著者

押尾 晃一

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

pp.2021-1752, (Released:2022-03-07)

参考文献数

10

---

Gradient echo sequences (GRE sequences) might look simple on the sequence diagram, but understanding their principles is more difficult. In this review, the four main types of GRE sequences are explained. Since GRE sequences rely on spin echoes as well as stimulated echoes, coherence pathways and echo formation are also explained. Moreover, the history of the development of GRE sequences is briefly described.

著者

藤原 康博 石田 翔太 木村 浩彦

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

pp.2020-1719, (Released:2020-09-28)

参考文献数

77

---

Arterial spin labeling (ASL) is a method for evaluating perfusion that uses magnetically labeled arterial blood water as an endogenous tracer. Although research and technical development have been conducted for a long time, introduction of ASL into clinical practice has been delayed because of its low signal-to-noise ratio (SNR). In recent years, advances in the pulse sequence and hardware, such as high static magnetic fields and high-sensitivity phased array coils, have made it possible to obtain high-SNR ASL images in a clinically acceptable time. In this regard, a consensus paper proposed simple and standard usage, including recommended techniques and parameters, to obtain a consistent image quality. Major MR manufacturers offered ASL pulse sequences based on this study. Hence, ASL has been used in clinical practice, and the effectiveness in measuring perfusion using ASL has been reported for the diagnosis of various neurological disorders. This article will review the technique for perfusion measurement and quantification and the recent technical progress in ASL.

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.2, pp.72-81, 2020-05-15 (Released:2020-06-15)

参考文献数

18

---

Recently, magnetic resonance imaging (MRI) of many medical devices has been allowed. However, risks of MRI of clothes, materials pasted on the body, body art, etc., are unclear. Moreover, the correspondence of the MRI operator with the patient varies. MRI is performed after removing such items that are removable. However, judgments regarding the items that are difficult to remove or cannot be removed are difficult to make. Operators need to correctly understand the risk level of each item to improve patient service and find out the appropriate method for performing MRI. As for dental implants, we need to understand their types, structure, and characteristics. For patients with tattoos, we must explain the risk of heating. Furthermore, we place a spacer between both legs, between a hand and gantry, when performing MRI to reduce the intensity of the induced current. As for nail art, thick gloves are effective for preventing suction and heating. As for thermal clothing, we should compare the risk level and frequency of occurrences of burns due to heating with fractures due to falling. When we perform MRI without removing thermal clothing, we should recognize the possibility of overheating and try to keep the patient from sweating. When we scanned cosmetics containing iron oxide with the upper limit level of the first standard management operation mode, the skin temperature rose by approximately 3℃ in approximately 10 min. When we perform MRI without removing makeup, we should tell the patient to use the emergency call instantly if a heat sensation is felt. When a heating test was performed under the same conditions as those created by cosmetics, the volunteers felt warm immediately after the start of the scan, and the scan had to be stopped within approximately 2 min because of heat. The temperature of hair rose to approximately 42℃. We should remove as much hair powder as possible because the head heats up and distorts the image. We performed MRI with a surgical hair cap on a patient. Risks posed by hair powder are higher than those posed by cosmetics. Furthermore, if hair powder splatters, the MRI scan becomes unusable. However, these items are not contraindications to MRI, and we may be able to perform MRI with adequate knowledge and attention. However, MRI cannot always be performed safely, and the highest risks during MRI are caused by incomplete knowledge and inappropriate techniques.

著者

三木 幸雄

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

pp.2020-1715, (Released:2020-09-28)

参考文献数

13

---

This article describes how to organize sentences in English papers on magnetic resonance field. In particular, “paragraph writing” and “coherence” are important skills required to logically organize sentences. This article explains them in detail with a number of examples from published papers on magnetic resonance. The ability to write in English may become less important in the near future due to the rapid progress of automatic translation technologies, using artificial intelligence (AI) such as Google Translate and DeepL. However, arranging English sentences and organizing them in a logical manner will continue to be an essential task for authors, even in the age of AI. I hope that this article will be of help to young researchers who plan to write manuscripts in English.

