Iwabuchi, Yu



School of Medicine, Department of Radiology (Diagnostic Radiology) (Shinanomachi)


Senior Assistant Professor (Non-tenured)/Assistant Professor (Non-tenured)


Papers 【 Display / hide

  • A diagnostic strategy for Parkinsonian syndromes using quantitative indices of DAT SPECT and MIBG scintigraphy: an investigation using the classification and regression tree analysis

    Iwabuchi Y., Kameyama M., Matsusaka Y., Narimatsu H., Hashimoto M., Seki M., Ito D., Tabuchi H., Yamada Y., Jinzaki M.

    European Journal of Nuclear Medicine and Molecular Imaging (European Journal of Nuclear Medicine and Molecular Imaging)  48 ( 6 ) 1833 - 1841 2021

    ISSN  16197070

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    Purpose: We aimed to evaluate the diagnostic performances of quantitative indices obtained from dopamine transporter (DAT) single-photon emission computed tomography (SPECT) and I-metaiodobenzylguanidine (MIBG) scintigraphy for Parkinsonian syndromes (PS) using the classification and regression tree (CART) analysis. Methods: We retrospectively enrolled 216 patients with or without PS, including 80 without PS (NPS) and 136 with PS [90 Parkinson’s disease (PD), 21 dementia with Lewy bodies (DLB), 16 progressive supranuclear palsy (PSP), and 9 multiple system atrophy (MSA). The striatal binding ratio (SBR), putamen-to-caudate ratio (PCR), and asymmetry index (AI) were calculated using DAT SPECT. The heart-to-mediastinum uptake ratio (H/M) based on the early (H/M [Early]) and delayed (H/M [Delay]) images and cardiac washout rate (WR) were calculated from MIBG scintigraphy. The CART analysis was used to establish a diagnostic decision tree model for differentiating PS based on these quantitative indices. Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 87.5, 96.3, 93.3, 92.9, and 93.1 for NPS; 91.1, 78.6, 75.2, 92.5, and 83.8 for PD; 57.1, 95.9, 60.0, 95.4, and 92.1 for DLB; and 50.0, 98.0, 66.7, 96.1, and 94.4 for PSP, respectively. The PCR, WR, H/M (Delay), and SBR indices played important roles in the optimal decision tree model, and their feature importance was 0.61, 0.22, 0.11, and 0.05, respectively. Conclusion: The quantitative indices showed high diagnostic performances in differentiating NPS, PD, DLB, and PSP, but not MSA. Our findings provide useful guidance on how to apply these quantitative indices in clinical practice. 123

  • [<sup>123</sup>I]-IMP single-photon emission computed tomography imaging in visual snow syndrome: A case series

    Shibata M., Tsutsumi K., Iwabuchi Y., Kameyama M., Takizawa T., Nakahara T., Fujiwara H., Jinzaki M., Nakahara J., Dodick D.W.

    Cephalalgia (Cephalalgia)  40 ( 14 ) 1671 - 1675 2020.12

    ISSN  03331024

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    © International Headache Society 2020. Background: Visual snow syndrome (VSS) is a neurological condition characterized by persistent flickering dots in the visual fields, palinopsia, enhanced entoptic phenomenon, photophobia, and nyctalopia. Neuroimaging evidence supports the role of the visual association cortex in visual snow syndrome. Case series: We provided clinical care to three patients with visual snow syndrome, in whom [123I]-IMP single-photon emission computed tomography (SPECT) imaging was performed. Case 1 was a 21-year-old male with a past history of migraine with aura who exhibited visual snow and entoptic phenomenon. In this patient, [123I]-IMP SPECT imaging revealed right occipital and temporal hypoperfusion with a distribution matching the ventral visual stream. [123I]-IMP SPECT imaging detected only mild bilateral frontal hypoperfusion in Case 2 and no overt abnormalities in Case 3. Conclusion: Although visual snow syndrome seems to be a heterogenous condition, our observations indicate that abnormal visual processing within the ventral visual stream may play a role in the pathogenesis of this condition.

  • Development of <sup>68</sup>Ga-labeled tin colloids for evaluating phagocytic function of Kupffer cells using preclinical PET imaging

    Matsusaka Y., Nakahara T., Takahashi K., Iwabuchi Y., Nakamura S., Jinzaki M.

    Annals of Nuclear Medicine (Annals of Nuclear Medicine)  34 ( 11 ) 807 - 814 2020.11

    ISSN  09147187

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    © 2020, The Japanese Society of Nuclear Medicine. Objective: This study aimed to investigate the optimal conditions for producing 68Ga-labeled tin colloid and the feasibility of 68Ga-tin colloid positron emission tomography (PET) for visualization and evaluation of the phagocytic function of Kupffer cells (KCs) in vivo. Methods: 68Ga-tin colloid was prepared by adding tin solution (1 mM, 0.2 mL) to 68Ga solution (1.0 mL), followed by pH adjustment with sodium acetate (1 M, 0.2 mL). Various labeling times were tested to find the optimal one. Colloid size was measured by filtering the solution through three-ply membrane filters (with pore sizes of 200, 3000, and 5000 nm), and radioactivity was measured in the whole filtrate and the filters using a gamma counter. The in vitro stability of the colloid was evaluated by the size measurement after incubation under ambient conditions for up to 60 min. PET scanning was performed for 30 min after intravenous administration of 68Ga-tin colloid solution (4 MBq) to healthy rats. Time-activity-curves for the liver, spleen, and blood pool were generated. Finally, liver uptake was compared before and after the establishment of KC-depletion and non-alcoholic steatohepatitis (NASH) rat models. Results: Colloid size increased with increasing labeling time. After pH adjustment, the colloid sizes remained nearly unchanged. The optimal labeling time was determined as 30 min. PET imaging of healthy rats revealed that liver uptake of the 68Ga-tin colloid increased with increasing colloid size. In KC-depleted rats, liver uptake significantly decreased (n = 4, p < 0.01). NASH model rats showed significantly decreased uptake of 68Ga-tin colloid in the livers (n = 5, p < 0.01). Conclusions: 68Ga-tin colloid, prepared by a simple radiolabeling method, enabled in vivo PET imaging to evaluate the phagocytic function of KCs.

