Presentation stateshow a view is stored and reapplied
The pixels of an image say what was measured, not how to show it. A presentation state is a small DICOM object that records how: contrast, rotation, shutter, annotations and more. This page lists what it can hold, the pipeline a viewer follows, and the rules about who wins.
51 rows
What a presentation state is and the rules around it
These are the rules PS3.4 Annex N sets for creating, storing and applying a Softcopy Presentation State.
| Topic | Rule |
|---|---|
| What it adds | It extends the Storage Service Class to convey an intended presentation, or to record an existing one. It does not change the images it refers to. |
| What it can specify | Output grayscale space in P-Values, color output as PCS-Values, grayscale contrast (modality, VOI and presentation LUT), mask subtraction for multi-frame images, the area to show and its rotation or flip, annotations (graphics, text, overlays), and blending of two image sets. |
| Which images it covers | One state per image, or one common state for several selected images. For grayscale, color and pseudo-color states, all images must be in the same study as the state and of one Composite Image Storage SOP Class. For blending states each set lies in one study, and the sets may be in different studies. |
| Immutable | The presentation attributes are never modified or updated. A different presentation is a derived SOP Instance with a new SOP Instance UID. |
| Replaces the image's own values | The transformations in the state replace those in the referenced image. A transformation absent from the state is identity, and the image's own equivalent is not used in its place. |
| Photometric Interpretation | The value in the referenced image (MONOCHROME1 or MONOCHROME2) is ignored. The grayscale pipeline of the state decides the polarity. |
| Overlays in the image | The state has a mechanism to switch bit-mapped overlays on or off. |
| How it is made | How an SCU records or generates a state is outside the standard. It may come from an operator action such as a window level change, or from an algorithm. |
| Several states for one image | How a viewer chooses between them is outside the standard. A viewer that conforms must make the state available to the user and, if the user selects it, apply all its transformations as defined. |
No rows match the filter in this table.
Two devices applying the same grayscale state should show a perceptually similar image, because P-Values are defined in the Grayscale Standard Display Function (PS3.14), whatever the actual displays can do.
The presentation state SOP Classes
Storage SOP Classes of PS3.4. The grayscale state is the one that radiology viewers meet most.
| SOP Class | UID | For |
|---|---|---|
| Grayscale Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.1 | Grayscale images: contrast, shutter, rotation, annotations. |
| Color Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.2 | Color images, with an ICC profile. |
| Pseudo-Color Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.3 | Grayscale images shown through a color palette. |
| Blending Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.4 | Two sets of images blended, such as PET over CT. |
| XA/XRF Grayscale Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.5 | Angiography and fluoroscopy, with mask handling per frame. |
| Advanced Blending Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.8 | Two or more image sets blended. |
| Variable Modality LUT Softcopy Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.12 | A modality LUT that varies. Optional companion of the Grayscale state for some enhanced images. |
| Grayscale Planar MPR Volumetric Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.6 | Multiplanar reformats of a volume. |
| Compositing Planar MPR Volumetric Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.7 | Multiplanar reformats combined from several volumes. |
| Volume Rendering Volumetric Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.9 | A rendered volume view. |
| Segmented Volume Rendering Volumetric Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.10 | A rendered volume with segmentation. |
| Multiple Volume Rendering Volumetric Presentation State Storage | 1.2.840.10008.5.1.4.1.1.11.11 | Several rendered volumes together. |
| Waveform Presentation State Storage | 1.2.840.10008.5.1.4.1.1.9.100.1 | The display of waveforms such as an ECG. |
| Waveform Acquisition Presentation State Storage | 1.2.840.10008.5.1.4.1.1.9.100.2 | The presentation of a waveform at acquisition. |
No rows match the filter in this table.
Some image SOP Classes are tied to a presentation state in PS3.4. For example an SCP of the Enhanced MR Color Image Storage SOP Class must also support the Color Softcopy Presentation State Storage SOP Class.
