The Print Management Data Flow Model (Figure H.2-1) consists of three main processes:
Film Session Management process
Note: The Standard uses the word film as a general name for different types of hard copy media (e.g. photographic film, paper).
Figure H.2-1 PRINT MANAGEMENT DATA FLOW MODEL
The Film Session Management process is responsible for acquiring all the information which is required to print the film session. The film session is the atomic work package of the Print Management Application and contains one or more films related in a user defined way (e.g., belonging to the same exam, patient) that are originated from one host (e.g., workstation, diagnostic modality) and that are printed on one hard copy printer.
Each film consists of one or more images and zero or more film related annotations. An annotation consists of one or more lines of text.
Each image consists of pixel data and zero or more overlay planes. The user controls the look of the film by assigning values to print parameters.
Print parameters are defined at film session, film, image and annotation levels. The parameter level determines the scope of operation of the print parameters (e.g., print parameters of the image level are valid for the corresponding image).
The inputs of the Film Session Management process are:
set of images and image related data
presentation data that describes the visual look of the films
The output of the Film Session Management process is the Print Job, which contains all the information to print the film session.
The Print process prints a set of films, based on the information in the Print Job. The Print process is implementation specific and its management is beyond the scope of the DICOM standard.
The Print Management Service Class supports two grayscale transformations and spatial transformations that converts an original image into a printed image.
The sequence of spatial transformations (e.g., magnification and merging of annotation with images) and their relationships with the grayscale transformations are implementation specific and fall beyond the scope of the DICOM Standard.
The sequence of grayscale transformations is important for achieving consistent image quality because of the non-orthogonal nature of the different transformations. Figure H.2-2 describes the sequence of grayscale transformations.
Note: This section previously described Modality LUT and VOI LUT transformations in more detail. Since Referenced Print SOP Classes have been retired, these descriptions no longer apply to the Print Management Service Class. See PS 3.4-1998.
[pic] Figure H.2-2 PRINT MANAGEMENT DATA FLOW MODEL
Examples of these transformations are Modality LUT, Mask Subtraction, and VOI LUT.
The Modality LUT transforms manufacturer dependent pixel values into pixel values which are meaningful for the modality and which are manufacturer independent.
The VOI LUT transforms the modality pixel values into pixel values which are meaningful for the user or the application. For example it selects of a range of pixel values to be optimized for display, such as soft tissue or bone windows in a CT image.
Polarity specifies whether minimum input pixel values shall be displayed as black or white. If Polarity (2020,0020) is NORMAL then the pixels will be displayed as specified by Photometric Interpretation; if Polarity is REVERSE then the pixels will be displayed with the opposite polarity as specified by Photometric Interpretation.
Polarity (2020,0020) is an Attribute of the Image Box IOD.
The Presentation LUT transforms the polarity pixel values into Presentation Values (P-Values), which are meaningful for display of the images. P-Values are approximately related to human perceptual response. They are intended to facilitate consistent display with common input for both hardcopy and softcopy display devices and be independent of the specific class or characteristics of the display device. It is used to realize image display tailored for specific modalities, applications, and user preferences
In the Print Management Service Class, the Presentation LUT is part of the Presentation LUT IOD.
Hardcopy devices convert P-Values into optical density for printing. This conversion depends on desired image D-max and D-min. It also depends on expected viewing conditions such as lightbox intensity for transparency films. The conversion to printed density is specified in the Presentation LUT SOP Class.
If the modality desires to natively specify P-Values as its output, it can negotiate for support of the Presentation LUT, but specify a LUT that is an identity function. The identity function informs the display device that no further translation is necessary.
Note: Performing this translation in the printer prevents potential loss of precision (detail) that would occur if this translation were to be performed on many of the existing 8-bit modalities.
The Print Management Service Class Structure is shown in Figure H.2-3.
The Print Management SCU and Print Management SCP are peer DICOM Print Management Application Entities. The Application Entity of the Print Management SCP corresponds with one or more hard copy printers. If the SCP Application Entity corresponds with multiple printers then the SCP Application Entity selects for each Print Job the printer where the Print Job will be printed.
Figure H.2-3 PRINT MANAGEMENT SERVICE CLASS STRUCTURE
The Print Management SCU and Print Management SCP establish an Association by using the Association Services of the OSI Upper Layer Service. During Association establishment, the DICOM Print Management Application Entities negotiate the supported SOP Classes. The negotiation procedure is defined in Section H.5.
