A.2 Abstract Multi-Dimensional Image Model
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## A.2 Abstract Multi-Dimensional Image Model

### A.2.1 Usage

The Abstract Multi-Dimensional Image Model can be used to refer to a discretely-sampled, multi-dimensional image data. The sample values may either be single-valued (a scalar) or a vector of values (a vector). An example would be a time varying series of three dimensional images set at multiple energy levels. The Abstract Multi-Dimensional Image Model is patterned after the Enhanced Multi-frame family of DICOM objects. In mathematical terms, this is any data set that is defined by a function I (x,y,z,t,…), where (x,y,z,t,…) are the dimensions, and the sample value of I is either a vector of components or a scalar (i.e., a single component). The primary purpose of this model is to allow applications to process image data without concern as to the underlying format of the data.

When converting DICOM SOP Instances into Abstract Multi-Dimensional Image Models, a provider of data shall follow these rules as closely as it practically can:

### Note

Deterministic behavior is not expected nor guaranteed when making conversions between DICOM SOP Instances and Abstract Multi-Dimensional Image Models. For example, given the same DICOM SOP Instances, different Hosting Systems may create Abstract Multi-Dimensional Image Models that differ in some details, such as the Units of the Component values or in the Dimensions.

1. Multiple DICOM SOP Instances from the same series that have the same Frame of Reference UID shall be combined into a single instance of the Abstract Multi-Dimensional Image Model. DICOM SOP Instances from multiple series that have the same Frame of Reference UUID may be combined into a single instance of the Abstract Multi-Dimensional Image Model, if appropriate.

2. A single DICOM SOP Instance shall not be divided into multiple instances of the Abstract Multi-Dimensional Image Model.

3. The coordinate system utilized within the Abstract Multi-Dimensional Image Model shall use the coordinate system defined by the DICOM objects utilized in the creation of the Abstract Multi-Dimensional Image Model instance if applicable. Where practical, the coordinate system and Dimension definitions utilized within the Abstract Multi-Dimensional Image Model shall be chosen such that interpolation is not required to covert the source data into the Abstract Multi-Dimensional Image Model.

   ### Note

   Interpolation may be necessary if the source data is not laid out on a frame-based Cartesian coordinate grid.

4. Spatial coordinates, such as Image Position (Patient) (0020,0032), shall be transformed into the coordinate system utilized within the Abstract Multi-Dimensional Image Model instance.

5. The Pixel Data shall be spatially transformed as needed to match the Semantics and Units of the Dimensions of the Abstract Multi-Dimensional Image Model into which the pixels values are being placed.

6. Any embedded overlays within the Pixel Data (7FE0,0010) Attribute shall be stripped out of the pixel values and the pixel values sign extended or converted as needed to match the datatype of the Component of the Abstract Multi-Dimensional Image Model into which the pixels values are being placed.

7. The pixel values of the Pixel Data shall be transformed as needed to match the Semantics and Units of the Component of the Abstract Multi-Dimensional Image Model into which the pixels values are being placed.

   ### Note

   Typically presentation settings such as VOI and Presentation LUTs are not used in creating Abstract Multi-Dimensional Image Models from DICOM SOP Instances. The exception is when the application of such LUTs is needed to match the Semantics and Units of the Component. Modality LUTs or Rescale Slope and Intercept often must be applied to match the Semantics and Units of the Abstract Multi-Dimensional Image Model.

8. Any pixel values that correspond to the pixel padding values shall be stripped out (i.e., set to zero or other suitable replacement value) and the spatially corresponding values in the PixelMapOfValidData shall be set to the outValue or something other than the inValue, as appropriate.

When converting data within an instance of the Abstract Multi-Dimensional Image Models into DICOM SOP Instances, the recipient of an abstract model instance shall convert the pixel data back into values compatible with the native form of the DICOM SOP Instances being created. This conversion may include recreating Modality LUT information, inserting pixel padding values, converting pixel spacing and origins, etc. as dictated by the SOP Class the data is being converted to. When converting a single Abstract Multi-Dimensional Image Model into multiple DICOM SOP Instances, the DICOM SOP Instances shall all have the same Frame of Reference UID (0020,0052), if permitted by the SOP Class.

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