The grayscale pipeline, step by step
The conceptual order in which a stored grayscale image becomes a displayed one. A viewer may implement it differently as long as the result looks the same.
| Step | What it does | Attributes | If image and state both have it |
|---|---|---|---|
| 1. Modality LUT | Turns manufacturer-specific pixel values into values meaningful for the modality, such as Hounsfield units. | Rescale Slope (0028,1053) and Intercept (0028,1052), or the Modality LUT Sequence | The state's is used. If the state has none, it is identity and the image's is not used. |
| 2. Mask | For multi-frame images: subtracts other frames from the current one. For X-ray the subtraction is done in a logarithmic space. | Mask Module | The state decides. A Modality LUT in the image is ignored when a mask is used. |
| 3. VOI LUT | The window: turns modality values into values meaningful to the user. | Window Center (0028,1050), Window Width (0028,1051), VOI LUT Sequence, VOI LUT Function (0028,1056) | The state's is used, otherwise identity. |
| 4. Presentation LUT | Turns the values into P-Values, the device independent perceptually linear space of PS3.14. Always present in a state. | Presentation LUT Shape (2050,0020) or the Presentation LUT Sequence | The state's is used. |
No rows match the filter in this table.
There is no separate polarity step. Inverting an image is done with the Presentation LUT: with the shape IDENTITY or INVERSE the minimum value shows as white or black. The minimum P-Value always commands the lowest intensity.
Shutter, annotation, rotation and displayed area
These steps apply after the contrast pipeline, to grayscale P-Values and to color PCS-Values alike.
| Step | What it does | Rule |
|---|---|---|
| Shutter | Excludes the perimeter outside a region and fills it with a given gray level. The region comes from the Display Shutter Module or from a bit-mapped overlay (Bitmap Display Shutter Module). | A shutter in the image itself is ignored. Annotations follow the shutter, so annotations inside a shuttered area stay visible. |
| Annotation in image space | Overlays, text and graphics defined on the pixels of the image. | Applied before the spatial transformation. |
| Spatial transformation | A rotation of 90, 180 or 270 degrees clockwise, followed by an optional horizontal flip. Rotation by another angle is not supported. | The displayed area (Displayed Area Module) selects the part of the image to show, which can magnify or minify it. The method of interpolation is implementation dependent. |
| Annotation in display space | Text and graphics defined on the displayed area, after all spatial transformations. | They may be anchored to points in either the displayed area or the image. |
No rows match the filter in this table.
The number of displayed pixels may differ from the number of image pixels through minification, magnification, interpolation and sub-sampling.
Color and blending
Color and blended states define colors in a device independent space instead of P-Values.
| Topic | Rule |
|---|---|
| ICC profile | Always present in a Color, Pseudo-Color or Blending state. It is an input profile that describes the device that produced the colors. The profile in the state replaces the one in the image. |
| Profile Connection Space | Output values are PCS-Values (CIEXYZ or CIELab). The viewer converts them for its own display, typically through a display profile. The method is outside the standard. |
| Image without an ICC profile | Has no defined color space. A color state that carries a profile defines one, often a well-known space such as sRGB. |
| Blending | The underlying set is grayscale, the superimposed set is mapped through a palette to color. Per pixel: Ro = Rs*A + Yu*(1-A), and the same for green and blue, with A the opacity and Yu the grayscale value. |
| Blending and registration | Spatial registration, resampling and interpolation are not specified. The two sets are not blended image by image. A viewer may support the Spatial Registration Storage SOP Class, but it is not required. |
| Color image on a grayscale display | The behavior is not defined. |
No rows match the filter in this table.
What a viewer or archive must state
In the conformance statement, as an SCU (a device that creates states) and as an SCP (a device that displays them).
| Role | What the conformance statement must say |
|---|---|
| SCU creating states | How the presentation attributes are derived from the displayed image, an operator action or defaults, and how they go into the IOD. |
| SCU creating states | Which Image Storage SOP Classes it also supports and that its states may refer to. |
| SCU creating states | Whether it supports the Compound Graphic Sequence (0070,0209) and which compound graphic types it generates. |
| SCP displaying states | How the presentation attributes influence the display of an image. |
| SCP displaying states | Which Image Storage SOP Classes it supports for states. |
| SCP displaying states | Whether it can render compound graphics, and which types. If it does, it shows the compound graphic and not the text and graphic objects that share its Compound Graphic Instance ID. |
No rows match the filter in this table.
An SCP must make all mandatory presentation attributes available for the user to apply to the referenced images, for every Image Storage SOP Class named in its conformance statement for which it supports the state.
