神経膠腫における遺伝子変異とMRI
キーワード：神経膠腫、MRI、ラジオゲノミクス
2017.04～2020.06.

IVIM MR画像を用いた脳腫瘍鑑別に関する研究
キーワード：IVIM; MR; 灌流強調画像; 拡散強調画像; 脳腫瘍
2014.04～2017.03.

Arterial spin labelingを用いた脳腫瘍の鑑別に関する研究
キーワード：ASL、MRI、脳腫瘍
2013.04～2016.03.

拡散強調画像を用いた真珠腫性中耳炎検出に関する研究

キーワード：真珠腫性中耳炎、側頭骨、MRI、拡散強調画像
2010.10.

MRI　IVIM法を用いた脳腫瘍診断への包括的アプローチ
2014.04～2017.03, 代表者：山下　孝二, 九州大学病院
MRI拡散強調像は脳腫瘍の質的診断や治療効果判定等、広く臨床的に使用されている。定量値としてみかけ上の拡散係数（ADC値）が利用されているが、実際には、現在汎用されている拡散強調像は基本的には分子拡散と毛細血管による血流（灌流）を区別する事はできない。これまで、拡散強調像は組織内の水分子拡散をターゲットに行うため灌流の影響がなるべく少なくなるようにパラメータを設定していた。しかし組織灌流はそれ自体が有用な情報であり，複数のb値を用いた拡散強調像をbi-exponential curveに近似する事で、灌流および真の拡散の両者を同時に定量するIVIM法が1980年代にLe Bihanらによって提唱された。ただ当時は、撮像時間が非常に長くなる事や大きな渦電流の影響などの問題があり、定着しなかった。近年3T MRIの普及により、拡散強調像の撮像時間は飛躍的に短縮され、非侵襲的な血流測定法として、IVIM法が最近になって再び注目されつつある。
　IVIM法はD値、D*値、f値を測定する事により組織の微小循環を定量可能であるとされるが、その生理学的な意義は解明されていない。従来の定量値測定法として、dynamic susceptibility contrast（DSC）法を用いた脳血液量測定、Arterial spin labeling（ASL）法を用いた脳血流量測定があるが、定量の際は動脈入力関数に依存し、特にASL法では脳血管障害を有する患者での定量性は疑問視されている。
本研究の成功により、脳腫瘍診断におけるIVIM法から得られるパラメータの意義が明らかとなれば、同時取得可能な拡散情報とあわせて脳腫瘍の診断・治療法および予後推定に有用となるだけでなく、将来的な医療費抑制にも貢献する事が期待される。
以下の3点をエンドポイントとしている。
１．脳腫瘍診断において高い再現性を実現できる実用的なIVIM画像の撮影法の最適化を行う
２．IVIM画像から得られる微小循環指標の生理学的な意義を明らかにする
３．脳腫瘍診断におけるIVIM画像の有用性を明らかにする.

