DICOM PS3.17 2018a - Explanatory Information

DDDD.2 Specification of Standard Measurements
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## DDDD.2 Specification of Standard Measurements

Clinical organizations publish recommendations for standardized measurements that comprise a necessary and sufficient quantification of particular anatomy and physiology useful in obtaining a clinical diagnosis. For each measurement recommendation, the measurement definition is specific enough so that any trained medical practitioner would know exactly how to acquire the measurement and how to interpret the measurement. Thus, there would be a 1:1 correspondence between the intended measurement recommendation and the practitioner's understanding of the intended measurement and the technique used to measure it (anatomy and physiology, image view, cardiac/respiratory phase, and position/orientation of measurement calipers). This is illustrated in Figure DDDD.2-1.

Figure DDDD.2-1. Matching Intended Quantity with Measurement Definition

The goal is for each recommended measurement to be fully specified such that every medical practitioner making the measurement on a given patient at a given time achieves the same result. However, if the recommendation were to be unclear or ambiguous, different qualified medical practitioners would achieve different results measuring the same quantity on the same patient, as illustrated in Figure DDDD.2-2.

Figure DDDD.2-2. Result of Unclear or Ambiguous Measurement Definition

There are a number of characteristics that should be included in a measurement recommendation in order to ensure that all practitioners making that measurement achieve the same results in making the measurement. Some characteristics are:

- Anatomy being measured, specified to appropriate level of detail

- Reference points (e.g., "OFD is measurement in the same plane as BPD from the outer table of the proximal skull with the cranial bones perpendicular to the US beam to the inner table of the distal skull")

- Type of measurement (distance, area, volume, velocity, time, VTI, etc.)

- Sampling method (average of several samples, peak value of several samples, etc.)

- Image view in which the measurement is made

- Cardiac and/or respiratory phase

The measurement definition should specify these characteristics in order that the definition is clear and unambiguous. Since the characteristics are published by the professional society as part of the Standard measurement definition document are incorporated in the codes that are added to LOINC, a pre-coordinated measurement code is sufficient to specify the measurement in a structured report.

Because of the detail in the definition of each standard measurement, it is sufficient to represent such measurements with a pre-coordinated measurement code and a minimum of circumstantial modifiers. This approach is being followed by TID 5301, for example.

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DICOM PS3.17 2018a - Explanatory Information