Viscoelasticity-based staging of hepatic fibrosis with multifrequency MR elastography. Asbach, P., Klatt, D., Schlosser, B., Biermer, M., Muche, M., Rieger, A., Loddenkemper, C., Somasundaram, R., Berg, T., Hamm, B., Braun, J., & Sack, I. Radiology, 257(1):80--86, Oct, 2010.
Viscoelasticity-based staging of hepatic fibrosis with multifrequency MR elastography. [link]Paper  doi  abstract   bibtex   
To analyze the dynamics of the shear modulus of the liver to assess the optimal driving frequency and to determine the diagnostic accuracy of generalized frequency-independent elasticity cutoff values for staging hepatic fibrosis.This institutional review board-approved prospective study included 16 healthy volunteers and 72 patients with biopsy-proved liver fibrosis. After obtaining written informed consent, imaging was performed at 1.5-T by using a motion-sensitized echo-planar imaging sequence. Wave excitation was performed by an actuator introducing a superposition of four frequencies (25.0, 37.5, 50.0, 62.5 Hz) of shear waves. The elasticity � value and the structure geometry parameter ? were calculated by using the two-parameter springpot model. The performance of magnetic resonance (MR) elastography in staging liver fibrosis was assessed with area under the receiver operating characteristic curve (AUROC) analysis and Spearman correlation analysis.Elasticity increased with stage of fibrosis, with mean values as follows: for volunteers, 2.25 kPa � 0.43 (standard deviation); stage F1, 2.61 kPa � 0.43; stage F2, 3.00 kPa � 0.63; stage F3, 3.86 kPa � 0.61; and stage F4, 5.86 kPa � 1.22. Frequency-independent cutoff values derived for fibrosis and AUROC values, respectively, were as follows: stage F1 or higher, 2.84 kPa and 0.9128; stage F2 or higher, 3.18 kPa and 0.9244; stage F3 or higher, 3.32 kPa and 0.9744; and equivalent to stage F4, 4.21 kPa and 0.9931. The geometry of the tissue (? value) did not correlate with fibrosis. Frequencies of 50.0 Hz and 62.5 Hz displayed the highest diagnostic accuracy.The diagnostic performance of multifrequency MR elastography in determining the degree of hepatic fibrosis increases with stage of fibrosis. Metrics obtained at the higher frequencies provide better diagnostic performance compared with the lower frequencies. Results of the AUROC analysis demonstrate the high accuracy of frequency-independent cutoff values for staging higher grades of hepatic fibrosis.
@article{ Asbach2010,
  author = {Asbach, Patrick and Klatt, Dieter and Schlosser, Beate and Biermer,
	Michael and Muche, Marion and Rieger, Anja and Loddenkemper, Christoph
	and Somasundaram, Rajan and Berg, Thomas and Hamm, Bernd and Braun,
	Juergen and Sack, Ingolf},
  title = {Viscoelasticity-based staging of hepatic fibrosis with multifrequency
	MR elastography.},
  journal = {Radiology},
  year = {2010},
  volume = {257},
  pages = {80--86},
  number = {1},
  month = {Oct},
  abstract = {To analyze the dynamics of the shear modulus of the liver to assess
	the optimal driving frequency and to determine the diagnostic accuracy
	of generalized frequency-independent elasticity cutoff values for
	staging hepatic fibrosis.This institutional review board-approved
	prospective study included 16 healthy volunteers and 72 patients
	with biopsy-proved liver fibrosis. After obtaining written informed
	consent, imaging was performed at 1.5-T by using a motion-sensitized
	echo-planar imaging sequence. Wave excitation was performed by an
	actuator introducing a superposition of four frequencies (25.0, 37.5,
	50.0, 62.5 Hz) of shear waves. The elasticity � value and the structure
	geometry parameter ? were calculated by using the two-parameter springpot
	model. The performance of magnetic resonance (MR) elastography in
	staging liver fibrosis was assessed with area under the receiver
	operating characteristic curve (AUROC) analysis and Spearman correlation
	analysis.Elasticity increased with stage of fibrosis, with mean values
	as follows: for volunteers, 2.25 kPa � 0.43 (standard deviation);
	stage F1, 2.61 kPa � 0.43; stage F2, 3.00 kPa � 0.63; stage F3, 3.86
	kPa � 0.61; and stage F4, 5.86 kPa � 1.22. Frequency-independent
	cutoff values derived for fibrosis and AUROC values, respectively,
	were as follows: stage F1 or higher, 2.84 kPa and 0.9128; stage F2
	or higher, 3.18 kPa and 0.9244; stage F3 or higher, 3.32 kPa and
	0.9744; and equivalent to stage F4, 4.21 kPa and 0.9931. The geometry
	of the tissue (? value) did not correlate with fibrosis. Frequencies
	of 50.0 Hz and 62.5 Hz displayed the highest diagnostic accuracy.The
	diagnostic performance of multifrequency MR elastography in determining
	the degree of hepatic fibrosis increases with stage of fibrosis.
	Metrics obtained at the higher frequencies provide better diagnostic
	performance compared with the lower frequencies. Results of the AUROC
	analysis demonstrate the high accuracy of frequency-independent cutoff
	values for staging higher grades of hepatic fibrosis.},
  doi = {10.1148/radiol.10092489},
  institution = {Department of Radiology, Charit�-Universit�tsmedizin Berlin, Charit�platz
	1, Berlin, Germany. patrick.asbach@charite.de},
  keywords = {Adult; Biopsy; Case-Control Studies; Echo-Planar Imaging; Elasticity
	Imaging Techniques, methods; Female; Humans; Image Interpretation,
	Computer-Assisted; Liver Cirrhosis, pathology; Magnetic Resonance
	Imaging, methods; Male; Middle Aged; Prospective Studies; ROC Curve;
	Sensitivity and Specificity; Severity of Illness Index},
  language = {eng},
  medline-pst = {ppublish},
  owner = {Heiko},
  pii = {radiol.10092489},
  pmid = {20679447},
  timestamp = {2013.07.26},
  url = {http://dx.doi.org/10.1148/radiol.10092489}
}
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