研究者詳細 - 田岡　俊昭

論文 - 田岡　俊昭

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Contribution of white matter microstructure to diffusion tensor image analysis along perivascular space in obstructive sleep apnea 査読有り Open Access

Taoka, T; Iwamoto, K; Miyata, S; Ito, R; Kamagata, K; Nakamichi, R; Nakane, T; Iima, M; Fujishiro, H; Ikeda, M; Ichikawa, K; Kamiunten, A; Ichinose, N; Kikuta, J; Aoki, S; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 43 巻 ( 12 ) 頁： 1926 - 1941 2025年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: We aimed to evaluate whether the ALPS index derived from diffusion tensor image analysis along the perivascular space (DTI-ALPS) is influenced by white matter fibres within the analysis region, particularly commissural fibres from the corpus callosum that traverse this area in psychiatric patients with suspected obstructive sleep apnea (OSA). We also investigated associations between diffusion-based parameters, sleep-related data, and neurofluid-related imaging metrics. Methods: Fifty participants with OSA underwent brain magnetic resonance imaging and polysomnography, including diffusion tensor and structural sequences. Among them, 8 participants had no psychiatric comorbidities, while the remaining 42 had various psychiatric disorders in addition to OSA. Diffusion-based parameters were obtained, and both the original and variant ALPS index were calculated. Correlation analyses were conducted with sleep-related data and neurofluid-related imaging parameters, including choroid plexus volume (CPV) and volume of white matter lesion burden (WMHV). Mediation analyses were also performed to explore the influence of white matter diffusivity on the perivascular diffusivity index. Results: The ALPS index showed weak to moderate correlations with multiple sleep-related variables. It also correlated with CPV and WMHV. Mediation analyses demonstrated that diffusivity within white matter fibres was associated with the ALPS index. Moreover, variant ALPS indices measured in the corpus callosum may reflect fluid motion in the direction of perivascular spaces. Conclusion: These findings suggest that the ALPS index is influenced by both diffusivity along perivascular spaces and white matter microstructure, particularly commissural fibres. Although it should not be regarded as a highly specific marker of perivascular space function, variant indices support partial perivascular contribution. Furthermore, associations with sleep and neurofluid-related metrics imply that white matter architecture and inter-fibre spaces may serve as plausible routes for interstitial fluid flow.

DOI： 10.1007/s11604-025-01838-x

MR Imaging Indices for Brain Interstitial Fluid Dynamics and the Effects of Orexin Antagonists on Sleep 査読有り Open Access

Taoka, T; Iwamoto, K; Miyata, S; Ito, R; Nakamichi, R; Nakane, T; Okada, I; Ichikawa, K; Kan, H; Kamagata, K; Kikuta, J; Aoki, S; Fujimoto, A; Kogo, Y; Ichinose, N; Naganawa, S; Ozaki, N

MAGNETIC RESONANCE IN MEDICAL SCIENCES 24 巻 ( 4 ) 頁： n/a 2025年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Magnetic Resonance in Medical Sciences

Purpose: The purpose of this study was to assess the extent to which improvement in sleep with lemborexant contributed to changes in interstitial fluid dynamics. Methods: The 3 methods including diffusion tensor image analysis along the perivascular space (DTI-ALPS), dynamic contrast-enhanced method to assess tissue vascular permeability (Ktrans), and choroid plexus volume (CPV) were used. Correlations between these imaging indices and sleep parameters (latency to persistent sleep [LPS], wake after sleep onset [WASO], total sleep time [TST], and sleep efficiency [SE]) were evaluated using Pearson correlation analysis. Additionally, multiple regression analysis and linear mixed model analysis were employed to assess the relationship between baseline sleep status and imaging parameter changes. MRI and sleep assessments were performed before treatment initiation (week 0, w0) and at 12 weeks after lemborexant administration (week 12, w12). Results: The ALPS-index was inversely correlated with LPS and positively correlated with TST and SE at w0. In multiple regression analysis, ALPS-index was lower when sleep parameters other than LPS were poor at w0. A linear mixed model analysis suggested that poor sleep status in LPS and SE at w0 may have an effect on greater ALPS-index. In the evaluation of Ktrans measurement, the single regression analysis showed a statistically significant correlation between the reduction in Ktrans and the shortening in LPS. Examination of CPV and sleep parameters showed a significant negative correlation between TST and CPV at w0 and w12. Multiple regression analysis also showed that TST of w12 had a significant effect on CPV at w12. Conclusion: Our results suggested that poor sleep status is related to the greater change of ALPS-index and CPV improvement after lemborexant administration may be related to in part to sleep parameter improvement.

