publications

Peer-reviewed

2024

1. CHI

   

   Embodied Tentacle: Mapping Design to Control of Non-Analogous Body Parts with the Human Body

   Shuto Takashita, Ken Arai, Hiroto Saito, and 2 more authors

   Proceedings of the 2024 CHI Conference on Human Factors in Computing Systems, May 2024

   Abs DOI Bib Video

   

   Manipulating a non-humanoid body using a mapping approach that translates human body activity into different structural movements enables users to perform tasks that are difficult with their innate bodies. However, a key challenge is how to design an effective mapping to control non-analogous body parts with the human body. To address this challenge, we designed an articulated virtual arm and investigated the effect of mapping methods on a user’s manipulation experience. Specifically, we developed an unbranched 12-joint virtual arm with an octopus-like appearance. Using this arm, we conducted a user study to compare the effects of several mapping methods with different arrangements on task performance and subjective evaluations of embodiment and user preference. As a result, we identified three important factors in mapping: “Visual and Configurational Similarity”, “Kinematics Suitability for the User”, and “Correspondence with Everyday Actions.” Based on these findings, we discuss a mapping design for non-humanoid body manipulation.

   @article{takashitaEmbodiedTentacleMapping2024a,
     title = {Embodied {{Tentacle}}: {{Mapping Design}} to {{Control}} of {{Non-Analogous Body Parts}} with the {{Human Body}}},
     author = {Takashita, Shuto and Arai, Ken and Saito, Hiroto and Kitazaki, Michiteru and Inami, Masahiko},
     year = {2024},
     month = may,
     journal = {Proceedings of the 2024 CHI Conference on Human Factors in Computing Systems},
     number = {222},
     pages = {19},
     doi = {10.1145/3613904.3642340},
     urldate = {2025-05-30},
     langid = {english},
     category = {peer-reviewed},
   }

2. 

   Quantum PC Algorithm: Data-Efficient and Nonlinear Causal Discovery

   Yota Maeda, Ken Arai, Yu Tanaka, and 3 more authors

   2024 IEEE International Conference on Quantum Computing and Engineering (QCE), Sep 2024

   Abs DOI Bib

   Causal discovery is the task of finding causal relationships between random variables from observed data. Typically, one assumes that the causal relationships can be represented by a directed acyclic graph (DAG), and makes additional assumptions to ensure that the DAG can be recovered from the observed data. In this study, we propose the quantum Peter-Clark (qPC) algorithm for nonlinear causal discovery based on quantum kernel methods. The qPC algorithm takes advantage of the quantum kernel-based conditional independent test. Through the synthetic data experiment, we show that the qPC algorithm outperforms the classical method in the regime of a small number of samples. This suggests that the kernel-based causal discovery can significantly improve performance under such conditions. Our experiments highlight that the proposed algorithm can accurately support classical algorithms in causal discovery, paving the way for future advances with the utilization of quantum computation.

   @article{maedaQuantumPCAlgorithm2024,
     title = {Quantum {{PC Algorithm}}: {{Data-Efficient}} and {{Nonlinear Causal Discovery}}},
     author = {Maeda, Yota and Arai, Ken and Tanaka, Yu and Terada, Yu and Ueno, Hiroshi and Tezuka, Hiroyuki},
     year = {2024},
     month = sep,
     journal = {2024 IEEE International Conference on Quantum Computing and Engineering (QCE)},
     pages = {2},
     doi = {10.1109/QCE60285.2024.10322},
     urldate = {2025-05-30},
     category = {peer-reviewed},
   }

2022

1. 

   Embodiment of Supernumerary Robotic Limbs in Virtual Reality

   Ken Arai, Hiroto Saito, Masaaki Fukuoka, and 4 more authors

   Scientific Reports, Jun 2022

   Abs DOI Bib

   

   The supernumerary robotic limb system expands the motor function of human users by adding extra artificially designed limbs. It is important for us to embody the system as if it is a part of one’s own body and to maintain cognitive transparency in which the cognitive load is suppressed. Embodiment studies have been conducted with an expansion of bodily functions through a “substitution” and “extension”. However, there have been few studies on the “addition” of supernumerary body parts. In this study, we developed a supernumerary robotic limb system that operates in a virtual environment, and then evaluated whether the extra limb can be regarded as a part of one’s own body using a questionnaire and whether the perception of peripersonal space changes with a visuotactile crossmodal congruency task. We found that the participants can embody the extra-limbs after using the supernumerary robotic limb system. We also found a positive correlation between the perceptual change in the crossmodal congruency task and the subjective feeling that the number of one’s arms had increased (supernumerary limb sensation). These results suggest that the addition of an extra body part may cause the participants to feel that they had acquired a new body part that differs from their original body part through a functional expansion.

