# 3. Volume Registrations ![](/files/YcgAnFLKCsCMIKR1Pqkk) First, Lead-DBS coregisters preoperative and postoperative images. MR images are coregistered to MR images by default with SPM. Postoperative CT images are coregistered to preoperative MR images with ANTs (red arrow number 1). Second, you can choose to normalize the volumes to the MNI nonlinear 2009b space with ANTs (red arrow 2). The ANTs settings are optimized for the subcortex, see [Ewert et al. (2019)](https://doi.org/10.1016/j.neuroimage.2018.09.061). With a multi-core computer, you can increase the number of threads to reduce computation time. To do this, click on `Settings`. Find more information about [MNI spaces here](https://www.lead-dbs.org/about-the-mni-spaces/). For more information about templates and other normalization methods, see [this page](/leaddbs/lead-dbs/step3-volume-registrations/normalization-of-images.md). Third, brainshift correction is recommended to improve lead localization (red arrow 3). Due to the lead implantation, brain shift is highly likely, i.e., the brain moves with respect to the skull. More information about the correction is on[ this page](/leaddbs/lead-dbs/step3-volume-registrations/subcortical-refine-post-to-pre-transforms.md). Finally, you can approve, recalculate or reject the registration and normalization results visually by ticking **Check Results. Warp Drive** allows for fine manual adjustments to better match, for instance, an atlas fit of the subthalamic nucleus with the patient-specific nucleus (red arrows 4 & 5). See [here](https://github.com/netstim/SlicerNetstim/tree/master/WarpDrive) for more information on WarpDrive. The following subpages provide more technical detail. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://netstim.gitbook.io/leaddbs/lead-dbs/step3-volume-registrations.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.