DOI： 10.2463/mrms.mp.2024-0176

Diffusion Tensor Image Analysis ALong the Perivascular Space (DTI-ALPS): Revisiting the Meaning and Significance of the Method 招待有り査読有り Open Access

Taoka, T; Ito, R; Nakamichi, R; Nakane, T; Kawai, H; Naganawa, S

MAGNETIC RESONANCE IN MEDICAL SCIENCES 23 巻 ( 3 ) 頁： 268 - 290 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Magnetic Resonance in Medical Sciences

More than 5 years have passed since the Diffusion Tensor Image Analysis ALong the Perivascular Space (DTI-ALPS) method was proposed with the intention of evaluating the glymphatic system. This method is handy due to its noninvasiveness, provision of a simple index in a straightforward formula, and the possibility of retrospective analysis. Therefore, the ALPS method was adopted to evaluate the glymphatic system for many disorders in many studies. The purpose of this review is to look back and discuss the ALPS method at this moment. The ALPS-index was found to be an indicator of a number of conditions related to the glymphatic system. Thus, although this was expected in the original report, the results of the ALPS method are often interpreted as uniquely corresponding to the function of the glymphatic system. However, a number of subsequent studies have pointed out the problems on the data interpretation. As they rightly point out, a higher ALPS-index indicates predominant Brownian motion of water molecules in the radial direction at the lateral ventricular body level, no more and no less. Fortunately, the term “ALPS-index” has become common and is now known as a common term by many researchers. Therefore, the ALPS-index should simply be expressed as high or low, and whether it reflects a glymphatic system is better to be discussed carefully. In other words, when a decreased ALPS-index is observed, it should be expressed as “decreased ALPS-index” and not directly as “glymphatic dysfunction”. Recently, various methods have been proposed to evaluate the glymphatic system. It has become clear that these methods also do not seem to reflect the entirety of the extremely complex glymphatic system. This means that it would be desirable to use various methods in combination to evaluate the glymphatic system in a comprehensive manner.

DOI： 10.2463/mrms.rev.2023-0175

Diffusion-weighted image analysis along the perivascular space (DWI-ALPS) for evaluating interstitial fluid status: age dependence in normal subjects 査読有り Open Access

Taoka, T; Ito, R; Nakamichi, R; Nakane, T; Sakai, M; Ichikawa, K; Kawai, H; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 40 巻 ( 9 ) 頁： 894 - 902 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: The purpose of this study was to evaluate the interstitial fluid status in a wide range of age groups using diffusion-weighted image analysis along the perivascular space (DWI–ALPS) method, which is a simplified variation of diffusion tensor image analysis along the perivascular space (DTI–ALPS). Materials and methods: This retrospective study included data from 128 patients who underwent clinical magnetic resonance imaging (MRI) studies, including DWI, and were found to have no abnormal findings in the brain on MRI. Three motion-probing gradients of the DWI were applied in an orthogonal direction to the imaging plane. Apparent diffusion coefficient images in the x-, y-, and z-axes were retrospectively generated, and composite color images were created to locate the projection and association fiber area on the slice including the body of the lateral ventricle. ALPS indices were calculated, and correlations with age were evaluated using linear and second-degree regression analysis. Linear regression analysis was also performed for a subgroup of patients older than 40 years. In addition, an analysis of variance (ANOVA) test among the generations was performed. Results: The linear regression analysis between age and the ALPS index showed a correlation coefficient of −0.20 for all age group and −0.51 for the subgroup older than 40 years. The second-degree regression analysis showed a correlation coefficient of 0.39. ANOVA showed that the 40’s generation showed a statistically significant higher value of ALPS index compared to all other generations except for the 30’s generation. While, the 70’s generation showed a statistically significant lower value of the ALPS index compared to all other generations. Conclusions: The analysis of the DWI–APLS method showed a correlation between age and the ALPS index in second-degree distribution which peaked in the 40’s generation. This finding in normal subjects may be fundamental in the analysis of disease cases. Secondary abstract: We tried to evaluate the glymphatic system status in a wide range of age groups using diffusion-weighted image analysis along the perivascular space (DWI–ALPS) method, and the results showed a correlation between age and the ALPS index in second-degree distribution which peaked in the 40’s generation.

