Config files

After following the steps outlined in Getting Started, you'll notice that the OHIF Viewer has data for several studies and their images. You didn't add this data, so where is it coming from?

By default, the viewer is configured to connect to a Amazon S3 bucket that is hosting a Static WADO server (see Static WADO DICOMWeb). By default we use default.js for the configuration file. You can change this by setting the APP_CONFIG environment variable and select other options such as config/local_orthanc.js or config/google.js.

Configuration Files

The configuration for our viewer is in the <root>platform/app/public/config directory. Our build process knows which configuration file to use based on the APP_CONFIG environment variable. By default, its value is config/default.js. The majority of the viewer's features, and registered extension's features, are configured using this file.

The simplest way is to update the existing default config:

platform/app/public/config/default.js

window.config = {
  routerBasename: '/',
  extensions: [],
  modes: [],
  showStudyList: true,
  dataSources: [
    {
      namespace: '@ohif/extension-default.dataSourcesModule.dicomweb',
      sourceName: 'dicomweb',
      configuration: {
        friendlyName: 'dcmjs DICOMWeb Server',
        name: 'DCM4CHEE',
        wadoUriRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/wado',
        qidoRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/rs',
        wadoRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/rs',
        qidoSupportsIncludeField: true,
        supportsReject: true,
        imageRendering: 'wadors',
        thumbnailRendering: 'wadors',
        enableStudyLazyLoad: true,
        supportsFuzzyMatching: true,
        supportsWildcard: true,
        omitQuotationForMultipartRequest: true,
      },
    },
  ],
  defaultDataSourceName: 'dicomweb',
};

As you can see a new change in OHIF-v3 is the addition of dataSources. You can build your own datasource and map it to the internal data structure of OHIF’s > metadata and enjoy using other peoples developed mode on your own data!

You can read more about data sources at Data Source section in Modes

The configuration can also be written as a JS Function in case you need to inject dependencies like external services:

window.config = ({ servicesManager } = {}) => {
  const { UIDialogService } = servicesManager.services;
  return {
    cornerstoneExtensionConfig: {
      tools: {
        ArrowAnnotate: {
          configuration: {
            getTextCallback: (callback, eventDetails) => UIDialogService.create({...
          }
        }
      },
    },
    routerBasename: '/',
    dataSources: [
    {
      namespace: '@ohif/extension-default.dataSourcesModule.dicomweb',
      sourceName: 'dicomweb',
      configuration: {
        friendlyName: 'dcmjs DICOMWeb Server',
        name: 'DCM4CHEE',
        wadoUriRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/wado',
        qidoRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/rs',
        wadoRoot: 'https://server.dcmjs.org/dcm4chee-arc/aets/DCM4CHEE/rs',
        qidoSupportsIncludeField: true,
        supportsReject: true,
        imageRendering: 'wadors',
        thumbnailRendering: 'wadors',
        enableStudyLazyLoad: true,
        supportsFuzzyMatching: true,
        supportsWildcard: true,
        omitQuotationForMultipartRequest: true,
      },
    },
  ],
  defaultDataSourceName: 'dicomweb',
  };
};

Configuration Options

Here are a list of some options available:

• disableEditing: If true, it disables editing in OHIF, hiding edit buttons in segmentation panel and locking already stored measurements.
• maxNumberOfWebWorkers: The maximum number of web workers to use for decoding. Defaults to minimum of navigator.hardwareConcurrency and what is specified by maxNumberOfWebWorkers. Some windows machines require smaller values.
• acceptHeader : accept header to request specific dicom transfer syntax ex : [ 'multipart/related; type=image/jls; q=1', 'multipart/related; type=application/octet-stream; q=0.1' ]
• investigationalUseDialog: This should contain an object with option value, it can be either always which always shows the dialog once per session, never which never shows the dialog, or configure which shows the dialog once and won't show it again until a set number of days defined by the user, if it's set to configure, you are required to add an additional property days which is the number of days to wait before showing the dialog again.
• groupEnabledModesFirst: boolean, if set to true, all valid modes for the study get grouped together first, then the rest of the modes. If false, all modes are shown in the order they are defined in the configuration.
• experimentalStudyBrowserSort: boolean, if set to true, you will get the experimental StudyBrowserSort component in the UI, which displays a list of sort functions that the displaySets can be sorted by, the sort reflects in all part of the app including the thumbnail/study panel. These sort functions are defined in the customizationModule and can be expanded by users.
• disableConfirmationPrompts: boolean, if set to true, it skips confirmation prompts for measurement tracking and hydration.
• showPatientInfo: string, if set to 'visible', the patient info header will be shown and its initial state is expanded. If set to 'visibleCollapsed', the patient info header will be shown but it's initial state is collapsed. If set to 'disabled', the patient info header will never be shown, and if set to 'visibleReadOnly', the patient info header will be shown and always expanded.
• requestTransferSyntaxUID : Request a specific Transfer syntax from dicom web server ex: 1.2.840.10008.1.2.4.80 (applied only if acceptHeader is not set)
• omitQuotationForMultipartRequest: Some servers (e.g., .NET) require the multipart/related request to be sent without quotation marks. Defaults to false. If your server doesn't require this, then setting this flag to true might improve performance (by removing the need for preflight requests). Also note that if auth headers are used, a preflight request is required.
• maxNumRequests: The maximum number of requests to allow in parallel. It is an object with keys of interaction, thumbnail, and prefetch. You can specify a specific number for each type.
• modesConfiguration: Allows overriding modes configuration.
  • Example config:

