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Contrast-enhanced magnetic resonance angiography.

Svensson, Jonas LU (2003) In Acta Radiologica 44(S429). p.7-7
Abstract
Contrast-enhanced magnetic resonance angiography (CE-MRA) is a diagnostic method for imaging of vascular structures based on nuclear magnetic resonance. Vascular enhancement is achieved by injection of a contrast medium (CM). Studies were performed using two different types of CM: conventional paramagnetic CM, and a new type of CM based on hyperpolarized (HP) nuclei.



The effects of varying CM concentration with time during image acquisition were studied by means of computer simulations using two different models. It was shown that a rapid concentration variation during encoding of the central parts of k-space could result in signal loss and severe image artifacts. The results were confirmed qualitatively with phantom... (More)
Contrast-enhanced magnetic resonance angiography (CE-MRA) is a diagnostic method for imaging of vascular structures based on nuclear magnetic resonance. Vascular enhancement is achieved by injection of a contrast medium (CM). Studies were performed using two different types of CM: conventional paramagnetic CM, and a new type of CM based on hyperpolarized (HP) nuclei.



The effects of varying CM concentration with time during image acquisition were studied by means of computer simulations using two different models. It was shown that a rapid concentration variation during encoding of the central parts of k-space could result in signal loss and severe image artifacts. The results were confirmed qualitatively with phantom experiments.



A postprocessing method was developed to address problems with simultaneous enhancement of arteries and veins in CE-MRA of the lower extremities. The method was based on the difference in flow-induced phase in the two vessel types. Evaluation of the method was performed with flow phantom measurements and with CE-MRA in two volunteers using standard pulse sequences. The flow-induced phase in the vessels of interest was sufficient to distinguish arteries from veins in the superior-inferior direction. Using this method, the venous enhancement could be extinguished.



The possibility of using HP nuclei as CM for CE-MRA was evaluated. Signal expressions for a flow of HP CM imaged with a gradient echo sequence were derived. These signal expressions were confirmed in phantom experiments using HP 129Xe dissolved in ethanol.



Studies were also performed with a new CM based on HP 13C. The CM had very long relaxation times (T1,in vivo/T2,in vivo≈ 38/1.3 s). The long relaxation times were utilized in imaging with a fully balanced steady-state free precession pulse sequence (trueFISP), where the optimal flip angle was found to be 180°. CE-MRA with the 13C-based CM in rats resulted in images with high vascular SNR (~500).



CE-MRA is a useful clinical tool for diagnosing vascular disease. With the development of new contrast media, based on hyperpolarized nuclei for example, there is a potential for further improvement in the signal levels that can be achieved, enabling a standard of imaging of vessels that is not possible today. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
magnetic resonance, hyperpolarized, contrast-enhanced MRA, angiography
in
Acta Radiologica
volume
44
issue
S429
pages
7 - 7
publisher
John Wiley & Sons
external identifiers
  • wos:000184335800001
  • scopus:0041508799
ISSN
1600-0455
DOI
10.1034/j.1600-0455.44.s.429.1.x
language
English
LU publication?
yes
id
d3bb3d3c-84d9-48d8-9d85-425dde5a25e1 (old id 113816)
date added to LUP
2007-07-30 14:07:05
date last changed
2018-05-29 11:29:26
@article{d3bb3d3c-84d9-48d8-9d85-425dde5a25e1,
  abstract     = {Contrast-enhanced magnetic resonance angiography (CE-MRA) is a diagnostic method for imaging of vascular structures based on nuclear magnetic resonance. Vascular enhancement is achieved by injection of a contrast medium (CM). Studies were performed using two different types of CM: conventional paramagnetic CM, and a new type of CM based on hyperpolarized (HP) nuclei.<br/><br>
<br/><br>
The effects of varying CM concentration with time during image acquisition were studied by means of computer simulations using two different models. It was shown that a rapid concentration variation during encoding of the central parts of k-space could result in signal loss and severe image artifacts. The results were confirmed qualitatively with phantom experiments.<br/><br>
<br/><br>
A postprocessing method was developed to address problems with simultaneous enhancement of arteries and veins in CE-MRA of the lower extremities. The method was based on the difference in flow-induced phase in the two vessel types. Evaluation of the method was performed with flow phantom measurements and with CE-MRA in two volunteers using standard pulse sequences. The flow-induced phase in the vessels of interest was sufficient to distinguish arteries from veins in the superior-inferior direction. Using this method, the venous enhancement could be extinguished.<br/><br>
<br/><br>
The possibility of using HP nuclei as CM for CE-MRA was evaluated. Signal expressions for a flow of HP CM imaged with a gradient echo sequence were derived. These signal expressions were confirmed in phantom experiments using HP 129Xe dissolved in ethanol.<br/><br>
<br/><br>
Studies were also performed with a new CM based on HP 13C. The CM had very long relaxation times (T1,in vivo/T2,in vivo≈ 38/1.3 s). The long relaxation times were utilized in imaging with a fully balanced steady-state free precession pulse sequence (trueFISP), where the optimal flip angle was found to be 180°. CE-MRA with the 13C-based CM in rats resulted in images with high vascular SNR (~500).<br/><br>
<br/><br>
CE-MRA is a useful clinical tool for diagnosing vascular disease. With the development of new contrast media, based on hyperpolarized nuclei for example, there is a potential for further improvement in the signal levels that can be achieved, enabling a standard of imaging of vessels that is not possible today.},
  author       = {Svensson, Jonas},
  issn         = {1600-0455},
  keyword      = {magnetic resonance,hyperpolarized,contrast-enhanced MRA,angiography},
  language     = {eng},
  number       = {S429},
  pages        = {7--7},
  publisher    = {John Wiley & Sons},
  series       = {Acta Radiologica},
  title        = {Contrast-enhanced magnetic resonance angiography.},
  url          = {http://dx.doi.org/10.1034/j.1600-0455.44.s.429.1.x},
  volume       = {44},
  year         = {2003},
}