DOI： 10.1007/s11604-022-01275-0

Reproducibility of diffusion tensor image analysis along the perivascular space (DTI-ALPS) for evaluating interstitial fluid diffusivity and glymphatic function: CHanges in Alps index on Multiple conditiON acquIsition eXperiment (CHAMONIX) study 査読有り Open Access

Taoka, T; Ito, R; Nakamichi, R; Kamagata, K; Sakai, M; Kawai, H; Nakane, T; Abe, T; Ichikawa, K; Kikuta, J; Aoki, S; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 40 巻 ( 2 ) 頁： 147 - 158 2022年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: The diffusion tensor image analysis along the perivascular space (DTI-ALPS) method was developed to evaluate the brain’s glymphatic function or interstitial fluid dynamics. This study aimed to evaluate the reproducibility of the DTI-ALPS method and the effect of modifications in the imaging method and data evaluation. Materials and methods: Seven healthy volunteers were enrolled in this study. Image acquisition was performed for this test–retest study using a fixed imaging sequence and modified imaging methods which included the placement of region of interest (ROI), imaging plane, head position, averaging, number of motion-proving gradients, echo time (TE), and a different scanner. The ALPS-index values were evaluated for the change of conditions listed above. Results: This test–retest study by a fixed imaging sequence showed very high reproducibility (intraclass coefficient = 0.828) for the ALPS-index value. The bilateral ROI placement showed higher reproducibility. The number of averaging and the difference of the scanner did not influence the ALPS-index values. However, modification of the imaging plane and head position impaired reproducibility, and the number of motion-proving gradients affected the ALPS-index value. The ALPS-index values from 12-axis DTI and 3-axis diffusion-weighted image (DWI) showed good correlation (r = 0.86). Also, a shorter TE resulted in a larger value of the ALPS-index. Conclusion: ALPS index was robust under the fixed imaging method even when different scanners were used. ALPS index was influenced by the imaging plane, the number of motion-proving gradient axes, and TE in the imaging sequence. These factors should be uniformed in the planning ALPS method studies. The possibility to develop a 3-axis DWI-ALPS method using three axes of the motion-proving gradient was also suggested.

DOI： 10.1007/s11604-021-01187-5

Diffusion analysis of fluid dynamics with incremental strength of motion proving gradient (DANDYISM) to evaluate cerebrospinal fluid dynamics 査読有り Open Access

Taoka, T; Kawai, H; Nakane, T; Abe, T; Nakamichi, R; Ito, R; Sato, Y; Sakai, M; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 39 巻 ( 4 ) 頁： 315 - 323 2021年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: To visualize and analyze the dynamics of cerebrospinal fluid (CSF) motion in the cranium, we evaluated the distribution of motion-related signal dephasing by CSF on Diffusion ANalysis of fluid DYnamics with Incremental Strength of Motion proving gradient (DANDYISM) method, a composite imaging method using various low b values. Materials and methods: This study examined ten subjects aged 25–58. We acquired DWIs on a 3T clinical scanner with b values 0, 50, 100, 200, 300, 500, 700, and 1000 s/mm2 in total imaging time of 4 min. We constructed DANDYISM images and evaluated the CSF area distribution with decreased motion-dephasing signal using a scoring method. Results: The DANDYISM images showed statistically significant higher CSF scores in the ventral posterior fossa, suprasellar cistern, and Sylvian vallecula compared to the lateral ventricle and frontal and parietal CSF spaces, indicating greater CSF movement in the former areas. Conclusion: The results indicated prominent CSF motions in the ventral portion of the posterior fossa, suprasellar cistern, and Sylvian fissure but smaller motions in the lateral ventricles and parietal subarachnoid space. This method may provide information of CSF dynamics in the clinical settings within short imaging time.