著者

対馬 義人

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.2, pp.55-61, 2020-05-15 (Released:2020-06-15)

参考文献数

27

---

In the European Society of Urogenital Radiology (ESUR) guidelines 10.0, the usefulness of premedication, such as steroids, which is widely used for patients with risk factors for acute (immediate) adverse effects, has been disproved, and the recommendation of premedication has been scrapped. Certainly, there is no evidence that premedication is effective for preventing the occurrence of adverse effects or reducing the severity. How this change would be applied in the actual clinical setting is controversial. There is no major change in management of acute adverse effects. For this point, however, recommendation no. 3 laid down by the Japan Medical Safety Research Organization in 2019 should be referred to. If anaphylaxis is suspected, 0.3 mg of adrenaline should be administered in the anterolateral thigh muscle without hesitation. Even if you are not convinced of anaphylaxis, an intramuscular injection of adrenaline must be given immediately. Moreover, adverse effects of intramuscular injections of 0.3 mg of adrenaline are not a cause for concern, as the injection route is not intravenous. The knowledge of nephrogenic systemic fibrosis (NSF) is already well established. This disease was first described in the 2018 edition of the Japanese National Examination Standard for Doctors. The use of linear gadolinium-based contrast agents with low chelate stability (except EOB Primovist) is extremely limited, and occurrence probability of NSF is extremely low as long as macrocyclic gadolinium-based contrast agents are used. Patient-related risk factors are eGFR <15 mL/min/1.73 m3 and dialysis. Gadolinium accumulation (retention) in the body and environmental diffusion have recently been described. Although the accumulation of gadolinium in the body is widely known, its clinical significance is unknown. Since gadolinium is an element, once it diffuses in the environment, it is almost impossible to recover it. However, its effect on humans is unknown.

著者

丸山 裕稔

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.2, pp.62-71, 2020-05-15 (Released:2020-06-15)

参考文献数

5

---

Optimization of scan parameter is important for acquiring high-quality image during MRI examination. This study describes the method of constructing a human-tissue-equivalent phantom useful in optimizing the scan parameter. The main ingredient of constructing phantom is gadolinium contrast agent. T1 and T2 values can be modulated by varying the concentration of gadolinium contrast agents and composing agarose. The construction of phantom is a time and effort intensive process. However, ample scan data are acquired using phantom scans. Comparing the phantom scans to that of volunteer scans will help objectively evaluate the quality of scanned images. Therefore, it is possible to set optimum scan parameter.

著者

礒田 治夫

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.39, no.4, pp.126-136, 2019-11-15 (Released:2019-12-05)

参考文献数

29

---

For larger blood vessels, such as cervical arteries and aortic arteries, 4D-Flow imaging with high signal to noise ratio (SNR) can be used to collect accurate measurements. When the SNR is sufficient and the voxel size is less than 30% of the vessel diameter, the error rate for the cross-sectional average flow velocity obtained by 4D-Flow is less than 10%. When the SNR is sufficient and the voxel size is less than 10% of the vessel diameter, error rate for the maximum flow velocity is also less than 10%. However, for smaller vessels, such as intracranial arteries, 4D-Flow imaging underestimates the flow velocities owing to the low spatial resolution or low SNR. Meanwhile, because of the partial volume phenomenon, the velocity of each voxel is underestimated within the vessel and overestimated near the vessel wall. Thus, the spatial resolution affects the velocity profile in the blood vessels. Higher spatial resolution leads to more accurate velocity profile and more accurate wall shear stress (WSS). However, it should be noted that the WSS determined by 4D-Flow is smaller compared to the true value. We can obtain the 3D velocity vector fields, maximum flow velocity, spatially averaged flow velocity, volume flow rate, streamlines, pathlines, streak lines, and WSS and its derivatives using a flow analysis software. The spatial resolution and SNR of 4D-Flow affects the accuracy of each voxel, velocity profile in blood vessels, and ultimately, the calculated WSS. However, there is a trade-off between the spatial resolution and SNR and hence there are limitations to increase the spatial resolution. Artificial intelligence (AI) may be able to interpolate lower spatial resolution data, and therefore, address this problem in the future. AI may also help us to obtain flow related biomarkers like WSS and its derivatives more easily and quickly in clinical practice. Development of the magnetic resonance fluid dynamics is ongoing and can provide a promising solution.

