The Optical Path Sequence (0048,0105) shall include an Item for every optical path used in the acquisition of the current image.
For single frame images that do not include the Multi-frame Functional Groups Module, this Sequence shall include only one Item.
For images that use the Multi-frame Functional Groups Module, the optical path associated with each frame is identified by reference to the Optical Path Identifier (0048,0106) of this Sequence (see Optical Path Identification Sequence (0048,0207) in Section C.126.96.36.199). The Optical Path Sequence may include Items for defined optical paths that are not referenced by any frame.
For Whole Slide Microscopy Image LOCALIZER images (see C.188.8.131.52.1 and C.8.12.7), all the optical paths associated with referenced images shall be described in Items of this Optical Path Sequence. The optical path associated with each referenced frame is identified in the Referenced Image Navigation Sequence (0048,0200) by reference to an Optical Path Identifier (0048,0106) of this Sequence. The Optical Path Identifiers used in the LOCALIZER image do not have to be identical to those used in the referenced images.
Notes: 1. For example, each of four referenced images may use a different optical path (color), and within each of those image SOP Instances the single Optical Path Sequence Item is identified as “1”, although the meaning of optical path “1” is different for each image. The LOCALIZER, however, must include all four optical paths with distinct identifiers “1”, “2”, “3”, and “4”.
2. The Optical Path Identifier is not necessarily numeric; it is a string of up to 16 characters (VR SH).