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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.

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).

Metadata Labels

Metadata labels can be used for information that you need to display across all label groups, eg history, accession number, report information.

  • Use the API to import information into the notes portion of the label. The text will be displayed in the UI.
  • Metadata labels can be at the image, series, or exam level.
  • Metadata labels have a special designation. They will not register as Annotated and are not included in the exported json.


An arbitrary number of sublabel layers can be created to streamline label appearance and annotation.

Reorder Labels

From Label Controls select Reorder Labels and drag and drop items in Labels Column in desired order. Click Label Controls again to set.

Annotation modes

Bounding Box

Bounding Box mode also calculates a width and height


Freeform annotation mode also calculates the longest diameter (even if that line is not fully contained within the freeform shape)

Edit the freeform shape 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.


Polygon annotation mode also calculates the longest diameter (even if that line is not fully contained within the polygon shape)

Edit the polygon shape by hovering over the edge and dragging one of the polygon corners.


Mask annotation mode allows multiple shapes to be drawn on the same image. The drawing tool includes pencil width and shape as well as an eraser for corrections. Undo and Redo will remove/reinstate the last drawing or erasing action.


Draws a line path with one or more segments


Simple location coordinates are applied in this mode

Label Notes

Simple text nodes can be added to each annotation. To add a note, click on the [+] for an applied label at the Annotations toolbar below the image

Notes can be added and viewed by all collaborators. Radlex tags can be added as well.

Label Owner

On the Annotations toolbar below the image, the owner of the label is indicated by the owner's avatar. Hovering over the label will also show the owner's name and avatar.

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