DOI： 10.1007/s11604-020-01075-4

その他リンク： http://link.springer.com/article/10.1007/s11604-020-01075-4/fulltext.html

Imaging for central nervous system (CNS) interstitial fluidopathy: disorders with impaired interstitial fluid dynamics Open Access

Taoka, T; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 39 巻 ( 1 ) 頁： 1 - 14 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

After the introduction of the glymphatic system hypothesis, an increasing number of studies on cerebrospinal fluid and interstitial fluid dynamics within the brain have been investigated and reported. A series of diseases are known which develop due to abnormality of the glymphatic system including Alzheimer’s disease, traumatic brain injury, stroke, or other disorders. These diseases or disorders share the characteristics of the glymphatic system dysfunction or other mechanisms related to the interstitial fluid dynamics. In this review article, we propose “Central Nervous System (CNS) Interstitial Fluidopathy” as a new concept encompassing diseases whose pathologies are majorly associated with abnormal interstitial fluid dynamics. Categorizing these diseases or disorders as “CNS interstitial fluidopathies,” will promote the understanding of their mechanisms and the development of potential imaging methods for the evaluation of the disease as well as clinical methods for disease treatment or prevention. In other words, having a viewpoint of the dynamics of interstitial fluid appears relevant for understanding CNS diseases or disorders, and it would be possible to develop novel common treatment methods or medications for “CNS interstitial fluidopathies.”

DOI： 10.1007/s11604-020-01017-0

Evaluation of glymphatic system activity with the diffusion MR technique: diffusion tensor image analysis along the perivascular space (DTI-ALPS) in Alzheimer's disease cases 査読有り Open Access

Taoka, T; Masutani, Y; Kawai, H; Nakane, T; Matsuoka, K; Yasuno, F; Kishimoto, T; Naganawa, S

JAPANESE JOURNAL OF RADIOLOGY 35 巻 ( 4 ) 頁： 172 - 178 2017年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: The activity of the glymphatic system is impaired in animal models of Alzheimer’s disease (AD). We evaluated the activity of the human glymphatic system in cases of AD with a diffusion-based technique called diffusion tensor image analysis along the perivascular space (DTI-ALPS). Materials and methods: Diffusion tensor images were acquired to calculate diffusivities in the x, y, and z axes of the plane of the lateral ventricle body in 31 patients. We evaluated the diffusivity along the perivascular spaces as well as projection fibers and association fibers separately, to acquire an index for diffusivity along the perivascular space (ALPS-index) and correlated them with the mini mental state examinations (MMSE) score. Results: We found a significant negative correlation between diffusivity along the projection fibers and association fibers. We also observed a significant positive correlation between diffusivity along perivascular spaces shown as ALPS-index and the MMSE score, indicating lower water diffusivity along the perivascular space in relation to AD severity. Conclusion: Activity of the glymphatic system may be evaluated with diffusion images. Lower diffusivity along the perivascular space on DTI-APLS seems to reflect impairment of the glymphatic system. This method may be useful for evaluating the activity of the glymphatic system.

DOI： 10.1007/s11604-017-0617-z

Diffusion anisotropy and diffusivity of white matter tracts within the temporal stem in Alzheimer disease: Evaluation of the "tract of interest" by diffusion tensor tractography 査読有り

T Taoka, S Iwasaki, M Sakamoto, H Nakagawa, A Fukusumi, K Myochin, S Hirohashi, T Hoshida, K Kichikawa

AMERICAN JOURNAL OF NEURORADIOLOGY 27 巻 ( 5 ) 頁： 1040 - 1045 2006年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC NEURORADIOLOGY