   @article{araiEmbodimentSupernumeraryRobotic2022a,
     title = {Embodiment of Supernumerary Robotic Limbs in Virtual Reality},
     author = {Arai, Ken and Saito, Hiroto and Fukuoka, Masaaki and Ueda, Sachiyo and Sugimoto, Maki and Kitazaki, Michiteru and Inami, Masahiko},
     year = {2022},
     month = jun,
     journal = {Scientific Reports},
     volume = {12},
     number = {1},
     pages = {9769},
     publisher = {Nature Publishing Group},
     issn = {2045-2322},
     doi = {10.1038/s41598-022-13981-w},
     urldate = {2025-05-30},
     copyright = {2022 The Author(s)},
     langid = {english},
     keywords = {Computer science,Human behaviour,Perception},
     file = {files/1030/Arai et al. - 2022 - Embodiment of supernumerary robotic limbs in virtu.pdf},
     category = {peer-reviewed},
   }

2. 

   Kinematic Altering Illusion: Acquiring Soft Body Perception by Wearing Octopus Arm-Shaped VR Avatar

   Shuto Takashita, Ken Arai, Hiroto Saito, and 1 more author

   Transactions of the Virtual Reality Society of Japan, Dec 2022

   Abs DOI Bib

   

   Many previous studies have reported on the transformation of perception/behavior, body image, and body schema due to the use of avatars in VR space. However, there are few previous studies on those transformations associated with the wearing of avatars with non-innate physical characteristics such as animal avatars, leaving many unexplored areas. In this study, we focused on the octopus as an example of an animal with non-native physical characteristics such as softness and structural consistency from arm to fingertip. Therefore, we developed an avatar that externally mimics the arm of an octopus, a box-shaped avatar, and a human arm-shaped avatar, and measured the movement of the right upper limb during manipulation and the sensory and cognitive changes after manipulation. The results showed that subjects felt their bodies became softer and their body image changed after manipulating the avatar that imitated an octopus arm. The possibility of behavioral change was also confirmed with the octopus avater.

   @article{takashitaKinematicAlteringIllusion2022,
     title = {Kinematic {{Altering Illusion}}: {{Acquiring}} Soft Body Perception by Wearing Octopus Arm-Shaped {{VR}} Avatar},
     shorttitle = {Kinematic {{Altering Illusion}}},
     author = {Takashita, Shuto and Arai, Ken and Saito, Hiroto and Inami, Masahiko},
     year = {2022},
     month = dec,
     journal = {Transactions of the Virtual Reality Society of Japan},
     volume = {27},
     number = {4},
     pages = {403--412},
     issn = {24239593},
     doi = {10.18974/tvrsj.27.4_403},
     keywords = {animal avater,embodiment,proteus effect,virtual reality},
     file = {files/1040/高下 et al. - 2022 - Kinematic Altering Illusion タコ腕型VRアバタの装用による柔らかい身体.pdf},
     category = {peer-reviewed},
   }

2011

1. 

   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},
   }

2. 

   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},
   }

Conference & Workshop (peer-reviewed, abstract)

2025

1. pre-print

   

   Quantum-Enhanced Causal Discovery for a Small Number of Samples

   Yu Terada, Ken Arai, Yu Tanaka, and 3 more authors

   In arXiv quant-ph, Jan 2025

   Abs DOI Bib

   The discovery of causal relationships from observed data has attracted significant interest from disciplines such as economics, social sciences, epidemiology, and biology. In practical applications, considerable knowledge of the underlying systems is often unavailable, and real data are often associated with nonlinear causal structures, which make the direct use of most conventional causality analysis methods difficult. This study proposes a novel quantum Peter-Clark (qPC) algorithm for causal discovery that does not assume any underlying model structures. Based on the independence conditional tests in a class of reproducing kernel Hilbert spaces characterized by quantum circuits, the proposed qPC algorithm can explore causal relationships from the observed data drawn from arbitrary distributions. We conducted systematic experiments on fundamental graph parts of causal structures, demonstrating that the qPC algorithm exhibits a significantly better performance, particularly with smaller sample sizes compared to its classical counterpart. Furthermore, we proposed a novel optimization approach based on Kernel Target Alignment (KTA) for determining hyperparameters of quantum kernels. This method effectively reduced the risk of false positives in causal discovery, enabling more reliable inference. Our theoretical and experimental results demonstrate that the proposed quantum algorithm can empower classical algorithms for robust and accurate inference in causal discovery, supporting them in regimes where classical algorithms typically fail. Additionally, the effectiveness of this method was validated using the Boston Housing dataset as a real-world application. These findings demonstrate the new potential of quantum circuit-based causal discovery methods in addressing practical challenges, particularly in small-sample scenarios where traditional approaches have shown limitations.

