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Your search keyword '"Kohei Hamamoto"' showing total 4 results
Start Over Author "Kohei Hamamoto" Journal magnetic resonance in medical sciences
4 results on '"Kohei Hamamoto"'

1. Ultra-short Echo-time MR Angiography Combined with a Modified Signal Targeting Alternating Radio Frequency with Asymmetric Inversion Slabs Technique to Assess Visceral Artery Aneurysm after Coil Embolization

Author

Kohei, Hamamoto, Emiko, Chiba, Noriko, Oyama-Manabe, Hironao, Yuzawa, Hiromi, Edo, Yohsuke, Suyama, and Hiroshi, Shinmoto

Subjects
Radiology, Nuclear Medicine and imaging
Abstract

Contrast-enhanced CT and MR angiography are widely used for follow-up of visceral artery aneurysms after coil embolization. However, potential adverse reactions to contrast agents and image deterioration due to susceptibility artifacts from the coils are major drawbacks of these modalities. Herein, we introduced a novel non-contrast-enhanced MR angiography technique using ultra-short TE combined with a modified signal targeting alternating radio frequency with asymmetric inversion slabs, which could provide a serial hemodynamic vascular image with fewer susceptibility artifacts for follow-up after coil embolization.

Published
2022
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2. Ultra-short Echo-time MR Angiography Combined with a Subtraction Method to Assess Intracranial Aneurysms Treated with a Flow-diverter Device.

Author

Yusuke Ayabe, Kohei Hamamoto, Yoshikazu Yoshino, Yoshimasa Ikeda, Emiko Chiba, Hironao Yuzawa, and Noriko Oyama-Manabe

Subjects
MAGNETIC resonance angiography, INTRACRANIAL aneurysms, MAGNETIC susceptibility, SPIN labels, TREATMENT effectiveness
Abstract

A flow-diverter (FD) device is a well-established tool for the treatment of unruptured intracranial aneurysms. Time-of-flight (TOF) MR angiography (MRA) is widely used for postoperative assessment after the treatment with FD; however, it cannot fully visualize intra-aneurysmal and intrastent flow signals due to the magnetic susceptibility from the FD. Recently, the utility of MRA with ultra-short TE (UTE) sequence and arterial spin labeling technique in assessing the therapeutic efficacy of intracranial aneurysms treated with metallic devices has been reported, but long image acquisition time is one of the drawbacks of this method. Herein, we introduce a novel UTE MRA using the subtraction method that enables the reduction in susceptibility artifacts with a short image acquisition time. [ABSTRACT FROM AUTHOR]

Published
2023
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3. Combining the Tumor Contact Length and Apparent Diffusion Coefficient Better Predicts Extraprostatic Extension of Prostate Cancer with Capsular Abutment: A 3 Tesla MR Imaging Study.

Author

Koichi Ito, Emiko Chiba, Noriko Oyama-Manabe, Satoshi Washino, Osamu Manabe, Tomoaki Miyagawa, Kohei Hamamoto, Masahiro Hiruta, Keisuke Tanno, and Hiroshi Shinmoto

Subjects
TUMORS, PROSTATE cancer, MAGNETIC resonance imaging, PROSTATECTOMY, RADIOLOGISTS
Abstract

