Rammohan Vadapalli MD, Presenter: Nothing to Disclose

Sita Jayalakshmi, Abstract Co-Author: Nothing to Disclose

Manas Panigrahi MChir, Abstract Co-Author: Nothing to Disclose

Anuj Jain MD, Abstract Co-Author: Nothing to Disclose

Abhinav Sriram Sriram Vadapalli, Abstract Co-Author: Nothing to Disclose

Meghna Vadapalli BEng, Abstract Co-Author: Nothing to Disclose

Purpose To evaluate the role of  new generation Diffusion tensor imaging Biomarkers for characterization of Focal cortical dysplasias, especially the Radial (perpendicular)Diffusivity(λ2+  λ3 );λ3 maps , Radial diffusivity:FA ratio by depicting the microstructural patterns.  

Material and methods seventy six patients in age group of 6 -44 years with M: F ratio of 3:2 with refractory epilepsy  had undergone a MRI study on a  3T MRI(achieva Philips) TLE+ETLE protocol (T2 relaxometry, volumetry and MRS of Hippocampi with MRS,3D T1,3D T2 followed by a Medium to high resolution DTI(diffusion Tensor Imaging) with following parameters. Axial Plane B value: 1000 Number of directions 15 ,TR 6248 TE 60 Slice thickness 2mm with 0.5 inter slice gap,NSA 2,Matrix 112x112 bandwidth 29.8 .These data were post processed.using Fibertrack and Intrasense (Myrian) SW to generate FA maps, Eigen vector Maps λ 1,2 ,3 Radial diffusivity maps with ROI and mirror ROI in contralateral side. Areas of Focal cortical dysplasia were mapped and analysed.

Results: Qualitative biomarkers like asymmetry,Fiber architecture in region of dysplasia and Quantitative Parameters like FA, Mean Diffusivity,Fiber density count were studied. Type 1B FCD(n=11) 1.reduced FA 2. Increased MD 3.Mean value of Radial Diffusivity(Perpendicular Diffusivity ) Increased 4.Fiber architecture appeared normal with Normal fiber density. 5. λ3 is significantly Increased. Type IIA ,IIB ((n=34). -reduced FA - abnormal color coded directionality maps due to disroganized fiber structure in dysplasia(n=34). -radial or Perpndiclar diffusivity is signficantly Increased with RD :FA ratio of >10. Type III: showed Ipsilateral MTS(n=26),Bilateral MTS(n=5). In all the cases of associated FCD with Secondary MTS reduced FA,Increased perpendicular diffusivity and fiber architectural abnormalities are evident.  

1.FCD Type IB are better seen on Radial Diffusivity maps. 2.Radial diffusivity is Increased in TypeIIB>IIA>IB(p=<.001) 3. λ3 Maps delineate FCD and its extent Better >MD or FA >Conventional MR sequences 4.FA/RD ratio is a specific biomarker of Type II FCD.(p=<.001)  

Dysplastic cortex is known to be extending beyond MR visible abnormality and DTI visible subtle White matter abnormaities also extend beyond ,hence these Biomarkers can  map the true extent of FCD.

Vadapalli, R, Jayalakshmi, S, Panigrahi, M, Jain, A, Vadapalli, A, Vadapalli, M, DTI Fiber Tracking Biomarkers for Characterization of Focal Cortical Dysplasias.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13014076.html