region and improves shear modulus quantitatively.
@inproceedings{sugaFocusedAcousticDriver2010, title = {Focused {{Acoustic Driver}} to {{Generate High-Frequency Shear Waves}} in {{Deep Regions}} for {{Magnetic Resonance Elastography}}}, booktitle = {International {{Society}} for {{Magnetic Resonace In Medicine}} ({{ISMRM}})}, author = {Suga, M and Obata, T and Sekine, M and Hirano, M and Miura, H and Arai, K and Ozawa, S and Ikehira, H}, year = {2010}, month = may, volume = {635}, publisher = {The 18th ISMRM Annual Meeting}, address = {Stockholm, Sweden}, langid = {english}, file = {files/1037/Suga et al. - Focused Acoustic Driver to Generate High-Frequency.pdf}, category = {peer-reviewed-abstract}, }
Examination of Vibration Vibration Apparatus for Improving Accuracy of Viscoelastic Modulus Estimation in MRE

Shinya Ozawa, Mikio Suga, Yusuke Takei, and 5 more authors

In The 59th National Congress of Theoretical and Applied Mechanics, Jun 2010
Examination of Vibratory Apparatus for MRE Using Elastic Wave Interference

Etsuko Kobayashi, Yusuke Takei, Mikio Suga, and 5 more authors

In The 59th National Congress of Theoretical and Applied Mechanics, Jun 2010
Improvement of elastic modulus estimation accuracy of MR Elastography by multipoint excitation

Shinya Ozawa, Mikio Suga, Etsuko Kobayashi, and 4 more authors

In The 38th Annual Meeting of the Japanese Society for Magnetic Resonance in Medicine, Oct 2010
Suppression of harmonic distortion on elastic wave images by optimizing pulse sequences for MR elastography

Ken Arai, Mikio Suga, Shinya Ozawa, and 3 more authors

In The symoposium for The Japanese Society for Medical and Biological Engineering 2010, Sep 2010
Estimation Method for Viscoelastic Modulus Distribution Considering Compressibility of Living Body

Mikio Suga, Hisayuki Miura, Hiroshi Fujiwara, and 5 more authors

In The 59th National Congress of Theoretical and Applied Mechanics, Jun 2010
Preliminary study of viscoelastic modulus distribution measurement of the brain by MR elastography using gantry vibration

Ken Arai, Mikio Suga, Shinya Ozawa, and 3 more authors

In The 38th Annual Meeting of the Japanese Society for Magnetic Resonance in Medicine, Oct 2010

2009

ISMRM
Inversion Algorithm by Integral Type Reconstruction Formula for Magnetic Resonance Elastography

M Suga, H Miura, H Fujiwara, and 8 more authors

In International Society for Magnetic Resonace In Medicine (ISMRM), Apr 2009

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Magnetic resonance elastography (MRE) can noninvasively visualize shear waves in tissue. One of the general approaches to estimating stiffness from MRE data is a local frequency estimation (LFE) algorithm, but the LFE estimate is blurred at sharp boundaries. Other methods are based on equations of motion, but they tend to be very sensitive to noise. In this study, we propose a new inversion algorithm that is applicable for noisy long shear wave images and the estimation of the shear modulus quantitatively with high spatial resolution. To confirm the reliability of this method, computer simulations and a phantom study were performed.
@inproceedings{sugaInversionAlgorithmIntegral2009, title = {Inversion {{Algorithm}} by {{Integral Type Reconstruction Formula}} for {{Magnetic Resonance Elastography}}}, booktitle = {International {{Society}} for {{Magnetic Resonace In Medicine}} ({{ISMRM}})}, author = {Suga, M and Miura, H and Fujiwara, H and Yamamoto, T and Tanaka, T and Yu, Q and Arai, K and Gong, J P and Nakamura, G and Ikehira, H and Obata, T}, year = {2009}, month = apr, volume = {2506}, publisher = {The 17th ISMRM Annual Meeting}, address = {Hawaii, United States}, langid = {english}, file = {files/1033/Suga et al. - Inversion Algorithm by Integral Type Reconstructio.pdf}, category = {peer-reviewed-abstract}, }
Development of an External Focus Vibration Apparatus for MR Elastography to Improve Quantification and Spatial Resolution of Viscoelastic Modulus Distribution in Vivo

Mikio Suga, Takayuki Obata, Masashi Sekine, and 3 more authors

In The 37th Annual Meeting of the Japanese Society for Magnetic Resonance in Medicine, Oct 2009
Optimization of Pulse Sequences for MR Elastography for Single Frequency Elastic Wave Image Acquisition

Ken Arai, Mikio Suga, Masaya Hirano, and 2 more authors

In The 37th Annual Meeting of the Japanese Society for Magnetic Resonance in Medicine, Oct 2009

TREMR: Table-resonance elastography with MR

Daniel Gallichan, Matthew D Robson, Andreas Bartsch, and 1 more author

Magnetic Resonance in Medicine: An Official Journal of the International Society for Magnetic Resonance in Medicine, Oct 2009

DOI Bib

@article{gallichan2009tremr,
  title = {TREMR: Table-resonance elastography with MR},
  author = {Gallichan, Daniel and Robson, Matthew D and Bartsch, Andreas and Miller, Karla L},
  journal = {Magnetic Resonance in Medicine: An Official Journal of the International Society for Magnetic Resonance in Medicine},
  volume = {62},
  number = {3},
  pages = {815--821},
  year = {2009},
  publisher = {Wiley Online Library},
  bibtex_show = true,
  doi = {10.1002/mrm.22046}
}

2008

Investigation of Pulse Sequence Optimization in MR Elastography

Masaya Hirano, Mikio Suga, Takashi Tanaka, and 4 more authors

In The 36th Annual Meeting of the Japanese Society for Magnetic Resonance in Medicine, Sep 2008

1995

Magnetic resonance elastography by direct visualization of propagating acoustic strain waves

R Muthupillai, DJ Lomas, PJ Rossman, and 3 more authors

science, Sep 1995

DOI Bib

@article{muthupillai1995magnetic,
  title = {Magnetic resonance elastography by direct visualization of propagating acoustic strain waves},
  author = {Muthupillai, R and Lomas, DJ and Rossman, PJ and Greenleaf, James F and Manduca, Armando and Ehman, Richard Lorne},
  journal = {science},
  volume = {269},
  number = {5232},
  pages = {1854--1857},
  year = {1995},
  publisher = {American Association for the Advancement of Science},
  doi = {10.1126/science.7569924},
  bibtex_show = true
}