Figure H.2-4 shows alternative configurations for printing images and image related data from one host to multiple printers.
Configuration 1: one SCU Application Entity corresponds with the host and one SCP Application Entity corresponds with multiple printers. The SCU has no control over the print parameters of each printer and over the print destination of the Print Job.
Configuration 2: one SCU Application Entity corresponds with the host and one Application Entity SCP corresponds with each printer. The SCU has explicit control over the print parameters of each printer and over the print destination of the Print Job. Each SCP Application Entity has one Association with the SCU Application Entity and is identified by its Application Entity title.
Figure H.2-4 CONFIGURATIONS FOR PRINTING ON MULTIPLE PRINTERS
The Print Management SCU controls the Print Process by manipulating the Print Management SOP Classes by means of the DIMSE Services. The Print Management SOP Classes are managed by the Print Management SCP.
The Print Management SOP Classes are classified as follows:
Content related SOP Classes: these SOP Classes are an abstraction of the contents of a film (e.g., pixel data, text string). The content related SOP Classes correspond with the Image related SOP Classes, which are described in Section H.4 of this Part.
Presentation related SOP Classes: these SOP Classes are an abstraction of the presentation of a film (e.g., layout information) and are defined by Normalized IODs and Normalized DIMSE-N Services. The presentation related SOP Classes are defined in Section H.4 of this Part.
Printer related SOP Classes: these SOP Classes are an abstraction of the printer configuration and status and are defined by Normalized IODs. The Printer SOP Class is defined in Section H.4 of this Part.
The building blocks of SOP Classes are Modules and DIMSE Services. The Modules contain related Attributes, which are Mandatory(M) or Optional (U). The usage may be different for the SCU and SCP. The usage is specified as a pair of letters: the former indicating the SCU usage, the latter indicating the SCP usage.
DIMSE Services may be Mandatory (M) or Optional (U) as specified in Section 5.4 of this Part.
The meaning and behavior of the usage specification for Attributes for the Print Management Service Class are:
M/M The SCU shall provide a value for the Attribute. If the SCU does not supply a value, the SCP shall return a Failure status (“Missing Attribute,” code 0120H). The SCP shall support at least one value of the Attribute. If the SCP does not support the value specified by the SCU, it shall return a Failure status (“Invalid Attribute Value,” code 0106H).
-/M The SCU’s usage of the Attribute is undefined. The SCP shall support at least one value of the Attribute.
U/M The SCU may provide a value for the Attribute. If the SCP does not support the value specified by the SCU, it shall return either a Failure status (“Invalid Attribute Value”, code 0106H) or return a Warning status (“Attribute Value Out of Range”, code 0116H). In the case of Warning status, the SCP will apply the default value as defined in the SCP Conformance Statement.
U/U The SCU may provide a value for the Attribute. If the SCP does not support the value specified by the SCU, but does support the Attribute, it shall return either a Failure status (“Invalid Attribute Value”, code 0106H) or a Warning status (“Attribute Value out of Range”, code 0116H.). In the case of Warning status, the SCP will apply the default value as defined in the SCP Conformance Statement.
If the SCP does not support the Attribute specified by the SCU, it shall return either a Failure status (“No Such Attribute”, code 0105H) or return a Warning status (“Attribute List Error”, code 0107H.)). In the case of Warning status, the behavior of the SCP is defined in the SCP Conformance Statement.
If the usage type designation is modified by a “C” (e.g., MC/M) the specification stated above shall be modified to include the requirement that the Attribute shall be supported if the specified condition is met.
For every operation requested on a SOP class of the print management service class, a status code will be returned. These status codes are grouped into success, warning or failure categories.
Note: These status codes categories are defined in PS 3.7:
Success – indicates that the SCP performed the requested operation as requested.
Warning – indicates that the SCP has received the request and will process it. However, immediate processing of the request, or processing in the way specified by the SCU, may not be possible. The SCP expects to be able to complete the request without further action by the SCU across the DICOM interface. The exact behavior of the SCP is described in the Conformance Statement.
Failure – indicates that the SCP is unable to perform the request. The request will not be processed unless it is repeated by the SCU at a later time. The exact behavior of the SCP is described in the Conformance Statement.