Yasuo Amano

Nippon Medical School, Tokyo, Tokyo-to, Japan

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Publications (94)149.72 Total impact

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    ABSTRACT: Purpose: A drawback of time-resolved 3-dimensional phase contrast magnetic resonance (4D Flow MR) imaging is its lengthy scan time for clinical application in the brain. We assessed the feasibility for flow measurement and visualization of 4D Flow MR imaging using Cartesian y-z radial sampling and that using k-t sensitivity encoding (k-t SENSE) by comparison with the standard scan using SENSE.Materials and Methods: Sixteen volunteers underwent 3 types of 4D Flow MR imaging of the brain using a 3.0-tesla scanner. As the standard scan, 4D Flow MR imaging with SENSE was performed first and then followed by 2 types of acceleration scan-with Cartesian y-z radial sampling and with k-t SENSE. We measured peak systolic velocity (PSV) and blood flow volume (BFV) in 9 arteries, and the percentage of particles arriving from the emitter plane at the target plane in 3 arteries, visually graded image quality in 9 arteries, and compared these quantitative and visual data between the standard scan and each acceleration scan.Results: 4D Flow MR imaging examinations were completed in all but one volunteer, who did not undergo the last examination because of headache. Each acceleration scan reduced scan time by 50% compared with the standard scan. The k-t SENSE imaging underestimated PSV and BFV (P < 0.05). There were significant correlations for PSV and BFV between the standard scan and each acceleration scan (P < 0.01). The percentage of particles reaching the target plane did not differ between the standard scan and each acceleration scan. For visual assessment, y-z radial sampling deteriorated the image quality of the 3 arteries.Conclusion: Cartesian y-z radial sampling is feasible for measuring flow, and k-t SENSE offers sufficient flow visualization; both allow acquisition of 4D Flow MR imaging with shorter scan time.
    Magnetic Resonance in Medical Sciences 01/2014; · 0.75 Impact Factor
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    ABSTRACT: This study aimed to determine the relationship between delayed enhancement magnetic resonance imaging (DE MRI) and ventricular tachyarrhythmia in patients with hypertrophic cardiomyopathy (HCM) with basal septal hypertrophy and preserved ejection fraction (EF). One hundred seven patients with HCM with basal septal hypertrophy and EF greater than 50% underwent cine and DE MRI. Myocardial scar was identified with DE MRI. We assessed whether patient,s background, cine MRI findings, presence of myocardial scar, or number of scarred myocardial segments was related to the occurrence of ventricular tachyarrhythmia. Patient,s age, family history of HCM, and number of scarred segments differed between the patients with and without the arrhythmia. A family history of HCM and number of scarred segments were significantly related to ventricular tachyarrhythmia (P < 0.01). The number of scarred segments is the significant DE MRI parameter related to ventricular tachyarrhythmia in HCM with basal septal hypertrophy and preserved EF.
    Journal of computer assisted tomography 12/2013; · 1.38 Impact Factor
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    ABSTRACT: Our aim was to evaluate the long-term efficacy and safety of percutaneous transhepatic obliteration (PTO) alone and combined with balloon-occluded retrograde transvenous obliteration (BRTO) for gastroesophageal varices refractory to BRTO alone. Between July 1999 and December 2010, 13 patients with gastroesophageal varices refractory to BRTO were treated with PTO (n = 6) or a combination of PTO and BRTO (n = 7). We retrospectively investigated the rates of survival, recurrence, or worsening of the varices; hepatic function before and after the procedure; and complications. The procedure achieved complete obliteration or significant reduction of the varices in all 13 patients without major complications. During follow-up, the varices had recurred in 2 patients, of which one had hepatocellular carcinoma, and the other died suddenly from variceal rebleeding 7 years after PTO. The remaining 11 patients did not experience worsening of the varices and showed significant improvements in the serum ammonia levels and prothrombin time. The mean follow-up period was 90 months, and the cumulative survival rate at 1, 3, and 5 years was 92.9%, 85.7%, and 85.7%, respectively. Both PTO and combined PTO and BRTO seem as safe and effective procedures for the treatment of gastroesophageal varices refractory to BRTO alone.
