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Liver ImagingForum -
related threadsMRI Resource Directory:
 - Liver Imaging -
 
Liver imaging can be performed with sonography, computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound is, caused by the easy access, still the first-line imaging method of choice; CT and MRI are applied whenever ultrasound imaging yields vague results. Indications are the characterization of metastases and primary liver tumors e.g., benign lesions such as focal nodular hyperplasia (FNH), adenoma, hemangioma and malignant lesions (cancer) such as hepatocellular carcinomas (HCC). The decision, which medical imaging modality is more suitable, MRI or CT, is dependent on the different factors. CT is less costly and more widely available; modern multislice scanners provide high spatial resolution and short scan times but has the disadvantage of radiation exposure.
With the introduction of high performance MR systems and advanced sequences the image quality of MRI for the liver has gained substantially. Fast spin echo or single shot techniques, often combined with fat suppression, are the most common T2 weighted sequences used in liver MRI procedures. Spoiled gradient echo sequences are used as ideal T1 weighted sequences for evaluating of the liver. The repetition time (TR) can be sufficiently long to acquire enough sections covering the entire liver in one pass, and to provide good signal to noise. The TE should be the shortest in phase echo time (TE), which provides strong T1 weighting, minimizes magnetic susceptibility effects, and permits acquisition within one breath hold to cover the whole liver. A flip angle of 80° provides good T1 weighting and less of power deposition and tissue saturation than a larger flip angle that would provide comparable T1 weighting.
Liver MRI is very dependent on the administration of contrast agents, especially when detection and characterization of focal lesions are the issues. Liver MRI combined with MRCP is useful to evaluate patients with hepatic and biliary disease.
Gadolinium chelates are typical non-specific extracellular agents diffusing rapidly to the extravascular space of tissues being cleared by glomerular filtration at the kidney. These characteristics are somewhat problematic when a large organ with a huge interstitial space like the liver is imaged. These agents provide a small temporal imaging window (seconds), after which they begin to diffuse to the interstitial space not only of healthy liver cells but also of lesions, reducing the contrast gradient necessary for easy lesion detection. Dynamic MRI with multiple phases after i.v. contrast media (Gd chelates), with arterial, portal and late phase images (similar to CT) provides additional information.
An additional advantage of MRI is the availability of liver-specific contrast agents (see also Hepatobiliary Contrast Agents). Gd-EOB-DTPA (gadoxetate disodium, Gadolinium ethoxybenzyl dimeglumine, EOVIST Injection, brand name in other countries is Primovist) is a gadolinium-based MRI contrast agent approved by the FDA for the detection and characterization of known or suspected focal liver lesions.
Gd-EOB-DTPA provides dynamic phases after intravenous injection, similarly to non-specific gadolinium chelates, and distributes into the hepatocytes and bile ducts during the hepatobiliary phase. It has up to 50% hepatobiliary excretion in the normal liver.
Since ferumoxides are not eliminated by the kidney, they possess long plasmatic half-lives, allowing circulation for several minutes in the vascular space. The uptake process is dependent on the total size of the particle being quicker for larger particles with a size of the range of 150 nm (called superparamagnetic iron oxide). The smaller ones, possessing a total particle size in the order of 30 nm, are called ultrasmall superparamagnetic iron oxide particles and they suffer a slower uptake by RES cells. Intracellular contrast agents used in liver MRI are primarily targeted to the normal liver parenchyma and not to pathological cells. Currently, iron oxide based MRI contrast agents are not marketed.
Beyond contrast enhanced MRI, the detection of fatty liver disease and iron overload has clinical significance due to the potential for evolution into cirrhosis and hepatocellular carcinoma. Imaging-based liver fat quantification (see also Dixon) provides noninvasively information about fat metabolism; chemical shift imaging or T2*-weighted imaging allow the quantification of hepatic iron concentration.