   @misc{maedaQuantumenhancedCausalDiscovery2025,
     title = {Quantum-Enhanced Causal Discovery for a Small Number of Samples},
     author = {Terada, Yu and Arai, Ken and Tanaka, Yu and Maeda, Yota and Ueno, Hiroshi and Tezuka, Hiroyuki},
     year = {2025},
     month = jan,
     number = {arXiv:2501.05007},
     eprint = {2501.05007},
     primaryclass = {quant-ph},
     publisher = {arXiv},
     doi = {10.48550/arXiv.2501.05007},
     urldate = {2025-05-30},
     archiveprefix = {arXiv},
     langid = {english},
     keywords = {Computer Science - Artificial Intelligence,Computer Science - Machine Learning,Quantum Physics,Statistics - Methodology},
     file = {files/1056/Maeda et al. - 2025 - Quantum-enhanced causal discovery for a small numb.pdf},
     category = {peer-reviewed-abstract},
     booktitle = {arXiv quant-ph},
   }

2024

1. Effects of an Embodied Artificial Finger on Body Representation in the Brain

   Rei Yasuda, Ken Arai, Yui Takahara, and 3 more authors

   In JNNS2024, Sep 2024

   HTML
2. ICRA

   The ’independent’ Sixth Finger Project

   Rei Yasuda, Yoichi Miyawaki, Ganesh Gaorinshankar, and 5 more authors

   In IEEE-ICRA2024 workshop : The robotics, psychology and neuroscience of body augmentation, Mar 2024

   HTML
3. SfN

   Neural Differences Induced by the Location of an Embodied Independent Supernumerary Finger

   Rei Yasuda, Ken Arai, Yui Takahara, and 4 more authors

   In Society for Neuroscience 2024, Oct 2024

   HTML

2022

1. JIZAI Body in the Human Brain: Embodiment of Independent Artificial Limb

   Yoichi Miyawaki, Ganesh Gowrinshankar, Kohei Umezawa, and 6 more authors

   In Augmented Humans 2022, Mar 2022

   HTML
2. SfN

   

   Neural Correlates of Independent Sixth Finger Embodiment

   Ken Arai, Yui Takahara, Daichi Ueda, and 3 more authors

   In Society for Neuroscience 2022, Nov 2022

   Abs HTML

   K Arai, Y Takahara, D Ueda, M Fukunaga, G Ganesh, Y Miyawaki, Society for Neuroscience 2022, 2022

3. Neural correlates of the embodiment of an independent supernumerary limb by humans: a functional magnetic resonance imaging study

   Yui Takahara, Ken Arai, Kelssy Kawata, and 3 more authors

   In NEURO2022, Jun 2022

   Bib HTML

   @misc{takaharaNeuralCorrelatesEmbodiment2022,
     title = {{Neural correlates of the embodiment of an independent supernumerary limb by humans: a functional magnetic resonance imaging study}},
     author = {Takahara, Yui and Arai, Ken and Kawata, Kelssy and Fukunaga, Masaki and Gowrinshankar, Ganesh and Miyawaki, Yoichi},
     year = {2022},
     month = jun,
     address = {Okinawa, Japan},
     urldate = {2025-05-30},
     langid = {japanese},
     category = {peer-reviewed-abstract},
     booktitle = {NEURO2022},
   }

4. Sixth Finger Project: The Optimal Design for Augmentation

   Daichi Ueda, Kohei Umezawa, Yui Takahara, and 4 more authors

   In Augmented Humans 2022, Mar 2022

   HTML
5. Symposium

   

   Body Function Augmentation Technology and Body Systems

   Ken Arai, Kazumichi Matsumiya, Ryota Kondo, and 1 more author

   Aug 2022

   Abs HTML

   Various systems (body function extension technology) have been proposed and investigated to improve physical function and movement. It has been suggested that this technology can enable tasks that are difficult to perform with innate limbs and intervene in motor control. It is desirable for this technology to be organically integrated with innate body parts, and it is essential to elucidate the effects on the body system that this technology can have from multiple perspectives, including neuroscience and cognitive science. This symposium will provide a forum for discussion and attempt to promote understanding of these issues.

