Hajime Nagahara

Hajime Nagahara

orcid

Research Focus & Metrics

Academic Career Length

26Years (2001-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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6 October 2018
Verified
Book Chapter
Closed access
PDF file
YIYasutaka Inagaki
Yasutaka Inagaki
YKYuto Kobayashi
Yuto Kobayashi
KTKeita Takahashi
Keita Takahashi
TFToshiaki Fujii
Toshiaki Fujii
HNHajime Nagahara
Hajime Nagahara

16 December 2022 in Cancer Cytopathology
Verified
Journal Article
Open access
MHMitsuyoshi Hirokawa
Mitsuyoshi Hirokawa
HNHirohiko Niioka
Hirohiko Niioka
ASAyana Suzuki
Ayana Suzuki
MAMasatoshi Abe
Masatoshi Abe
YAYusuke Arai
Yusuke Arai
TATakashi Akamizu
Takashi Akamizu
Background: Several studies have used artificial intelligence (AI) to analyze cytology images, but AI has yet to be adopted in clinical practice. The objective of this study was to demonstrate the accuracy of AI‐based image analysis for thyroid fine‐needle aspiration cytology (FNAC) and to propose its application in clinical practice.Methods: In total, 148,395 microscopic images of FNAC were obtained from 393 thyroid nodules to train and validate the data, and EfficientNetV2‐L was used as the image‐classification model. The 35 nodules that were classified as atypia of undetermined significance (AUS) were predicted using AI training.Results: The precision‐recall area under the curve (PR AUC) was >0.95, except for poorly differentiated thyroid carcinoma (PR AUC = 0.49) and medullary thyroid carcinoma (PR AUC = 0.91). Poorly differentiated thyroid carcinoma had the lowest recall (35.4%) and was difficult to distinguish from papillary thyroid carcinoma, medullary thyroid carcinoma, and follicular thyroid carcinoma. Follicular adenomas and follicular thyroid carcinomas were distinguished from each other by 86.7% and 93.9% recall, respectively. For two‐dimensional mapping of the data using t‐distributed stochastic neighbor embedding, the lymphomas, follicular adenomas, and anaplastic thyroid carcinomas were divided into three, two, and two groups, respectively. Analysis of the AUS nodules showed 94.7% sensitivity, 14.4% specificity, 56.3% positive predictive value, and 66.7% negative predictive value.Conclusions: The authors developed an AI‐based approach to analyze thyroid FNAC cases encountered in routine practice. This analysis could be useful for the clinical management of AUS and follicular neoplasm nodules (e.g., an online AI platform for thyroid cytology consultations).

17 January 2019 in IEEE Transactions on Computational Imaging
Verified
Journal Article
Closed access
YXYichao Xu
Yichao Xu
HNHajime Nagahara
Hajime Nagahara
ASAtsushi SHIMADA
Atsushi SHIMADA
RTRin-ichiro Taniguchi
Rin-ichiro Taniguchi
Transparent object segmentation can be very useful in computer vision applications. However, because the transparent objects borrow texture from their background and have a similar appearance to their surroundings, they are not handled well by regular image segmentation methods. We propose a method that overcomes these problems using the consistency and distortion properties in a light-field image. The light-field linearity is used to estimate the likelihood of a pixel belonging to the transparent object or Lambertian background, and the occlusion detector is used to find the occlusion boundary. Graph-cut optimization is applied for the pixel labeling problem. We acquire light field datasets from both camera array and lenslet camera for the transparent object, and use these datasets to evaluate our method. The results demonstrate that the proposed method successfully segments transparent objects from the background under various conditions.

22 March 2021 in IEEE Access
Verified
Journal Article
Open access
BWBowen Wang
Bowen Wang
LLLiangzhi Li
Liangzhi Li
YNYuta Nakashima
Yuta Nakashima
RKRyo Kawasaki
Ryo Kawasaki
HNHajime Nagahara
Hajime Nagahara
YYYasushi Yagi
Yasushi Yagi
Semantic video segmentation is a key challenge for various applications. This paper presents a new model named Noisy-LSTM, which is trainable in an end-to-end manner, with convolutional LSTMs (ConvLSTMs) to leverage the temporal coherence in video frames, together with a simple yet effective training strategy that replaces a frame in a given video sequence with noises. Our training strategy spoils the temporal coherence in video frames and thus makes the temporal links in ConvLSTMs unreliable; this may consequently improve the ability of the model to extract features from video frames and serve as a regularizer to avoid overfitting, without requiring extra data annotations or computational costs. Experimental results demonstrate that the proposed model can achieve state-of-the-art performances on both the CityScapes and EndoVis2018 datasets. The code for the proposed method is available at https://github.com/wbw520/NoisyLSTM.

16 August 2021 in IEEE Access
Verified
Journal Article
Open access
RKRyosuke Kawamura
Ryosuke Kawamura
SSShizuka Shirai
Shizuka Shirai
NTNoriko Takemura
Noriko Takemura
MAMehrasa Alizadeh
Mehrasa Alizadeh
MCMutlu Cukurova
Mutlu Cukurova
HNHajime Nagahara
Hajime Nagahara
Learners are expected to stay wakeful and focused while interacting with e-learning platforms. Although wakefulness of learners strongly relates to educational outcomes, detecting drowsy learning behaviors only from log data is not an easy task. In this study, we describe the results of our research to model learners’ wakefulness based on multimodal data generated from heart rate, seat pressure, and face recognition. We collected multimodal data from learners in a blended course of informatics and conducted two types of analysis on them. First, we clustered features based on learners’ wakefulness labels as generated by human raters and ran a statistical analysis. This analysis helped us generate insights from multimodal data that can be used to inform learner and teacher feedback in multimodal learning analytics. Second, we trained machine learning models with multiclass-Support Vector Machine (SVM), Random Forest (RF) and CatBoost Classifier (CatBoost) algorithms to recognize learners’ wakefulness states automatically. We achieved an average macro-F1 score of 0.82 in automated user-dependent models with CatBoost. We also showed that compared to unimodal data from each sensor, the multimodal sensor data can improve the accuracy of models predicting the wakefulness states of learners while they are interacting with e-learning platforms.