Limits...
Caveat of measuring perfusion indexes using intravoxel incoherent motion magnetic resonance imaging in the human brain.

Wu WC, Chen YF, Tseng HM, Yang SC, My PC - Eur Radiol (2015)

Bottom Line: Based on our experimental setting (SNRb1000 ~ 30), the average error/variability is ~5 %/25 % for f and ~100 %/30 % for D* in gray matter, and ~10 %/50 % for f and ~300 %/60 % for D* in white matter.Correlation was found between f and DSC-derived cerebral blood volume in gray matter (r = 0.29 - 0.48 across subjects, p < 10(-5)), but not in white matter.No correlation was found between f-D* product and ASL-derived cerebral blood flow. f may provide noninvasive measurement of cerebral blood volume, particularly in gray matter.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, wenchau@ntu.edu.tw.

ABSTRACT

Objectives: To numerically and experimentally investigate the robustness of intravoxel incoherent motion (IVIM) magnetic resonance imaging in measuring perfusion indexes in the human brain.

Methods: Eighteen healthy volunteers were imaged on a 3 T clinical system. Data of IVIM imaging (12 b-values ranging from 0 to 1000 s/mm(2), 12 repetitions) were fitted with a bi-exponential model to extract blood volume fraction (f) and pseudo-diffusion coefficient (D*). The robustness of measurement was assessed by bootstrapping. Dynamic susceptibility contrast (DSC) imaging and arterial spin-labelling (ASL) imaging were performed for cross-modal comparison. Numerical simulations were performed to assess the accuracy and precision of f and D* estimates at varied signal-to-noise ratio (SNRb1000).

Results: Based on our experimental setting (SNRb1000 ~ 30), the average error/variability is ~5 %/25 % for f and ~100 %/30 % for D* in gray matter, and ~10 %/50 % for f and ~300 %/60 % for D* in white matter. Correlation was found between f and DSC-derived cerebral blood volume in gray matter (r = 0.29 - 0.48 across subjects, p < 10(-5)), but not in white matter. No correlation was found between f-D* product and ASL-derived cerebral blood flow.

Conclusions: f may provide noninvasive measurement of cerebral blood volume, particularly in gray matter. D* has limited robustness and should be interpreted with caution.

Key points: • A minimum SNR b1000 of 30 is recommended for reliable IVIM imaging. • f may provide noninvasive measurement of cerebral blood volume. • f correlates with CBV DSC in gray matter. • There is no correlation between fD* and CBF ASL . • D* has limited robustness and should be interpreted with caution.

No MeSH data available.


Simulated accuracy of IVIM-derived diffusion coefficient (D), blood volume fraction (f), and pseudo-diffusion coefficient (D*). Gray matter (blue squares) and white matter (red upward triangles = axial diffusion in white matter, black downward triangles = radial diffusion in white matter) are shown separately. D was assumed to be 0.8 × 10-3, 1.2 × 10-3, and 0.4 × 10-3 mm2/s for gray matter, axial diffusion in white matter, and radial diffusion in white matter, respectively. Gray matter and white matter were assumed to have an f of 0.08 and 0.03, respectively, and the same D* (1.2 × 10-2 mm2/s) for simplicity. Gray dotted lines indicate the assigned values. Signal-to-noise ratio was defined at b = 1,000 s/mm2 (SNRb1000)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4495260&req=5

Fig2: Simulated accuracy of IVIM-derived diffusion coefficient (D), blood volume fraction (f), and pseudo-diffusion coefficient (D*). Gray matter (blue squares) and white matter (red upward triangles = axial diffusion in white matter, black downward triangles = radial diffusion in white matter) are shown separately. D was assumed to be 0.8 × 10-3, 1.2 × 10-3, and 0.4 × 10-3 mm2/s for gray matter, axial diffusion in white matter, and radial diffusion in white matter, respectively. Gray matter and white matter were assumed to have an f of 0.08 and 0.03, respectively, and the same D* (1.2 × 10-2 mm2/s) for simplicity. Gray dotted lines indicate the assigned values. Signal-to-noise ratio was defined at b = 1,000 s/mm2 (SNRb1000)

Mentions: Figure 2 shows the comparison of D/f/D* estimates and their theoretical values. The estimate of D has high accuracy (error <5 %) regardless of SNR, gray/white matter, and axial/radial diffusion. In contrast, f and D* are overestimated at low SNR and gradually converge to the theoretical values when SNR increases. As compared with gray matter, white matter, particularly the radial diffusion, demands higher SNR to achieve a comparable level of accuracy. Again, variance decreases with the increase of SNR (see the error bars that indicate the standard deviation of 1,000 estimates). For a given SNR level, the variance is notably smaller for f than for D*. Note that in white matter, the coefficient of variation of D* is greater than 100 % even when SNRb1000 = 100.Fig. 2


Caveat of measuring perfusion indexes using intravoxel incoherent motion magnetic resonance imaging in the human brain.

