Liver MRI Technique: Pulse Sequences and Contrast Agents

2010 ◽  
Vol 41 (2) ◽  
pp. 47-56 ◽  
Author(s):  
Joseph Trieu ◽  
Louis Wu
Keyword(s):  
Contrast Agents ◽  
Pulse Sequences ◽  
Liver Mri

scholarly journals Magnetic Nanoparticles as In Vivo Tracers for Alzheimer’s Disease

2020 ◽  
Vol 6 (1) ◽  
pp. 13
Author(s):  
Bhargy Sharma ◽  
Konstantin Pervushin
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Diagnosis ◽  
Contrast Agents ◽  
Neurological Diseases ◽  
Pulse Sequences ◽  
Experimental Conditions ◽  
Magnetic Resonance Imaging Mri ◽  
The Brain

Drug formulations and suitable methods for their detection play a very crucial role in the development of therapeutics towards degenerative neurological diseases. For diseases such as Alzheimer’s disease, magnetic resonance imaging (MRI) is a non-invasive clinical technique suitable for early diagnosis. In this review, we will discuss the different experimental conditions which can push MRI as the technique of choice and the gold standard for early diagnosis of Alzheimer’s disease. Here, we describe and compare various techniques for administration of nanoparticles targeted to the brain and suitable formulations of nanoparticles for use as magnetically active therapeutic probes in drug delivery targeting the brain. We explore different physiological pathways involved in the transport of such nanoparticles for successful entry in the brain. In our lab, we have used different formulations of iron oxide nanoparticles (IONPs) and protein nanocages as contrast agents in anatomical MRI of an Alzheimer’s disease (AD) brain. We compare these coatings and their benefits to provide the best contrast in addition to biocompatibility properties to be used as sustainable drug-release systems. In the later sections, the contrast enhancement techniques in MRI studies are discussed. Examples of contrast-enhanced imaging using advanced pulse sequences are discussed with the main focus on important studies in the field of neurological diseases. In addition, T1 contrast agents such as gadolinium chelates are compared with the T2 contrast agents mainly made of superparamagnetic inorganic metal nanoparticles.

OPTIMAL DOSE OF MR CONTRAST AGENT IN T1-WEIGHTED MRI

2004 ◽  
Vol 16 (06) ◽  
pp. 331-336 ◽  
Author(s):  
C-C HSIAO ◽  
J-C JAO ◽  
Y-N TING ◽  
H-B PAN ◽  
P-C CHEN
Keyword(s):  
Contrast Agents ◽  
Pulse Sequences ◽  
Optimal Dose ◽  
Mri Contrast Agents ◽  
Lesion Detection ◽  
The Body ◽  
Rapid Expansion ◽  
Enhanced Mri ◽  
Contrast Enhanced ◽  
Contrast Enhanced Mri

Nowadays magnetic resonance imaging (MRI) has been commonly used in many indications. Concurrent development of MRI contrast agents has aided the rapid expansion and increased clinical efficacy. The use of contrast agents can improve lesion detection and characterization. With the contrast enhancement, lesion conspicuity is dramatically increased. Therefore, contrast enhanced MRI could provide more accurate diagnosis and be helpful for further therapy. The routinely used dose of contrast agents suggested by the documents only relies on the body weight of the subject. However, the relationship between the signal enhancement and the dose of contrast agents needs to be further investigated in order to achieve the maximum enhancement from optimal dose of the contrast agents. The aim of this study is to obtain the optimal dose of two contrast agents (Magnivist and Omniscan) for various T1-weighted pulse sequences (SE, SPGR, 2D TOF and 3D TOF) and various coils (body coil, NV array coil and head coil). The optimal dose is defined as achieving the MR images with the highest enhancement. The results show that there are significant differences in optimal dose among various pulse sequences. However, there are no significant differences in optimal dose among various coils and these two contrast agents. The advantage of finding optimal dose is to minimize dose and potential toxicity, and furthermore to decrease the cost of contrast agents. This study was done on a phantom, and it is expected to provide useful information to the contrast enhanced MRI in the routine clinical diagnosis and research in the future.

