TY - JOUR
T1 - Quantitative characterization of carotid plaque components using MR apparent diffusion coefficients and longitudinal relaxation rates at 3T
T2 - A comparison with histology
AU - Ota, Hideki
AU - Tamura, Hajime
AU - Itabashi, Ryo
AU - Yazawa, Yukako
AU - Nakamura, Yasuhiro
AU - Hisamatsu, Kenji
AU - Takamatsu, Manabu
AU - Endo, Hidenori
AU - Niizuma, Kuniyasu
AU - Enomoto, Yukiko
AU - Nagasaka, Tatsuo
AU - Kajita, Kimihiro
AU - Watanabe, Mika
AU - Yoshimura, Shinichi
AU - Yuan, Chun
N1 - Funding Information:
We thank Prof. Akira Hara, Department of Tumor Pathology, Gifu University Graduate School of Medicine, for coordination of the pathological evaluation. We also thank Dr. Makoto Obara, Philips Electronics Japan Ltd., Healthcare for the image sequence optimization.
PY - 2018/12
Y1 - 2018/12
N2 - Background: There is limited evidence of parametric MR mapping to characterize carotid plaques associated with cerebral ischemic events. Purpose: To explore the apparent diffusion coefficients (ADCs) and longitudinal relaxation rates (R1) of carotid plaques, including areas of hemorrhage, lipid-rich/necrotic core (LR/NC) without hemorrhage, and fibrous tissue (Fbr). Study Type: Prospective. Subjects: Twelve patients who underwent carotid endarterectomy. Field Strength/Sequence: R1 was measured using double angle Look–Locker acquisition on 3T systems. Single-shot spin-echo echo-planar imaging with fat suppression and outer-volume suppression (OVS-DWEPI) with b values of 10 and 500 s/mm2 was used for diffusion-weighted imaging. Assessment: A phantom study using diluted gadolinium solutions and polyvinyl alcohol solutions was used to validate the two protocols. Regions of interest (ROIs) were manually outlined on MR images for areas of LR/NC, hemorrhage, and Fbr based on histological cross-sections. Pixel-based R1 and ADC values in the ROIs were plotted for each component. The probability density function of the plots determined the optimum contours to separate the three components in the ADC-R1 plane. The LR/NC, hemorrhage, and Fbr regions were mapped on MR images based on the above results and compared to histological results. Statistical Tests: The R1 values of the phantom measurements were tested using Bland–Altman analysis. The accuracies of the MRI classification were calculated. Results: R1 values <8 s−1 calculated using our method agreed with those calculated using an inversion-recovery fast-spin-echo sequence (error, ≤0.1 s−1). ADC values obtained using OVS-DWEPI were 4.1% higher than those obtained using standard echo-planar imaging. LR/NC (R1, 0.4–1.2 s−1; ADC, 0–1.5 μm2/ms), hemorrhage (R1 ≥ 1.5 s−1; ADC, 0.5–1.5 μm2/ms), and Fbr (R1, 0.2–0.8 s−1; ADC, 1.5–2.9 μm2/ms) were separated on the plots. The accuracies of MRI classification were LR/NC, 0.86; hemorrhage, 0.79; and Fbr, 0.77. Conclusion: The combination of ADC and R1 values measured using our method enabled differentiation among LR/NC, hemorrhage, and Fbr. Level of Evidence: 1. Technical Efficacy: Stage 2. J. Magn. Reson. Imaging 2018;48:1657–1667.
AB - Background: There is limited evidence of parametric MR mapping to characterize carotid plaques associated with cerebral ischemic events. Purpose: To explore the apparent diffusion coefficients (ADCs) and longitudinal relaxation rates (R1) of carotid plaques, including areas of hemorrhage, lipid-rich/necrotic core (LR/NC) without hemorrhage, and fibrous tissue (Fbr). Study Type: Prospective. Subjects: Twelve patients who underwent carotid endarterectomy. Field Strength/Sequence: R1 was measured using double angle Look–Locker acquisition on 3T systems. Single-shot spin-echo echo-planar imaging with fat suppression and outer-volume suppression (OVS-DWEPI) with b values of 10 and 500 s/mm2 was used for diffusion-weighted imaging. Assessment: A phantom study using diluted gadolinium solutions and polyvinyl alcohol solutions was used to validate the two protocols. Regions of interest (ROIs) were manually outlined on MR images for areas of LR/NC, hemorrhage, and Fbr based on histological cross-sections. Pixel-based R1 and ADC values in the ROIs were plotted for each component. The probability density function of the plots determined the optimum contours to separate the three components in the ADC-R1 plane. The LR/NC, hemorrhage, and Fbr regions were mapped on MR images based on the above results and compared to histological results. Statistical Tests: The R1 values of the phantom measurements were tested using Bland–Altman analysis. The accuracies of the MRI classification were calculated. Results: R1 values <8 s−1 calculated using our method agreed with those calculated using an inversion-recovery fast-spin-echo sequence (error, ≤0.1 s−1). ADC values obtained using OVS-DWEPI were 4.1% higher than those obtained using standard echo-planar imaging. LR/NC (R1, 0.4–1.2 s−1; ADC, 0–1.5 μm2/ms), hemorrhage (R1 ≥ 1.5 s−1; ADC, 0.5–1.5 μm2/ms), and Fbr (R1, 0.2–0.8 s−1; ADC, 1.5–2.9 μm2/ms) were separated on the plots. The accuracies of MRI classification were LR/NC, 0.86; hemorrhage, 0.79; and Fbr, 0.77. Conclusion: The combination of ADC and R1 values measured using our method enabled differentiation among LR/NC, hemorrhage, and Fbr. Level of Evidence: 1. Technical Efficacy: Stage 2. J. Magn. Reson. Imaging 2018;48:1657–1667.
KW - apparent diffusion coefficient
KW - carotid plaque components
KW - histology
KW - longitudinal relaxation rate
KW - magnetic resonance imaging
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U2 - 10.1002/jmri.26216
DO - 10.1002/jmri.26216
M3 - Article
C2 - 30325551
AN - SCOPUS:85055036582
VL - 48
SP - 1657
EP - 1667
JO - Journal of Magnetic Resonance Imaging
JF - Journal of Magnetic Resonance Imaging
SN - 1053-1807
IS - 6
ER -