Modality Worklist SOP Class

6.7. Modality Worklist SOP Class#

This normative section contains a description of the DICOM tags which are necessary to request for orthodontic photographs to be taken (acquired).

The Modality Worklist is designed to streamline the exchange of clinical information between devices, minimizing the need for manual data entry across multiple systems. Proper implementation of Modality Worklists can reduce staff burnout and human errors, ultimately enhancing patient care.

This section aims to promote the widespread adoption of the Modality Worklist workflow by simplifying its implementation and reducing associated costs to a minimum.

6.7.1. Modality Worklist Workflow#

  1. Request Generation by Practice Management System (PMS) The Practice Management System (PMS) is responsible for generating requests for acquiring photographs or radiographs.

  2. Determination of Image Type The PMS uses information from the appointment type or the procedure associated with the appointment to determine the specific images required, such as panoramic (PX), CBCT (CT), Digital Radiographs (DX) or intraoral photographs taken with an External Camera (XC).

  3. Image Acquisition Request Upon patient check-in, the PMS generates a request for the required images to be acquired via the DICOM network.

  4. Modality Query When a staff member operates an imaging device (referred to as a Modality in DICOM terminology), the device queries the PMS using DICOM language to understand the imaging requirements.

  5. PMS Response with Modality Worklist The PMS responds with a Modality Worklist DICOM object, which includes specific information such as patient demographics, type of image to be acquired (e.g., CT, PX, DX, XC), and the required protocol.

  6. Pre-Population of Fields The imaging device pre-populates all necessary fields based on the Modality Worklist and presents only the relevant options required for the image acquisition.

  7. Image Acquisition The staff member proceeds to acquire the images as specified.

  8. Image Formatting and Transmission The imaging device uses information from the Modality Worklist to create properly tagged and formatted medical images in DICOM format, which are then sent to the imaging server (PACS).

6.7.2. Modality Worklist in Orthodontics#

There are three main building blocks of a modality worklist. This explanation will describe how these components apply to the orthodontic domain, specifically for orthodontic photographs. For further details, refer to DICOM Part 3.4, Section K.6 and the IHE RAD-5 Profile.

  1. Requested Procedure

    This represents a high-level procedure associated with an appointment, such as an Initial Visit or Initial Records. During such appointments, the patient may need to collect various types of images, including Digital X-rays (DX), Panoramic X-rays (PX), Computed Tomography (CT), and Extraoral Photographs (XC).

  2. Scheduled Procedure Step

    Each requested procedure can have multiple procedure steps, which are modality-specific. For instance, for an Initial Visit, the following steps might be required:

    • One PX

    • Two DX (PA and lateral)

    • Eight XC (intraoral and extraoral)

  3. Scheduled Protocol Code Sequence (0040,0008)

    Each procedure step can include one or more scheduled protocol codes. For example, the PX scheduled procedure step might use the code 89846007 | Orthopantogram (procedure), while the XC scheduled procedure step may include codes such as:

    • 1306665006 | Photographic extraoral image of full face with full smile and jaws in centric relation (record artifact)

    • 1306651009 | Photographic extraoral image of left half of face with full smile and teeth in centric occlusion (record artifact)

    • …

    This section specifies where the different image types defined in ADA Standard 1100 (referred to as views in the standard) can be saved.

  4. Accession Number (0008,0050)

    The DICOM Accession Number may be used to identify the patient’s appointment. According to IHE RAD-5 Vol1, the Accession Number may group one or more Requested Procedures. In orthodontics, an example situation where this might occur could be when a patient has a Fixed Appliance Initial Visit appointment. This includes both Initial Records before installing the fixed appliance and records after having applied the fixed appliance. In this case, one Requested Procedure, possibly with two Scheduled Procedure Steps (one for XC modality, one for CT modality to capture and record patient state before anything has been done), could be associated with the same Accession Number of a second Requested Procedure. This second Requested Procedure includes only the XC modality to record the status of the oral cavity after the appliance has been installed.

6.7.3. Unique Identification of a Photographic Session#

In the context of orthodontic photography software development, it is useful to uniquely identify each photographic session. This ensures that images are correctly associated with the patient and the specific appointment. Since the DICOM Query Retrieve and Modality Worklist do not directly support querying and indexing by a unique identifier, the following DICOM tags are recommended to uniquely identify a photographic session within the Modality Worklist:

  • AccessionNumber

  • RequestedProcedureID

  • ScheduledProcedureStepID

A combination of these three tags can be used to uniquely identify a photographic session. In orthodontic practice, querying by accession number should typically return no more than two requested procedures or Modality Worklist instances. Therefore, it is feasible to query by accession number and then filter the results based on the requested procedure ID and scheduled procedure step ID.

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