WebParc: a tool for analysis of the topography and volume of stroke from MRI

Abstract

The quantitative assessment of the anatomic consequences of cerebral infarction is critical in the study of the etiology and therapeutic response in patients with stroke. We present here an overview of the operation of "WebParc," a computational system that provides measures of stroke lesion volume and location with respect to canonical forebrain neural systems nomenclature. Using a web-based interface, clinical imaging data can be registered to a template brain that contains a comprehensive set of anatomic structures. Upon delineation of the lesion, we can express the size and localization of the lesion in terms of the regions that are intersected within the template. We demonstrate the application of the system using MRI-based diffusion-weighted imaging and document measures of the validity and reliability of its uses. Intra- and inter-rater reliability is demonstrated, and characterized relative to the various classes of anatomic regions that can be assessed. The WebParc system has been developed to meet criteria of both efficiency and intuitive operator use in the real time analysis of stroke anatomy, so as to be useful in support of clinical care and clinical research studies. This article is an overview of its base-line operation with quantitative anatomic characterization of lesion size and location in terms of stroke distribution within the separate gray and white matter compartments of the brain.

Fig. 1

Overview figure showing the data flow and modular design of the WebParc system

Fig. 2

WebParc visualization interface. The user can visualize the clinical images (upper left), visually validate the registration between clinical case and template (lower left), and then proceed to make the lesion segmentation using mouse-driven cursor (upper right). Upon completion of the segmentation, the user initiates the intersection of the lesion mask with the template-based regions of anatomic interest, yielding a “lesion volume” for each anatomic region that the lesion intersects with (lower right)

Fig. 3

WebParc database schema. Detailed depictions of the study, scan, template, mask, result and usr database constructs are displayed

Fig. 4

Web-based interface to WebParc results. Top panel shows the quantitative results of the lesion intersection with the specified template. The lower panel shows the cortical parcellation intersection results on an idealized template for simplified visual interpretation. Regional abbreviations are provided in Table 1

Fig. 5

cardviews–WebParc regression plots. a “General segmentation”: regression for all (N = 67) general segmentation measures across all subjects (left) and regression for the volume estimate of cerebral white matter involvement across the 21 subjects (right). b Cortical parcellation: regression for all (N = 336) parcellation unit measures across all subjects (left) and regression for the volume estimate of insula involvement across the 16 of the 21 subjects that had involvement of this region (right). c Intrarater correlation plots for total lesion (left) and all parcellation units (right). Note that the r² value for the intrarater correlation plots for total lesion plot goes to 0.356 when the large lesion is excluded

Fig. 6

Multimodality examples of WebParc use. The top four panels represent different MR imaging modes in a single patient, and include diffusion-weighted imaging (DWI), cerebral blood volume (CBV). Cerebral blood flow (CBF), and mean transit time (MTT). Spatial details of the user-perceived lesion in each of these modalities can be different, and these differences were quantified using this application. The bottom panel demonstrates the WebParc functionality on CT imaging