Magnetic Resonance - Technology Information Portal Welcome to MRI Technology
Info
  Sheets


Out-
      side
 



 
 'tof' 
SEARCH FOR    
 
  2 3 5 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
 TOF            Time Of Flight 
Searchterm 'tof' was found in the Abbreviation Register. 
Result : Searchterm 'tof' found in 0 term [] and 40 definitions []
1 - 5 (of 40)     next
Result Pages : [1 2 3 4 5 6 7 8]
Searchterm 'tof' was also found in the following services: 
spacer
Resources  (5)  Forum  (2)  
 
Multiple Overlapping Thin Slab (Slice) Acquisition
 
(MOTSA) This technique combines the best features of 2D time of flight angiography (2D TOF) and 3D TOF MRA. The MOTSA technique consists of multiple 2 cm thick 3D TOF slabs (which minimize saturation effects for through plane flow) combine to provide unlimited coverage similar to multiple 2D TOF slices. High resolution imaging of the carotid arteries is possible when image quality is of greater concern than acquisition time. Images with 1 mm (or less) spatial resolution in all three planes are required. The slabs typically overlap 25-40 to minimize the venetian blind artifact venetian blind artifact due to minimal saturation effects. MOTSA is an useful technique for the evaluation of vertebrobasilar ischemia and aneurysm scanning from the foramen magnum through the circle of Willis.
 
Images, Movies, Sliders:
 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
spacer
 
• Share the entry 'Multiple Overlapping Thin Slab (Slice) Acquisition':  Facebook  Twitter  LinkedIn  
MRI Resources 
Claustrophobia - Spine MRI - MRA - Services and Supplies - Safety pool - Databases
 
2 Dimensional Time of Flight Magnetic Resonance AngiographyInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - MRA -
 
(2D TOF MRA) This form of MR angiography is based on the acquisition of multiple, short-TR, gradient echo single slice images. 2D TOF MRA is the preferred technique for visualizing slow flow, how for example it happens in veins. 2D TOF MRA consists of multiple sequentially-acquired single slices, therefore the saturation effects are minimized.
spacer
MRI Resources 
Developers - Pathology - IR - Corporations - Services and Supplies - Online Books
 
3 Dimensional Magnetic Resonance AngiographyInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - MRA -
 
(3D MRA) The 3D angiography technique can be applied to focus on fast flowing (arterial) blood and to visualize small tortuous vessels. 3D TOF images are less sensitive to turbulent flow artifacts. The advantage of this approach is that the signal, acquired from the entire volume has an increased signal to noise ratio. Slices are defined by a second phase encoded axis, which divides the volume into 'partitions'. 3D TOF MRA is acquired with 3D FT slabs or multiple overlapping thin 3D FT slabs (MOTSA) depending on the coverage required and the range of flow-velocities under examination.
Such 3D techniques can provide equal spatial resolution along all three axes, i.e. be 'isotropic', or the partition thickness can be greater or less than the in plane spatial resolution in which case can be said to be 'anisotropic'. The circle of Willis, anatomy as well as its fast arterial flow, lends itself well to both 3D TOF and 2D or 3D phase contrast angiography.
 
Images, Movies, Sliders:
 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 PCA-MRA 3D Brain Venography Colored MIP  Open this link in a new window
    

 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
spacer

• View the DATABASE results for '3 Dimensional Magnetic Resonance Angiography' (2).Open this link in a new window

 
Further Reading:
  Basics:
CHAPTER 55: Ischemia
2003
Magnetic resonance angiography: current status and future directions
Wednesday, 9 March 2011   by www.jcmr-online.com    
Searchterm 'tof' was also found in the following services: 
spacer
Resources  (5)  Forum  (2)  
 
Magnetic Resonance Angiography MRAMRI Resource Directory:
 - MRA -
 
(MRA) Magnetic resonance angiography is a medical imaging technique to visualize blood filled structures, including arteries, veins and the heart chambers. This MRI technique creates soft tissue contrast between blood vessels and surrounding tissues primarily created by flow, rather than displaying the vessel lumen. There are bright blood and black blood MRA techniques, named according to the appearance of the blood vessels. With this different MRA techniques both, the blood flow and the condition of the blood vessel walls can be seen. Flow effects in MRI can produce a range of artifacts. MRA takes advantage of these artifacts to create predictable image contrast due to the nature of flow.
Technical parameters of the MRA sequence greatly affect the sensitivity of the images to flow with different velocities or directions, turbulent flow and vessel size.
This are the three main types of MRA:
time of flight angiography (TOF)
phase contrast angiography (PCA)
contrast enhanced magnetic resonance angiography (CE-MRA)
All angiographic techniques differentially enhance vascular MR signal. The names of the bright blood techniques TOF and PCA reflect the physical properties of flowing blood that were exploited to make the vessels appear bright. Contrast enhanced magnetic resonance angiography creates the angiographic effect by using an intravenously administered MR contrast agent to selectively shorten the T1 of blood and thereby cause the vessels to appear bright on T1 weighted images.
MRA images optimally display areas of constant blood flow-velocity, but there are many situations where the flow within a voxel has non-uniform speed or direction. In a diseased vessel these patterns are even more complex. Similar loss of streamline flow occurs at all vessel junctions and stenoses, and in regions of mural thrombosis. It results in a loss of signal, due to the loss of phase coherence between spins in the voxel.
This signal loss, usually only noticeable distal to a stenosis, used to be an obvious characteristic of MRA images. It is minimized by using small voxels and the shortest possible TE. Signal loss from disorganized flow is most noticeable in TOF imaging but also affects the PCA images.
Indications to perform a magnetic resonance angiography (MRA):
Detection of aneurysms and dissections
Evaluation of the vessel anatomy, including variants
Blockage by a blood clot or stenosis of the blood vessel caused by plaques (the buildup of fat and calcium deposits)
Conventional angiography or computerized tomography angiography (CT angiography) may be needed after MRA if a problem (such as an aneurysm) is present or if surgery is being considered.
See also Magnetic Resonance Imaging MRI.
 
