ManagedImage.checkIn();

var doc = app.activeDocument;
var managedImages = doc.managedImages;

var im;
var md;
var core_name;
var id;

for(i=0; i<managedImages.length; i++) {
    im = managedImages[i];
    md = im.entMetaData;
    core_name = md.get( "Core_Name");
    id = doc.entMetaData.get("Core_ID");
    alert( "image name = [" + core_name + "] ; document id = [" + id + "]");
    im.checkOut();
    alert( "Now update the image in the woodwing.noindex folder");
    im.checkIn();
}