Masamichi Imai

Hybrid of opposite-contrast magnetic resonance angiography of the brain by combining time-of-flight and black blood sequences: its value in moyamoya disease.

Objective: We assessed the value of a new magnetic resonance angiography (MRA) technique named hybrid of opposite-contrast (HOP) MRA in the diagnosis of moyamoya disease. Methods: Using a dual-echo sequence, we obtained the first echo for time-of-flight (TOF) MRA followed by the second echo for black blood MRA. We then subtracted the black blood MRA data set from that of the TOF MRA followed by maximum-intensity projection. In 14 patients, we performed HOP MRA and compared the findings with those on 3-dimensional TOF MRA and MR images. The HOP MRA was also compared with a radionuclide perfusion study (7 patients). Results: The HOP MRA technique improved the demonstration of distal arteries in 13 patients. The findings in HOP MRA correlated with MR images in 9 patients as well as with the perfusion study in 6 patients. Conclusions: The HOP MRA technique demonstrated the distal arterial branches in moyamoya disease well and facilitated the perfusion assessment with MR imaging.

Postoperative evaluation of superficial temporal artery-middle cerebral artery bypass using an MR angiography technique with combined white-blood and black-blood sequences

To assess the performance of the hybrid of opposite‐contrast MR angiography (HOP MRA) technique, which combines flow dephasing and compensating sequences, in the postoperative evaluation of superficial temporal artery (STA)‐middle cerebral artery (MCA) bypass.

Clinical application of an automatic slice-alignment method for cardiac MR imaging.

PURPOSE We evaluated the usefulness of an automatic slice-alignment method to simplify planning of cardiac magnetic resonance (MR) scans with a 3-tesla scanner. METHODS We obtained 2-dimensional (2D) axial multislice images using steady-state free precession (SSFP) sequences covering the whole heart at the end-diastole phase with electrocardiography (ECG) gating in 38 patients. We detected several anatomical feature points of the heart and calculated all planes required for cardiac imaging based on those points. We visually evaluated the acceptability of an acquired imaging plane and measured the angular differences of each view between the results obtained by this method and by a conventional manual pointing approach. RESULTS The average visual scores were 3.4 ± 1.0 for short-axis images, 3.2 ± 0.9 for 4-chamber images, 3.2 ± 0.8 for 2-chamber images, and 3.3 ± 0.8 for 3-chamber images; average angular differences were 5.8 ± 5.1 (short axis), 7.7 ± 5.7 (4-chamber), 11.5 ± 6.7 (2-chamber), and 9.1 ± 4.6 degrees (3-chamber). Processing time was within 1.8 s in all subjects. CONCLUSION The proposed method can provide planes within the clinically acceptable range and within a short time in cardiac imaging of patients with various cardiac shapes and diseases without the need for high level operator proficiency in performing the examination and interpreting results.

Influence of MRI-Conditional Cardiac Pacemakers on Quality and Interpretability of Images Acquired in 1.5-T Cardiac MRI

Purpose: The influence of MRI-conditional cardiac pacemakers on the quality and interpretability of images acquired in cardiac MRI (CMR) examinations was retrospectively investigated. Materials and methods: The subjects in this study were 12 patients (7 men and 5 women, mean age: 68.4 ± 8.7 years) with MRI-conditional cardiac pacemakers who underwent CMR examinations at our institution between July 2013 and December 2014. Two readers graded the quality of the acquired cine images, fat-suppressed black blood T2-weighted images, and late gadolinium enhancement (LGE) images. The extent of the artifacts caused by the implantable pulse generator (IPG) and the size of the artifacts caused by the leads were also measured. Results: All CMR examinations were performed safely. Image quality and interpretability were acceptable for the analysis of cardiac function and the evaluation of myocardial edema, scarring, and fibrosis, although deterioration of uniformity within the lumens due to magnetic field in homogeneity, artifacts from the leads (particularly those covering the left ventricular septal wall), and artifacts from the IPGs (particularly those covering the left ventricular anterior wall) were observed. Conclusion: CMR can be performed safely in patients with MRIconditional cardiac pacemakers, and images of sufficient quality for the assessment of cardiac anatomy and function can be obtained.

