Achieve consistent output or display of digital medical images: Ihe CPI Integrated Model

Achieve consistent output or display of digital medical images:

IHE CPIIntegration Model

In the process of medical imaging-based patient diagnosis and treatment, the display and display status of medical images are consistent, it is a key factor to ensure consistent interpretation and diagnosis of patient medical imaging, and to ensure the normal and smooth implementation of patient medical imaging. In the traditional film-based medical image publishing model, the images produced by patients during the medical imaging examination are carried on the film media as the only method for publishing medical images, this ensures consistent display and presentation of medical images during the release process. However, in an information environment, medical images may be published and presented through a variety of different media. For example, digital image copies published and transmitted over the network may be displayed on displays with different configurations and resolutions; it is also possible to output digital images as hard copies of films for transmission and processing. Therefore, in the information environment, establishing consistent display and presentation of medical images in different publishing methods and bearer media is an important issue that affects the quality of patient care. To solve this problem, Ihe defines the consistent presentation of images profile.

1.Basic definition and application characteristics of the Ihe CPI Integration Model

   The Ihe CPI integration model defines a set of transactions to ensure grayscale images and their display status information (such as comments, display areas, image rotation, enlargement and reduction) consistent presentation and presentation in different output environments (such as workstation screens and film printers. In addition, CPI defines and references a standard contrast curve and a grayscale standard display function (gsdf ), different types of image display devices and image hard copy output devices can be collimated based on this, CPI provides support for the consistency of hard copy and soft copy output of images, as well as image information table and presentation consistency in a hybrid operation environment.

   The standardized operation of the CPI integration model controls the basic services provided by the Medical Imaging discipline, namely the soft copy and hard copy output of medical images. CPI defines in detail the execution process of DICOM standard grayscale standard display function (gsdf, DICOM standard p3.14) and DICOM Grayscale Softcopy Presentation State (GSPs, the goal is to ensure that similar presentation statuses and consistent observation results can be obtained in different image output and browsing environments, such as film (reading lamp observation), image diagnostic workstation, or common PC. The implementation of this capability is of great significance to the clinical medical treatment process, such as remote (network) Discussions and consultations based on soft copies of electronic images, consistent reproduction of features of the same image on different display devices in different locations may be crucial for the results of such imaging consultations and discussions.

The execution of the CPI integration model is also important for filmless radiology management. In the film-based radiology management model, the quality control management process of films is an important management link to ensure that unqualified images are not released. However, in the non-film operating environment, the film image publishing management and control process may no longer exist, and the diagnostic operations of radiologists are completed based on soft copies of images, therefore, the printing and Output Processes of physical films and the output quality of images may no longer be strictly controlled. In this case, hard copies of images with unqualified quality and display status may be released. As a solution, the CPI integration model is applied and supported in radiology workflows to ensure the consistency between soft copy display and hard copy output presentation, which may avoid such situations.

    The results or objectives of Ihe CPI integration model execution can be roughly summarized as follows:

●   Ensures the consistency of digital medical images observed on different soft copy display devices. This goal is mainly based on DICOM GSPs.

●   Ensure that digital medical images are on different hard copy output devices, such as film printers from different providers, and the output results are consistent. This result can usually be implemented by executing DICOM basic print SOP that supports the presentation LUT option.

●   Ensures the consistency of the observed results of digital medical images in the soft copy output device and hard copy output device. The implementation of this goal requires the establishment of a Collimated process for the Image Display Device Based on the DICOM gsdf definition.

2.   Ihe cpi Integration Model workflow and its basic content

    The Ihe CPI integration model mainly defines the consistency processing and presentation processes of medical images. The information systems involved are PACS and related systems. Therefore, the workflow defined by CPI is mainly composed of Information System units related to image soft and hard copy operations. The key transactions defined by CPI is the transaction processing capability to ensure the consistency of medical image information.

 

1)  Key actors in CPI Workflow

The actors defined in the Ihe CPI integration model mainly include information system roles related to image generation, management, and output, for example, acquisition modality, evistmcreator, image archive, image display, print composer, and print server constitute the image storage process (between acquisition modality/evistmcreator and image archive) the image application process (between image archive and Image Display) and the image print output process (between print composer and print server ). In the above actors, the evistmcreator represents the information system function modules that can generate evidence objects except acquisition modality, such as the processing module of the image post-processing workstation; print composer is usually a function module embedded in the information system of image workstations or image collection devices, while the Print Server is a printing device that generates hard copy physical output of images. Other actors have been defined in multiple integration models such as SWF.

