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AJNR - American Journal of Neuroradiology

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Diffusion Tensor Imaging in Hydrocephalus: Initial Experience

Y. Assaf^a,b, L. Ben-Sira^c, S. Constantini^d,e, L.C. Chang^f and L. Beni-Adani^d

^a The Levie-Edersheim-Gitter Institute for Functional Brain Imaging, Tel Aviv Sourasky Medical Center and Tel Aviv University, Israel
^b Department of Neurobiochemistry, Tel Aviv University, Tel Aviv, Tel Aviv, Israel
^c Department of Neuroradiology, Tel Aviv-Sourasky Medical Center, Tel Aviv, Israel
^d Department of Pediatric Neurosurgery, Dana Children’s Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
^e Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
^f Section on Tissue Biophysics and Biomimetics, Laboratory of Integrative and Medical Biophysics, National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Md

View larger version (42K): [in a new window]   Fig 1. ROI selection in a control subject (A) and a patient with acute HCP (B). A, Three representative images of color-coded FA maps. Using a DTI-based atlas of white matter tracts, one can define specific white matter fascicules.(20) Superimposed polygons on color-coded maps identifies the 7 ROI groups that were analyzed in this study (magnified below). For each ROI group, data were measured in another 2 sections and for the left and right hemispheres (not shown). The ROI groups include the following: the posterior limb of the internal capsule,(1) the genu of the corpus callosum,(2) the splenium of the corpus callosum,(3) the subcortical frontal white matter,(4) the subcortical temporal white matter,(5) the optic radiation,(6) and the superior longitudinal fascicules.(7) B, The same ROI groups are used for the patient with acute HCP with the largest ventriculomegaly. All ROI groups except the splenium of the corpus callosum could be identified for this patient.

View larger version (75K): [in a new window]   Fig 2. ADC (top row) and FA (bottom row) of a healthy subject (A and D), and 2 patients with acute HCP (B and F, patients 3 and 1 in the Table). The patients with HCP show significantly increased ventricular volume with significant asymmetry in one of them (C). FA maps of the 2 patients with acute HCP show increased FA in corona radiata fibers (arrows) and normal ADC values (C and F).

View larger version (30K): [in a new window]   Fig 3. Midsagittal view of the 3 subjects shown in Fig 1 depicting the genu, splenium, and body of the corpus callosum. Top row: ADC images. Bottom row: FA maps. In the patients with HCP, the corpus callosum is displaced superiorly (B–F) and appears generally degenerated. The displaced corpus callosum has slightly elevated ADC (yellow arrows) and reduced FA (see enlarged color scale images) compared with those areas in control subjects (A and B).

View larger version (23K): [in a new window]   Fig 4. ROI analysis of FA and ADC values in the internal capsule and genu of the corpus callosum for controls and patients with acute HCP (data are the mean of all patients in each group). A, FA values in the internal capsule are significantly increased (P < .001) for the patients with acute HCP compared with control subjects. B, FA values in the genu of the corpus callosum are significantly decreased (P < .01) for the patients with acute HCP compared with control subjects. C, ADC values in the internal capsule are similar for all subjects with no statistical difference between the 2 groups. D, ADC values in the genu of the corpus callosum are significantly higher for the patients with acute HCP (P < .01) compared with the control subjects.

View larger version (24K): [in a new window]   Fig 5. Pre- and postsurgery DTI-based images at similar section locations for patient 1 (Table). The patient underwent endoscopic septum pellucidotomy. ADC maps before (A) and after (C) surgery show significant reduction in ventricle volume with no apparent change in ADC values. FA maps before (B) and after (D) surgery show significant reduction in FA values of the internal capsule after surgery (see enlarged color-scale images). E and F, ROI analyses for the same patient before and after surgery: FA is significantly reduced after surgery (P < .001) in the internal capsule, whereas ADC values remain the same.

View larger version (24K): [in a new window]   Fig 6. Pre- and postsurgery DTI-based images at similar section locations for patient 2 (Table). The patient underwent ventriculoperitoneal shunt proximal revision. ADC maps before (A) and after (C) surgery show significant reduction in ventricle volume with no apparent change in ADC values. FA maps before (B) and after (D) surgery show significant reduction in FA values of the internal capsule after surgery (see enlarged color-scale images). E and F, ROI analysis for this patient before and after surgery: FA is significantly reduced after surgery (P < .001) in the internal capsule, whereas ADC values remain the same.

View larger version (11K): [in a new window]   Fig 7. ROI analysis for patients with acute HCP, before and after surgery at the level of the internal capsule (data are averaged over all patients in each group). A, Analysis of the radial diffusivity shows significantly lower values before surgery compared with those of control subjects and increased values after surgery approximating control values. B, Analysis of the parallel diffusivity shows significantly higher values before surgery compared with those of control subjects and decreased values after surgery approximating control values. C, To reduce intersubject variability, we compared data for each subject with his or her own presurgery values; this analysis showed 25% increase in radial diffusivity and 10% decrease in parallel diffusivity after surgery.