See also Abdominal Imaging, Primovistâ„¢, Liver Acquisition with Volume Acquisition (LAVA), T1W High Resolution Isotropic Volume Examination (THRIVE) and Bolus Injection.

For Ultrasound Imaging (USI) see Liver Sonography at Medical-Ultrasound-Imaging.com.
 
Images, Movies, Sliders:
 Anatomic Imaging of the Liver  Open this link in a new window
      

 MRI Liver T2 TSE  Open this link in a new window
    
 
Radiology-tip.comradAbdomen CT,  Biliary Contrast Agents
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Medical-Ultrasound-Imaging.comLiver Sonography,  Vascular Ultrasound Contrast Agents
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• Related Searches:
    • Contrast Enhanced MRI
    • 2 Dimensional Acquisition
    • Abdominal Imaging
    • Reticuloendothelial Contrast Agents
    • Respiratory Compensation
 
Further Reading:
  Basics:
Comparison of liver scintigraphy and the liver-spleen contrast in Gd-EOB-DTPA-enhanced MRI on liver function tests
Thursday, 18 November 2021   by www.nature.com    
Liver Imaging Today
Friday, 1 February 2013   by www.healthcare.siemens.it    
Elastography: A Useful Method in Depicting Liver Hardness
Thursday, 15 April 2010   by www.sciencedaily.com    
Iron overload: accuracy of in-phase and out-of-phase MRI as a quick method to evaluate liver iron load in haematological malignancies and chronic liver disease
Friday, 1 June 2012   by www.ncbi.nlm.nih.gov    
  News & More:
Utility and impact of magnetic resonance elastography in the clinical course and management of chronic liver disease
Saturday, 20 January 2024   by www.nature.com    
Even early forms of liver disease affect heart health, Cedars-Sinai study finds
Thursday, 8 December 2022   by www.eurekalert.org    
For monitoring purposes, AI-aided MRI does what liver biopsy does with less risk, lower cost
Wednesday, 28 September 2022   by radiologybusiness.com    
Perspectum: High Liver Fat (Hepatic Steatosis) Linked to Increased Risk of Hospitalization in COVID-19 Patients With Obesity
Monday, 29 March 2021   by www.businesswire.com    
EMA's final opinion confirms restrictions on use of linear gadolinium agents in body scans
Friday, 21 July 2017   by www.ema.europa.eu    
T2-Weighted Liver MRI Using the MultiVane Technique at 3T: Comparison with Conventional T2-Weighted MRI
Friday, 16 October 2015   by www.ncbi.nlm.nih.gov    
EORTC study aims to qualify ADC as predictive imaging biomarker in preoperative regimens
Monday, 4 January 2016   by www.eurekalert.org    
MRI effectively measures hemochromatosis iron burden
Saturday, 3 October 2015   by medicalxpress.com    
Total body iron balance: Liver MRI better than biopsy
Sunday, 15 March 2015   by www.eurekalert.org    
MRI Resources 
Musculoskeletal and Joint MRI - Manufacturers - Movies - Intraoperative MRI - Online Books - Supplies
 