2)  Key transactions in CPI Workflow

Because the CPI integration model is mainly used for operations and processing tasks on the presentation status of evidence objects, its key transactions are related to the transmission, processing, query, and acquisition of information object presentation statuses, including creator presentation States stored/modality presentation States stored, query presentation states/retrieve presentation states and print request with presentation LUT; CPI includes otherTransactions, such as modality/creator image stored, storage commitment, query images, and retrieve images, have the same definitions as those in the SWF integration model. See SWF documentation. The following describes the key transactions in the CPI integration model:

●  Creator presentation States stored/modality presentation States stored, that is, the evidence objects related to the image presentation status are submitted and processed along with the image objects themselves during the storage process. This set of transactions mainly executes the generation of GSPs objects and the behavior passed to the image archive. GSPs objects include all gray-scale processing operations, spatial location operations, and graphic operation information of their associated images and image sets, such as contrast setting, rotation, and text tagging, the image (SET) associated with the GSPs object should have the same uid attribute (such as study instance UID), so that the GSPs object and its associated image object are stored in the image archive (such as the PACS server) storage management can be performed synchronously in the system. The Creator presentation States stored/modality presentation States stored execution mechanism defined by Ihe mainly references the storage SOP class of DICOM standard and the implementation of GSPs storage SOP class.

●  Query presentation states/retrieve presentation states: this group of transactions occurs between Image Display and image archive, that is, the process of publishing an image application, execute the GSPs object query and retrieval request proposed by image display. Its behavior is similar to the query images/retrieve images processing of the image iod, but its operation object is GSPs IOD. In practical applications, the query/retrieve behavior of GSPs is often performed simultaneously with the query/retrieve process associated with the image object, or after the image object query/retrieve is completed, the purpose of obtaining GSPs is to ensure that the submission and display status of the associated image objects are consistent. Query presentation states/retrieve presentation States execution mechanism is implemented based on DICOM standard query/retrieve SOP and GSPs storage sop.

●    Print request with presentation LUT: this transaction is used between the print output process of the image consisting of print composer and print server. That is, when the image data Print Output request is passed, the presentation LUT setting information is passed along to ensure the consistency of the conversion process from the pixel information of the image data to the grayscale display information output by the Print Server Information System. The expression LUT output is similar to the p-values information of the Human Visual Sensing response, it is usually used to produce consistent soft or hard copies of modulated image pixel data on devices (such as monitors or printers) that support DICOM gsdf definition. Implement print request with presentation LUT defined by IHE. The required DICOM standard definitions and mechanisms include the basic print management SOP class and the presentation lut sop class that can be selected, as a printing output device (such as an image or film printer), it also needs to support the DICOM standard gsdf definition.

3. Application of Ihe CPI Integrated Model workflow

    The Ihe technical framework defines a special type of integration functions in the CPI integration model to ensure that in the hospital information application environment, access and reading of medical images and collection and production of medical images are fully consistent in the presentation and presentation of image data. This consistent image access reading process can occur within the medical imaging department or department, such as the conventional diagnostic access process of the image, or between the medical imaging department or department, for example, the ultrasound department and radiology department exchange images and reference during their respective implementation of the image diagnostic report; or the access to medical images from other departments and departments of the hospital outside the medical imaging department.

  The implementation of the CPI integration model can further improve the image and related data objects (such as GSPs, Ko, or SR) in hospital medical imaging applications and procedures) the browsing and observation processes and their results. This type of clinical medical imaging workflow process that can apply the CPI integrated model processing function includes:

●    The diagnostic physician of the medical imaging department wants to retain the operation parameters (such as window width/window value) of Image Browsing during initial or review of medical images) and the annotation of the lesion features of the image.

●    Physicians in the clinical department, who want to query and access the Image Object Sequence of the patient's recent medical imaging examination based on the patient's ID information.

●    Physicians in the clinical department want to access and view the critical images associated with the diagnostic report when visiting the patient's medical imaging diagnostic report.

●    When a clinician views a patient's medical imaging or imaging consultation, the images to be viewed/consulted maintain the same image display and presentation status as the imaging physician performs diagnostic browsing.

●    Prior to performing the imaging examination, the Health examiner wishes to extract the imaging examination performed previously by the patient to ensure consistent positioning of the patient's examination, such as imaging follow-up and review of the tumor patient.

●    When performing the diagnostic procedure for the current imaging examination, the photo diagnostic physician wishes to compare the image with the patient's previous imaging procedures (such as imaging follow-up and review of the tumor patient ); it is also necessary to re-access and read the images of previous examinations when performing a new imaging diagnostic browsing procedure for a patient whose diagnostic conclusions have been established during previous imaging procedures.

