DICOM PS3.17 2020b - Explanatory Information

DDDD.3 Specification of Non-standard Measurements (Current)
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## DDDD.3 Specification of Non-standard Measurements

Non-Standard Measurements are defined by a particular vendor or clinical institution, and are not necessarily understood by users of other vendors' equipment or practitioners in other clinical institutions. A system producing such measurements cannot expect a consuming application to implicitly understand the measurement and its characteristics. Further, such measurements may not be fully understood by the medical practitioners who are acquiring the measurements, so there is some risk that the measurement acquired may not match the real-world quantity intended by the measurement definition, as illustrated by Figure DDDD.3-1.

Figure DDDD.3-1. Inadequate Definition of Non-Standard Measurement

It is important for all non-standard measurement definitions to include all the characteristics of the measurement as would have been specified for Standard (baseline) measurement definitions, such as:

- 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

Fully specifying the characteristics of such measurements is important for several reasons:

1. Ensuring medical practitioners correctly measure the intended real-world quantity

2. Aiding receiving applications in correctly interpreting the non-standard measurement and mapping the non-standard measurement to the most appropriate internally-supported measurement.

3. Aid in determining whether non-standard measurements from different sources are in fact equivalent measurements and could thus be described by a common measurement definition.

Each of these reasons is elaborated upon in the sections to follow. This is the justification for representing such non-standard measurements using both post-coordinated concepts and a pre-coordinated concept code for the measurement, such as is done in TID 5302 “Post-coordinated Echo Measurement”.

### DDDD.3.1 Acquiring the Intended Real-World Quantity

A medical practitioner can be expected to correctly acquire the real-world quantity intended by the non-standard measurement definition only if it is completely specified. This includes explicitly specifying all the essential clinical characteristics as are described for Standard measurements. While the resultant measurement value can be described by a pre-coordinated concept code, the characteristics of the intended real-world quantity must be defined and known.

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DICOM PS3.17 2020b - Explanatory Information