MAGNETOM Aera
 
www.healthcare.siemens.com/magnetic-resonance-imaging/0-35-to-1-5t-mri-scanner/magnetom-aera/ From Siemens Medical Systems;
Received FDA clearance in 2010.
The MAGNETOM Aera is a patient friendly, comfortable 1.5 Tesla MRI system with advanced radio frequency chain.
The system is equipped with the Tim 4G and Dot system (Total imaging matrix + Day optimizing throughput), to enhance both productivity and image quality.
Tim 4G technology provides improved SNR. The standard system configuration of 48 radio frequency channels and 204 coil elements creates an imaging matrix that allows maximum use of coil elements at full field of view. Dot provides improved image consistency through new features like auto align, auto FoV and automatic bolus detection.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Open bore
Head, spine, torso/ body coil, neurovascular, cardiac, neck, shoulder, knee, wrist, foot//ankle and multi-purpose flex coils. Peripheral vascular, breast, shoulder. Up to 60% more SNR with Tim 4G.
CHANNELS (min. / max. configuration)
48, 64
IMAGING TECHNIQUES
iPAT, mSENSE and GRAPPA (image, k-space), noncontrast angiography, plaque imaging, radial motion compensation, Dixon, improved workflow with Dot, Caipirinha - single digit breath-holds for 3-D body imaging.
MINIMUM TR
3-D GRE: 0.95 (256 matrix)
MINIMUM TE
3-D GRE: 0.22 (256 matrix), Ultra-short TE
FOV
0.5 - 50
BORE DIAMETER
or W x H
At isocenter: L-R 70 cm, A-P (with table) 55 cm
TABLE CAPACITY
250 kg
MAGNET WEIGHT (gantry included)
3121 kg
DIMENSION H*W*D (gantry included)
145 x 231 x 219 cm
5-GAUSS FRINGE FIELD
2.5 m / 4.0 m
CRYOGEN USE
Zero boil off rate, approx. 10 years
COOLING SYSTEM
Water
up to 200 T/m/s
MAX. AMPLITUDE
33 or 45 mT/m
3 linear with 20 coils, 5 nonlinear 2nd-order
POWER REQUIREMENTS
380 / 400 / 420 / 440 / 460 / 480 V, 3-phase + ground; 85 kVA
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MRI Resources 
Resources - MRI Reimbursement - Examinations - Homepages - Directories - Liver Imaging
 
Magnetization Prepared Rapid Gradient EchoInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(MP-GRE / MPRAGE / MP-RAGE) A fast 3D gradient echo pulse sequence using a magnetization preparation pulse like TurboFLASH. Only one segment or partition of a 3D data record is obtained per inversion preparation pulse. After the acquisition, for all rows a delay time (TD) is used to prevent saturation effects.
MPRAGE is designed for rapid acquisition with T1 weighted dominance. Fast gradient echoes are characterized by their rapid sampling time, high signal intensity and image contrast while approaching steady state (the echo is collected during the time when tissues are experiencing T1 relaxation). The rapid speed of the acquisition makes it an excellent alternative to breath-hold abdominal imaging, neuro, dynamic bolus, MR angiography and cardiac imaging.

See Gradient Echo Sequence.
 
Images, Movies, Sliders:
 Brain MRI Sagittal T1 001  Open this link in a new window
    
 
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• View the DATABASE results for 'Magnetization Prepared Rapid Gradient Echo' (3).Open this link in a new window

Searchterm 'bolus' was also found in the following service: 
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Nonionic Intravenous Contrast AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Radiographic low-osmolar nonionic contrast agents have less side effects and fewer nephrotoxicity than ionic, high-osmolar agents. Gadolinium-based MRI contrast agents have a different formulation from iodinated X-ray contrast media, and there is no known cross sensitivity between these two types of contrast agents. Intravenous MRI contrast agents, specifically the gadolinium chelates have a high safety and lack of nephrotoxicity compared with X-ray contrast media.
The used gadolinium chelates differ in following properties: linear (e.g., gadodiamide and gadoversetamide have nonionic linear structures) vs. macrocyclic cores, and ionic vs. nonionic types. The nonionic molecules have lower osmolality and viscosity, which increase digestibility at greater concentrations, and make faster bolus injections conceivable. The macrocyclic molecules (e.g., gadoteridol has a nonionic macrocyclic ring structure) are more stable and show fewer tendencies to dissociate free Gd.