PURPOSE: Our aim was to determine whether diffusion anisotropy and diffusivity of white matter tracts of the temporal stem in patients with Alzheimer (AD) can be evaluated independently by using diffusion tensor tractography.
MATERIALS AND METHODS: Subjects included 15 patients with AD (11 women and 4 men; mean age, 74 years) and 15 age-matched control subjects (11 women and 4 men; mean age, 72 years). Diffusion tensor images were acquired by using echo-planar imaging. We drew tractographies of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer's loop, with diffusion tensor analysis software. We measured diffusion anisotropy, diffusivity, and the number of voxels along the "tracts of interest" and used the Sludent t test to compare results between patients with AD and controls.
RESULTS: Values of diffusion anisotropy of the bilateral uncinate fasciculus and left inferior occipitofrontal fasciculus were significantly lower for patients with AD than for controls. Also, values of diffusivity in the bilateral uncinate fasciculus were significantly greater for patients with AD than for controls. There was no significant difference in diffusion anisotropy or diffusivity along Meyer's loop between the 2 groups. There was no significant difference in the number of voxels included in all constructed tracts between patients with AD and controls.
CONCLUSION: White matter tracts of the temporal stem can be evaluated independently by using diffusion tensor tractography, which appears to be a promising technique for determining changes in white matter in degenerative diseases.

Substantially Higher Vestibular Hydrops Agreement in Older Patients Assessed by Non-contrast vs. Contrast-enhanced MRI: A Preliminary Study Open Access

Naganawa, S; Ito, R; Kato, Y; Kobayashi, M; Taoka, T; Yoshida, T; Sone, M

MAGNETIC RESONANCE IN MEDICAL SCIENCES advpub 巻 ( 0 ) 2026年2月

MRI-based analysis of facial and hypoglossal nerves in patients with spinal and bulbar muscular atrophy

Mori, Y; Kawase, T; Yamada, S; Hashizume, A; Ito, D; Kondo, A; Obara, K; Yamamoto, M; Taoka, T; Katsuno, M

JOURNAL OF THE NEUROLOGICAL SCIENCES 480 巻 2025年12月

Pharmacokinetics and safety of gadopiclenol in Japanese healthy volunteers 査読有り Open Access

Eto, T; Taoka, T; Felices, M; Pitrou, C

JAPANESE JOURNAL OF RADIOLOGY 43 巻 ( 12 ) 頁： 1962 - 1970 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Radiology

Purpose: The aim of this study was to evaluate the pharmacokinetics and safety of gadopiclenol in Japanese healthy volunteers. A population-based pharmacokinetic approach was used to compare pharmacokinetic parameters with a non-Japanese adult population. Materials and methods: In this double-blind, placebo-controlled phase I study, Japanese healthy volunteers were randomized to receive gadopiclenol (at 0.025, 0.05, or 0.1 mmol/kg) or a placebo. Blood and urine samples were collected up to 24- and 48-h post-administration, respectively. The pharmacokinetic profile of gadopiclenol was evaluated using standard non-compartmental analysis. Adverse events (AEs) were collected during the whole study period. Results: Overall, 27 participants were randomized (median [range] age: 22 [20–43] years; 52% male): 18 received gadopiclenol (6 in each dose group), and 9 received the placebo. The mean systemic exposure of gadopiclenol increased proportionally with the injected dose (area under the curve [AUC]: 215–1034 μg/mL.h) and was comparable between the three dose groups when normalized to dose (AUC/dose: 182–189 μg/mL/g.h) and to non-Japanese (168–183 μg/mL.h). The mean terminal half-life (1.43–1.86 h), and the distribution volume (11.3–15.2 L) were also similar to those of non-Japanese healthy volunteers (1.50–1.73 h and 13.0–15.5 L, respectively). The mean fraction of gadopiclenol excreted in urine was between 87 and 95%, depending on the administered dose. Most of gadopiclenol (median of 95.7%) was excreted within 24 h after administration. The mean total clearance was comparable between the different administered doses (5.3–5.6 L/h) and similar to the mean renal clearance. No gadopiclenol-related AEs were reported. Conclusions: The pharmacokinetic profile of gadopiclenol is similar in Japanese and non-Japanese healthy volunteers. The population pharmacokinetic analysis showed no significant ethnic disparities between these two populations and suggested that no dose adjustment was required for Japanese patients. Gadopiclenol had a very good tolerability in Japanese healthy volunteers with no adverse reactions reported.