    The Scientific World Journal 12/2013; 2013:498535. · 1.73 Impact Factor
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    ABSTRACT: PurposeTo evaluate the distribution and extent of myocardial fibrosis identified by either contrast-enhanced Look–Locker or late gadolinium enhancement magnetic resonance imaging (LGE MRI) and their relationships between ventricular tachyarrhythmia or risk factors in apical hypertrophic cardiomyopathy (APH). Materials and Methods Twenty-five APH patients were examined using a 3.0 T or 1.5 T instrument. We used MRI to evaluate myocardial T1 values and scar. We compared the myocardial fibrosis assessed by contrast-enhanced Look–Locker or LGE MRI with ventricular tachyarrhythmia or risk factors for hypertrophic cardiomyopathy. ResultsMyocardial scar was present in 17 of the 25 patients with APH. Myocardial scar was distributed predominantly in the apical myocardium (P < 0.01), whereas myocardial T1 values did not differ between the apical, midventricular, and basal septum. The extent of myocardial scar according to 16-segment model and ejection fraction were related to ventricular tachyarrhythmia or risk factors in APH (P < 0.05 for both). The myocardial T1 value was not associated with the tachyarrhythmia or risk factors. Conclusion In APH, the extent of myocardial scar on LGE MRI is associated with ventricular tachyarrhythmia and risk factors. Quantification of the myocardial T1 value is not necessary for its risk stratification.J. Magn. Reson. Imaging 2013; © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 10/2013; · 2.57 Impact Factor
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    ABSTRACT: To evaluate the capability of MRI to differentiate cardiac amyloidosis (CA), end-stage hypertrophic cardiomyopathy (HCM), and hypertensive heart disease (HHD), which are important etiologies of left ventricular hypertrophy (LVH) and heart failure. We enrolled 26 patients presenting with both LVH and heart failure: six with CA, nine with end-stage HCM, and 11 with HHD. Cardiac function, presence of pericardial or pleural effusion, and the extent and patterns of late gadolinium enhancement (LGE) were compared among the three diseases. Myocardial LGE was observed in all six CA patients, eight end-stage HCM patients, and six HHD patients. The number of LGE segments was significantly greater in CA than in HCM or HHD (p = 0.02 for both), and all patients with CA showed a global endocardial pattern of LGE. There were significant differences among CA, HCM, and HHD in ejection fraction and end-diastolic and end-systolic volume indices (p < 0.05 for all). Pericardial effusion was observed more frequently in CA than in HCM or HHD (p = 0.04 or 0.01, respectively). MRI is valuable for distinguishing among CA, end-stage HCM, and HHD, all of which present with LVH and heart failure.
    Japanese journal of radiology 08/2013; · 0.73 Impact Factor
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    ABSTRACT: To assess relationship between nonscarred myocardial T1 value measured using contrast-enhanced Look-Locker MRI and cardiac function in dilated cardiomyopathy (DCM) at 1.5 Tesla (T) and 3.0T MRI. Contrast-enhanced Look-Locker MRI was performed in 35 DCM patients. Nonscarred myocardial and blood T1 values were calculated from the signal intensity values and the delay time obtained on Look-Locker MRI. We assessed the correlation between the myocardial T1 value or myocardial T1 minus blood T1 value and cardiac function estimated using cine MRI (e.g., end-diastolic volume: EDV, left ventricular ejection fraction: LVEF) or brain natriuretic peptide (BNP). With 1.5T MRI (n = 16), the myocardial T1 value correlated negatively with the EDV(r = -0.66) and end-systolic volume (ESV; r = -0.68), and positively with the LVEF (r = 0.51); the myocardial T1 minus blood T1 value correlated inversely with EDV (r = -0.70), ESV (r = -0.62), and brain natriuretic peptide (BNP; r = -0.56). With 3.0T MRI (n = 17), the myocardial T1 value correlated negatively with ESV (r = -0.44), septal thickness (r = -0.60), and BNP (r = -0.51), and positively with LVEF (r = 0.61); the myocardial T1 minus blood T1 value negatively correlated with BNP (r = -0.50) and positively with LVEF (r = 0.54). The nonscarred myocardial T1 value measured with either 1.5T or 3.0T contrast-enhanced Look-Locker MRI is significantly related to cardiac dysfunction in DCM. J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 07/2013; · 2.57 Impact Factor
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    ABSTRACT: Cardiac magnetic resonance (CMR) imaging is an established method of detecting myocardial fibrosis related to prognosis in patients with dilated cardiomyopathy (DCM). Recent studies have found that (99m)Tc-methoxy-isobutyl-isonitrile (MIBI) and (123)I-15-(p-iodophenyl)-3(R,S)-methylpentadecanoic acid (BMIPP) dual single-photon-emission computerized tomography (MIBI-BMIPP dual SPECT) can detect perfusion-metabolism mismatches. We compared MIBI-BMIPP dual SPECT with CMR findings and assessed their prognostic abilities to determine the significance of abnormal metabolism in patients with DCM. Fifty inpatients with DCM (age 58 ± 12 y; 14 female) were assessed with the use of MIBI-BMIPP dual SPECT and CMR. Perfusion-metabolism mismatches were identified mainly at the left ventricular free wall, whereas late gadolinium enhancement (LGE) was evident mostly at the septal wall. During a median follow-up of 33 months, 9 patients developed cardiac events including death, heart failure, and fatal arrhythmia. Event-free survival rates were significantly lower for patients with LGE plus a mismatch than with other abnormalities (P = .001). Among clinical and imaging variables, LGE plus a mismatch was significantly associated with cardiac events (hazard ratio 7.9, 95% confidence interval 1.8-35.6; P = .007). Coexisting LGE and a perfusion-metabolism mismatch accurately predict future cardiac events in patients with DCM.
