Complex Principle Component Analysis on Dynamic Correlation Structure in Price Index Data

AbstractWe carry out multivariate time series analysis on price indices of individual goods and services collected over the last 35 years in Japan. Adoption of the complex principal component analysis (CPCA) enables us to have a new insight into dynamic correlation structure involved in the price data. The CPCA is based on complexification of real data using the Hilbert transformation; lead-lag relations between individual prices manifest in a form of instantaneous phases of the complex time series. The correlation matrix in the CPCA is purified by adopting the random matrix theory as a null hypothesis for removal of statistical noises. We identify four significant eigenmodes for price movement which are free from seasonal variations. Each of them has different characteristics of dynamical correlations and is shown to be responsive to different economic events

Dual-Energy CTを用いた肺血液量画像の定量的評価：急性肺血栓塞栓症患者に対する定量的重症度評価

BACKGROUND:Regional iodine distribution assessment on dual-energy computed tomography (DECT) has been suggested as useful for management of acute pulmonary thromboembolism (APTE) patients. However, no reported studies have made a direct comparison between quantitatively assessed DECT and right-to-left ventricular (RV/LV) ratio on CT for differentiation of right heart dysfunction (RHD) from non-right heart dysfunction (NRHD) in APTE patients. PURPOSE:To determine the capability of DECT for differentiation of RHD from NRHD in APTE patients. MATERIAL AND METHODS:Thirteen APTE patients underwent DECT and echocardiography at onset of APTE. Patients were divided into RHD (n = 7) and NRHD (n = 6) groups based on echocardiography. A normalized lung perfused blood volume map was generated, and two kinds of overall perfusion (OP) index were determined, one placed over each lung field (OP index A) and as the average from six regions of interest (ROIs) placed over each lung field (OP index B). The heterogeneity index was also determined as the standard deviation for the six ROIs. RV/LV ratio evaluations were also performed. To assess differences between the two groups, each index was statistically compared with the Mann-Whitney U test. The receiver-operating curve-based positive test was then performed to determine the feasible threshold value for dividing patients into the two groups. Finally, differentiation capabilities of the indexes were compared using McNemar's test. RESULTS:Significant differences between the two groups were found for both OP indexes and RV/LV ratio (P < 0.05). For each of the feasible threshold values, accuracy of each OP index with and without RV/LV ratio was better than that of the RV/LV ratio. CONCLUSION:Quantitative DECT has good potential for differentiation of APTE patients with and without right heart dysfunction.博士（医学）・乙第1350号・平成26年12月3日© The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav

Hierarchical communities in the walnut structure of the Japanese production network

This paper studies the structure of the Japanese production network, which includes one million firms and five million supplier-customer links. This study finds that this network forms a tightly-knit structure with a core giant strongly connected component (GSCC) surrounded by IN and OUT components constituting two half-shells of the GSCC, which we call a\textit{walnut} structure because of its shape. The hierarchical structure of the communities is studied by the Infomap method, and most of the irreducible communities are found to be at the second level. The composition of some of the major communities, including overexpressions regarding their industrial or regional nature, and the connections that exist between the communities are studied in detail. The findings obtained here cause us to question the validity and accuracy of using the conventional input-output analysis, which is expected to be useful when firms in the same sectors are highly connected to each other.Comment: 38 pages, 17 figure

超常磁性体酸化鉄造影MRIを用いた大動脈ステントグラフ治療後のエドリークの検出 : 造影CTとの比較検討

OBJECTIVE: Contrast-enhanced computed tomography (CE-CT) has been commonly used for follow-up imaging after endovascular aneurysm repair (EVAR), but it is difficult to use on patients with renal insufficiency. Superparamagnetic iron oxide (SPIO) particles, contrast medium for magnetic resonance imaging (MRI) that has been widely used for detection of the liver tumor, rarely affects renal function. The present study examined SPIO-enhanced dynamic MRI as a potential alternative to CE-CT for detection of endoleaks after EVAR. METHODS: Institutional review board approval was obtained for this prospective study. Twenty-three consecutive patients with normal renal function were evaluated using both CE-CT and SPIO-enhanced MRI within 2 weeks after EVAR. The median interval between the two modalities was 2 days. SPIO-enhanced MRI was performed at 1.5 T with T1-weighted, SPIO-enhanced dynamic, and postcontrast T1-weighted gradient echo sequences. The CE-CT protocol consisted of triple scans. Two experienced, blinded observers evaluated all images. Consensus reading of CE-CT and SPIO-MRI was defined as the reference standard. Interobserver, intraobserver, and intermodality agreement for endoleak detection was assessed by κ statistics. RESULTS: A total of 11 type II endoleaks originating from either the lumbar or inferior mesenteric artery were detected. Eight were able to be detected by CE-CT (8/11:73%) and 10 (10/11:91%) by SPIO-enhanced MRI. Interobserver (κ = 0.91; 95% CI, 0.74-1.00) and intraobserver agreement for MRI (κ = 1.00) were excellent. Intermodality agreement for endoleak detection was moderate (κ = 0.63; 95% CI, 0.32-0.94; and κ = 0.62; 95% CI, 0.29-0.95 for observers A and B, respectively). CONCLUSIONS: SPIO-enhanced MRI could represent a useful alternative to CE-CT, as it offers excellent interobserver, intraobserver agreement, and could detect more endoleaks than CE-CT.博士（医学）・乙第1379号・平成28年7月8日Copyright © 2013 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved

