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 'Inversion Recovery Sequence' 
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Result : Searchterm 'Inversion Recovery Sequence' found in 1 term [] and 8 definitions [], (+ 10 Boolean[] results
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Double Inversion Recovery T1 MeasurementInfoSheet: - Sequences - 
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(DIR or DIRT1) Double inversion recovery T1 measurement is a T1 weighted black blood MRA sequence in which the signal from blood is suppressed. The inversion time to suppress blood is described as the duration between the initial inversion pulse and time point that the longitudinal magnetization of blood reaches the zero point. The readout starts at the blood suppression inversion time (BSP TI) and blood in the imaging slice gives no signal. This inversion time is around 650 ms with a 60 beat per minute heart rate at 1.5 T.
The TI can be decreased by using a wider receive bandwidth, shorter echo train length and/or narrow trigger window. Wide bandwidth also decreases the blurring caused by long echo trains at the expense of signal to noise ratio. In case of in plane or slow flow the suppression of the signal from blood may be incomplete. With increased TE or change of the image plane the blood suppression can be improved.
Double inversion recovery is a breath hold technique with one image per acquisition used in cardiovascular imaging. The patient is instructed to hold the breath in expiration (if not possible also inspiration can be taken), so that the end diastolic volume in the cardiac chambers would be the same during entire scanning. DIR provides fine details of the boundary between the lumen and the wall of the cardiac chambers and main vascular and heart structures, pericardium, and mediastinal tissues.
 
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 Normal Dual Inversion Fast Spin-echo  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 
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Flow Sensitive Alternating Inversion RecoveryInfoSheet: - Sequences - 
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(FAIR) In this sequence 2 inversion recovery images are acquired, one with a nonselective and the other with a slice selective inversion pulse. The z-magnetization in the first sequence is independent of flow. Inflowing spins give z-magnetization from second pulse. A major signal loss in FAIR is the T1 relaxation of tagged blood in transit to the imaging slice. Sharper edges of the inversion pulse give narrow spacing between the inversion edge and the 1st slice because reduced transit time gives lower T1 relaxation induced signal loss. The difference of the images in a consequence contains information proportional to flow (blood partition coefficient). Standard adiabatic inversion RF pulse does not have good slice-profile, because of power/SAR limitation. A c-shaped frequency offset corrected inversion (FOCI) RF pulse can help to increase the signal.
Perfusion imaging, e.g. myocardial, using tissue water as endogenous contrast is suggested.
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Inversion Recovery Fast Gradient Recalled Acquisition in the Steady StateInfoSheet: - Sequences - 
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(IR FGR) A gradient echo sequence with an inversion pulse.
See Gradient Recalled Echo Sequence, Inversion Recovery and Steady State Free Precession.
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Spin Echo Multi SliceInfoSheet: - Sequences - 
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(SEMS) This pulse sequence is composed of a 90 RF pulse followed by a 180 refocusing pulse. Both RF pulses are applied in the presence of a slice select gradient.
By choosing of different TR and TE, depending on the T1 and T2 values of the tissues, proton density, T1 weighted and T2 weighted images can be acquired.
The inversion recovery option enlarge the RF pulses with a 180 inverting pulse, applied a TI time before the beginning of the pulse sequence in order to manipulate image contrast.
See also Spin Echo Sequence.
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Further Reading:
  Basics:
Fast Spin Echo(.pdf)
Tuesday, 24 January 2006   by www.81bones.net    
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Saturation Recovery
 
(SR) Particular type of partial saturation pulse sequence in which the preceding pulses leave the spins in a state of saturation, so that recovery at the time of the next pulse has taken place from an initial condition of no magnetization. A rare used MRI pulse sequence that generates a predominantly proton density dependent signal, basically employing a 90 RF excitation pulse, with a very long repetition time. With this technique T1 times can be measured faster than with inversion recovery pulse sequences.
This saturation recovery sequence consists of multiple 90 radio frequency (RF) pulses with a short repetition time. A spoiler gradient pulse dephases the longitudinal magnetization that remains after the first 90 radio frequency pulse. A repetition time interval after the application of this spoiling gradient turns an additional 90 pulse the new developed longitudinal magnetization into the transverse plane, followed by recording a gradient echo.
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• View the DATABASE results for 'Saturation Recovery' (5).Open this link in a new window

 
Further Reading:
  Basics:
Contrast mechanisms in magnetic resonance imaging
2004   by www.iop.org    
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