MRI contrast agents

2018 ◽  
pp. 63-69
Author(s):  
Kim-Lien Nguyen ◽  
J Paul Finn
Keyword(s):  
Contrast Agents ◽  
Common Factor ◽  
Pulse Sequences ◽  
Negative Contrast ◽  
Positive Contrast ◽  
Mri Contrast Agents ◽  
Magnetic Resonance Imaging Examination ◽  
Hypersensitivity Reactions ◽  
Mri Contrast ◽  
Tissue Contrast

Pharmacologic agents used in the context of a cardiovascular magnetic resonance imaging examination can be divided into three main groups: contrast agents, stress-testing agents (dobutamine, adenosine, regadenoson, dipyridamole), and agents used for treatment of hypersensitivity reactions. The safety of stress agents will be elaborated in the chapter on ischaemic heart disease. This chapter will focus on contrast agents and briefly touch upon medications used in the setting of hypersensitivity reactions. Contrast agents are used to further augment tissue contrast and have become an integral component of cardiovascular imaging. These agents typically exert strong T1 shortening (gadolinium or manganese chelates, positive contrast) or T2 shortening (iron oxide particles, negative contrast). In some cases, very small iron particles may produce enhancement on either T1- or T2-weighted pulse sequences. The common factor lies in the paramagnetic properties of the material when exposed to an external magnetic field. The largest group of compounds consists of gadolinium-based contrast agents (GBCAs). Since the first description of nephrogenic systemic fibrosis in patients with renal insufficiency in 2000, and subsequent alerts by the US Food and Drug Administration and the European Medicines Association, interest in the safety of GBCAs has increased, along with concerted efforts to seek alternative contrast agents. Overall however, GBCAs are well tolerated.

Use of contrast agents for liver MRI

Radiography ◽  
2007 ◽  
Vol 13 ◽  
pp. e54-e72 ◽  
Author(s):  
Janice Ward
Keyword(s):  
Contrast Agents ◽  
Liver Mri

scholarly journals MRI- and CT-venography in the diagnosis of hemodynamic disorders in patients suffering from lower extremities chronic venous disorders. Part II. Possibilities of MRI in diagnostics of the deep vein thrombosis

2021 ◽  
Vol 25 (1) ◽  
pp. 117-139
Author(s):  
E. V. Shajdakov ◽  
A. B. Sannikov ◽  
V. M. Emelyanenko ◽  
L. N. Kryukova ◽  
A. E. Baranova ◽  
...  
Keyword(s):  
Blood Flow ◽  
Magnetic Resonance ◽  
Contrast Agents ◽  
Lower Limb ◽  
Pulse Sequences ◽  
Vena Cava ◽  
Venous Blood Flow ◽  
Vein Thrombosis ◽  
Thrombus Imaging ◽  
Specificity And Sensitivity

