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Dive into the research topics where Hiroyuki Ishikawa is active.

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Featured researches published by Hiroyuki Ishikawa.


Digestive Diseases and Sciences | 1992

Intestinal fatty acid-binding protein as a sensitive marker of intestinal ischemia.

Tatsuo Kanda; Yasuo Nakatomi; Hiroyuki Ishikawa; Masahiro Hitomi; Yoichi Matsubara; Teruo Ono; Terukazu Muto

Determination of the serum level of intestinal fatty acid-binding protein has been used to detect rat intestinal ischemia following ligation or 30-min occlusion of the superior mesenteric artery. The normal values were under the minimal detectable level of less than 2 ng/ml in all the 10 rats. The serum fatty acid-binding protein level increased rapidly, to 340.7±54.6, 438.5±40.1, 388.1±37.4, and 292.2±95.7 ng/ml (P<0.01) at 1, 2, 4, and 8 hr after ligation respectively. It also increased, to 347.2±127.7 ng/ml (P<0.01) at 1 hr, after a 30-min transient occlusion and then returned to a normal level. Histological studies showed destruction of the villi, disappearance of the mucosa, and transmural necrosis with the progress of time after ligation, while no remoarkable morphological change was observed following 30-min transieent occlusion. These observations strongly suggest that the intestinal fatty acid-binding protein is a useful biochemical marker for intestinal ischemia, particularly in the early reversible phase.


Academic Radiology | 2012

Measurement of Focal Ground-glass Opacity Diameters on CT Images: Interobserver Agreement in Regard to Identifying Increases in the Size of Ground-Glass Opacities

Ryutaro Kakinuma; Kazuto Ashizawa; Keiko Kuriyama; Aya Fukushima; Hiroyuki Ishikawa; Hisashi Kamiya; Naoya Koizumi; Yuichiro Maruyama; Kazunori Minami; Norihisa Nitta; Seitaro Oda; Yasuji Oshiro; Masahiko Kusumoto; Sadayuki Murayama; Kiyoshi Murata; Yukio Muramatsu; Noriyuki Moriyama

PURPOSEnTo evaluate interobserver agreement in regard to measurements of focal ground-glass opacities (GGO) diameters on computed tomography (CT) images to identify increases in the size of GGOs.nnnMATERIALS AND METHODSnApproval by the institutional review board and informed consent by the patients were obtained. Ten GGOs (mean size, 10.4 mm; range, 6.5-15 mm), one each in 10 patients (mean age, 65.9 years; range, 58-78 years), were used to make the diameter measurements. Eleven radiologists independently measured the diameters of the GGOs on a total of 40 thin-section CT images (the first [n = 10], the second [n = 10], and the third [n = 10] follow-up CT examinations and remeasurement of the first [n = 10] follow-up CT examinations) without comparing time-lapse CT images. Interobserver agreement was assessed by means of Bland-Altman plots.nnnRESULTSnThe smallest range of the 95% limits of interobserver agreement between the members of the 55 pairs of the 11 radiologists in regard to maximal diameter was -1.14 to 1.72 mm, and the largest range was -7.7 to 1.7 mm. The mean value of the lower limit of the 95% limits of agreement was -3.1 ± 1.4 mm, and the mean value of their upper limit was 2.5 ± 1.1 mm.nnnCONCLUSIONnWhen measurements are made by any two radiologists, an increase in the length of the maximal diameter of more than 1.72 mm would be necessary in order to be able to state that the maximal diameter of a particular GGO had actually increased.


Journal of Computer Assisted Tomography | 2005

Ultrasmall pulmonary opacities on multidetector-row high-resolution computed tomography: a prospective radiologic-pathologic examination.