Purpose: To assess the diagnostic performance of the tumor contact length (TCL) and apparent diffusion coefficient (ADC) for predicting extraprostatic extension (EPE) of prostate cancer with capsular abutment (CA). Methods: Ninety-three patients with biopsy-proven prostate cancer underwent 3-Tesla MRI, including diffusion-weighted imaging (b value = 0, 2000 s/mm²) and radical prostatectomy. Two experienced radiologists, blinded to the clinicopathological data, retrospectively assessed the presence of CA on T2-weighted imaging (T2WI). TCL on T2WI and ADC values were measured on detecting CA in prostate cancer. We used the receiver operating characteristic curves to assess the diagnostic performance of TCL and ADC values for predicting EPE. Results: CA was present in 58 prostate cancers among 93 patients. The cut-off value for TCL was 6.9 mm, which yielded an area under the curve (AUC) of 0.75. This corresponded to a sensitivity, specificity, and accuracy of 84.2%, 61.5%, and 69.0%, respectively. The cut-off value for ADC was 0.63 × 10-3 mm²/s, which yielded an AUC of 0.76. This, in turn, corresponded to a sensitivity, specificity, and accuracy of 84.2%, 59.0%, and 67.2%, respectively. The combined cut-off value of TCL and ADC yielded an AUC of 0.82. The specificity (84.6%) and accuracy (81.0%) of the combined value were superior to their individual values (P < 0.05). Conclusion: A combination of TCL and ADC values provided high specificity and accuracy for detecting EPE of prostatic cancer with CA. [ABSTRACT FROM AUTHOR]

Published
2022
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4. Feasibility of Non-contrast-enhanced MR Angiography Using the Time-SLIP Technique for the Assessment of Pulmonary Arteriovenous Malformation

Author

Tomohisa Okochi, Emiko Chiba, Keisuke Tanno, Osamu Tanaka, Katsuhiko Matsuura, and Kohei Hamamoto

Subjects
Adult, Male, medicine.medical_specialty, Image quality, Contrast Media, Pulmonary Artery, coil embolization, Sensitivity and Specificity, Magnetic resonance angiography, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, Young Adult, 0302 clinical medicine, Text mining, Occlusion, time-spatial labeling inversion pulse (time-SLIP), medicine, fast advanced spin echo (FASE), non-contrast-enhanced magnetic resonance angiography, Humans, Radiology, Nuclear Medicine and imaging, Prospective Studies, Pulmonary arteriovenous malformation, Prospective cohort study, Aged, Aged, 80 and over, medicine.diagnostic_test, business.industry, Angiography, Digital Subtraction, Digital subtraction angiography, Middle Aged, pulmonary arteriovenous malformations, Pulmonary Veins, 030220 oncology & carcinogenesis, Angiography, Arteriovenous Fistula, Female, Radiology, business, Nuclear medicine, Major Paper, Magnetic Resonance Angiography
Abstract

Purpose The purpose of this study was to evaluate the diagnostic performance of non-contrast-enhanced magnetic resonance angiography with time-spatial labeling inversion pulse (time-SLIP MRA) in the assessment of pulmonary arteriovenous malformation (PAVM). Methods Eleven consecutive patients with 38 documented PAVMs underwent time-SLIP MRA with a 3-tesla unit. Eight patients with 25 lesions were examined twice, once before and once after embolotherapy. The lesions were divided into two groups-initial diagnosis (n = 35) and follow-up (n = 28)-corresponding to untreated and treated lesions, respectively, and were evaluated separately. To evaluate the initial diagnosis group, two reviewers assessed image quality for visualization of PAVMs by using a qualitative 4-point scale (1 = not assessable to 4 = excellent). The location and classification of PAVMs were also evaluated. The results were compared with those from digital subtraction angiography. For evaluation of the follow-up group, the reviewers assessed the status of treated PAVMs. Reperfusion and occlusion were defined respectively as visualization or disappearance of the aneurysmal sac. The diagnostic accuracy of time-SLIP MRA was assessed and compared with standard reference images. Interobserver agreement was evaluated with the κ statistic. Results In the initial diagnosis group, time-SLIP MRA correctly determined the PAVMs in all but one patient with one lesion who had image degradation due to irregular breath. Image quality was considered excellent (median = 4) and the κ coefficient was 0.85. Additionally, both readers could correctly localize and classify the PAVMs on time-SLIP MRA images with both κ coefficient of 1.00. In the follow-up group, the sensitivity and specificity of time-SLIP MRA for reperfusion of PAVMs were both 100%, and the κ coefficient was 1.00. Conclusion Time-SLIP MRA is technically and clinically feasible and represents a promising technique for noninvasive pre- and post-treatment assessment of PAVMs.

Published
2016

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