Helen L Carlson1, Christianne Laliberté2, Brian L Brooks3, Jacquie Hodge4, Adam Kirton3, Luis Bello-Espinosa3, Walter Hader5, Elisabeth M S Sherman6. 1. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; Alberta Children's Hospital Research Institute (ACHRI), Room 293, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada. Electronic address: Helen.carlson@albertahealthservices.ca. 2. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada. 3. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; Alberta Children's Hospital Research Institute (ACHRI), Room 293, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada; University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada. 4. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada. 5. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; Alberta Children's Hospital Research Institute (ACHRI), Room 293, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada; University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Foothills Medical Centre, 1403 29 Street NW, Calgary, AB T2N 2T9, Canada. 6. Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; Alberta Children's Hospital Research Institute (ACHRI), Room 293, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada; University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Copeman Healthcare Centre, 400-628 12 Avenue SW, Calgary, AB T2R 0H6, Canada.
Abstract
BACKGROUND: Diffusion tensor imaging (DTI) tractography is useful for isolating white matter (WM) trajectories and exploring microstructural integrity. Tractography can be performed on atypical brain anatomy when landmarks are malformed or displaced but has been criticized for its subjectivity even when investigators have advanced anatomical knowledge. Also, little is known about the variability and reliability of tractography as a tool for assessing white matter damage in clinical populations such as children with pediatric epilepsy. METHODS: Children diagnosed with epilepsy [N=43, mean age=11.7 years, standard deviation=3.7 years, 53% male] underwent a DTI sequence (6 directions, 2×2×3 mm voxels). Tractography for six white matter tracts (anterior forceps, fornices, bilateral arcuate fasciculi, and bilateral anterior cingula) was conducted twice by two experienced tractographers. Percent coefficient of variation (CV; for measuring variability) and intraclass correlation coefficients (ICCs; for measuring reliability) were calculated for tract volume and diffusion variables (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [AD] and radial diffusivity [RD]). RESULTS: Diffusion variables showed low variability (CV=2.7-8.8%) and very high reliability (ICC=.97-.99) except for limbic tracts [fornix (ICC=.75-.94); cingulum (ICC=.71-.98)]. Tract volume measurements showed high variability (CV=21.9-62.0%) and moderate reliability (ICC=.54-.99). Overall, tract volume measurements were much more variable and less reliable than diffusion characteristics. Limbic structures showed more variability compared with others. CONCLUSIONS: This suggests that DTI tractography and resulting diffusivity variables can reliably inform on the integrity of WM structures in a clinical sample with pediatric epilepsy and highlights the importance of reporting reliability information in studies that aim to answer clinical questions about WM integrity.
BACKGROUND: Diffusion tensor imaging (DTI) tractography is useful for isolating white matter (WM) trajectories and exploring microstructural integrity. Tractography can be performed on atypical brain anatomy when landmarks are malformed or displaced but has been criticized for its subjectivity even when investigators have advanced anatomical knowledge. Also, little is known about the variability and reliability of tractography as a tool for assessing white matter damage in clinical populations such as children with pediatric epilepsy. METHODS:Children diagnosed with epilepsy [N=43, mean age=11.7 years, standard deviation=3.7 years, 53% male] underwent a DTI sequence (6 directions, 2×2×3 mm voxels). Tractography for six white matter tracts (anterior forceps, fornices, bilateral arcuate fasciculi, and bilateral anterior cingula) was conducted twice by two experienced tractographers. Percent coefficient of variation (CV; for measuring variability) and intraclass correlation coefficients (ICCs; for measuring reliability) were calculated for tract volume and diffusion variables (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [AD] and radial diffusivity [RD]). RESULTS: Diffusion variables showed low variability (CV=2.7-8.8%) and very high reliability (ICC=.97-.99) except for limbic tracts [fornix (ICC=.75-.94); cingulum (ICC=.71-.98)]. Tract volume measurements showed high variability (CV=21.9-62.0%) and moderate reliability (ICC=.54-.99). Overall, tract volume measurements were much more variable and less reliable than diffusion characteristics. Limbic structures showed more variability compared with others. CONCLUSIONS: This suggests that DTI tractography and resulting diffusivity variables can reliably inform on the integrity of WM structures in a clinical sample with pediatric epilepsy and highlights the importance of reporting reliability information in studies that aim to answer clinical questions about WM integrity.
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