著者

北尾 梓 松井 修 米田 憲秀 小坂 一斗 小林 聡 香田 渉 井上 大 扇 尚弘 吉田 耕太郎 蒲田 敏文

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.3, pp.102-109, 2020-08-15 (Released:2020-09-26)

参考文献数

26

---

Hepatobiliary specific contrast medium Gd-EOB-DTPA-enhanced MRI (EOB-MRI) is excellent for the detection and characterization of nodular lesions and plays an important role in the diagnosis of hepatocellular carcinoma (HCC). Gd-EOB-DTPA is received by normal hepatocytes, and then, excreted into bile ducts, under mediation by hepatocyte membrane transporters. The expression of uptake transporter organic anion transporting polypeptide 1B3 (OATP1B3) correlates with the enhancement ratio in the hepatobiliary phase of HCC. Consequently, OATP1B3 is the main uptake transporter of Gd-EOB-DTPA in HCC. The hepatobiliary phase of EOB-MRI can sensitively detect pathologically early HCC as a hypointense nodule, because the OATP1B3 expression decreases at an early stage of multistep hepatocarcinogenesis. Hypervascular HCC commonly presents hypointensity in the hepatobiliary phase with the decrease in the OATP1B3 expression ; however, approximately 10% of HCC atypically demonstrates hyperintensity, owing to OATP1B3 overexpression. HCC presenting hyperintensity in the hepatobiliary phase is a unique genetic subtype of HCC with a biologically less aggressive nature and mature hepatocyte-like molecular/genetic features. The interaction between β-catenin signaling and hepatocyte nuclear factor (HNF) 4α may plays an important role in the OATP1B3 expression and less aggressive biological nature of the hyperintense HCC in the hepatobiliary phase. Thus, EOB-MRI is crucial for the detection and characterization of HCC as well as for personalized medicine, such as an imaging biomarker.

著者

藤原 康博 石田 翔太 木村 浩彦

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.4, pp.149-168, 2020-11-15 (Released:2020-12-15)

参考文献数

77

---

Arterial spin labeling (ASL) is a method for evaluating perfusion that uses magnetically labeled arterial blood water as an endogenous tracer. Although research and technical development have been conducted for a long time, introduction of ASL into clinical practice has been delayed because of its low signal-to-noise ratio (SNR). In recent years, advances in the pulse sequence and hardware, such as high static magnetic fields and high-sensitivity phased array coils, have made it possible to obtain high-SNR ASL images in a clinically acceptable time. In this regard, a consensus paper proposed simple and standard usage, including recommended techniques and parameters, to obtain a consistent image quality. Major MR manufacturers offered ASL pulse sequences based on this study. Hence, ASL has been used in clinical practice, and the effectiveness in measuring perfusion using ASL has been reported for the diagnosis of various neurological disorders. This article will review the technique for perfusion measurement and quantification and the recent technical progress in ASL.

著者

吉田 学誉

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.40, no.2, pp.48-54, 2020-05-15 (Released:2020-06-15)

参考文献数

12

---

Contrast-enhanced magnetic resonance imaging (CE-MRI) has overcome the drawback of non-CE-MRI of incomplete image information. However, the use of contrast agents requires consideration of the side effects and accident risks during injection, and the ability to respond promptly requires knowledge of treatment and management for the same. Side effects of contrast agents and accidents during contrast injections occur with a fixed probability. Attached documents and manuals describing side effects of contrast agents are provided by pharmaceutical companies, and many hospitals prepare manuals based on such information. However, little is known about puncture accidents during contrast agent injection, and the knowledge of treatment in case of accidents is often obtained from experience. Preventive measures for accidents during contrast media injections are necessary. Here, we elaborate our ideas on these safety measures.

著者

大内 翔平 伊藤 聡志

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.39, no.1, pp.29-32, 2019-02-15 (Released:2019-03-18)

参考文献数

5

---

Compressive sensing (CS) is an effective approach for fast magnetic resonance imaging (MRI). To improve the reconstruction accuracy and computational speed, we propose a novel deep architecture using deep learning. Experiments on MR image reconstruction demonstrate that proposed method significantly accelerates the reconstruction time, with image quality comparable to that of traditional iterative reconstruction.

