DICOM PS3.17 2018b - Explanatory Information

FFF.2.4.2.4 Examples
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##### FFF.2.4.2.4 Examples

###### FFF.2.4.2.4.1 Various Successive Derivations

In this example, the acquisition modality creates two instances of the Enhanced XA object: the instance "A" with mask frames and the instance "B" with contrast frames. A temporal filtering has been applied by the modality before the creation of the instances.

The workstation 1 performs a digital subtraction of the frames of the instance "B" by using the frames of the instance "A" as mask, then the resulting subtracted frames are stored in a new instance "C".

Finally the workstation 2 processes the instance "C" by applying a zoom and edge enhancement, and the resulting processed frames are stored in a new instance "D".

Figure FFF.2.4-2. Example of various successive derivations

Figure FFF.2.4-3 shows the values of the attributes of the instance "D" in the corresponding modules and macros related to derivation information. The Source Image Sequence (0008,2112) of the Derivation Image Sequence (0008,9124) does not contain the attribute Referenced Frame Number (0008,1160) because all the frames of the source images are used to generate the derived images.

Figure FFF.2.4-3. Attributes of the Example of Various Successive Derivations

###### FFF.2.4.2.4.2 Derivation by Applying A Square Root Transformation

In this example, the acquisition modality creates the instance "A" of the Enhanced XA object with 14 bits stored where the relationship between the pixel intensity and the X-Ray intensity is linear.

A workstation reads the instance "A", transforms the pixel values of the stored pixel data by applying a square root function and stores the resulting frames on the instance "B" with 8 bits stored.

Figure FFF.2.4-4. Example of Derivation by Square Root Transformation

The following figure shows the values of the attributes of the instance "B" in the corresponding modules and macros related to derivation information.

Note that the Derivation Code Sequence (0008,9215) is present when the Derivation Image Sequence (0008,9124) includes one or more items, even if the derivation code is not defined in the CID 7203 “Image Derivation”.

The Pixel Intensity Relationship LUT Sequence (0028,9422) contains a LUT with the function "TO_LINEAR" to allow the calculation of the gray level intensity to be linear to the X-Ray intensity. Since the instance "B" has 8 bits stored, this LUT contains 256 entries (starting the mapping at pixel value 0) and is encoded in 16 bits.

The value of the Pixel Intensity Relationship (0028,1040) in the Frame Pixel Data Properties Sequence (0028,9443) could be "OTHER" as it is described in the defined terms. However, a more explicit term like "SQRT" is also allowed and will have the same effect in the reading application.

In the case of a modification of the pixel intensity relationship of an image, the value of the attribute Image Processing Applied (0028,9446) in the Frame Pixel Data Properties Sequence (0028,9443) can be "NONE" in order to indicate to the reading applications that there was no image processing applied to the original image that could modify the spatial or temporal characteristics of the pixels.

Figure FFF.2.4-5. Attributes of the Example of Derivation by Square Root Transformation

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DICOM PS3.17 2018b - Explanatory Information