The image looks different from what the radiologist saw
Each cause follows from a rule above. The first check is whether a presentation state exists for the image at all.
| Symptom | Likely cause | Rule behind it |
|---|---|---|
| Window level, rotation or annotations missing in a second viewer | The first viewer kept its view in its own database and never stored a presentation state, or stored it in a private format. | The standard does not require a viewer to create a state. Only a stored state travels with the study. |
| The state exists but the viewer ignores it | The viewer does not support that presentation state SOP Class, or the SOP Class was not negotiated in the association. | The conformance statement lists the SOP Classes. Support is per SOP Class. |
| Annotations visible, contrast different | The viewer applied the graphic annotations but not the VOI LUT, or applied the image's own window instead of the state's. | When a state is applied, its transformations replace the image's. A missing one is identity. |
| Image inverted | The viewer used the Photometric Interpretation of the image instead of the Presentation LUT of the state. | With a state, Photometric Interpretation is ignored and the Presentation LUT decides polarity. |
| Several views of the same image, the wrong one shown | More than one state refers to the image and the viewer picked another by its own rule. | How a viewer chooses between states is not defined by the standard. |
| Annotations in black areas missing | The viewer drew the annotation before the shutter. | Annotations follow the shutter, so they are visible inside shuttered regions. |
| Two monitors look different | Different calibration of the displays, not a different state. | P-Values give a perceptually similar result within the limits of the displays and PS3.14. |
| A correction after sending is not seen | The state was edited in place, but viewers cache the old SOP Instance UID. | A state is immutable: a changed view is a new object with a new SOP Instance UID. |
No rows match the filter in this table.
Glossary
- Presentation state
- A DICOM object that records how images should be displayed, without changing the images.
- GSPS
- Grayscale Softcopy Presentation State. The common name for the grayscale presentation state.
- LUT
- Look-up table. A table that maps one set of values to another, such as stored pixel values to display values.
- Modality LUT
- The first step: it gives pixel values a meaning for the modality, for example Hounsfield units in CT.
- VOI LUT / window
- Value of interest. The window center and width that choose which values are shown with how much contrast.
- P-Values
- Presentation values: a device independent, perceptually linear grayscale space defined in PS3.14.
- PCS-Values
- Profile Connection Space values: the device independent color space of ICC profiles.
- Shutter
- A mask that hides the edge of an image, for example the area outside the collimated X-ray field.
- Immutable
- Cannot be edited. A changed presentation is a new object with its own SOP Instance UID.
Summary
- A presentation state stores how to show images, not the images themselves. It is sent with
C-STORElike any other object. - The grayscale pipeline is Modality LUT, mask, VOI LUT and Presentation LUT, giving P-Values. Then shutter, annotation, rotation and displayed area follow.
- When a state is applied, its transformations replace the image's. A transformation the state lacks is identity, and the image's own is not used.
- Photometric Interpretation in the image is ignored when a grayscale state is applied.
- A state is immutable. A changed view is a new SOP Instance with a new UID.
- The standard does not say which state a viewer picks when there are several, and does not require a viewer to create one.
- The Grayscale Softcopy Presentation State SOP Class is
1.2.840.10008.5.1.4.1.1.11.1.
Common questions
What is a DICOM presentation state?
A DICOM object that records how to display one or more images: contrast, shutter, rotation, the displayed area, annotations and overlays, and for color images an ICC profile and blending. It refers to the images and leaves them unchanged. It is stored and retrieved like any composite object.
What is a GSPS?
The Grayscale Softcopy Presentation State: the presentation state for grayscale images, with SOP Class UID 1.2.840.10008.5.1.4.1.1.11.1. Viewers use it to share window level, annotations and similar settings between workstations.
Does a presentation state change the image?
No. The pixel data stays as stored. The state only describes the transformations that a viewer applies when it displays the image.
Which wins when the image and the presentation state both contain a window?
The presentation state. Its transformations replace those in the image, and a transformation that the state does not contain is identity: the viewer must not fall back on the image's own.
Can a presentation state be edited?
No. Its presentation attributes are never modified. A different presentation is created as a new SOP Instance with a new SOP Instance UID.
Does the PACS have to support presentation states?
The archive stores them like other objects when it supports the SOP Class, and the viewer applies them. Support is per SOP Class and is listed in the DICOM conformance statements of both, so check that the Grayscale Softcopy Presentation State Storage SOP Class appears in both.
How is a presentation state different from a hanging protocol?
A presentation state describes how to show particular images. A hanging protocol describes how to arrange images on the screens, for example which series goes where. See the hanging protocol lesson.