| DICOM PS3.17 2026d - Explanatory Information |
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In medical imaging, diverse types of X-Ray attenuators are employed to influence the quality and characteristics of ionizing radiation. These devices play a critical role in optimizing image quality, reducing patient dose, and ensuring diagnostic accuracy. While the physical diversity of attenuators is broad, the DICOM standard classifies them into four distinct categories for consistent encoding and interoperability:
X-Ray Filters modify the energy spectrum of the X-Ray beam. They can be uniform (e.g., spectral filters) or non-uniform (e.g., wedge filters), and help optimize image quality and reduce patient dose.
Collimators are devices that limit the X-Ray beam to the area of interest, reducing unnecessary exposure and enhancing image contrast. They are essential for precise beam shaping.
X-Ray Grids (anti-scatter grids) are placed between the patient and detector to absorb scattered radiation, improving image clarity and contrast.
X-Ray Attenuators include other objects in the beam path, such as patient tables or support devices, which affect radiation attenuation and must be accounted for in imaging and dose calculations.
TID 10003B “Irradiation Event X-Ray Source Data” encodes the X-Ray Filters Container that can be repeatedly included for each filter applied during an irradiation event. The Container has concepts to specify the X-Ray Filter Type, X-Ray Filter Material, X-Ray Filter Thickness Minimum and X-Ray Filter Thickness Maximum. The codes for filter types and filter material are defined in CID 10007 and CID 10006. The typical filtration with a copper filter is declared by the filter type of "Flat filter". If no filtration was used during an Irradiation Event, the value "No Filter" is used. In the typical case that the filter has a homogeneous thickness, the same value is encoded in the minimum and maximum thickness concepts.
Non-uniform filters are listed in the filter types, but the Concept Items in the X-Ray Filters containers cannot fully describe the profile and geometry of such modulating filters rather than indicating that one of these filters was used.
TID 10003B also encodes concepts to specify the collimation, such as height, width, and area, but it cannot fully describe the profile and geometry of the collimation which typically include multiple blades.
TID 10003B also encodes the X-Ray Grid to indicate if an anti-scatter grid was used by describing the related grid type (see CID 10017). A value of "No grid" is available to indicate it was removed or it is not supported by the equipment.
Other X-Ray attenuators such as patient support (e.g., X-Ray Table) are described in TID 10003C “Irradiation Event X-Ray Mechanical Data”.
| DICOM PS3.17 2026d - Explanatory Information |
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