Iwabuchi, Yu



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




Papers 【 Display / hide

  • Focal 123I-MIBG Uptake in the Medial Segment of the Normal Liver

    Matsusaka Y., Nakahara T., Iwabuchi Y., Minami Y., Jinzaki M.

    Clinical Nuclear Medicine (Clinical Nuclear Medicine)  44 ( 3 ) e170 - e171 2019.03

    ISSN  03639762

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    © 2019 Wolters Kluwer Health, Inc. All rights reserved. An 84-year-old man with parkinsonism was referred for 123 I-MIBG scintigraphy. Abnormal uptake in the right upper abdomen was incidentally seen in planar image, and SPECT revealed focal uptake in the medial segment (S4) of the liver. Subsequent triple-phase contrast-enhanced CT showed no evidence of hepatic tumors, although in the arterial phase, there were an enhanced region corresponding to the uptake area and the enhanced vein of Sappey that flowed into S4. In this case, the focal 123 I-MIBG uptake would be attributable to hemodynamic change in the liver.

  • Impact of a combination of quantitative indices representing uptake intensity, shape, and asymmetry in DAT SPECT using machine learning: comparison of different volume of interest settings

    Iwabuchi Y., Nakahara T., Kameyama M., Yamada Y., Hashimoto M., Matsusaka Y., Osada T., Ito D., Tabuchi H., Jinzaki M.

    EJNMMI Research (EJNMMI Research)  9 2019

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    © 2019, The Author(s). Background: We sought to assess the machine learning-based combined diagnostic accuracy of three types of quantitative indices obtained using dopamine transporter single-photon emission computed tomography (DAT SPECT)—specific binding ratio (SBR), putamen-to-caudate ratio (PCR)/fractal dimension (FD), and asymmetry index (AI)—for parkinsonian syndrome (PS). We also aimed to compare the effect of two different types of volume of interest (VOI) settings from commercially available software packages DaTQUANT (Q) and DaTView (V) on diagnostic accuracy. Methods: Seventy-one patients with PS and 40 without PS (NPS) were enrolled. Using SPECT images obtained from these patients, three quantitative indices were calculated at two different VOI settings each. SBR-Q, PCR-Q, and AI-Q were derived using the VOI settings from DaTQUANT, whereas SBR-V, FD-V, and AI-V were derived using those from DaTView. We compared the diagnostic value of these six indices for PS. We incorporated a support vector machine (SVM) classifier for assessing the combined accuracy of the three indices (SVM-Q: combination of SBR-Q, PCR-Q, and AI-Q; SVM-V: combination of SBR-V, FD-V, and AI-V). A Mann-Whitney U test and receiver-operating characteristics (ROC) analysis were used for statistical analyses. Results: ROC analyses demonstrated that the areas under the curve (AUC) for SBR-Q, PCR-Q, AI-Q, SBR-V, FD-V, and AI-V were 0.978, 0.837, 0.802, 0.906, 0.972, and 0.829, respectively. On comparing the corresponding quantitative indices between the two types of VOI settings, SBR-Q performed better than SBR-V (p = 0.006), whereas FD-V performed better than PCR-Q (p = 0.0003). No significant difference was observed between AI-Q and AI-V (p = 0.56). The AUCs for SVM-Q and SVM-V were 0.988 and 0.994, respectively; the two different VOI settings displayed no significant differences in terms of diagnostic accuracy (p = 0.48). Conclusion: The combination of the three indices obtained using the SVM classifier improved the diagnostic performance for PS; this performance did not differ based on the VOI settings and software used.

  • Bilateral Adrenal Hyperplasia Due to Adrenocorticotropic Hormone-Secreting Esthesioneuroblastoma on FDG PET and 111In-Pentetreotide Scintigraphy

    Matsusaka Y., Nakahara T., Kurihara I., Iwabuchi Y., Jinzaki M.

    Clinical Nuclear Medicine (Clinical Nuclear Medicine)  43 ( 6 ) 452 - 453 2018.06

    ISSN  03639762

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    © 2018 Wolters Kluwer Health, Inc. All rights reserved. A 53-year-old woman with metastatic esthesioneuroblastoma was referred for FDG PET/CT imaging. FDG PET/CT showed symmetrical uptake in bilaterally enlarged adrenal glands, in addition to abnormal uptake in bone and lymph node metastases. 111In-pentetreotide scintigraphy was further performed and revealed the lack of adrenal uptake. The patient's serum adrenocorticotropic hormone (ACTH) level was extremely high, suggesting that hyperplastic condition in the adrenal glands due to ACTH stimulation from the metastatic esthesioneuroblastoma was responsible for increased FDG uptake. The combination of FDG PET and 111In-pentetreotide scintigraphy was useful for the pathophysiological evaluation of ACTH-secreting esthesioneuroblastoma.

