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Current Protocols in Magnetic Resonance Imaging最新文献

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Motion Artifacts, Motion Compensation, and Magnetic Resonance Angiography 运动伪影，运动补偿和磁共振血管造影
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0700s13
Yu-Chung Norman Cheng, E. Mark Haacke
{"title":"Motion Artifacts, Motion Compensation, and Magnetic Resonance Angiography","authors":"Yu-Chung Norman Cheng, E. Mark Haacke","doi":"10.1002/0471142719.mib0700s13","DOIUrl":"10.1002/0471142719.mib0700s13","url":null,"abstract":"M otion artifacts can cause both blurring and ghosting of an image. It is thus important to understand the source of these artifacts in order to be able to avoid or eliminate them. UNIT B7.1 discusses the phase induced by motion and how it leads to these artifacts. Effects caused by motion in the read and phase-encoding direction are discussed, with the latter shown to be the culprit producing the majority of the artifacts. If this extra phase dependence on motion or flow can be eliminated, then the artifacts will be removed. This is best accomplished by redesigning the gradients in the sequence so that the motion-induced phase is zero at the echo time. Such a sequence is referred to as a velocity-compensated (gradient-moment-nulling) sequence. This is the subject of UNIT B7.2. Blood flow in vessels suffers from the above mentioned artifacts unless these velocity-compensation techniques are used. When these special motion compensation methods are successful, the blood vessels become very bright and are easily distinguished from the surrounding tissue. Imaging vessels using MRI is referred to as magnetic resonance angiography (MRA). In UNIT B7.3, the inflow effects (i.e., how the speed of blood flow affects the signal intensity of the blood in the images) is discussed. In addition, how the use of a contrast agent can be used to reduce T1 and thus further enhance the blood’s signal for a short TE, T1-weighted sequence is also treated in this unit.","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0700s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72626668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Imaging Concepts 成像的概念
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0400s13
Weili Lin
{"title":"Imaging Concepts","authors":"Weili Lin","doi":"10.1002/0471142719.mib0400s13","DOIUrl":"10.1002/0471142719.mib0400s13","url":null,"abstract":"T he first unit in this chapter (UNIT B4.1), addresses how echoes, including both spin and gradient echoes, are formed in an MR imaging experiment. After the application of an rf pulse, the longitudinal magnetization will be rotated from the direction parallel to the external magnetic field to the transverse plane. Because of the interaction among spins, as well as the potential field variation across the sample of interest, the spins will start to precess at different resonance frequencies, resulting in a signal reduction in MR images. This phenomenon is referred to as dephasing, one of the main topics addressed in this unit. Therefore, in order to obtain the maximal available MR signal, an echo will need to be formed so that all spins will again have the same phase. The basic concept of an echo is introduced and the characteristics as well as the pros and cons of the two different echoes, namely gradient and spin echoes, are also discussed.","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0400s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83759479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Phase Dependence on Motion 运动的相位依赖
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0701s13
Yu-Chung Norman Cheng, E. Mark Haacke
{"title":"Phase Dependence on Motion","authors":"Yu-Chung Norman Cheng,&nbsp;E. Mark Haacke","doi":"10.1002/0471142719.mib0701s13","DOIUrl":"10.1002/0471142719.mib0701s13","url":null,"abstract":"<p>This unit introduces the sources of variable phase in the presence of motion. The sources of these phase changes can come from the read gradient, from the slice select gradient and from the phase encoding gradient. Motion during the gradient moves the spin from one location to another and, therefore, changes the effective field it sees. This field change leads to a frequency change in time during either the dephasing or rephasing gradient or both. As a result, the spins do not refocus at the expected time.</p>","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0701s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83781326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Radiofrequency Excitation and Reception 射频激发与接收
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0200s13
Yu-Chung Norman Cheng, E. Mark Haacke
{"title":"Radiofrequency Excitation and Reception","authors":"Yu-Chung Norman Cheng,&nbsp;E. Mark Haacke","doi":"10.1002/0471142719.mib0200s13","DOIUrl":"10.1002/0471142719.mib0200s13","url":null,"abstract":"","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0200s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88705380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Infectious Diseases of the Brain 大脑传染病
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mia0400s13
Andrew E. Auber, Clifford Belden
{"title":"Infectious Diseases of the Brain","authors":"Andrew E. Auber,&nbsp;Clifford Belden","doi":"10.1002/0471142719.mia0400s13","DOIUrl":"10.1002/0471142719.mia0400s13","url":null,"abstract":"","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mia0400s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91307730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Shoulder 肩膀
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mia2200s13
Charles P. Ho
