Expressions

Actions on specific tags

This profile element applies an expression to a tag or a group of tags defined by the user. An expression is based on Spring Expression Language (SpEL) and returns a value or an action according to a certain condition.

Parameters

This profile element requires the following parameters:

Parameter	Required	Description
name	Yes	Description of the action applied
codename	Yes	Must be `expression.on.tags`
arguments	Yes	Definition of the expression with the `expr` argument
tags	Yes	List of tags the action should be applied to
condition	No	Optional condition to evaluate if this profile element should be applied to this DICOM instance
excludedTags	No	List of tags that will be ignored by this action

Expression Context

The expression is contained in the expr argument. When executed, it can either:

Return an action to be executed
Return a null value (does nothing and moves to the next profile element)

Available Variables

The following variables are available in the expression context, containing information about the current attribute:

Variable	Description	Example
`tag`	Current attribute tag	`(0010,0010)`
`vr`	Current attribute VR	`PN`
`stringValue`	Current element value	`'John^Doe'`

Constants

Constants improve readability and reduce errors:

Constant	Description	Example
`#Tag`	Retrieve any tag integer value from the DICOM standard	`#Tag.PatientBirthDate` returns (0010,0030)
`#VR`	Retrieve any VR value from the DICOM standard	`#VR.LO` returns the Long String type

Utility Functions

The following utility functions help work with tags:

Function	Description	Return Value
`getString(int tag)`	Returns the value of the given tag in the DICOM instance	String value or null if tag is not present
`tagIsPresent(int tag)`	Checks if the tag exists in the DICOM instance	`true` if present, `false` otherwise

Available Actions

Actions are defined as functions and set the operation to perform on the current tag:

Action	Description
`ReplaceNull()`	Sets the current tag value to empty
`Replace(String dummyValue)`	Replaces the current tag value with the specified value
`Remove()`	Removes the tag from the DICOM instance
`Keep()`	Keeps the tag unchanged
`UID()`	Replaces the current tag value with a newly generated UID and sets the tag’s VR to UI
`Add(int tagToAdd, int vr, String value)`	Adds a new tag to the DICOM instance
`ComputePatientAge()`	Replaces the current tag value with a computed patient’s age at the time of the exam
`ExcludeInstance()`	Interrupts the transfer of this instance (appears as Rejected in monitoring)

Examples

Conditional replacement based on tag value and type

Replace the Patient Name with the Institution Name if the current value is ‘John’, otherwise keep it unchanged:

  - name: "Expression"
    codename: "expression.on.tags"
    arguments:
      expr: "stringValue == 'John' and tag == #Tag.PatientName? Replace(getString(#Tag.InstitutionName)) : Keep()"
    tags: 
      - "(xxxx,xxxx)"

Info

This example applies to all attributes in the DICOM instance. For each tag, it either applies Keep or Replace, which prevents further profile elements from modifying those tags.

Remove tags with undefined values

Remove tags with ‘UNDEFINED’ value, otherwise keep them:

  - name: "Expression"
    codename: "expression.on.tags"
    arguments:
      expr: "stringValue == 'UNDEFINED'? Keep() : Remove()"
    tags: 
      - "(0010,0010)" #PatientName
      - "(0010,0212)" #StrainDescription

Concatenate multiple tag values

Replace Study Description with a concatenation of Institution Name and Station Name:

- name: "Expression"
  codename: "expression.on.tags"
  arguments:
    expr: "Replace(getString(#Tag.InstitutionName) + '-' + getString(#Tag.StationName))"
  tags: 
    - "(0008,1030)" #StudyDescription

Compute patient age

Calculate and set the patient’s age at the time of the exam:

- name: "Expression"
  codename: "expression.on.tags"
  arguments:
    expr: "ComputePatientAge()"
  tags: 
    - "(0010,1010)" #PatientAge

Exclude instances conditionally

Exclude all instances that contain a name in the image (where Specimen Label In Image is set to YES):

  - name: "Expression"
    codename: "expression.on.tags"
    arguments:
      expr: "getString(#Tag.SpecimenLabelInImage) == 'YES' ? ExcludeInstance() : null"
    tags: 
      - "(xxxx,xxxx)"