Automatic slice-alignment method in cardiac magnetic resonance imaging for evaluation of the right ventricle in patients with pulmonary hypertension

We propose a new automatic slice-alignment method, which enables right ventricular scan planning in addition to the left ventricular scan planning developed in our previous work, to simplify right ventricular cardiac scan planning and assess its accuracy and the clinical acceptability of the acquired imaging planes in the evaluation of patients with pulmonary hypertension. Steady-state free precession (SSFP) sequences covering the whole heart in the end-diastolic phase with ECG gating were used to acquire 2D axial multislice images. To realize right ventricular scan planning, two morphological feature points are added to be detected and a total of eight morphological features of the heart were extracted from these series of images, and six left ventricular planes and four right ventricular planes were calculated simultaneously based on the extracted features. The subjects were 33 patients (25 with chronic thromboembolic pulmonary hypertension and 8 with idiopathic pulmonary arterial hypertension). The fou...

Multi-ethnic evaluation of fully automatic planning assist system for cardiac magnetic resonance imaging.

Background We have been developing an automatic planning assist system for coach adjustment, local shimming scan plan, axial multi slice scan plan for slice-alignment, and whole-heart MR imaging plan (motion probes and an axial slab of main scan) [1,2]. However, the previous reposts of the system evaluated only Japanese patient’s and healthy volunteer’s datasets. The purpose of this study is to evaluate the accuracy for multi-ethnic datasets based on the inter-observer error in manual annotation.

Automatic 14-plane slice-alignment method for ventricular and valvular analysis in cardiac magnetic resonance imaging

Background Cardiac MRI examinations for valvular heart diseases have recently been a focus of attention [1]. However, the slice-alignment settings for valvular heart diseases are complex, difficult, and time-consuming operations. The purpose of this study is to develop an advanced automatic slice-alignment method that simultaneously detects the six left-ventricular planes (vertical long-axis, horizontal long-axis, short-axis, 4-chamber, 2-chamber, and 3-chamber views), the four right-ventricular planes (short-axis, 4-chamber, 2-chamber, and 3-chamber views), and also the four cardiac valvular planes (LVOT, RVOT, aortic valve, and pulmonary valve views) by extension of a previous work [2]. “’How I do’ CMR in valvular heart disease”, http://www.scmr.org.

Effects of quality of dictionary in knowledge- based 6-plane automatic slice-alignment method for cardiac magnetic resonance imaging

Summary We have developed a new automatic slice-alignment method that employs a combination of knowledge-based algorithm and model based algorithm to determine six planes at the same time. We have also evaluated the effects of the quality of the dictionary used in this method. The results showed that the robustness of slice determination in the proposed method can be improved as compared to the model-based only algorithm by using an appropriate dictionary and can be further improved if a larger number of patient datasets is used. Background We have developed a new automatic slice-alignment method that employs a combination of knowledge-based algorithm and model based algorithm to determine six planes at the same time. We have also evaluated the effects of the quality of the dictionary used in this method.

Improvement of knowledge-based automatic slice-alignment method for cardiac magnetic resonance imaging

Background Automatic slice alignment allows images of the six standard cardiac planes as defined in the SCMR Image Acquisition Protocols to be obtained by simple and quick operation. Our previously reported method can detect these planes using ECG-gated breath-hold axial multislice images [1]. Achieving higher accuracy and greater robustness for variation in clinical images will lead to improved usability and reliability, resulting in easier cardiac MR examinations. To achieve these goals, we have substantially refined our previously reported automatic slice-alignment method. A combination of knowledge-based recognition and image processing techniques is applied to multiple feature point search to reduce errors in automatic detection. Volunteer and clinical data were used to evaluate of the degree of improvement.