# FFF.1.2.5.2 Field of View

The following concepts illustrate the model of the field of view:

The field of view (FOV) corresponds to a region of the physical detector array that has been irradiated.

The field of view image is the matrix of pixels of a rectangle circumscribing the field of view. Each pixel of the field of view image may be generated by multiple physical detector elements.

The attribute FOV Origin (0018,7030) contains the two values (FOV idet, FOV jdet ), which represent the offset of the center of the detector element at the TLHC of the field of view image, before rotation or flipping, from the center of the detector TLHC element. It is measured in physical detector elements. FOV Origin = (0,0) means that the detector TLHC element is at the TLHC of a rectangle circumscribing the field of view.

The attribute FOV Dimension (0018,9461) contains the two values FOV row dimension and FOV column dimension, which represent the dimension of the FOV in mm:

• FOV row dimension = dimension in mm of the field of view in the row direction;

• FOV column dimension = dimension in mm of the field of view in the column direction.

FOV pixel coordinates represented as (i , j) are columns and rows of the pixels in the field of view image.

FOV TLHC pixel is the pixel in the Top Left Hand Corner of the field of view image and corresponds to (i , j) = (0,0).

As an example, the point (ISO_P i, ISO_P j ) representing the projection of the Isocenter on the field of view image, and measured in FOV pixels as the offset from the center of the FOV TLHC pixel, can be calculated as follows:

ISO_P i = (ISO_P idet - FOV idet ) . Δ idet / Δ i - (1 - Δ idet / Δ i ) / 2

ISO_P j = (ISO_P jdet - FOV jdet ) . Δ jdet / Δ j - (1 - Δ jdet / Δ j ) / 2

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Figure FFF.1.2-10Field of View Image