Measurements and Annotation

Annotation

There are two types of annotation:

• System annotation which is automatically supplied by the system and is always displayed in the same place. The type and amount of annotation displayed can be modified but not moved.
• User annotation which is annotation you add. This annotation can be text or measurements and can be placed anywhere on the viewport.

  Table 1. Types of user annotation

  Annotation type	Description
  Text annotation	You can add notes and comments directly on the views, and use a marker with the annotation to point out anatomical features. User text annotations can be edited, moved or deleted as necessary. When images are saved, any annotations shown on the images are saved with them.
  Arrow annotation	You can add an arrow to point to anatomy or pathology.
  Preset annotation	Preset annotations are those which have already been created and saved for future use. These annotations can consist of text or text with measurement annotations. The preset measurement annotations vary depending on the current protocol. In addition to the supplied default annotations supplied, you can create and save annotations.
  Measurement annotation	You can create and view various measurements (voxel value, distance, angle, area, volume) on the views. Like text annotations, they can be moved, deleted or edited as necessary.

Measurement

You can use the Measurement tools to acquire:

• Distance measurements
• Angle measurements
• Volume measurements

It is very important to understand the accuracy of on-view measurements. For details, see Measurement accuracy.

Cursor and ROI

In order to perform measurements on an image that can be expressed in absolute values (mm), the image must be calibrated, i.e. the relationship between image pixels and true anatomical distance in the patient’s body (the scale factor) must be known. For images such as CT and MR this information is automatically recorded during image acquisition and stored with the image. Measurements on such images can therefore be expressed directly in mm, using the patient-based RAS (Right/Anterior/Superior) coordinate system.

Ensure that there is no discrepancy between functional maps, graphs, statistics, and ROI numbers due to various screen saves taken after re-computation of the maps or modification of the ROIs.

Measure and annotation procedures and concepts

• Active annotation concept
• Active graph annotation concept
• Add annotation to an image
• Add annotation with a pointer
• Create annotation presets
• Arrows: deposit, size and position
• Deposit a 2D ROI
• Deposit a 3D ROI
• Auto contour: contour semi-spherical structures on 3D images
• Report cursor: activate
• Modify measurements
• Create a distance measurement
• Create a curved distance measurement
• Measure an angle
• Measure a volume
• Measurement accuracy concept
• Resize/Rotate image graphics
• Remove image graphics