UUUU.4.5.2 Equipment Geometry in Traditional RDSR

UUUU.4.5.2 Equipment Geometry in Traditional RDSR (Current)
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In order to translate the value of Air Kerma at Reference Point to the Air Kerma at any other point on the patient (i.e., for organ dose calculations), additional geometric information is needed about the components of the imaging equipment as well as the patient location with respect to those components.

Depending on the modality and the type of equipment, the Reference Points are defined in different ways (e.g., based on Isocenter, detector, table, X-Ray source, breast support,…) so the required geometric information will vary from one RDSR to another.

RDSR encodes the orientation of the center of the X-Ray beam, the collimated area, as well as the positions, angulations and distances between the equipment components related to the Reference Point.

DICOM allows equipment to arbitrarily choose the origin of the coordinate system used. The equipment should use it consistently over the scope of accumulation of the RDSR to allow comparing values and deriving conclusions on the relative positions between all performed irradiation events.

The origin of the table coordinates should be consistent with the image header Attribute Table Height (0018,1130). The positioner/column angles are used to calculate the incidence of the X-Ray beam with respect to a patient.

System geometry distances are encoded per Irradiation Event in TID 10003C “Irradiation Event X-Ray Mechanical Data”, some of these distances are defined in the CID 10008 “Dose Related Distance Measurement”. Additionally, TID 10007 “Accumulated Total Projection Radiography Dose” allows encoding the Distance Source to Reference Point for the whole RDSR, but this is only applicable if this distance does not change through the RDSR.

Table UUUU.4.5.2-1 shows an example of encoding equipment geometry at the Irradiation Event level in Traditional RDSR for a patient positioned Head-First Supine.

Table UUUU.4.5.2-1. Example of Encoding Equipment Geometry at the Irradiation Event Level

NL	Concept Name	Code or Example Value	TID
	(113706, DCM, "Irradiation Event X-Ray Data")		TID 10003
…
>	(113745, DCM, "Patient Table Relationship")	(102540008, SCT, "headfirst")	TID 10003
>	(113743, DCM, "Patient Orientation")	(102538003, SCT, "recumbent")	TID 10003
>>	(113744, DCM, "Patient Orientation Modifier")	(40199007, SCT, "supine")	TID 10003
>	(113790, DCM, "Collimated Field Area")	0.04 m2	TID 10003B
>	(113788, DCM, "Collimated Field Height")	200.0 mm	TID 10003B
>	(113789, DCM, "Collimated Field Width")	200.0 mm	TID 10003B
>	(112011, DCM, "Positioner Primary Angle")	30.0 deg	TID 10003C
>	(112012, DCM, "Positioner Secondary Angle")	0.0 deg	TID 10003C
>	(113739, DCM, "Positioner Primary End Angle")	-10.0 deg	TID 10003C
>	(113740, DCM, "Positioner Secondary End Angle")	0.0 deg	TID 10003C
>	(113754, DCM, "Table Head Tilt Angle")	0.0 deg	TID 10003C
>	(113755, DCM, "Table Horizontal Rotation Angle")	0.0 deg	TID 10003C
>	(113756, DCM, "Table Cradle Tilt Angle")	0.0 deg	TID 10003C
Next rows are multiple inclusions from CID 10008 “Dose Related Distance Measurement”
>	(113751, DCM, "Table Longitudinal Position")	50.0 mm	TID 10003C
>	(113752, DCM, "Table Lateral Position")	400.0 mm	TID 10003C
>	(113753, DCM, "Table Height Position")	150.0 mm	TID 10003C
>	(113750, DCM, "Distance Source to Detector")	1100.0 mm	TID 10003C
>	(113737, DCM, "Distance Source to Reference Point")	650.0 mm	TID 10003C