●    Surgeons need to perform a 3-dimensional reconstruction and volumetric analysis of patient images during the preparation of the surgical plan.

4.  Brief description of DICOM standard processing applied by Ihe CPI Integrated Model workflow

In general, gray-scale digital images are displayed and displayed differently on different soft copy display devices and hard copy output devices, IHE Technical Architecture Definition CPI integration model is dedicated to solving this problem. Its implementation of the DICOM standard is mainly based on the following three definitions and mechanisms:

1)   Grayscale standard display function (gsdf ):

    DICOM gsdf (DICOM standard p3.14) defines a standard curve and applies it to medical imaging to establish a Collimated process of rendering status on different types of soft copy display devices and hard copy output devices. Human Visual Perception is non-linear in response to different Luminance Levels (luminance, lumens), and its sensitivity to brightness changes in the bright and dark regions varies, DICOM gsdf defines a standard characteristic curve that represents the sensitivity of the eye to brightness changes, that is, the JND (just noticeable differences) curve, it converts a non-linear Human Visual luminance horizontal sensing State to a Visual Sensing Linear JND curve (Figure 2), while the JND curve corresponds to the p-value that reflects the human visual sensing response, in this way, the consistency of the pixel data converted from different image outputs or display devices to the gray-scale display level is achieved.

 

2)   Grayscale Softcopy Presentation State (GSPs ):

    This is a data object defined in the DICOM standard for storing and communicating image display parameters. This data object contains various types of transformation processing information applied to its associated image rendering attributes: for example, perform various gray-scale contrast transformations (such as modality LUT and voi LUT) and spatial transformations (such as rotation, flip, and display of selected interest areas) and comments (including image or text comments and overlay) of the image and display field. The GSPs object also supports the presentation LUT conversion, that is, output the grayscale sequence value corresponding to the p-Volue.

3)  Supports basic print management SOP for the presentation LUT attribute:

Execute the DICOM basic grayscale print management SOP class that supports presentation LUT to print and output medical images, so that the same image (SET) in all print devices, the same p-value sequence data is converted to the grayscale display Sequence Value output to ensure the consistency of the output image presentation status. In the SOP definition of DICOM standard printing, presentation lut sop is optional and is not included in the basic print management SOP definition of DICOM standard. Therefore, only printing and output devices that support the Standard Basic grayscale print meta SOP cannot support the CPI integration model, that is, the foundation for establishing the image hard copy output process to comply with the Ihe CPI integration model is that such hard copy output devices provide support for the presentation lut sop option attribute.

5.   Other major Ihe workflows associated with the CPI Integration Model

The Ihe CPI Integration Model workflow is mainly associated with the process of generating medical images, soft copy applications, and hard copy output. Therefore, in the logical process of the PACS system, any process of generating, storing, releasing, and outputting medical images may be required to provide CPI support, any other Ihe workflow that contains such a processing process may also be associated with the CPI Integrated Model workflow. The most closely associated is the SWF and kin Integrated Model workflow:

1)  SWF integrated model (scheduled workflow profile)

The Ihe SWF integration model represents the workflow of imaging examination in the medical imaging field. It defines the processes of generating, transferring, archiving, and applying image objects, the process of GSPs object generation, transfer, archive storage, and application operations in the CPI process is closely related to the logical process of images. Therefore, the CPI Integration Model workflow can be regarded as a subsidiary process that completely overlaps with the SWF workflow and serves as its supplement and extension. In application practice, the function processing defined by CPI does not need to completely cover the SWF process associated with it, it can occur independently in the image production and storage processes or the application release processes of images.

2)  Key image note Profile)

The Ko object in the kin integration model process is similar to the GSPs object in the CPI integration model. They are all evidence objects attached to image objects and released along with image objects. Therefore, most of kin integration model workflows and CPI integration model workflows overlap completely. CPI only further includes the image hard copy output process. The relationship, association, and operation methods between GSPs of CPI and Ko objects of kin and image objects have many commonalities. At the same time, GSPs and Ko objects are also correlated, that is, during the image publishing and application operations, you can call the GSPs object and Ko object associated with the image object separately or synchronously; when a KO object is generated, called, and operated, the relevant GSPs object can also be obtained to process the rendering status of the image (SET) associated with Ko.

 

 Reprinted from: http://www.med-informatics.cn/Myarticles/show_pages/IHE_CPI.htm