DOI： 10.1007/s11604-025-01842-1

Association between frontal pole atrophy and glymphatic dysfunction in patients with bipolar disorder 査読有り国際誌

Kikuta, J; Nagai, Y; Kamagata, K; Chen, HK; Yamada, Y; Kitagawa, T; Uchida, W; Iseki, R; Guo, S; Takabayashi, K; Hagiwara, A; Wada, A; Taoka, T; Kato, T; Aoki, S

JOURNAL OF AFFECTIVE DISORDERS 389 巻頁： 119686 - 119686 2025年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Affective Disorders

Background: Patients with bipolar disorder (BD) are highly at risk for dementia and may develop brain atrophy, which is linked to cognitive decline. One possible reason for brain atrophy is cellular damage resulting from waste product accumulation caused by glymphatic dysfunction. This study evaluated the glymphatic system in patients with BD, using diffusion tensor image analysis along the perivascular space (DTI-ALPS) and choroid plexus volume (CPV) in two separate BD cohorts. The insight into whether these clearance indices were associated with brain atrophy was also investigated. Methods: The discovery cohort consisted of 28 patients with BD and 28 healthy controls (HCs). The validation cohort included 42 patients with BD and 42 HCs. BD group and HCs in both cohorts underwent group comparisons of the ALPS index, CPV relative to the total intracranial volume (CPV/TIV), and brain gray matter volume. The relationships between the ALPS index and frontal pole volume were determined. Results: The ALPS index decreased in BD group compared with that in HCs in both cohorts (p < 0.05). While BD group showed increased CPV/TIV and frontal pole atrophy in the discovery cohort, such increase was insignificant in the validation cohort. In the discovery cohort, frontal pole atrophy was related to the ALPS index decrement (r = 0.34, p = 0.02), and the ALPS index–mediated frontal pole atrophy was associated with BD. Conclusion: Middle-aged patients with BD may experience dysfunction in the excretory pathway of the perivascular space around the medullary veins, likely contributing to frontal pole atrophy.

DOI： 10.1016/j.jad.2025.119686

Evaluation of Approved AI-based Brain Aneurysm Detection Software in Clinical Practice: Comparison with Radiologist Assessment and Image Re-review Open Access

Ito, R; Asai, R; Nakamichi, R; Nakane, T; Taoka, T; Naganawa, S

MAGNETIC RESONANCE IN MEDICAL SCIENCES 25 巻 ( 1 ) 頁： n/a 2025年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Magnetic Resonance in Medical Sciences

Purpose: This study evaluated the performance of artificial intelligence (AI)-based brain aneurysm detection software in clinical settings, aiming to assess its utility as a supportive tool for radiologists. Metrics included sensitivity, positive predictive value (PPV), F1 score, and false positives (FPs) per case. Methods: A retrospective analysis of 442 cases (March 2023–August 2024) compared AI detections against a reference standard derived from the radiologists’ assessments and image re-review. Findings were categorized into true positives (TPs), FPs, and false negatives (FNs). Subgroup analyses covered aneurysm size, magnetic field strength of the MRI, patient age, and aneurysm location. Results: The study included 442 cases (226 males, 216 females; median age 72). Out of 94 total aneurysms, the AI detected 73 TP and missed 21 FN. It also identified 520 FP. Overall, sensitivity was 77.7%, PPV was 12.3%, and the F1 score was 0.212. The FPs averaged 1.18 per case. Sensitivity varied by aneurysm size: 85.1% for ≤ 3 mm, 69.2% for 3–5 mm, and 50.0% for > 5 mm. Significant variability in FPs per case was observed across different magnetic field strengths. Performance also varied by patient age and aneurysm location. Conclusion: The AI software demonstrated moderate sensitivity, especially for smaller aneurysms. Variations in performance across different magnetic field strengths and aneurysm size suggest a need for more robust AI algorithms. Detailed analysis of aneurysm locations provides insights into areas where AI performance could be enhanced. Integrating the AI software as a supportive tool, combined with radiologist expertise, is hypothesized to enhance detection accuracy, though further studies are needed to quantify this combined effect.

