C.11.7 Overlay Activation Module
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### C.11.7 Overlay Activation Module

This Module defines a manner of controlling whether or not bit-mapped overlay and curve information are displayed.

If the corresponding Overlay Group activated is present within the Presentation State, then that Overlay shall be activated and any corresponding Overlay in the referenced image(s) ignored, otherwise the Overlay within the referenced image(s) shall be activated.

An Overlay Group referenced in the Bitmap Display Shutter Module described in Section C.7.6.15 shall not be activated using the Overlay Activation Module.

Table C.11.7-1 specifies the Attributes that describe the Overlay Activation Module.

Table C.11.7-1. Overlay Activation Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Overlay Activation Layer | (60xx,1001) | 2C | The layer (defined in Graphic Layer (0070,0002) of the Graphic Layer Module Section C.10.7) in which the Overlay described in group 60xx shall be displayed. If no layer is specified (zero length) then the overlay shall not be displayed. Required if Group 60xx is present in the referenced image(s) or the Presentation State instance containing this Module.

### Note

1. Previously, those bits that are stored in Pixel Data (7FE0,0010) above High Bit (0028,0102) could be used as overlay bit planes if they were referenced by an Overlay Bit Position (60xx,0102). This usage has been retired. See PS3.3-2004. Their contents are unspecified in DICOM and should not be displayed. Usually they will be zero, though if the pixel data is signed, i.e., Pixel Representation (0028,0103) is 0001H, then it is possible that the sign bit may be "extended" through these values. Alternatively, they may have been "masked off" even if the value is signed and negative.

2. Previously, Curve Activation Layer (50xx,1001) was defined in this Module. Its usage has been retired. See PS3.3-2004.

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