主要著書

主要原著論文

1.	Koji Yamashita, Ryotaro Kamei, Hiroshi Sugimori, Takahiro Kuwashiro, So Tokunaga, Keisuke Kawamata, Kiyomi Furuya, Shino Harada, Junki Maehara, Yasushi Okada, Tomoyuki Noguchi, Interobserver reliability on intravoxel incoherent motion imaging in patients with acute ischemic stroke. , AJNR Am J Neuroradiol., 10.3174/ajnr.A7486 , 10.3174/ajnr.A7486 , 2022.05.
2.	Yamashita Koji, Hiwatashi Akio, Osamu Togao, Kazufumi Kikuchi, Koji Yoshimoto, Satoshi O Suzuki, Hiroshi Honda, MR imaging Based Analysis of Glioblastoma multiforme: Estimation of IDH1 Mutation Status., AJNR Am J Neuroradiol., 37, 1, 58-65, 37(1):58-65, 2016.01, BACKGROUND AND PURPOSE: Glioblastoma multiforme is highly aggressive and the most common type of primary malignant brain tumor in adults. Imaging biomarkers may provide prognostic information for patients with this condition. Patients with glioma with isocitrate dehydrogenase 1 (IDH1) mutations have a better clinical outcome than those without such mutations. Our purpose was to investigate whether the IDH1 mutation status in glioblastoma multiforme can be predicted by using MR imaging. MATERIALS AND METHODS: We retrospectively studied 55 patients with glioblastoma multiforme with wild type IDH1 and 11 patients with mutant IDH1. Absolute tumor blood flow and relative tumor blood flow within the enhancing portion of each tumor were measured by using arterial spin-labeling data. In addition, the maximum necrosis area, the percentage of cross-sectional necrosis area inside the enhancing lesions, and the minimum and mean apparent diffusion coefficients were obtained from contrast-enhanced T1-weighted images and diffusion-weighted imaging data. Each of the 6 parameters was compared between patients with wild type IDH1 and mutant IDH1 by using the Mann-Whitney U test. The performance in discriminating between the 2 entities was evaluated by using receiver operating characteristic analysis. RESULTS: Absolute tumor blood flow, relative tumor blood flow, necrosis area, and percentage of cross-sectional necrosis area inside the enhancing lesion were significantly higher in patients with wild type IDH1 than in those with mutant IDH1 (P < .05 each). In contrast, no significant difference was found in the ADCminimum and ADCmean. The area under the curve for absolute tumor blood flow, relative tumor blood flow, percentage of cross-sectional necrosis area inside the enhancing lesion, and necrosis area were 0.850, 0.873, 0.739, and 0.772, respectively. CONCLUSIONS: Tumor blood flow and necrosis area calculated from MR imaging are useful for predicting the IDH1 mutation status..
3.	Yamashita Koji, Takashi Yoshiura, Hiwatashi Akio, Osamu Togao, Kazufumi Kikuchi, Makoto Obara, Nozomu Matsumoto, Hiroshi Honda, High-resolution Three-dimensional Diffusion-weighted Imaging of Middle Ear Cholesteatoma at 3.0 T MRI: Usefulness of 3D Turbo Field-echo with Diffusion-Sensitized Driven-equilibrium Preparation (TFE-DSDE) Compared to Single-shot Echo-planar Imaging., Eur J Radiol., pii: S0720-048X(13)00214-3. 10.1016/j.ejrad.2013.04.018. , 82, 9, 471-475, 2013.09, Objective: To prospectively evaluate the usefulness of a newly developed high-resolution three-dimensional diffusion-weighted imaging method, turbo field-echo with diffusion-sensitized driven-equilibrium (TFE–DSDE) in diagnosing middle-ear cholesteatoma by comparing it to conventionalsingle-shot echo-planar diffusion-weighted imaging (SS-EP DWI).Materials and methods: Institutional review board approval and informed consent from all participantswere obtained. We studied 30 patients with preoperatively suspected acquired cholesteatoma. Eachpatient underwent an MR examination including both SS-EP DWI and DSDE-TFE using a 3.0 T MR scan-ner. Images of the 30 patients (60 temporal bones including 30 with and 30 without cholesteatoma) werereviewed by two independent neuroradiologists. The confidence level for the presence of cholesteatomawas graded on a scale of 0–2 (0 = definite absence, 1 = equivocal, 2 = definite presence). Interobserveragreement as well as sensitivity, specificity, and accuracy for detection were assessed for the two review-ers.Results: Excellent interobserver agreement was shown for TFE–DSDE ( = 0.821) whereas fair agreementwas obtained for SS-EP DWI ( = 0.416). TFE–DSDE was associated with significantly higher sensitivity(83.3%) and accuracy (90.0%) compared to SS-EP DWI (sensitivity = 35.0%, accuracy = 66.7%; p < 0.05). Nosignificant difference was found in specificity (96.7% for TFE–DSDE, 98.3% for SS-EP DWI)Conclusion: With increased spatial resolution and reduced susceptibility artifacts, TFE–DSDE improvesthe accuracy in diagnosing acquired middle ear cholesteatomas compared to SS-EP DWI..
4.	Yamashita K, Yoshiura T, Hiwatashi A, Togao O, Yoshimoto K, Suzuki SO, Abe K, Kikuchi K, Maruoka Y, Mizoguchi M, Iwaki T, Honda H, Differentiating primary central nervous system lymphoma from glioblastoma multiforme: assessment using arterial spin labeling, diffusion weighted imaging, and 18F-fluorodeoxyglucose positron emission tomography., Neuroradiology, 55, 2, 135-143, 2013.02, Introduction: Our purpose was to evaluate the diagnostic performance of arterial spin labeling (ASL) perfusion imaging, diffusion-weighted imaging (DWI), and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in differentiating primary central nervous system lymphomas (PCNSLs) from glioblastoma multiformes (GBMs). Methods: Fifty-six patients including 19 with PCNSL and 37 with GBM were retrospectively studied. From the ASL data, an absolute tumor blood flow (aTBF) and a relative tumor blood flow (rTBF) were obtained within the enhancing portion of each tumor. In addition, the minimum apparent diffusion coefficient (ADCmin) and the maximum standard uptake value (SUVmax) were obtained from DWI and FDG-PET data, respectively. Each of the four parameters was compared between PCNSLs and GBMs using Kruskal–Wallis test. The performance in discriminating between PCNSLs and GBMs was evaluated using the receiver-operating characteristics analysis. Area-under-the curve (AUC) values were compared among the four parameters using a nonparametric method. Results: The aTBF, rTBF, and ADCmin were significantly higher in GBMs (mean aTBF ± SD = 91.6±56.0 mL/100 g/ min, mean rTBF ± SD = 2.61±1.61, mean ADCmin ± SD = 0.78±0.19×10^−3 mm^2/s) than in PCNSLs (mean aTBF ± SD = 37.3±10.5 mL/100 g/min, mean rTBF ± SD = 1.24±0.37, mean ADCmin ± SD = 0.61±0.13×10^−3 mm^2/s) (p< 0.005, respectively). In addition, SUVmax was significantly lower in GBMs (mean ± SD = 13.1±6.34) than in PCNSLs (mean ± SD = 22.5±7.83) (p<0.005). The AUC for aTBF (0.888) was higher than those for rTBF (0.810), ADCmin (0.768), and SUVmax (0.848), although their difference was not statistically significant. Conclusion: ASL perfusion imaging is useful for differentiating PCNSLs from GBMs as well as DWI and FDG-PET..
5.	Yamashita K, Yoshiura T, Hiwatashi A, Kamano H, Dashjamts T, Shibata S, Tamae A, Honda H., Detection of Middle Ear Cholesteatoma by Diffusion-Weighted MR Imaging: Multishot Echo-Planar Imaging Compared with Single-Shot Echo-Planar Imaging., AJNR Am J Neuroradiol., 32, 10, 1915-1918, 2011.11.
6.	Yamashita K, Yoshiura T, Arimura H, Mihara F, Noguchi T, Hiwatashi A, Togao O, Yamashita Y, Shono T, Kumazawa S, Higashida Y, Honda H, Performance evaluation of radiologists with artificial neural network for differential diagnosis of intra-axial cerebral tumors on MR images, Am J Neuroradiol., 2008.06.