    Journal of cardiac failure 07/2013; 19(7):445-53. · 3.25 Impact Factor
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    ABSTRACT: BACKGROUND: The aim of the present study is to quantify the degree of the error as a function of the left ventricular (LV) wall thickness, in calculation of the ejection fraction (EF) using gated single-photon emission computed tomography (SPECT). The essential error of quantitative gated SPECT (QGS) software in patients with myocardial hypertrophy has not been quantitatively estimated. METHODS: Forty-six patients with known or suspected hypertrophic cardiomyopathy underwent gated myocardial perfusion SPECT and cardiac magnetic resonance (MR) imaging. The EF value was automatically calculated from gated SPECT using the QGS software. Twelve points of regional LV wall thickness and the EF value were estimated from MR images. RESULTS: Only a fair correlation was found between the QGS-EF and the MR-EF values (r = 0.48, y = 0.49x + 26.80, p < 0.01), and the QGS-EF was underestimated (r = 0.25, y = 0.90x) in 30 patients with myocardial hypertrophy (mean wall thickness > 12 mm). The magnitude of the error of the EF quantification from gated SPECT showed a significant negative correlation with the mean 12-point LV wall thickness in all 46 patients (r = -0.67, y = -4.12x + 40.44, p < 0.0001). The degree of the error of the ESV and that of the EDV showed positive correlation with the mean LV wall thickness (r = 0.55, y = 5.46x - 56.13, p < 0.0001; r = 0.31, y = 4.20x - 55.28, p < 0.05, respectively). CONCLUSIONS: The underestimation of EF increases with the degree of myocardial hypertrophy, because of the overestimation of the LV cavity especially in the end-systolic phase.
    Annals of Nuclear Medicine 03/2013; · 1.41 Impact Factor
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    ABSTRACT: Replacement of aneurysm clips or temporary parent artery occlusion during aneurysm clipping (AC) carries the risk of inducing postoperative neurologic deficits. When studying the risk of surgical complications associated with cerebral aneurysms, patients with similar conditions should be compared to eliminate the influence of rupture and location of aneurysm. MATERIAL and We used 3.0-Tesla (3.0T) magnetic resonance diffusion-weighted imaging (DWI) and magnetic resonance angiography (MRA) to analyze surgical complications after AC. A total of 42 AC procedures for 40 unruptured and 2 delayed-phase ruptured MCA aneurysms were evaluated. In six patients, temporary parent artery occlusion was performed. Asymptomatic hyperintensities were observed on DWI of three patients. In one patient, an asymptomatic lesion was most likely caused by a small contusion that occurred during dissection of an aneurysm attached to the brain surface. In two patients, asymptomatic cortical lesions were caused by brain surface contusions due to lacerations of the open dura. No symptomatic hyperintensities on DWI were observed after surgery. No fixed ischaemic neurologic deficits resulted from AC. Although some postoperative abnormalities were observed with 3.0T DWI, we found clipping of MCA aneurysms to be a safe procedure with a low risk of ischaemic complications.
    Turkish neurosurgery 01/2013; 23(6):772-7. · 0.58 Impact Factor
  • Journal of Nippon Medical School 01/2013; 80(1):2-3.