DOI： 10.2463/mrms.mp.2024-0183

Validation of Fractional Anisotropy and Apparent Diffusion Coefficient Obtained From Diffusion Tensor Imaging With Reverse Encoding Distortion Correction. Open Access

Ichikawa K, Taoka T, Kan H, Ichinose N, Ozaki M, Kamiunten A, Naganawa S

Cureus 17 巻 ( 11 ) 頁： e97540 2025年11月

Vision-language model performance on the Japanese Nuclear Medicine Board Examination: high accuracy in text but challenges with image interpretation 査読有り Open Access

Ito, R; Kato, K; Higashi, M; Abe, Y; Minamimoto, R; Kato, K; Taoka, T; Naganawa, S

ANNALS OF NUCLEAR MEDICINE 39 巻 ( 11 ) 頁： 1258 - 1266 2025年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Annals of Nuclear Medicine

Objective: Vision language models (VLMs) allow visual input to Large Language Models. VLMs have been developing rapidly, and their accuracy is improving rapidly. Their performance in nuclear medicine compared to state-of-the-art models, including reasoning models, is not yet clear. We evaluated state-of-the-art VLMs using problems from the past Japan Nuclear Medicine Board Examination (JNMBE) and assessed their strengths and limitations. Methods: We collected 180 multiple-choice questions from JNMBE (2022–2024). About one-third included diagnostic images. We used eight latest VLMs. ChatGPT o1 pro, ChatGPT o1, ChatGPT o3-mini, ChatGPT-4.5, Claude 3.7, Gemini 2.0 Flash thinking, Llama 3.2, and Gemma 3 were tested. Each model answered every question three times in a deterministic setting, and the final answer was set by majority vote. Two board-certified nuclear medicine physicians independently provided reference answers, with a third expert resolving disagreements. We calculated overall accuracy with 95% confidence intervals and performed subgroup analyses by question type, content, and exam year. Results: Overall accuracies ranged from 36.1% (Gemma 3) to 83.3% (ChatGPT o1 pro). ChatGPT o1 pro achieved the highest score (150/180, 83.3% [95% CI: 77.1–88.5%]), followed by ChatGPT o3-mini (82.8%) and ChatGPTo1 (78.9%). All models performed better on text-only questions than on image-based ones; ChatGPT o1 pro correctly answered 89.5% of text questions versus 66.0% of image questions. VLMs demonstrated limitations in handling with questions on Japanese regulations. ChatGPT 4.5 excelled in neurology-related image-based questions (76.9%). Accuracy was slightly lower from 2022 to 2024 for most models. Conclusions: VLMs demonstrated high accuracy on the JNMBE, especially on text-based questions, but exhibited limitations with image recognition questions. These findings show that VLMs can be a good assistant for text-based questions in medical domains but have limitations when it comes to comprehensive questions that include images. Currently, VLMs cannot replace comprehensive training and expert interpretation. Because VLMs evolve rapidly and exam difficulty varies annually, these findings should be interpreted in that context.

DOI： 10.1007/s12149-025-02084-x

Editorial for "Cognition-Eye-Brain Connection in Alzheimer's Disease Spectrum Revealed by Multimodal Imaging" 国際誌

Taoka, T

JOURNAL OF MAGNETIC RESONANCE IMAGING 62 巻 ( 4 ) 頁： 1131 - 1132 2025年10月

Ocular Solute Movement Direction and Intracranial Clearance via Vitreous Gadolinium-based Contrast Agent MR Imaging: Potential as a Novel Biomarker for Glymphatic Dysfunction Open Access

Naganawa, S; Ito, R; Kawamura, M; Taoka, T; Yoshida, T; Sone, M

MAGNETIC RESONANCE IN MEDICAL SCIENCES 25 巻 ( 1 ) 頁： 202 - 212 2025年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Magnetic Resonance in Medical Sciences