Images, Movies, Sliders:
 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 TOF-MRA Circle of Willis Inverted MIP  Open this link in a new window
    

 PCA-MRA 3D Brain Venography Colored MIP  Open this link in a new window
    

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
Radiology-tip.comCT Angiography,  Angiogram
spacer
Radiology-tip.comVascular Ultrasound,  Intravascular Ultrasound
spacer

• View the DATABASE results for 'Magnetic Resonance Angiography MRA' (3).Open this link in a new window


• View the NEWS results for 'Magnetic Resonance Angiography MRA' (10).Open this link in a new window.
 
Further Reading:
  Basics:
MR–ANGIOGRAPHY(.pdf)
Magnetic resonance angiography: current status and future directions
Wednesday, 9 March 2011   by www.jcmr-online.com    
  News & More:
CHAPTER 55: Ischemia
2003
TOSHIBA'S CONTRAST-FREE MRA TECHNIQUES IMPROVE PATIENT SAFETY AT LITTLE COMPANY OF MARY
Thursday, 25 February 2010   by medical.toshiba.com    
MRI Resources 
General - Shielding - Abdominal Imaging - Patient Information - Breast MRI - Movies
 
Time of Flight AngiographyInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - MRA -
 
(TOF) The time of flight angiography is used for the imaging of vessels. Usually the sequence type is a gradient echo sequences with short TR, acquired with slices perpendicular to the direction of blood flow.
The source of diverse flow effects is the difference between the unsaturated and presaturated spins and creates a bright vascular image without the invasive use of contrast media. Flowing blood moves unsaturated spins from outside the slice into the imaging plane. These completely relaxed spins have full equilibrium magnetization and produce (when entering the imaging plane) a much higher signal than stationary spins if a gradient echo sequence is generated. This flow related enhancement is also referred to as entry slice phenomenon, or inflow enhancement.
Performing a presaturation slab on one side parallel to the slice can selectively destroy the MR signal from the in-flowing blood from this side of the slice. This allows the technique to be flow direction sensitive and to separate arteriograms or venograms. When the local magnetization of moving blood is selectively altered in a region, e.g. by selective excitation, it carries the altered magnetization with it when it moves, thus tagging the selected region for times on the order of the relaxation times.
For maximum flow signal, a complete new part of blood has to enter the slice every repetition (TR) period, which makes time of flight angiography sensitive to flow-velocity. The choice of TR and slice thickness should be appropriate to the expected flow-velocities because even small changes in slice thickness influences the performance of the TOF sequence. The use of sequential 2 dimensional Fourier transformation (2DFT) slices, 3DFT slabs, or multiple 3D slabs (chunks) are depending on the coverage required and the range of flow-velocities.
3D TOF MRA is routinely used for evaluating the Circle of Willis.
See also Magnetic Resonance Angiography and Contrast Enhanced Magnetic Resonance Angiography.
 
Images, Movies, Sliders:
 TOF-MRA Circle of Willis Inverted MIP  Open this link in a new window
    

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 
Radiology-tip.comCT Angiography,  Coronary Angiogram
spacer
Radiology-tip.comColor Power Angio,  Doppler Ultrasound
spacer

• View the DATABASE results for 'Time of Flight Angiography' (11).Open this link in a new window

 
Further Reading:
  Basics:
MR–ANGIOGRAPHY(.pdf)
  News & More:
Magnetic resonance angiography: current status and future directions
Wednesday, 9 March 2011   by www.jcmr-online.com    
MRI Resources 
MRI Centers - MR Guided Interventions - Education pool - Diffusion Weighted Imaging - Portals - Universities
 
     1 - 5 (of 40)     next
Result Pages : [1 2 3 4 5 6 7 8]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

MR-TIP    
Community   
User
Pass
Forgot your UserID/Password ?  



Difference between ARMRIT and ARRT is :
cost 
duration 
exam 
acceptance 
salary 
all 
none 

Look
      Ups





Magnetic Resonance - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • US-TIP • The-Medical-Market
Copyright © 2003 - 2014 SoftWays. All rights reserved. [ 23 October 2014]
Terms of Use | Privacy Policy | Advertising
 [last update: 2014-09-28 05:33:09]