See also ProHance®, Omniscan®, OptiMARK®, Ionic Intravenous Contrast Agents.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'
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• View the DATABASE results for 'Nonionic Intravenous Contrast Agents' (4).Open this link in a new window

 
Further Reading:
  News & More:
Spurious Hypocalcemia After Omniscan- or OptiMARK-Enhanced Magnetic Resonance Imaging: An Algorithm for Minimizing a False-Positive Laboratory Value
   by arpa.allenpress.com    
MRI Resources 
MRA - Pediatric and Fetal MRI - MRI Training Courses - - Sequences - Chemistry
 
Perfusion ImagingForum -
related threadsInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(PWI - Perfusion Weighted Imaging) Perfusion MRI techniques (e.g. PRESTO - Principles of Echo Shifting using a Train of Observations) are sensitive to microscopic levels of blood flow. Contrast enhanced relative cerebral blood volume (rCBV) is the most used perfusion imaging. Both, the ready availability and the T2* susceptibility effects of gadolinium, rather than the T1 shortening effects make gadolinium a suitable agent for use in perfusion imaging. Susceptibility here refers to the loss of MR signal, most marked on T2* (gradient echo)-weighted and T2 (spin echo)-weighted sequences, caused by the magnetic field-distorting effects of paramagnetic substances.
T2* perfusion uses dynamic sequences based on multi or single shot techniques. The T2* (T2) MRI signal drop within or across a brain region is caused by spin dephasing during the rapid passage of contrast agent through the capillary bed. The signal decrease is used to compute the relative perfusion to that region. The bolus through the tissue is only a few seconds, high temporal resolution imaging is required to obtain sequential images during the wash in and wash out of the contrast material and therefore, resolve the first pass of the tracer. Due to the high temporal resolution, processing and calculation of hemodynamic maps are available (including mean transit time (MTT), time to peak (TTP), time of arrival (T0), negative integral (N1) and index.
An important neuroradiological indication for MRI is the evaluation of incipient or acute stroke via perfusion and diffusion imaging. Diffusion imaging can demonstrate the central effect of a stroke on the brain, whereas perfusion imaging visualizes the larger 'second ring' delineating blood flow and blood volume. Qualitative and in some instances quantitative (e.g. quantitative imaging of perfusion using a single subtraction) maps of regional organ perfusion can thus be obtained.
Echo planar and potentially echo volume techniques together with appropriate computing power offer real time images of dynamic variations in water characteristics reflecting perfusion, diffusion, oxygenation (see also Oxygen Mapping) and flow.
Another type of perfusion MR imaging allows the evaluation of myocardial ischemia during pharmacologic stress. After e.g., adenosine infusion, multiple short axis views (see cardiac axes) of the heart are obtained during the administration of gadolinium contrast. Ischemic areas show up as areas of delayed and diminished enhancement. The MRI stress perfusion has been shown to be more accurate than nuclear SPECT exams. Myocardial late enhancement and stress perfusion imaging can also be performed during the same cardiac MRI examination.
 
Images, Movies, Sliders:
 Normal Lung Gd Perfusion MRI  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 Left Circumflex Ischemia First-pass Contrast Enhancement  Open this link in a new window
 
Radiology-tip.comradPerfusion Scintigraphy
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Medical-Ultrasound-Imaging.comBolus Injection
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• View the DATABASE results for 'Perfusion Imaging' (16).Open this link in a new window


• View the NEWS results for 'Perfusion Imaging' (3).Open this link in a new window.
 
Further Reading:
  Basics:
CHAPTER 55: Ischemia
2003
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
  News & More:
Non-invasive diagnostic procedures for suspected CHD: Search reveals informative evidence
Wednesday, 8 July 2020   by medicalxpress.co    
Implementation of Dual-Source RF Excitation in 3 T MR-Scanners Allows for Nearly Identical ADC Values Compared to 1.5 T MR Scanners in the Abdomen
Wednesday, 29 February 2012   by www.plosone.org    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by www.imm.dtu.dk    
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
Measuring Cerebral Blood Flow Using Magnetic Resonance Imaging Techniques
1999   by www.stanford.edu    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
MRI Resources 
Movies - Contrast Enhanced MRI - Liver Imaging - MR Myelography - Abdominal Imaging - NMR
 
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