Hiroyuki Ishikawa; Naoya Koizumi; Tetsuro Morita; Yoshiko Tani; Masanori Tsuchida; Hajime Umezu; Makoto Naito; Keisuke Sasai

Objective: To clarify the pathologic findings of ultrasmall pulmonary opacities (5 mm or smaller in diameter) found on multidetector-row high-resolution computed tomography (MD-HRCT). Methods: Ten lobes in 10 patients were included in this study. Each lobe had a primary lung tumor and was removed surgically. Two thoracic radiologists noted any tiny nonlinear opacity on preoperative MD-HRCT films (1.25-mm thickness) covering the whole lobe. Pathologic findings of detected opacities were evaluated macroscopically and microscopically. Results: Among 139 ultrasmall opacities 5 mm or smaller in diameter, 94 corresponded to normal anatomic structures (partial volume averaging or motion artifact), 36 corresponded to pathologic abnormalities, and 9 were unidentified. Histologic diagnoses of 36 pathologic abnormalities were inflammatory lesions (n = 16), intrapulmonary lymph nodes (IPLN; n = 7), atypical adenomatous hyperplasia (AAH; n = 7), bronchioloalveolar carcinoma (BAC; n = 5), and another neoplastic lesion (n = 1). Conclusion: Tiny pulmonary lesions, such as AAHs, BACs, and IPLNs, were identified among ultrasmall opacities found on MD-HRCT.


PLOS ONE | 2015

Ultra-High-Resolution Computed Tomography of the Lung: Image Quality of a Prototype Scanner

Ryutaro Kakinuma; Noriyuki Moriyama; Yukio Muramatsu; Shiho Gomi; Masahiro Suzuki; Hirobumi Nagasawa; Masahiko Kusumoto; Tomohiko Aso; Yoshihisa Muramatsu; Takaaki Tsuchida; Koji Tsuta; Akiko Miyagi Maeshima; Naobumi Tochigi; Shun Watanabe; Naoki Sugihara; Shinsuke Tsukagoshi; Yasuo Saito; Masahiro Kazama; Kazuto Ashizawa; Kazuo Awai; Osamu Honda; Hiroyuki Ishikawa; Naoya Koizumi; Daisuke Komoto; Hiroshi Moriya; Seitaro Oda; Yasuji Oshiro; Masahiro Yanagawa; Noriyuki Tomiyama; Hisao Asamura

Purpose The image noise and image quality of a prototype ultra-high-resolution computed tomography (U-HRCT) scanner was evaluated and compared with those of conventional high-resolution CT (C-HRCT) scanners. Materials and Methods This study was approved by the institutional review board. A U-HRCT scanner prototype with 0.25 mm x 4 rows and operating at 120 mAs was used. The C-HRCT images were obtained using a 0.5 mm x 16 or 0.5 mm x 64 detector-row CT scanner operating at 150 mAs. Images from both scanners were reconstructed at 0.1-mm intervals; the slice thickness was 0.25 mm for the U-HRCT scanner and 0.5 mm for the C-HRCT scanners. For both scanners, the display field of view was 80 mm. The image noise of each scanner was evaluated using a phantom. U-HRCT and C-HRCT images of 53 images selected from 37 lung nodules were then observed and graded using a 5-point score by 10 board-certified thoracic radiologists. The images were presented to the observers randomly and in a blinded manner. Results The image noise for U-HRCT (100.87 ± 0.51 Hounsfield units [HU]) was greater than that for C-HRCT (40.41 ± 0.52 HU; P < .0001). The image quality of U-HRCT was graded as superior to that of C-HRCT (P < .0001) for all of the following parameters that were examined: margins of subsolid and solid nodules, edges of solid components and pulmonary vessels in subsolid nodules, air bronchograms, pleural indentations, margins of pulmonary vessels, edges of bronchi, and interlobar fissures. Conclusion Despite a larger image noise, the prototype U-HRCT scanner had a significantly better image quality than the C-HRCT scanners.


Journal of Gastroenterology | 2003

Eosinophilic colitis accompanied by Tolosa–Hunt syndrome: report of a case

Shin-ichi Kosugi; Kazutoshi Date; Masahiro Minagawa; Hiroyuki Ishikawa; Katsuyoshi Hatakeyama; Kazuhiko Endo; Yoshihiko Kimura

presented in this case has been documented only rarely.1–3 With regard to laboratory findings, peripheral hypereosinophilia and elevation of serum IgE levels occur variably and are not reliable prerequisites for diagnosis.1,2 Because definite diagnosis requires microscopic evidence, multiple biopsies by endoscopy or fullthickness biopsies by minimal invasive surgery such as laparoscopy should be considered.2,4 The most interesting symptom seen in this case was painful ophthalmoplegia, which is produced by involvement of the cranial nerves passing through the cavernous sinus. This case was thought to be THS from his clinical course, the diagnosis of which is made only after other possible diseases, such as tumors and aneurysm, have been excluded. The etiology of THS is poorly understood, although the pathology is considered to be a non-specific granulomatous inflammation in the region of the cavernous sinus.5 Corticosteroids are the mainstay of treatment for EGE1,3,4 as well as for THS,5 and surgery is reserved for medically refractory EGE, usually either obstructive or perforated cases.1,4 In this case, it is possible that initial administration of corticosteroids could have prevented surgical intervention and provided relief from all symptoms. To the best of our knowledge, this is the first case of eosinophilic colitis and THS coexisting, probably merging accidentally.