  • Egested Feces Revealed Massive Protein Loss in <sup>99m</sup>Tc-HSA-D Scintigraphy

    Matsusaka Y., Nakahara T., Iwabuchi Y., Owaki Y., Narimatsu H., Jinzaki M.

    Clinical Nuclear Medicine (Clinical Nuclear Medicine)  45 ( 7 ) e329 - e330 2020.07

    ISSN  03639762

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    © 2020 Wolters Kluwer Health, Inc. All rights reserved. A 66-year-old man with severe diarrhea and severe hypoproteinemia was referred for 99mTc-DTPA-human serum albumin (HSA-D) scintigraphy. The scintigraphy at 24 hours postinjection showed strong accumulation of 99mTc-HSA-D in not only the colon but also all his diapers containing his egested feces. The ratio of the diapers counts to the total counts was 17.0%, and a considerable amount of protein loss was confirmed. 99mTc-HSA-D scintigraphy has an important role in diagnosing protein-losing enteropathy, but the abdomen is the only routinely scanned area. Additional scanning of egested radiotracer and the whole body can be useful for evaluating the disease severity.

  • Usefulness of <sup>18</sup>F-fluorodeoxyglucose positron emission tomography/computed tomography for predicting the prognosis and treatment response of neoadjuvant therapy for pancreatic ductal adenocarcinoma

    Yokose T., Kitago M., Matsusaka Y., Masugi Y., Shinoda M., Yagi H., Abe Y., Oshima G., Hori S., Endo Y., Toyama K., Iwabuchi Y., Takemura R., Ishii R., Nakahara T., Okuda S., Jinzaki M., Kitagawa Y.

    Cancer Medicine (Cancer Medicine)  9 ( 12 ) 4059 - 4068 2020.06

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    © 2020 The Authors. Cancer Medicine published by John Wiley & Sons Ltd. Background: The Response Evaluation Criteria in Solid Tumors (RECIST) for computed tomography (CT) is preoperatively used to evaluate therapeutic effects. However, it does not reflect the pathological treatment response (PTR) of pancreatic ductal adenocarcinoma (PDAC). The Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) for positron emission tomography (PET)/CT is effective in other cancers. This study aimed to confirm the usefulness of PERCIST and the prognostic utility of PET/CT for PDAC. Methods: Forty-two consecutive patients with PDAC who underwent neoadjuvant therapy (NAT) and pancreatectomy at our institution between 2014 and 2018 were retrospectively analyzed. We evaluated the treatment response and prognostic significance of PET/CT parameters and other clinicopathological factors. Results: Twenty-two patients who underwent PET/CT both before and after NAT with the same protocol were included. RECIST revealed stable disease and partial response in 20 and 2 cases, respectively. PERCIST revealed stable metabolic disease, partial metabolic response, and complete metabolic response in 8, 9, and 5 cases, respectively. The PTR was G3, G2, and G1 in 8, 12, and 2 cases, respectively. For comparing the concordance rates between PTR and each parameter, PERCIST (72.7% [16/22]) was significantly superior to RECIST (36.4% [8/22]) (P =.017). The area under the curve survival values of PET/CT parameters were 0.777 for metabolic tumor volume (MTV), 0.500 for maximum standardized uptake value, 0.554 for peak standardized uptake value corrected for lean body mass, and 0.634 for total lesion glycolysis. A 50% cut-off value for the MTV reduction rate yielded the largest difference in survival between responders and nonresponders. On multivariate analysis, MTV reduction rates < 50% were independent predictors for relapse-free survival (hazard ratio [HR], 3.92; P =.044) and overall survival (HR, 14.08; P =.023). Conclusions: PERCIST was more accurate in determining NAT’s therapeutic effects for PDAC than RECIST. MTV reduction rates were independent prognostic factors for PDAC.

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Reviews, Commentaries, etc. 【 Display / hide

Presentations 【 Display / hide

  • DAT SPECTにおけるCSFマスク補正のSBR値の診断能への影響

    岩渕雄 他



    Poster presentation

  • Effects of TOF and PSF on the detection of small-sized intrahepatic hypermetabolic lesions with FDG PET/CT: a phantom study

    Iwabuchi Yu



    Oral presentation (general)

  • Effect of time-of-flight (TOF) and point spread function (PSF) on the detection of small-sized hepatic metastasis in FDG-PET/CT

    Iwabuchi Yu



    Oral presentation (general)

  • 右腎被膜静脈経由で B-RTO を施行した十二指腸静脈瘤の一例

    Iwabuchi Yu

    第6回 日本IVR学会関東地方会, 


Research Projects of Competitive Funds, etc. 【 Display / hide

  • パーキンソン症候群診断におけるDAT SPECTの定量化と機械学習への応用


    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists , Principal investigator