In this literature review, the analysis of the studies of venous blood flow pathology in the inferior Vena cava system using magnetic resonance imaging (MRI) is carried out. Special attention is paid to the attempts made to use this method in the diagnosis of chronic lower limb vein disorders (CVD) through magnetic resonance venography (MRV). Historically and methodically, the gradual introduction of MRV methods in the diagnosis of lower limb vein thrombosis (LEDVT) and venous thromboembolism (VTE) has been shown.Methods of non-contrast MRV based on the effect of blood flow, as in the case of MR-Angiography, are divided into two principal groups: methods based on the amplitude effects of Time-of-Flight (TOF) and methods based on Phase Contrast effects (PC). Techniques for conducting contrast-free MRV are described in detail. Attention is paid to pulse sequences used in the world for visualization of veins in contrast-free MRV in TOF and PC mode (FR-FBI, SPADE, SSFP) and post-processing methods: 2D-TOF MRV FLASH, 2D-TOF MRV CRASS, FIPS, VED, VENS.Contrast-enhanced MRV (CE MRV) is based on the use of “blood pool” contrast agents, which feature the ability to form stable compounds with blood plasma proteins. Worldwidesubstances with magnetic and supermagnetic properties based on gadolinium or iron oxide are used as contrast agents for CE MRV. The result of using these contrast agents is an increase in the quality of visualization due to a better signal to noise ratio (SNR) using 3D image processing (3D CE MRV) using fast sequences: GRE, TFLAS, VESPA, CAT, in conditions of direct and indirect CE MRV.It is noted that in recent years, certain restrictions have been imposed on certain linear contrast agents containing gadolinium in their further use. Therefore, for the purpose of CE MRV, it is efficientl to use only cyclic contrast agents to avoid unnecessary risks.Contrast-free MRV has again received intensive development in recent years, due to the restrictions imposed, one of these methods is direct thrombus imaging (Direct Thrombus Imaging – DTI or Magnetic Resonance Direct Thrombus Imaging - MRDTI) using fast pulse sequences: bSSFP, BBTI, DANTE. The latest research on this LEDVT diagnostic method was published in 2019 and has shown high diagnostic value.For all the most commonly used methods of MRV, specificity and sensitivity are shown.Further MRV in patients with CVD and DVT is a promising diagnostic task in modern phlebology. MRV should be introduced into clinical practice more actively than it is today.

scholarly journals Ultrafast amplitude modulation for molecular and hemodynamic ultrasound imaging

2021 ◽  
Author(s):  
Claire Rabut ◽  
Di Wu ◽  
Bill Ling ◽  
Zhiyang Jin ◽  
Dina Malounda ◽  
...  
Keyword(s):  
Contrast Agents ◽  
Amplitude Modulation ◽  
Imaging Modality ◽  
Pulse Sequences ◽  
Frame Rate ◽  
Wide Field ◽  
Contrast Imaging ◽  
Rapid Discrimination

Ultrasound is playing an emerging role in molecular and cellular imaging thanks to new micro- and nanoscale contrast agents and reporter genes. Acoustic methods for the selective in vivo detection of these imaging agents are needed to maximize their impact in biology and medicine. Existing ultrasound pulse sequences use the nonlinearity in contrast agents response to acoustic pressure to distinguish them from mostly linear tissue scattering. However, such pulse sequences typically scan the sample using focused transmissions, resulting in a limited frame rate and restricted field of view. Meanwhile, existing wide-field scanning techniques based on plane wave transmissions suffer from limited sensitivity or nonlinear artifacts. To overcome these limitations, we introduce an ultrafast nonlinear imaging modality combining amplitude-modulated pulses, multiplane wave transmissions and selective coherent compounding. This technique achieves contrast imaging sensitivity comparable to much slower gold-standard amplitude modulation sequences and enables the acquisition of larger and deeper fields of view, while providing a much faster imaging framerate of 3.2kHz. Additionally, it enables simultaneous nonlinear and linear image formation, and allows concurrent monitoring of phenomena accessible only at ultrafast framerates, such as blood volume variations. We demonstrate the performance of this ultrafast amplitude modulation (uAM) technique by imaging gas vesicles, an emerging class of genetically encodable biomolecular contrast agents, in several in vitro and in vivo contexts. These demonstrations include the rapid discrimination of moving contrast agents and the real-time monitoring of phagolysosomal function in the mouse liver.

scholarly journals Four pulse sequences necessary for liver MRI interpretation

2020 ◽  
pp. 56-67
Author(s):  
Linda Brown
Keyword(s):  
Imaging Modality ◽  
Pulse Sequences ◽  
Liver Mri ◽  
Multiple Pulse

MRI is the best imaging modality for detection and characterization of liver masses. There are multiple pulse sequences used in MRI and they can be confusing and difficult to understand. Therefore, four important pulse sequences are introduced in this article in order to simplify the seemingly complex pulse sequences, and allow general radiologists and clinicians of all specialties to approach MRI of liver masses with ease.

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