Hideki Ota1, Hajime Tamura2, Ryo Itabashi3, Yukako Yazawa3, Yasuhiro Nakamura4, Kenji Hisamatsu5,6, Manabu Takamatsu7, Hidenori Endo8, Kuniyasu Niizuma8, Yukiko Enomoto9, Tatsuo Nagasaka10, Kimihiro Kajita11, Mika Watanabe12, Shinichi Yoshimura13, Chun Yuan14. 1. Department of Diagnostic Radiology, Tohoku University Hospital, Miyagi, Japan. 2. Division of Medical Physics, Tohoku University Graduate School of Medicine, Miyagi, Japan. 3. Department of Stroke Neurology, Kohnan Hospital, Miyagi, Japan. 4. Division of Pathology, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Miyagi, Japan, Miyagi, Japan. 5. Pathology Division, Gifu University Hospital, Gifu, Japan. 6. Department of Tumor Pathology, Gifu University Graduate School of Medicine, Gifu, Japan. 7. Department of Pathology, The Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan. 8. Department of Neurosurgery, Tohoku University Graduate School of Medicine, Miyagi, Japan. 9. Department of Neurosurgery, Gifu University Graduate School of Medicine, Gifu, Japan. 10. Department of Radiological Technology, Tohoku University Hospital, Miyagi, Japan. 11. Department of Radiology service, Gifu University Hospital, Gifu, Japan. 12. Department of Pathology, Tohoku University Hospital, Miyagi, Japan. 13. Department of Neurosurgery, Hyogo College of Medicine, Hyogo, Japan. 14. Department of Radiology, University of Washington, Seattle, Washington, USA.
Abstract
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.
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.
Authors: Luca Saba; Skandha S Sanagala; Suneet K Gupta; Vijaya K Koppula; Amer M Johri; Narendra N Khanna; Sophie Mavrogeni; John R Laird; Gyan Pareek; Martin Miner; Petros P Sfikakis; Athanasios Protogerou; Durga P Misra; Vikas Agarwal; Aditya M Sharma; Vijay Viswanathan; Vijay S Rathore; Monika Turk; Raghu Kolluri; Klaudija Viskovic; Elisa Cuadrado-Godia; George D Kitas; Neeraj Sharma; Andrew Nicolaides; Jasjit S Suri Journal: Ann Transl Med Date: 2021-07