WWWC Region Tool
How to set up the WwwcRegion tool:
// Init cornerstone tools
cornerstoneTools.init();
// Enable any elements, and display images
// ...
// Add our tool, and set it's mode
const WwwcRegionTool = cornerstoneTools.WwwcRegionTool;
cornerstoneTools.addTool(WwwcRegionTool)
cornerstoneTools.setToolActive('WwwcRegion', { mouseButtonMask: 1 })