--- a
+++ b/R/create_ct_head_mask.R
@@ -0,0 +1,25 @@
+#' Create CT Head Mask
+#'
+#' @param img CT image of class \code{\link{nifti}}
+#' @param fill_size Size of fill (in voxels),
+#' passed to \code{\link[extrantsr]{filler}}
+#'
+#' @return An object of class \code{\link{nifti}}
+#' @export
+create_ct_head_mask = function(img, fill_size = 11) {
+  img = neurobase::check_nifti(img)
+  head_mask = img >= -100 & img <= 1000
+  cc = extrantsr::largest_component(head_mask)
+  filled = extrantsr::filler(cc, fill_size = fill_size)
+  return(filled)
+}
+
+#' @export
+#' @rdname create_ct_head_mask
+segment_ct_head = function(img, fill_size = 11) {
+  img = neurobase::check_nifti(img)
+  mask = create_ct_head_mask(img, fill_size = fill_size)
+  head_img = neurobase::mask_img(img + 1024, mask)
+  head_img = head_img - 1024
+  return(img)
+}
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