主要総説, 論評, 解説, 書評, 報告書等

主要学会発表等

1.	Yamashita K, Wu Z, Zhang H, Yin W, Zhu Z, Luo T, Wen X, Jing B, Kam TE, Ksu LM, Yap PT, Wang L, Li G, Li T, Baluyot KR, Howell BR, Styner MA, Yacoub E, Chen G, Potts T, Gilmore JH, Piven J, Smith JK, Ugurbil K, Hazlett H, Zhu H, Elison JT, Shen D, Lin W, Prediction of Motor Function Development in Infants Using the Thickness of the Primary Motor Cortex, 25th Annual Meeting of the Organization for Human Brain Mapping, 2019.06.
2.	Yamashita Koji, Predicting IDH1 and TERT Mutation Status in the patients with Glioblastoma, AIMS Neuro Imaging 2017, 2017.10.
3.	Yamashita Koji, Hiwatashi Akio, Osamu Togao, Kazufumi Kikuchi, Ryusuke Hatae, Koji Yoshimoto, Masahiro Mizoguchi, Satoshi O Suzuki, Takashi Yoshiura, Hiroshi Honda, MR imaging Based Analysis of Glioblastoma multiforme: Estimation of IDH1 Mutation Status, ASNR 52th Annual Meeting & NER Foundation Symposium 2014, 2014.05.
4.	Koji Yamashita, Takashi Yoshiura, Akio Hiwatashi, Hironori Kamano, Yukihisa Takayama, Eiki Nagao, Hiroshi Honda, Ultrashort echo time imaging of middle ear ossicle: a pilot study. , International Society for Magnetic Resonance in Medicine, 2010.05.

所属学会名

学会大会・会議・シンポジウム等における役割

学術論文等の審査