著者

伊藤 憲之 濵﨑 望 堂領 和彦 尾﨑 裕

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.43, no.4, pp.174-181, 2023-11-15 (Released:2023-12-08)

参考文献数

15

---

Golden Angle Radial Sparse Parallel-Volumetric Interpolated Breath hold Examination (GRASP-VIBE) using compressed sensing and golden-angle radial sampling is a gradient echo (GRE) sequence that provides an inflow effect. The purpose of this study was to investigate parameters for non-contrast visualization of the renal artery using GRASP-VIBE with respiratory synchronization by the liver gate. We used a flow phantom and a self-made phantom to determine effective fat suppression methods and appropriate settings for repetition time (TR) and flip angle (FA). We also performed imaging on five healthy volunteers and compared the ability to visualize the renal artery. In the phantom study, water excitation showed the highest fat suppression effect ; the flow phantom was well visualized at TR 7.2 ms~9.0 ms and FA 9°~13°. In the volunteer study, the renal artery was best visualized at TR 7.2 ms and FA 13°. The results suggest that GRASP-VIBE can be used to visualize the renal artery without contrast enhancement by using the parameter settings examined in this study.

著者

桑島 成子

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.39, no.2, pp.39-47, 2019-05-15 (Released:2019-06-18)

参考文献数

15

---

Fetal magnetic resonance imaging (MRI) is an important diagnostic modality in adjunct with ultrasound (US). The purpose of fetal MRI is to complement an US, either by confirming the US findings or by acquiring additional findings. The use of fetal MRI has been increasing in the prenatal diagnosis of fetal neck, chest, and abdominal malformations, and it is well established in other fields, especially in that of fetal CNS anomalies. This study aimed to review the application and safety of fetal MRI.

著者

斎藤 勇哉 Peter A. Wijeratne 鎌形 康司 Christina Andica 内田 航 明石 俊昭 和田 昭彦 堀 正明 青木 茂樹

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

pp.2023-1790, (Released:2023-05-25)

参考文献数

28

---

Corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP) are sporadic atypical parkinsonian disorders associated with 4-repeat tauopathies. These neurodegenerative conditions closely overlap in their clinical information, pathology, and genetic risk factors ; therefore, it is difficult to accurately diagnose CBS and PSP. Recently, an unsupervised machine-learning technique, called Subtype and Stage Inference (SuStaIn), has been proposed to reveal the data-driven disease phenotypes with distinct temporal progression patterns from widely available cross-sectional data. To clarify the differences in the temporal white matter (WM) degeneration patterns between CBS and PSP, this study applied SuStaIn for fractional anisotropy (FA) in regional WM, which was sensitive to WM degeneration, based on cross-sectional brain diffusion MRI (dMRI) data. We obtained dMRI data from 15 healthy controls, 26 patients with CBS, and 25 patients with PSP. FA was calculated after fitting the diffusion tensor model to the corrected dMRI data for susceptibility and eddy-current induced geometric distortions and inter-volume subject motion. SuStaIn was applied to the cross-sectional regional WM tract FAs to identify both the disease subtypes and their trajectories with distinct WM degeneration patterns. To assess the performance of SuStaIn, the classification accuracy and sensitivity for CBS and PSP were calculated. SuStaIn revealed that the CBS degeneration started from the fornix and stria terminalis (FSTs) and corpus callosum (CC), followed by the posterior corona radiata (PCR), posterior thalamic radiation (PTR), and cerebral peduncle (CP), and subsequently extended to the cingulum. Finally, it reached the superior cerebral peduncle (SCP) and corticospinal tract (CST). In contrast, the PSP degeneration started from the SCP and cingulum, followed by the CST, and subsequently extended to the FST and CC. Eventually, it reached the PCR, PTR, and CP. Accordingly, SuStaIn classified CBS and PSP with 0.863 accuracy (sensitivity : CBS, 0.885 ; PSP, 0.840). The results suggested the utility of SuStaIn for classifying patients with CBS and PSP and identifying temporal WM degeneration patterns in patients with CBS and PSP.