2017

1. ISMRM

   Fat Suppressed Highly Accelerated Dynamic Imaging Utilizing View Sharing, Compressed Sensing and Parallel Imaging

   Naoyuki Takei, Wang Kang, Lloyd Estkowski, and 4 more authors

   In International Society for Magnetic Resonace In Medicine (ISMRM), Apr 2017

   Abs Bib HTML

   

   DISCO (Differential Subsampling with Cartesian Ordering) is high spatial-temporal imaging technique with Dixon based fat suppression for 3D volumetric Abdominal imaging. We developed DISCO with frequency selective presaturation pulse for fat suppression (FatSAT) called FatSAT DISCO. The feasibility study explores the computational advantage of FatSAT DISCO in accelerating scan time with compressed sensing technique and demonstrated that it is a promising technique for achieving faster imaging for 4D dynamic MR imaging with robustness to image artifact and light computation demand for clinical use.

   @inproceedings{takeiFatSuppressedHighly2017,
     title = {Fat {{Suppressed Highly Accelerated Dynamic Imaging}} Utilizing {{View Sharing}}, {{Compressed Sensing}} and {{Parallel Imaging}}},
     booktitle = {International {{Society}} for {{Magnetic Resonace In Medicine}} ({{ISMRM}})},
     author = {Takei, Naoyuki and Kang, Wang and Estkowski, Lloyd and Arai, Ken and Bekku, Mitsuhiro and Kabasawa, Hiroyuki and Bayram, Ersin},
     year = {2017},
     month = apr,
     volume = {5184},
     publisher = {The 25th ISMRM Annual Meeting},
     urldate = {2025-05-30},
     langid = {english},
     category = {peer-reviewed-abstract},
   }

2014

1. 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

1. 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
2. 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
3. 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

1. 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

   Abs Bib HTML

   

   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},
   }

2. 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

3. 

   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
4. 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
5. 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
6. 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
7. 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

2009

1. 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

   Abs Bib HTML

   

   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},
   }

2. 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
3. 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

2008

1. 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

Patent

2017

1. 

   Magnetic Resonance Apparatus and Method for Preparing a Sensitivity Map

   Yusuke Asaba, Ken Arai, Janeiro Aguilar, and 2 more authors

   Sep 2017

   HTML

   

Media Coverage

2022

1. 

   People Come to Grips with Having an Extra Pair of Arms—in VR

   Sasha Warren

   Scientific American, Jul 2022

   Bib HTML

   @article{scientificamerican_vr_superlimbs,
     title = {People Come to Grips with Having an Extra Pair of Arms—in VR},
     author = {Warren, Sasha},
     year = {2022},
     month = jul,
     journal = {Scientific American},
     category = {media}
   }

2. 

   (Japanese article) Successful Embodiment of ’Third and Fourth Arms’ in VR Space: Could New Sensations Emerge in Metaverse Experiences Too?

   Kenichi Shoji

   DG Lab Haus, Sep 2022

   Bib HTML

   @article{dglab_vrsl,
     title = {(Japanese article) Successful Embodiment of 'Third and Fourth Arms' in VR Space: Could New Sensations Emerge in Metaverse Experiences Too?},
     author = {Shoji, Kenichi},
     year = {2022},
     month = sep,
     journal = {DG Lab Haus},
     category = {media}
   }

3. 

   6th Finger Project - promotion video

   Miyawaki-lab

   YouTube, Apr 2022

   Bib Video

   @article{sixthfinger_video,
     title = {6th Finger Project - promotion video},
     author = {Miyawaki-lab},
     year = {2022},
     month = apr,
     journal = {YouTube},
     category = {media}
   }

Lecture

2025

1. A Researcher’s Journey: Finding Your Path in Medical Imaging and Beyond

   Ken Arai

   Nov 2025

   Guest lecture for young investigators

   Abs HTML

   From CT/MRI research and development at university and GE Healthcare, to pursuing a PhD while working, and continuing with next-generation computing research at Sony R&D. This presentation shares how foundational knowledge in medical imaging engineering can open doors across different fields, the thoughtful decisions between stability and new challenges, specialization and broader expertise, adapting to various corporate environments, and pursuing growth while balancing family life. I’ll share authentic experiences and insights from my research journey that extend beyond what we typically learn in academic settings. I hope this talk will offer valuable perspectives to support young researchers as they explore and shape their own career paths.

2018

1. Beam Hardening and Scatter Radiation

   Ken Arai

   In Proceedings of Kyushu CT Research Conference, Aug 2018

   Guest lecture, Session 4, 17:50-18:50, Moderator: Masato Ogawa (University of Occupational and Environmental Health, Wakamatsu Hospital)