Purpose: The ocular and brain glymphatic systems may share common physiological pathways. We hypothesized that the anteroposterior movement of gadolinium-based contrast agent (GBCA) that has leaked into the vitreous could serve as a biomarker for brain glymphatic function. This study aimed to retrospectively investigate the association between the intravitreal GBCA distribution on MRI and recently proposed imaging markers of impaired brain waste clearance. Methods: We analyzed 156 eyes from 78 adult participants who underwent 3T MRI 4 hr after standard-dose GBCA administration. On 3D-real IR images, we calculated a “contrast shift index” (the signal difference between anterior and posterior vitreous volumes of interest: VOIa-VOIp) to quantify the anteroposterior GBCA distribution. The primary outcome was a composite endpoint of positivity for either putative meningeal lymphatics at the posterior sigmoid sinus (PML-PSS) or enhanced basal ganglia perivascular spaces (PVS-BG). Multivariable logistic regression with cluster-robust inference was used to assess predictors, including the contrast shift index, mean vitreous contrast distribution, age, sex, and axial length of the eye. Results: A positive contrast shift index, indicating preferential anterior GBCA distribution, was significantly and independently associated with the composite outcome of impaired brain clearance (P = 0.006). Age (P < 0.001) and male sex (P = 0.009) were also independent predictors. A predictive model incorporating these factors demonstrated high discrimination, with an area under the receiver operating characteristic curve (AUC) of 0.872. Axial length of the eye and mean vitreous contrast distribution were not significant independent predictors. Conclusion: The anteroposterior distribution of GBCA in the vitreous is a novel, non-invasive imaging biomarker associated with impaired brain clearance function. This “contrast shift index” may reflect systemic glymphatic dysregulation common to both the eye and brain, offering a new avenue for assessing neurodegenerative risk.

DOI： 10.2463/mrms.mp.2025-0127

Whole-body fat-referenced MRI measures disease progression in patients with spinal and bulbar muscular atrophy

Karlsson, M; Widholm, P; Ahlgren, A; Hatsis, P; Gentry, C; Grunseich, C; Gharib, A; Kokkinis, A; Alqahtani, A; Fratta, P; Zampedri, L; Jayaseelan, D; Mckenzie, H; Wastling, S; Katsuno, M; Yamada, S; Kishimoto, Y; Kawase, T; Taoka, T; Vigiletta, V

NEUROMUSCULAR DISORDERS 53 巻 2025年9月

Magnetic resonance imaging indices for early Alzheimer's disease detection: Brain clearance markers 国際誌 Open Access

Nakaya, M; Kamagata, K; Takabayashi, K; Andica, C; Uchida, W; Hagiwara, A; Akashi, T; Wada, A; Taoka, T; Naganawa, S; Abe, O; Aoki, S

JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM 45 巻 ( 8 ) 頁： 1558 - 1568 2025年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Cerebral Blood Flow and Metabolism

The Alzheimer’s disease (AD) continuum is characterized by amyloid and tau protein deposition, which is partly attributable to the dysfunction of the brain clearance system. However, the specific phase in the AD continuum wherein aberrant clearance is present remains unclear. This study aimed to assess noninvasive magnetic resonance imaging (MRI) indices related to brain clearance functions, such as choroid plexus volume (CPV), lateral ventricular volume (LVV), and the index of diffusivity along the perivascular space (ALPS index), across the Alzheimer’s disease (AD) spectrum. The CPV, LVV, and ALPS index in amyloid beta (Aβ)-negative healthy controls (HCs) and Aβ-positive HCs as well as in patients with Aβ-negative subjective cognitive decline (SCD), with Aβ-positive SCD, with mild cognitive impairment, and with AD were evaluated. The CPV and LVV were higher, whereas the ALPS index was lower in the patients with more severe disease. The ALPS index was significantly lower in Aβ-positive HCs than in Aβ-negative HCs. In SCD patients and those in the AD continuum, the MRI-based clearance markers were correlated with P-tau and T-tau protein levels and cognitive scores. In summary, brain clearance markers on MRI are associated with tau deposition, neurodegeneration and cognitive dysfunction.

DOI： 10.1177/0271678X251321305

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