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In vivo assessment of optimal b ‐value range for perfusion‐insensitive apparent diffusion coefficient imaging
Author(s) -
Freiman Moti,
Voss Stephan D.,
Mulkern Robert V.,
PerezRossello Jeannette M.,
Callahan Michael J.,
Warfield Simon K.
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4736516
Subject(s) - intravoxel incoherent motion , effective diffusion coefficient , diffusion mri , nuclear medicine , estimator , mathematics , medicine , magnetic resonance imaging , statistics , radiology
Purpose: To assess the optimal b ‐values range for perfusion‐insensitive apparent diffusion coefficient (ADC) imaging of abdominal organs using short‐duration DW‐MRI acquisitions with currently available ADC estimation methods. Methods: DW‐MRI data of 15 subjects were acquired with eight b ‐values in the range of 5–800 s/mm 2 . The reference‐standard, a perfusion insensitive, ADC value (ADC IVIM ), was computed using an intravoxel incoherent motion (IVIM) model with all acquired diffusion‐weighted images. Simulated DW‐MRI data was generated using an IVIM model with b ‐values in the range of 0–1200 s/mm 2 . Monoexponential ADC estimates were calculated using: (1) Two‐point estimator (ADC 2 ); (2) least squares three‐point (ADC 3 ) estimator and; (3) Rician noise model estimator (ADC R ). The authors found the optimal b ‐values for perfusion‐insensitive ADC calculations by minimizing the relative root mean square error (RRMS) between the ADC IVIM and the monoexponential ADC values for each estimation method and organ. Results: Low b ‐value = 300 s/mm 2 and high b ‐value = 1200 s/mm 2 minimized the RRMS between the estimated ADC and the reference‐standard ADC IVIM to less than 5% using the ADC 3 estimator. By considering only the in vivo DW‐MRI data, the combination of low b ‐value = 270 s/mm 2 and high b ‐value of 800 s/mm 2 minimized the RRMS between the estimated ADC and the reference‐standard ADC IVIM to <7% using the ADC 3 estimator. For all estimators, the RRMS between the estimated ADC and the reference standard ADC correlated strongly with the perfusion‐fraction parameter of the IVIM model (r = [0.78–0.83], p ≤ 0.003). Conclusions: The perfusion compartment in DW‐MRI signal decay correlates strongly with the RRMS in ADC estimates from short‐duration DW‐MRI. The impact of the perfusion compartment on ADC estimations depends, however, on the choice of b ‐values and estimation method utilized. Likewise, perfusion‐related errors can be reduced to <7% by carefully selecting the b ‐values used for ADC calculations and method of estimation.