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    ABSTRACT: BACKGROUND: Cerebral revascularization surgery (CRS) is increasingly recognized as an important component in the treatment of complex cerebral vascular disease and tumors. CRS requires that the incidence of perioperative neurological complications should be minimized, because CRS for ischemic disease is often not the goal of treatment, but rather a prophylactic surgery. CRS carries the risk of focal postoperative neurological deficits. Little has been established concerning mechanisms of post-CRS ischemia. We used 3.0-T diffusion-weighted magnetic resonance imaging (DWI) and magnetic resonance angiography (MRA) to analyze the incidence and mechanism of ischemic lesions. METHODS: We studied the anterior circulation territory after 20 CRS procedures involving 33 vascular anastomosis procedures (13 double anastomoses and 7 single anastomoses) in 12 men and 8 women between June 2007 and October 2011. The operations included single or double superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis to treat internal carotid artery/MCA occlusions or severe MCA stenosis. A combined STA-MCA anastomosis and indirect bypass were performed for moyamoya disease. Postoperative DWI and MRA were obtained in all patients between 24 and 96h after surgery to detect thromboembolism, hypoperfusion, or procedural ischemic complications and vasospasms of the donor STA. RESULTS: Follow-up DWI and MRA were carried out 1.8±0.6 days after CRS (range, 1-4 days). Temporary occlusion time for anastomoses averaged 18.9min (range, 16-32min). Asymptomatic new hyperintensities occurred in the ipsilateral hemisphere of 2 patients on postoperative DWI (10% patients/6.0% anastomoses), and 1 moyamoya patient (5.0% patients/3.0% anastomoses) developed a symptomatic hyperintensity in the ipsilateral occipital lobe in response to the operation. Two abnormal small (<5mm) cortical DWI lesions were caused by sacrifices of a small branch of the recipient MCA. CONCLUSION: This study is the first postoperative 3.0-T DWI study of CRS and related clinical events. The incidence of symptomatic postoperative DWI abnormalities was restricted to 1 moyamoya patient representing 5.0% of total patients and 3.0% anastomoses. Although some postoperative DWI abnormalities occurred, CRS was found to be safe with a low risk of symptomatic ischemia.
    Clinical neurology and neurosurgery 11/2012; · 1.30 Impact Factor
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    ABSTRACT: Background Two-dimensional (2D) Look-Locker MRI technique can identify myocardial fibrosis, but cannot cover the whole left ventricle during a single scan.PurposeTo develop breath-hold three-dimensional (3D) Look-Locker MRI for the evaluation of postcontrast myocardial and blood T1 values and myocardial scarring in the left ventricle.Material and MethodsA phantom and 24 patients with myocardial diseases underwent gadolinium-enhanced 2D and 3D Look-Locker MRI using a 1.5-T unit. We compared the T1 value of the phantom and the values of the myocardium and blood in the patients between the two Look-Locker MRI sequences. In the patient study, the scan ordering of the two Look-Locker MRI was selected randomly. We also assessed the ability of the 3D imaging to detect myocardial scarring that was confirmed by late gadolinium enhancement MRI.ResultsThe phantom study showed a good agreement for the T1 value between 2D and 3D Look-Locker MRI. There were no significant differences in the myocardial T1 values after contrast between 2D and 3D Look-Locker MRI or in the T1 values between the two imaging slices on the 3D Look-Locker MRI (P > 0.10). A better agreement for the myocardial T1 values was found when the 3D Look-Locker imaging was performed first. The T1 values for blood were affected by the scan order (P < 0.05). The 3D Look-Locker MRI showed myocardial scarring with a shorter T1 value (290.4 ± 62.7 ms) than those for unscarred myocardium (360.8 ± 30.3 ms).Conclusion Three-dimensional Look-Locker MRI may precisely estimate the postcontrast myocardial and blood T1 values for the entire left ventricle during a single scan.