  • Quantitative evaluation of the tracer distribution in dopamine transporter SPECT for objective interpretation

    Iwabuchi Y., Nakahara T., Kameyama M., Yamada Y., Hashimoto M., Ogata Y., Matsusaka Y., Katagiri M., Itoh K., Osada T., Ito D., Tabuchi H., Jinzaki M.

    Annals of Nuclear Medicine (Annals of Nuclear Medicine)  32 ( 5 ) 363 - 371 2018.06

    ISSN  09147187

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    © 2018, The Japanese Society of Nuclear Medicine. Purpose: Quantification of the tracer distribution would add objectivity to the visual assessments of dopamine transporter (DAT) single photon emission computed tomography (SPECT) data. Our study aimed to evaluate the diagnostic utility of fractal dimension (FD) as a quantitative indicator of tracer distribution and compared with the conventional quantitative value: specific binding ratio (SBR). We also evaluated the utility of the combined index SBR/FD (SBR divided by FD). Materials and methods: We conducted both clinical and phantom studies. In the clinical study, 150 patients including 110 patients with Parkinsonian syndrome (PS) and 40 without PS were enrolled. In the phantom study, we used a striatal phantom with the striatum chamber divided into two spaces, representing the caudate nucleus and putamen. The SBR, FD, and SBR/FD were calculated and compared between datasets for evaluating the diagnostic utility. Mann–Whitney test and receiver-operating characteristics (ROC) analysis were used for analysis. Results: ROC analysis revealed that the FD value had high diagnostic performance [the areas under the curve (AUC) = 0.943] and the combined use of SBR and FD (SBR/FD) delivered better results than the SBR alone (AUC, 0.964 vs 0.899; p < 0.001). The sensitivity, specificity, and accuracy, respectively, were 79.1, 85.0, and 80.7% with SBR, 84.5, 97.5, and 88.0% with FD, and 92.7, 87.5, and 91.3% with SBR/FD. Conclusion: Our results confirmed that the FD value is a useful diagnostic index, which reflects the tracer distribution in DAT SPECT images. The combined use of SBR and FD was more useful than either used alone.

  • Preclinical evaluation of heat-denatured [ <sup>18</sup> F]FDG-labeled red blood cells for detecting splenic tissues with PET in rats

    Matsusaka Y., Nakahara T., Takahashi K., Iwabuchi Y., Ogata Y., Nishime C., Kajimura M., Jinzaki M.

    Nuclear Medicine and Biology (Nuclear Medicine and Biology)  56   26 - 30 2018.01

    ISSN  09698051

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    © 2017 Elsevier Inc. Introduction Heat-denatured 99m Tc-labeled red blood cells (RBCs) are used for detecting splenic tissues with scintigraphy. The present study aimed to evaluate the feasibility of using heat-denatured [ 18 F]fluorodeoxyglucose ([ 18 F]FDG)-labeled RBCs in detecting splenic tissues using positron emission tomography (PET) in rats. Methods RBCs were washed with phosphate buffered saline, labeled with [ 18 F]FDG at 38°C, and heat-denatured at 50°C for 15 min. In vitro stability was assessed by measuring extracellular radioactivity during the 0–180 min incubation at 37°C. Thin layer chromatography (TLC) of the extracellular fluid was performed. The autologous RBCs were intravenously injected in four rats and PET scanning was simultaneously performed for 30 min. Time-activity curves of several organs, including the spleen, were analyzed on the PET images. Results Labeling efficiency was 92%. Low levels of radioactivity were released from the labeled RBCs for 180 min. TLC revealed that 80% of the released radioactivity was due to [ 18 F]FDG-6-phosphate. Whole body images showed strong uptake of heat-denatured [ 18 F]FDG-labeled RBCs in the spleen soon after injection in all four rats. Time-activity curves revealed that the splenic uptake continued to increase for 30 min and the amount of radioactivity in the other organs, except the urinary bladder, decreased after the initial surge. Conclusions Heat-denatured [ 18 F]FDG-labeled RBCs are suitable spleen-specific agents for PET. This method is clinically relevant as an alternative for heat-denatured 99m Tc-labeled RBC scintigraphy.

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Presentations 【 Display / hide

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

    Iwabuchi Yu

    第74回日本医学放射線学会総会, 2015.04, 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

    第73回日本医学放射線学会総会, 2014.04, 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, 2011.07

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, 岩渕 雄, Grant-in-Aid for Early-Career Scientists , Principal Investigator