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Labels Annotator has a flexible labeling system that helps you annotate for all kinds of medical AI projects, including for classification, localization, segmentation, and regression models.

Annotator supports both Global and Local labels

Global Labels

A global label is applied to the whole image (eg, Normal) which is useful for letting your training algorithm know that this particular image should be in a particular category. It can also be used to label a series or entire exam.

Create a global label:

A global label can only be applied once per image.

You can also use a global label as metadata, for example Ignore for images of insufficient quality or perhaps an image that doesn't belong in the dataset.

Local Labels

A local label can be applied to a specific region on an image (eg, Lung Nodule). For a particular local label, multiple instances of that label can be applied to different regions on the same image (eg, for multiple lung nodules).

Create a local label:

When creating a local label, select one of the annotation modes which will be used throughout the project for that particular label.


An arbitrary number of sublabel layers can be created to streamline label appearance and annotation. Any type of annotation can be chosen for the main header label and sublabel. You can also mix and match modes and types of annotations.

Note - it's important to plan out the structure of your labels and sublabels before you start creating them. If you're not sure, create extra sublabels and you can delete them later by turning on Show All Sublabels.

Create a sublabel:

Annotation modes

  • Bounding Box which also calculates a width and height

  • Freeform annotation. Edit by mouse hovering over the edge and dragging and/or sliding any of the dots that appear. You can add control points to the figure for fine tuning. Freeform mode also calculates the longest diameter (even if that line is not fully contained within the freeform shape).

  • Polygon annotation mode calculates the longest diameter. Edit the polygon shape by hovering over the edge and dragging one of the polygon corners.

  • Simple Location coordinates are applied in this mode

Cloning a Label Group

Open the settings icon next to Label Group, enter name for the new clones group, and hit Clone button. All the labels from the first group will be duplicated and entered into the cloned group.

Preventing Additional Labels

Open the settings icon next to Label Group, chose the checkbox No Adding New Labels to prevent administrators from creating new labels for the group. Chose the checkbox No Applying Labels to prevent users from applying further labels to the group.

This allows you to freeze the label group.

Radlex Tags

Radlex coding tags can be added to global and local labels in order to use standardized terms for labels. They can also be added to notes.

Label Thumbs Up or Thumbs Down

Clicking on the Thumbs Up icon on the label tag will add a Positive Review to the label. Conversely, clicking on the Thumbs Down icon will add a Negative Review

Label Controls

All users can Filter and Hide labels. Administrators can edit labels, delete labels, and bulk remove annotations.

Bulk Remove Annotations

An administrator only function that will remove all annotations from an image, series, or study. This allows user to start again.