    Acta Radiologica 11/2012; · 1.33 Impact Factor
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    ABSTRACT: PURPOSE: To evaluate the usefulness of magnetic resonance imaging (MRI) for detection and quantification of myocardial damage related to clinical phases and cardiac function during eosinophilic myocarditis. MATERIALS AND METHODS: Four eosinophilic myocarditis patients received seven MRI studies. The left ventricular myocardium was divided into 48 layers, and we quantified the extent of abnormal intensity detected by T2-weighted or delayed enhancement MRI relative to the clinical phase and global cardiac function. RESULTS: T2-weighted imaging detected extensive myocardial hyperintensity during the acute phase of eosinophilic myocarditis. Diffuse myocardial delayed enhancement was observed in one patient during the acute phase, but not in the other. Little or no hyperintensity was detected by T2-weighted imaging or myocardial delayed enhancement during the convalescent phase. The extent of hyperenhancing myocardial layers was inversely correlated with the ejection fraction (EF) (r = -0.87). CONCLUSION: MRI can evaluate the presence and extent of myocardial damage related to the clinical phases and EF during eosinophilic myocarditis.
    Japanese journal of radiology 09/2012; · 0.73 Impact Factor
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    ABSTRACT: Gastric schwannoma is a rare tumor that accounts for only 0.2 % of all gastric tumors. We report a case of gastric schwannoma that underwent computed tomography (CT), magnetic resonance imaging (MRI), and [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET), and its histological confirmation was acquired. Gastric schwannoma showed high intensity on T2-weighted and diffusion-weighted MRI and high maximum standardized uptake on [(18)F]-FDG-PET. Lymphadenopathy close to the tumor was also found. Although diffusion-weighted MRI, [(18)F]-FDG-PET, and the presence of lymphadenopathy could suggest malignant tumors, the detail interpretation of the other CT and MRI findings may give a clue for the diagnosis of gastric schwannoma.
    Japanese journal of radiology 06/2012; 30(7):602-5. · 0.73 Impact Factor
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    ABSTRACT: Asymmetric septal hypertrophic cardiomyopathy (ASH) is the common phenotype of hypertrophic cardiomyopathy (HCM). We sought to classify ASH using magnetic resonance imaging (MRI) and to determine whether the MRI classification of ASH is related to the presence of risk factors for HCM. Ninety-three patients with ASH underwent cine and delayed-enhancement MRI. The ASH was classified morphologically using cine MRI at end-diastole. We evaluated the association between the MRI findings and the presence of risk factors in the ASH. The ASH was classified into three subtypes by MRI: contiguous subtype showing various clinical and MRI features (57%), sigmoid subtype (29%) with fewer risk factors, and reverse-curve subtype (14%) in younger patients with the larger myocardial mass and delayed-enhancement, which were significantly related to the risk factors. MRI was used to classify ASH into three subtypes, which might be related to the presence of risk factors.
    The international journal of cardiovascular imaging 03/2012; · 2.15 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:P302. · 4.44 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:P152. · 4.44 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:W40. · 4.44 Impact Factor
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    ABSTRACT: To compare the antitumor efficacy and safety of transcatheter arterial chemoembolization (TACE) by epirubicin suspension (epirubicin suspension: epirubicin-iodized oil mixture without solution) to that by epirubicin emulsion (epirubicin emulsion: epirubicin-iodized oil mixture with solution), the efficacy of treatment by administration of either an epirubicin suspension or emulsion was examined in an animal model. Changes in plasma epirubicin concentration were compared over 24 h immediately after treatment, and enhanced ultrasonographic and histopathological analysis subsequently conducted 7 days after treatment to determine the growth ratio and proportion of viable tumor cells. The growth ratio and proportion of viable tumor cells were found to be significantly lower in the suspension group than in the emulsion group while the plasma epirubicin concentration was found to be significantly higher in the suspension group than in the emulsion group. These results indicate that administration of an epirubicin suspension is a superior form of TACE compared to that of administration of an epirubicin emulsion.
    The Scientific World Journal 01/2012; 2012:961986. · 1.73 Impact Factor
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    ABSTRACT: Sarcoidosis is a multisystem disorder of unknown etiology that involves multiple organs. Computed tomography is the first-line imaging modality for diagnosing sarcoidosis because of its capacity to detect hilar lymphadenopathy and pulmonary lesions. Magnetic resonance (MR) imaging provides good soft tissue contrast that is useful for detecting sarcoidosis in some body parts, including skeletal muscle. Signal intensity on pre- and postcontrast T(1)- and T(2)-weighted imaging may reflect disease activity and the pathological appearance of sarcoidosis. In this review, we demonstrate these conventional MR imaging findings of hepatosplenic and muscular sarcoidosis and describe the usefulness of diffusion-weighted imaging for detecting sarcoidosis.
    Magnetic Resonance in Medical Sciences 01/2012; 11(2):83-9. · 0.75 Impact Factor