{"title":"Shoulder","authors":"Charles P. Ho","doi":"10.1002/0471142719.mia2200s13","DOIUrl":"10.1002/0471142719.mia2200s13","url":null,"abstract":"T he second most frequently and widely performed musculoskeletal extremity MRI examination involves the shoulder. Patients presenting with shoulder pain and dysfunction may have many derangements which can potentially coexist and can frequently overlap in clinical presentation. When physical examination is insufficient for diagnosis, or when additional information defining structural lesions is desired to assist the treating physician in planning medical or operative management, MRI can present a comprehensive examination of osseous and soft tissue structures about the shoulder. The two most frequently suspected sources of shoulder derangement involve rotator cuff disease and instability. The standard shoulder MRI protocol should evaluate both of these possibilities because of the very real possibility and frequency of overlap and coexistence of these problems in any given patient. In UNIT A22.1, the authors present their standard shoulder MRI examination, written to address possible cuff disease; however, this protocol also presents a very comprehensive look at possible instability lesions as well as other sources of shoulder problems.","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mia2200s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89193716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 96
Signal Detection 信号检测
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0201s13
Yu-Chung Norman Cheng, E. Mark Haacke
{"title":"Signal Detection","authors":"Yu-Chung Norman Cheng,&nbsp;E. Mark Haacke","doi":"10.1002/0471142719.mib0201s13","DOIUrl":"10.1002/0471142719.mib0201s13","url":null,"abstract":"<p>The bulk magnetization represents the equilibrium value of the magnetization when all spins have aligned themselves parallel to the main field. When this magnetization is tipped into the transverse plane, it precesses about the main field. This precession generates a changing flux through the face of an appropriately placed coil inducing an electromotive force (emf) in the coil. The measured signal is proportional to the induced emf. This unit discusses the basic physics behind detecting MR signal. The process of calculating induced emf based on Faradays law of induction is explained.</p>","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0201s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81474664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Basic Spin Properties and the Bloch Equations 基本自旋性质和布洛赫方程
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0300s13
Hongyu An, Weili Lin
{"title":"Basic Spin Properties and the Bloch Equations","authors":"Hongyu An,&nbsp;Weili Lin","doi":"10.1002/0471142719.mib0300s13","DOIUrl":"10.1002/0471142719.mib0300s13","url":null,"abstract":"In reality, spins are not isolated; instead, they interact with each other and their environment. The interaction of the spins with their surroundings leads to important modifications in their behavior. The experimentally determined spin-lattice relaxation time, T1, characterizes how quickly the longitudinal magnetization can grow back to its maximum value along the magnetic field direction. In contrast, T2 and T ∗ 2 are experimentally determined characteristic times describing the vanishing rate of the transverse magnetization. The T2 decay of signal is time-dependent and cannot be recovered, whereas part of the time-independent T ∗ 2 effect can be reversed by spin echo experiments.","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0300s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89350048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Rule Out (R/O) Migraine 排除(R/O)偏头痛
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mia0107s13
Steven Thibodeau, Ellen Grant
{"title":"Rule Out (R/O) Migraine","authors":"Steven Thibodeau,&nbsp;Ellen Grant","doi":"10.1002/0471142719.mia0107s13","DOIUrl":"10.1002/0471142719.mia0107s13","url":null,"abstract":"<p>When imaging patients with headaches, the goals are: (1) to rule out a more ominous etiology for their headaches and (2) to assess the degree of hemodynamic and parenchymal involvement when atypical or complicated migraine is suspected. The standard images allow other etiologies, such as mass lesions, to be excluded and an MR venogram can rule out venous sinus thrombosis. Contrast may be helpful in differentiating multiple small metastases, demylinating lesions with inflammatory components, and subcortical infarcts from the nonspecific foci of increased T<sub>2</sub> associated with migraines that do not enhance. Perfusion-weighted imaging allows detection assessment of hemodynamic compromise. Diffusion-weighted imaging, in combination with the standard MR images, allows assessment of parenchymal involvement. This unit contains a basic protocol which can be used for the evaluation of patients as well as an alternative protocol for the assessment of cerebral perfusion in patients with visual auras.</p>","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mia0107s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83054242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Sequences 序列
Current Protocols in Magnetic Resonance Imaging Pub Date : 2005-05-01 DOI: 10.1002/0471142719.mib0500s13
E. Mark Haacke
{"title":"Sequences","authors":"E. Mark Haacke","doi":"10.1002/0471142719.mib0500s13","DOIUrl":"10.1002/0471142719.mib0500s13","url":null,"abstract":"T his chapter introduces the reader to the signal response associated with different types of sequences. The first two units discuss short TR gradient echo sequences. Second only to spin-echo methods, these powerful gradient-echo techniques are used for rapid conventional and dynamic 2and 3-D imaging, most often for 3-D imaging of the brain and MR angiography. A proper understanding of the imaging parameters such as TR, TE, and flip angle are critical to their proper use.","PeriodicalId":100347,"journal":{"name":"Current Protocols in Magnetic Resonance Imaging","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/0471142719.mib0500s13","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76107258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 582
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