Journal of Computer Assisted Tomography | 2007

Ultrasmall intrapulmonary lymph node: usual high-resolution computed tomographic findings with histopathologic correlation.

Hiroyuki Ishikawa; Naoya Koizumi; Tetsuro Morita; Masanori Tsuchida; Hajime Umezu; Keisuke Sasai

Objective: To clarify high-resolution computed tomographic findings of ultrasmall intrapulmonary lymph node (IPLN) with histopathologic correlation. Methods: Fourteen IPLNs 3 to 6 mm in diameter were identified in 7 lobectomy specimens. Preoperative multidetector-row, high-resolution computed tomography covering the whole lobe was evaluated and compared with histopathologic findings. Results: Thirteen of 14 nodules appeared as well-defined solid nodules. The shape was polygonal or angular in 11 and round or oval in 3. Thirteen of 14 nodules were located within 15 mm of pleura. All 11 nodules apart from pleura were accompanied with linear opacity contiguous with pleura. Ten of 14 nodules were adjacent to peripheral pulmonary veins, and 4 were adjacent to linear opacity from pulmonary veins. These findings were confirmed pathologically, and linear opacities were consistent with thickened or normal interlobular septa. Conclusions: Ultrasmall IPLN has usual high-resolution computed tomographic findings reflecting histopathologic findings.


European Journal of Radiology | 2014

Analysis of decrease in lung perfusion blood volume with occlusive and non-occlusive pulmonary embolisms

Yohei Ikeda; Norihiko Yoshimura; Yoshiro Hori; Yosuke Horii; Hiroyuki Ishikawa; Motohiko Yamazaki; Yoshiyuki Noto

PURPOSEnThe aim of this study was to determine if lung perfusion blood volume (lung PBV) with non-occlusive pulmonary embolism (PE) differs quantitatively and visually from that with occlusive PE and to investigate if lung PBV with non-occlusive PE remains the same as that without PE.nnnMATERIALS AND METHODSnTotally, 108 patients suspected of having acute PE underwent pulmonary dual-energy computed tomography angiography (DECTA) between April 2011 and January 2012. Presence of PE on DECTA was evaluated by one radiologist. Two radiologists visually evaluated the PE distribution (segmental or subsegmental) and its nature (occlusive or non-occlusive) on DECTA and classified perfusion in lung PBV as decreased, slightly decreased, and preserved. Two radiologists used a lung PBV application to set a region of interest (ROI) in the center of the lesion and measured HU values of an iodine map. In the same slice as the ROI of the lesion and close to the lesion, another ROI was set in the normal perfusion area without PE, and HUs were measured. The proportion of lesions was compared between the occlusive and non-occlusive groups. HUs were compared among the occlusive, non-occlusive, and corresponding normal groups.nnnRESULTSnTwenty-five patients had 80 segmental or subsegmental lesions. There were 37 and 43 lesions in the occlusive and non-occlusive groups, respectively. The proportion of decreased lesions was 73.0% (27/37) in the occlusive group, while that of preserved lesions in the non-occlusive group was 76.7% (33/43). There was a significant difference in the proportion of lesions (P<0.001) between the two groups. HUs of the iodine map were significantly higher in the non-occlusive group than in the occlusive group (33.8 ± 8.2 HU vs. 11.9 ± 6.1 HU, P<0.001). There was no significant difference in HUs for the entire lesion between the non-occlusive (33.8 ± 8.2 HU) and corresponding normal group (34.5 ± 6.8 HU; P=0.294).nnnCONCLUSIONnIodine perfusion tended to be visually and quantitatively preserved in lungs with nonocclusive PE. Lung PBV is required to evaluate pulmonary blood flow.


