View source for The CTP DICOM Filter

The CTP DicomFilter is a pipeline stage that provides preprocessing of DicomObjects, quarantining those which do not meet the conditions of a script program. This article describes the script language. The intended audience for this article is CTP administrators setting up a processing pipeline.
==The Script Language==
The script language interrogates a received DICOM object and computes a boolean result that, if <b>true</b>, results in the object being accepted for further processing in the pipeline, and if <b>false</b>, results in the object being quarantined, aborting further processing. 

An expression in the language consists of terms separated by operators and/or parentheses. There are three operators, listed in order of increasing precedence:
*<b>+</b> is logical <b>or</b>
*<b>*</b> is logical <b>and</b>
*<b>!</b> is unary logical <b>negation</b>

Examples:
*term
*<b>!</b>term
*term + term * term
*term * (term + term) + term * !term

Terms in the language are either reserved words (<b>true.</b> or <b>false.</b>) (note the periods after the words) or expressions in the form: 

::<b><font color=red>identifier</font>.method("<font color=blue>string</font>")</b>

An identifier is either a DICOM element name as defined in the CTP DICOM Anonymizer (e.g. SOPInstanceUID) or a DICOM tag, specified in square brackets (e.g. [0008,0018]). No spaces are permitted in identifiers, and tags are required to contain all eight hexadecimal digits identifying the group and element.

The language supports these methods:
*<b>equals</b> returns <b>true</b> if the value of the <b>identifier</b> exactly equals the <b>string</b> argument; otherwise, it returns <b>false</b>.
*<b>matches</b> returns <b>true</b> if the value of the <b>identifier</b> matches the regular expression specified in the <b>string</b> argument; otherwise, it returns <b>false</b>.
*<b>contains</b> returns <b>true</b> if the value of the <b>identifier</b> contains the the <b>string</b> argument anywhere within it; otherwise, it returns <b>false</b>.
*<b>startsWith</b> returns <b>true</b> if the value of the <b>identifier</b> starts with the <b>string</b> argument; otherwise, it returns <b>false</b>.
*<b>endsWith</b> returns <b>true</b> if the value of the <b>identifier</b> ends with the <b>string</b> argument; otherwise, it returns <b>false</b>.

The value of an identifier is the string value stored in the received DICOM object in the element associated with the identifier. If an identifier is missing from the received DICOM object, an empty string is provided.

Script Example:
Suppose that images are to be rejected if they are of type "SECONDARY". Such images could be filtered out of the pipeline with a script like:

::<b>!ImageType.contains("SECONDARY")</b>

Note the unary negation operator, which is necessary to generate <b>true</b> for images which do <b>not</b> contain the string <b>SECONDARY</b>.

Suppose that images are to be rejected if they are of type "SECONDARY" or of type "DERIVED". Such images could be filtered out of the pipeline with a script like:

::<b>!(ImageType.contains("SECONDARY") + ImageType.contains("DERIVED"))</b>

Note again the unary negation operator, and also note the parentheses and the logical <b>or</b> operator, all of which combine to generate <b>true</b> only if the type is neither <b>SECONDARY</b> nor <b>DERIVED</b>.

Finally, suppose that images containing any non-empty value in the ImageType element are to be rejected. Such images could be filtered out with a script like:

::<b>ImageType.equals("")</b>