Wu WC, Chen YF, Tseng HM, Yang SC, My PC - Eur Radiol (2015)

Simulated accuracy of IVIM-derived diffusion coefficient (D), blood volume fraction (f), and pseudo-diffusion coefficient (D*). Gray matter (blue squares) and white matter (red upward triangles = axial diffusion in white matter, black downward triangles = radial diffusion in white matter) are shown separately. D was assumed to be 0.8 × 10-3, 1.2 × 10-3, and 0.4 × 10-3 mm2/s for gray matter, axial diffusion in white matter, and radial diffusion in white matter, respectively. Gray matter and white matter were assumed to have an f of 0.08 and 0.03, respectively, and the same D* (1.2 × 10-2 mm2/s) for simplicity. Gray dotted lines indicate the assigned values. Signal-to-noise ratio was defined at b = 1,000 s/mm2 (SNRb1000)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4495260&req=5

Fig2: Simulated accuracy of IVIM-derived diffusion coefficient (D), blood volume fraction (f), and pseudo-diffusion coefficient (D*). Gray matter (blue squares) and white matter (red upward triangles = axial diffusion in white matter, black downward triangles = radial diffusion in white matter) are shown separately. D was assumed to be 0.8 × 10-3, 1.2 × 10-3, and 0.4 × 10-3 mm2/s for gray matter, axial diffusion in white matter, and radial diffusion in white matter, respectively. Gray matter and white matter were assumed to have an f of 0.08 and 0.03, respectively, and the same D* (1.2 × 10-2 mm2/s) for simplicity. Gray dotted lines indicate the assigned values. Signal-to-noise ratio was defined at b = 1,000 s/mm2 (SNRb1000)
Mentions: Figure 2 shows the comparison of D/f/D* estimates and their theoretical values. The estimate of D has high accuracy (error <5 %) regardless of SNR, gray/white matter, and axial/radial diffusion. In contrast, f and D* are overestimated at low SNR and gradually converge to the theoretical values when SNR increases. As compared with gray matter, white matter, particularly the radial diffusion, demands higher SNR to achieve a comparable level of accuracy. Again, variance decreases with the increase of SNR (see the error bars that indicate the standard deviation of 1,000 estimates). For a given SNR level, the variance is notably smaller for f than for D*. Note that in white matter, the coefficient of variation of D* is greater than 100 % even when SNRb1000 = 100.Fig. 2

Bottom Line: Based on our experimental setting (SNRb1000 ~ 30), the average error/variability is ~5 %/25 % for f and ~100 %/30 % for D* in gray matter, and ~10 %/50 % for f and ~300 %/60 % for D* in white matter.Correlation was found between f and DSC-derived cerebral blood volume in gray matter (r = 0.29 - 0.48 across subjects, p < 10(-5)), but not in white matter.No correlation was found between f-D* product and ASL-derived cerebral blood flow. f may provide noninvasive measurement of cerebral blood volume, particularly in gray matter.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, wenchau@ntu.edu.tw.

ABSTRACT

Objectives: To numerically and experimentally investigate the robustness of intravoxel incoherent motion (IVIM) magnetic resonance imaging in measuring perfusion indexes in the human brain.

Methods: Eighteen healthy volunteers were imaged on a 3 T clinical system. Data of IVIM imaging (12 b-values ranging from 0 to 1000 s/mm(2), 12 repetitions) were fitted with a bi-exponential model to extract blood volume fraction (f) and pseudo-diffusion coefficient (D*). The robustness of measurement was assessed by bootstrapping. Dynamic susceptibility contrast (DSC) imaging and arterial spin-labelling (ASL) imaging were performed for cross-modal comparison. Numerical simulations were performed to assess the accuracy and precision of f and D* estimates at varied signal-to-noise ratio (SNRb1000).

Results: Based on our experimental setting (SNRb1000 ~ 30), the average error/variability is ~5 %/25 % for f and ~100 %/30 % for D* in gray matter, and ~10 %/50 % for f and ~300 %/60 % for D* in white matter. Correlation was found between f and DSC-derived cerebral blood volume in gray matter (r = 0.29 - 0.48 across subjects, p < 10(-5)), but not in white matter. No correlation was found between f-D* product and ASL-derived cerebral blood flow.

Conclusions: f may provide noninvasive measurement of cerebral blood volume, particularly in gray matter. D* has limited robustness and should be interpreted with caution.

Key points: • A minimum SNR b1000 of 30 is recommended for reliable IVIM imaging. • f may provide noninvasive measurement of cerebral blood volume. • f correlates with CBV DSC in gray matter. • There is no correlation between fD* and CBF ASL . • D* has limited robustness and should be interpreted with caution.

No MeSH data available.