    modesConfiguration: {
      '@ohif/mode-longitudinal': {
        displayName: 'Custom Name',
        routeName: 'customRouteName',
          routes: [
            {
              path: 'customPath',
              layoutTemplate: () => {
                /** Custom Layout */
                return {
                  id: ohif.layout,
                  props: {
                    leftPanels: [tracked.thumbnailList],
                    rightPanels: [dicomSeg.panel, tracked.measurements],
                    rightPanelClosed: true,
                    viewports: [
                      {
                        namespace: tracked.viewport,
                        displaySetsToDisplay: [ohif.sopClassHandler],
                      },
                    ],
                  },
                };
              },
            },
          ],
      }
    },
  Note: Although the mode configuration is passed to the mode factory function, it is up to the particular mode itself if its going to use it to allow overwriting its original configuration e.g.

    function modeFactory({ modeConfiguration }) {
    return {
      id,
      routeName: 'viewer',
      displayName: 'Basic Viewer',
      ...
      onModeEnter: ({ servicesManager, extensionManager, commandsManager }) => {
        ...
      },
      /**
       * This mode allows its configuration to be overwritten by
       * destructuring the modeConfiguration value from the mode fatory function
       * at the end of the mode configuration definition.
       */
      ...modeConfiguration,
    };
  }
• showLoadingIndicator: (default to true), if set to false, the loading indicator will not be shown when navigating between studies.
• useNorm16Texture: (default to false), if set to true, it will use 16 bit data type for the image data wherever possible which has significant impact on reducing the memory usage. However, the 16Bit textures require EXT_texture_norm16 extension in webGL 2.0 (you can check if you have it here https://webglreport.com/?v=2). In addition to the extension, there are reported problems for Intel Macs that might cause the viewer to crash. In summary, it is great a configuration if you have support for it.
• useSharedArrayBuffer (default to 'TRUE', options: 'AUTO', 'FALSE', 'TRUE', note that these are strings), for volume loading we use sharedArrayBuffer to be able to load the volume progressively as the data arrives (each webworker has the shared buffer and can write to it). However, there might be certain environments that do not support sharedArrayBuffer. In that case, you can set this flag to false and the viewer will use the regular arrayBuffer which might be slower for large volume loading.
• supportsWildcard: (default to false), if set to true, the datasource will support wildcard matching for patient name and patient id.
• allowMultiSelectExport: (default to false), if set to true, the user will be able to select the datasource to export the report to.
• activateViewportBeforeInteraction: (default to true), if set to false, tools can be used directly without the need to click and activate the viewport.
• autoPlayCine: (default to false), if set to true, data sets with the DICOM frame time tag (i.e. (0018,1063)) will auto play when displayed
• addWindowLevelActionMenu: (default to true), if set to false, the window level action menu item is NOT added to the viewport action corners
• dangerouslyUseDynamicConfig: Dynamic config allows user to pass configUrl query string. This allows to load config without recompiling application. If the configUrl query string is passed, the worklist and modes will load from the referenced json rather than the default .env config. If there is no configUrl path provided, the default behaviour is used and there should not be any deviation from current user experience.
  Points to consider while using dangerouslyUseDynamicConfig:
  
  • User have to enable this feature by setting dangerouslyUseDynamicConfig.enabled:true. By default it is false.
  • Regex helps to avoid easy exploit. Default is /.*/. Setup your own regex to choose a specific source of configuration only.
  • System administrators can return cross-origin: same-origin with OHIF files to disallow any loading from other origin. It will block read access to resources loaded from a different origin to avoid potential attack vector.
  • Example config:

    dangerouslyUseDynamicConfig: {
      enabled: false,
      regex: /.*/
    }

  Example 1, to allow numbers and letters in an absolute or sub-path only.
  regex: /(0-9A-Za-z.]+)(\/[0-9A-Za-z.]+)*/
  Example 2, to restricts to either hosptial.com or othersite.com.
  regex: /(https:\/\/hospital.com(\/[0-9A-Za-z.]+)*)|(https:\/\/othersite.com(\/[0-9A-Za-z.]+)*)/
  Example usage:
  http://localhost:3000/?configUrl=http://localhost:3000/config/example.json
  

• onConfiguration: Currently only available for DicomWebDataSource, this option allows the interception of the data source configuration for dynamic values e.g. values coming from url params or query params. Here is an example of building the dicomweb datasource configuration object with values that are based on the route url params:

  {
    namespace: '@ohif/extension-default.dataSourcesModule.dicomweb',
    sourceName: 'gcpdicomweb',
    configuration: {
      friendlyName: 'GCP DICOMWeb Server',
      name: 'gcpdicomweb',
      qidoSupportsIncludeField: false,
      imageRendering: 'wadors',
      thumbnailRendering: 'wadors',
      enableStudyLazyLoad: true,
      supportsFuzzyMatching: false,
      supportsWildcard: false,
      singlepart: 'bulkdata,video,pdf',
      onConfiguration: (dicomWebConfig, options) => {
        const { params } = options;
        const { project, location, dataset, dicomStore } = params;
        const pathUrl = `https://healthcare.googleapis.com/v1/projects/${project}/locations/${location}/datasets/${dataset}/dicomStores/${dicomStore}/dicomWeb`;
        return {
          ...dicomWebConfig,
          wadoRoot: pathUrl,
          qidoRoot: pathUrl,
          wadoUri: pathUrl,
          wadoUriRoot: pathUrl,
        };
      },
    },
  },

This configuration would allow the user to build a dicomweb configuration from a GCP healthcare api path e.g. http://localhost:3000/projects/your-gcp-project/locations/us-central1/datasets/your-dataset/dicomStores/your-dicom-store/study/1.3.6.1.4.1.1234.5.2.1.1234.1234.123123123123123123123123123123

note

You can stack multiple panel components on top of each other by providing an array of panel components in the rightPanels or leftPanels properties.

For instance we can use

rightPanels: [[dicomSeg.panel, tracked.measurements], [dicomSeg.panel, tracked.measurements]]

This will result in two panels, one with dicomSeg.panel and tracked.measurements and the other with dicomSeg.panel and tracked.measurements stacked on top of each other.

Study Prefetcher

You can enable the study prefetcher so that OHIF loads the next/previous series/display sets based on the proximity to the current series/display set. This can be useful to improve the user experience

  studyPrefetcher: {
    /* Enable/disable study prefetching service (default: false) */
    enabled: true,
    /* Number of displaysets to be prefetched  (default: 2)*/
    displaySetCount: 2,
    /**
     * Max number of concurrent prefetch requests (default: 10)
     * High numbers may impact on the time to load a new dropped series because
     * the browser will be busy with all prefetching requests. As soon as the
     * prefetch requests get fulfilled the new ones from the new dropped series
     * are sent to the server.
     *
     * TODO: abort all prefetch requests when a new series is loaded on a viewport.
     * (need to add support for `AbortController` on Cornerstone)
     * */
    maxNumPrefetchRequests: 10,
    /* Display sets loading order (closest (deafult), downward or upward) */
    order: 'closest',
  },

More on Accept Header Configuration

In the previous section we showed that you can modify the acceptHeader configuration to request specific dicom transfer syntax. By default we use acceptHeader: ['multipart/related; type=application/octet-stream; transfer-syntax=*'] for the following reasons:

• Ensures Optimal Transfer Syntax: By allowing the server to select the transfer syntax, the client is more likely to receive the image in a syntax that's well-suited for fast transmission and rendering. This might be the original syntax the image was stored in or another syntax that the server deems efficient.

• Avoids Transcoding: Transcoding (converting from one transfer syntax to another) can be a resource-intensive process. Since the OHIF Viewer supports all transfer syntaxes, it is fine to accept any transfer syntax (transfer-syntax=*). This allows the server to send the images in their stored syntax, avoiding the need for costly on-the-fly conversions. This approach not only saves server resources but also reduces response times by leveraging the viewer's capability to handle various syntaxes directly.

• Faster Data Transfer: Compressed transfer syntaxes generally result in smaller file sizes compared to uncompressed ones. Smaller files transmit faster over the network, leading to quicker load times for the end-user. By accepting any syntax, the client can take advantage of compression when available.

However, if you would like to get compressed data in a specific transfer syntax, you can modify the acceptHeader configuration or requestTransferSyntaxUID configuration.

Environment Variables

We use environment variables at build and dev time to change the Viewer's behavior. We can update the HTML_TEMPLATE to easily change which extensions are registered, and specify a different APP_CONFIG to connect to an alternative data source (or even specify different default hotkeys).

Environment Variable	Description	Default
HTML_TEMPLATE	Which HTML template to use as our web app's entry point. Specific to PWA builds.	index.html
PUBLIC_URL	The route relative to the host that the app will be served from. Specific to PWA builds.	/
APP_CONFIG	Which [configuration file][config-file] to copy to output as app-config.js	config/default.js
PROXY_TARGET	When developing, proxy requests that match this pattern to PROXY_DOMAIN	undefined
PROXY_DOMAIN	When developing, proxy requests from PROXY_TARGET to PROXY_DOMAIN	undefined
OHIF_PORT	The port to run the webpack server on for PWA builds.	3000

You can also create a new config file and specify its path relative to the build output's root by setting the APP_CONFIG environment variable. You can set the value of this environment variable a few different ways:

• Add a temporary environment variable in your shell
  • Previous react-scripts functionality that we need to duplicate with dotenv-webpack
• Add environment specific variables in .env file(s)
  • Previous react-scripts functionality that we need to duplicate with dotenv-webpack
• Using the cross-env package in a npm script:
  • "build": "cross-env APP_CONFIG=config/my-config.js react-scripts build"

After updating the configuration, yarn run build to generate updated build output.