遺残胎盤組織：診断と臨床的取り扱いにおけるMRI所見の役割

OBJECTIVE:To assess the role of MRI in diagnosis and predicting clinical outcome in women with retained placental tissue. PATIENTS AND METHODS:Eleven patients with pathologically proven RPT were retrospectively studied. All underwent MRI. The following MRI parameters of RPT were studied: size, signal intensity on T1- and T2-weighted images, enhancement pattern on dynamic study, extent of attachment to the uterine myometrium, and myometrial thickness at the attachment site. Clinical reports were reviewed and MRI findings were compared with respect to outcome. RESULTS:RPT diameter varied from 30 to 102 mm. On T2-weighted images, 10 cases showed high intensity, while on T1-weighted images, seven cases showed high intensity. Nine cases were hypervascular. The myometrium was thinner at the attachment side than at the opposite side. All five cases in which RPT was delivered spontaneously showed an attachment area of less than a semicircle, hence broad attachment appears to impede detachment and necessitate additional therapy. After uterine arterial embolization, two patients showed complete infarction of RPT on enhanced MRI. CONCLUSION:MRI is useful for diagnosis and follow-up of RPT. The evaluation of extent of RPT attachment to the myometrium and vascularity on MRI can help the clinical assessment.博士（医学）・乙第1351号・平成26年12月3日© Springer Verlag. The definitive version is available at " http://dx.doi.org/10.1007/s00261-010-9604-x

3.OT MRA で観察される外側線条体動脈の分枝形態

PURPOSE:We hypothesized that the pattern of branching of the lenticulostriate arteries (LSAs) is involved in the variation of the distribution of the infarction within the LSA region. Our purpose was to evaluate the visibility of LSAs in 3D time-of-flight (TOF) MR angiography (MRA) with a 3.0 T scanner and to investigate the branching patterns of LSAs.MATERIALS AND METHODS:We performed 3D TOF MRA at 3.0 T for 100 healthy subjects. We assessed the number of LSAs and the number of branches arising from each LSA by evaluating MRA source images.RESULTS:In 200 hemispheres, 330 LSAs were visualized (mean = 1.65/hemisphere). In 3.5% of all hemispheres, no LSA was depicted; one LSA was depicted in 39%, two in 46.5%, and three in 11%. The maximum number of depicted LSA branches was five in 2% of all subjects, four in 7%, three in 26%, and two in 49% (mean = 2.3/subject). A large LSA trunk with three or more branches was found in 35% of subjects.CONCLUSION: Visualization of LSAs was possible in 96.5% of subjects by use of 3.0 T MRA. LSA branching patterns were variable, and a large LSA trunk with three or more branches was common.博士（医学）・乙第1305号・平成24年11月27日© Springer International Publishing AG,2012Copyright © 2012 Japan Radiological Societ

下部直腸癌におけるMRIを用いた歯状線浸潤の診断精度

Purpose: To retrospectively assess the accuracy of magnetic resonance imaging (MRI) in predicting dentate line invasion in low rectal cancer. Materials and methods: Eighty-one patients with primary rectal cancer were assessed by dynamic contrast-enhanced MRI. The location of the dentate line was assessed on MRI in 27 patients with upper-mid rectal cancer. Two observers independently evaluated the distance between the distal tumor edge and the MRI-defined dentate line in 54 patients with low rectal cancer, and the imaging and histological findings were compared. Results: The MRI-defined dentate line was 24.0 ± 3.8 mm above the anal verge in patients with upper-mid rectal cancer. The dentate line invasion status agreed with the histological findings in 49/54 (91%) patients (κ = 0.72 [95% CI 0.50-0.95]) for observer 1, and in 51/54 (94%) patients (κ = 0.83 [0.65-1.00]) for observer 2 in patients with low rectal cancer. Interobserver agreement was good (κ = 0.83 [0.65-1.00]). The MRI-derived distance between the distal tumor edge and the dentate line had significant correlation with the histological distance (r = 0.86 for reader 1 and 0.75 for observer 2). Conclusion: MRI demonstrates high accuracy in predicting dentate line invasion in low rectal cancer.博士（医学）・甲第748号・令和2年6月30日© Japan Radiological Society 2020© 2020 Springer Nature Switzerland AG. Part of Springer Nature.This is a post-peer-review, pre-copyedit version of an article published in Japanese journal of radiology. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11604-020-00933-5