Материал: part17

Note​

This is the same as for the CLASSIC view, except that Query/Retrieve View (0008,0053) has a value of ENHANCED rather​ than CLASSIC, the SOP Classes in Study (0008,0062) has a different value for the Image Storage SOP Class, and the​ Number of Study Related Instances (0020,1208) is fewer.​

Study Root Study Level C-MOVE Request with Study Instance UID as unique key:​

Note​

This is exactly the same as for the CLASSIC view, except that Query/Retrieve View (0008,0053) has a value of ENHANCED​ rather than CLASSIC. In particular, the same Study Instance UID is retrieved.​

Study Root Study Level C-MOVE Pending Responses illustrating SOP Instances retrieved:​

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Note​

Only the converted instances are transferred with this STUDY level request, including the Legacy Enhanced image and the​ converted Presentation State with updated UID references.​

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NNN Corneal Topography and Tomography​

Maps (Informative)​

NNN.1 Introduction​

Several ophthalmic devices produce curvature and/or elevation measurements of corneal anterior and posterior surfaces (e.g., maps​ that display corneal curvatures, corneal elevations, and corneal power, etc.). The principle methods used include reflection of light​ from the corneal surface (e.g., Placido ring topography) and multiple optical sectioning or slit beam imaging (e.g., Scheimpflug​ tomography). The measurements are mapped topographically as pseudo-color maps, and used extensively for diagnostic purposes​ by clinicians and to fit contact lenses in difficult cases. The underlying data from these measurements is also used to guide laser​ sculpting in keratorefractive surgery.​

NNN.2 Corneal Topography Scales and Color Palettes​

The method for presenting corneal topography maps with pseudo-colored images has been studied extensively. Contour maps are​ effective for diagnostic purposes. The proper scaling is important so that clinically important detail is not obscured as well irrelevant​ detail masked. This can be done with a scale that has fixed dioptric intervals. The choice of color palette to represent different levels​ of corneal power is equally important. There must be enough contrast between adjacent contour colors to provide pattern recognition;​ it is the corneal topography pattern that is used for clinical interpretation. A color palette can be chosen so that lower corneal powers​ are represented with cooler colors (blue shades), while higher corneal powers are represented with the warmer colors (red shades).​ Green shades are used to represent corneal powers associated with normal corneas. The standard scale is shown in Figure NNN.2-​ 1.​

Figure NNN.2-1. Scale and Color Palette for Corneal Topography Maps​

NNN.3 Corneal Topography Examples​

Quantitative measurements of anterior corneal surface curvature (corneal topography) are made with the Placido ring approach.​ Patterns on an illuminated target take the form of mires or a grid pattern. Their reflection from the anterior corneal surface tear film,​ shown in Figure NNN.3-1, is captured with a video camera. Their positions relative to the instrument axis are determined through​ image analysis and these data are used to calculate anterior corneal curvature distribution.​

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Figure NNN.3-1. Placido Ring Image Example​

Corneal curvature calculations are accomplished with three different methods that provide corneal powers. The axial power map,​ shown in Figure NNN.3-2, is most useful clinically for routine diagnostic use as the method of calculation presents corneal topography​ mapsthatmatchthetransitionsknownforcornealshape-thecorneaisrelativelysteepinitscentralarea,flatteningtowardtheperiphery.​ This figure shows an example where the map is superimposed over the source image based upon the corneal vertex Frame of Ref-​ erence. The Blending Presentation State SOP Class may be used to specify this superimposed processing.​

Figure NNN.3-2. Corneal Topography Axial Power Map Example​

The instantaneous power map, shown in Figure NNN.3-3, reveals more detail for corneas that have marked changes in curvature as​ with the transition zone that rings the intended optical zone of a refractive surgical procedure.​

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Figure NNN.3-3. Corneal Topography Instantaneous Power Map Example​

The refractive power map, shown in Figure NNN.3-4, uses Snell's Law of refraction to calculate corneal power to reveal, for example,​ uncompensated spherical aberration.​

Figure NNN.3-4. Corneal Topography Refractive Power Map Example​

The height map, shown in Figure NNN.3-5, displays the height of the cornea relative to a sphere or ellipsoid.​

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