Clinical Radiology | 2014

Relationship between CT features and high preoperative serum carcinoembryonic antigen levels in early-stage lung adenocarcinoma

Motohiko Yamazaki; Hiroyuki Ishikawa; Ryosuke kunii; Akiko Tasaki; Suguru Sato; Yohei Ikeda; Norihiko Yoshimura

AIMnTo assess the relationship between thin-section computed tomography (CT) features of primary tumour and high preoperative serum carcinoembryonic antigen (CEA) levels that reportedly suggest poor prognoses in early-stage lung adenocarcinoma.nnnMATERIALS AND METHODSnTwo hundred and seventy-five consecutive patients who underwent resection of pathological stage I (T1-2aN0M0) adenocarcinomas with a maximum diameter of ≤ 3 cm (144 men, 131 women; mean age 67.8 years) were enrolled. CT features of the primary tumours and clinical characteristics of these patients were statistically evaluated to identify the factors associated with high serum CEA levels (>5 ng/ml).nnnRESULTSnEighty-one patients (29.5%) had high serum CEA levels. In univariate analysis, lower ground-glass opacity ratio (p < 0.001), lower tumour shadow disappearance rate (TDR: the ratio of tumour area in mediastinal window to that of lung window, p < 0.001), presence of notch (p = 0.015), and coexistence with bullae or honeycomb cysts (p < 0.001) were observed more frequently in the group with high serum CEA levels than that of the group with normal levels. TDR [odds ratio (OR) 0.984; 95% confidence interval (CI): 0.976-0.993; p < 0.001] and coexistence with bullae or honeycomb cysts (OR = 3.08; 95% CI: 1.55-6.12; p = 0.001) remained significant, even after adjusting patients age, gender, and smoking status.nnnCONCLUSIONSnAdenocarcinomas with lower TDR and coexisting with bullae or honeycomb cysts are associated with high preoperative serum CEA levels. Although some CEA elevations may be due to benign pulmonary diseases, such tumours are suspected to have poor prognoses, even for early-stage diseases.


Japanese Journal of Radiology | 2012

Where is the most common site of DVT? Evaluation by CT venography

Norihiko Yoshimura; Yoshiro Hori; Yosuke Horii; Toru Takano; Hiroyuki Ishikawa

PurposeOur aim was to clarify the common site of deep venous thrombosis (DVT) in patients suspected of having pulmonary embolism using computed tomography pulmonary angiography with computed tomography venography (CTV).Materials and methodsWe evaluated 215 patients. For all studies, 100xa0ml of 370xa0mgxa0I/ml nonionic contrast material was administered. CTV were scanned with helical acquisition starting at 3xa0min in four-slice multidetector-row computed tomography (MDCT) or 5xa0min in 64-MDCT after the start of contrast material injection. The site of DVT was divided into iliac vein, femoral vein, popliteal vein, or calf vein. Calf vein was divided into muscular (soleal and gastrocnemius) and nonmuscular (anterior/posterior tibial and peroneal) veins. The 2xa0×xa02 chi-square test was used.ResultsOne hundred and thirty-seven patients showed DVT; the muscular calf vein was more prevalent than other veins (Pxa0<xa00.01).ConclusionsOur study showed that the most common site of DVT was the muscular calf vein.


IEEE Transactions on Applied Superconductivity | 2005

Performance comparison of a DC hybrid type FCLI with other types

Hongtian Shao; Mitsugi Yamaguchi; Satoshi Fukui; Jun Ogawa; Takao Sato; Hiroyuki Ishikawa

Fault current limiting and interrupting performances of three types of fault current limiting interrupter (FCLI) are compared; a DC reactor type, a DC S/N transition type and a DC hybrid type, which are made of the Bi-2223 tape and bulk. The DC hybrid type FCLI can limit a fault current by means of the inductance of HTS coil and the normal resistance of high temperature superconducting bulk (HTSB). In the case of an accident, the normal transition of the bulk can be accelerated by the magnetic field of the HTS coil. In this paper, performances of the DC hybrid type three-phase FCLI are compared analytically with the DC reactor type and the DC S/N transition type. Features derived from the combination of a reactor coil and an S/N transition element for the DC hybrid type are discussed and as an example it is applied to 6.6 kV-2000 A power distribution system.

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