著者

巨瀬 勝美

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.41, no.3, pp.61-66, 2021-08-15 (Released:2021-09-06)

参考文献数

9

---

Recent MRI technology and pulse sequences have become increasingly complex and difficult to understand. However, the Bloch equations, which are the basic principle of MRI, have remained unchanged since it was proposed in 1973. Here we have presented a method to numerically solve the Bloch equations to understand the principle of MRI. This method enables us to reproduce complex pulse sequences on a computer and to understand various phenomena related to pulse sequences.

著者

押尾 晃一

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.41, no.2, pp.37, 2021-05-15 (Released:2021-06-04)

参考文献数

1

---

According to the view that cerebrospinal fluid (CSF) and ISF exchange dynamically and form a pathway to remove waste products from the brain, CSF is likely to contain a high concentration of waste products. Based on recent results of T2 analyses, CSF seems to contain low protein, suggesting that this might not be the case.

著者

山口 さち子 井澤 修平 前谷津 文雄 圡井 司 引地 健生 藤田 秀樹 今井 信也 赤羽 学 王 瑞生

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.38, no.4, pp.103-119, 2018 (Released:2018-12-10)

参考文献数

27

---

In this study, we surveyed policies on allocating MRI scan duties to pregnant employees, and investigated the respondents' level of awareness of non-ionizing radiation. We sent 5763 questionnaires to facilities equipped with MRI devices in Japan (the corresponding respondent was a member of the personnel responsible for MRI scan duties). The questionnaire comprised: 1) Basic information; 2) General questions about the employees' pregnancies (e.g., whether the hospital has a particular policy); 3) The policy on MRI scan duties while pregnant and alternative duties ; and 4) Level of awareness of non-ionizing radiation in general. The results revealed inconsistent handling within Japan. Answers stating that ``increase the opportunity of allocation to MRI scan duties compared with the current situation'' accounted for 7.6%, ``maintaining the current frequency of allocation to MRI scan duties'' for 32.3%, and ``reduce the opportunity of allocation to MRI scan duties compared with current situation'' for 52.6%. Around half of facilities prepared work options (e.g. access restriction into MRI scan room or assign extra staff to MRI scan duties) in MRI scan duties during pregnancy. In an attitude survey for non-ionizing radiation emitted by medical devices, respondents showed higher attention compared with that for the radiation emitted by home electronic devices. This report describes a summary of the survey. Further analysis is in progress and will be reported soon.

著者

五十嵐 博中 湯浅 龍彦

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.38, no.4, pp.93-95, 2018 (Released:2018-12-10)

参考文献数

3

著者

曽我 茂義 大西 文夫 奥田 茂男 見越 綾子 三鍋 俊春 陣崎 雅弘 新本 弘

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.42, no.2, pp.53-57, 2022-05-15 (Released:2022-06-10)

参考文献数

11

---

This retrospective study analyzed the magnetic resonance lymphography (MRL) findings of 112 lower limbs of 56 lymphedema patients, and identified characteristic patterns of lymphatic impairment that change with the location in lower limbs and clinical stage. The authors proposed an MRL staging system that enables a new patient stratification based on the severity of the lymphatic injury, thus potentially improving clinical management.

著者

松田 豪

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.38, no.4, pp.96-102, 2018 (Released:2018-12-10)

参考文献数

23

---

Proton magnetic resonance spectroscopy (MRS) is widely used to detect alterations in cerebral metabolite levels in various neurological disorders. Data acquisitions with a short echo-time (TE) are recommended. Subsequently, provided that time permits, it is also recommended to apply long TE with shimming/adjustment of radiofrequency pulses and careful setting of voxels of interest. In those cases where contrast agents are administered, it is preferable to perform short-TE acquisitions using non-ionic media. Advanced systems with higher static magnetic field enable the detection of low-concentration metabolites, particularly when using short TE. MRS data acquisition and processing can be performed semi-automatically; however, sufficient knowledge and skills are needed to obtain high quality spectra.