Материал: part03

C.8.8.14.10 Compensator Transmission and Thickness Data Direction​

ThedirectionoftherowsandcolumnsinCompensatorTransmissionData(300A,00EB)andCompensatorThicknessData(300A,00EC)​ is defined as follows: The direction of rows goes along the positive Xb direction and the direction of the columns does along the​ negative Yb direction of the IEC X-BEAM LIMITING DEVICE coordinate system. Other interpretations shall be documented in an​ implementation's conformance statement.​

C.8.8.14.11 Block and Compensator Precedence for Dosimetric Calculations​

If Block Thickness (300A,0100) and Block Transmission (300A,0102) are present, Block Transmission shall have precedence for​ dosimetriccalculations.IfCompensatorTransmissionData(300A,00EB)andCompensatorThicknessData(300A,00EC)arepresent,​ Compensator Transmission Data shall have precedence for dosimetric calculations.​

C.8.8.14.12 Table Top Pitch and Table Top Roll​

Pitch and Roll Coordinate Systems of the Table Top are defined in IEC 61217 Edition 1.2 2008-04. These angles are defined as ro-​ tations of the IEC Table Top System as indicated below.​

The Table Top Pitch Angle is defined as the rotation of the coordinate axes Yt, Zt about axis Xt by an angle ψt; See Figure C.8.8.14-​ 1.AnincreaseinthevalueofangleψtcorrespondstotheclockwiserotationoftheTableTopasviewedfromtheTableTopcoordinate​ system origin along the positive Xt axis.​

The Table Top Roll Angle is defined as the rotation of the coordinate axes Xt, Zt about axis Yt by an angle ψt; See Figure C.8.8.14-​ 2.AnincreaseinthevalueofangleψtcorrespondstotheclockwiserotationoftheTableTopasviewedfromtheTableTopcoordinate​ system origin along the positive Yt axis.​

It is important to observe that the point of rotation is the origin of the table top system after the rotation of the PATIENT SUPPORT(s)​ system about Zs by θs after the rotation of the Table top eccentric rotation (e) system about Ze by θe and after the translation of Table​ top (t) system along Xe Ye Ze. This means that the rotation point of the Pitch and Roll angles is typically not the isocenter. The​ translational values Xt Yt Zt may need to be adjusted to preserve the patient position at the isocenter. e.g., a rotation of the Pitch​ angle by a positive angle at a position originally at Xt=0, Yt=100 and Zt=0 will lead to a negative Zt value and a slightly lower Yt if the​ patient position at isocenter is to be maintained.​

Z’t

Y’t

Ψt

Y t

Xt - Yt Plane

X t

Figure C.8.8.14-1. Table Top Pitch Angle​

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φt

Z t

Z’t

Y’t

Xt - Yt Plane

X t

X’t φt

Figure C.8.8.14-2. Table Top Roll Angle​

C.8.8.14.13 Angular Values in RT Beams Module​

TheAttributesthatdefineanglesrefertocoordinatesystemsdefinedbyIEC61217.WhereindicatedintheDICOMAttributedefinition,​ the angle uses the coordinate system (orientation of the rotation axis and the origin of the rotating coordinate system) defined in IEC​ 61217, however DICOM makes no restrictions on the range of values stored. IEC 61217 defines restrictions that only apply to user​ interface presentation.​

C.8.8.14.14 Effective Wedge Angle​

The Effective Wedge Angle (300A,00DE) and Radiation Beam Effective Wedge Angle (300A,0654) describe the dosimetric angle of​ a motorized wedge accounting for the partial presence of the wedge in the beam. The presence of the wedge in the beam is either​ specified by the Wedge Position (300A,0118) in the Wedge Position Sequence (300A,0116) included in the Control Point Sequence​ (300A,0111) of the current beam or the RT Control Point Sequence of the current Radiation. When the wedge is in the beam​ throughout all control points, the Effective Wedge Angle (300A,00DE) and Radiation Beam Effective Wedge Angle (300A,0654) will​ havethesamevalueastheWedgeAngle(300A,00D5)orRadiationBeamWedgeAngle(300A,0652).OtherwisetheEffectiveWedge​ Angle(300A,00DE)orRadiationBeamEffectiveWedgeAngle(300A,0654)willhavealowervaluethantheWedgeAngle(300A,00D5)​ or Radiation Beam Wedge Angle (300A,0652).​

C.8.8.14.15 Source to External Contour Distance and External Contour Entry Point​

The Source to External Contour Distance (300A,0132) is the distance to the beam entry point (External Contour Entry Point), which​ may include Bolus, Patient Positioning Devices, Patient Immobilization Devices or other devices. This value is useful for including​ the attenuation effects of external devices on the dose calculation and for patient setup.​

C.8.8.14.16 Referenced Control Point​

The number of Items in the Beam Dose Verification Control Point Sequence (300A,008C) is not required to be the same as in the​ Control Point Sequence (300A,0111). A different sampling can be chosen for the Beam Dose Verification Control Point Sequence,​ but where the Cumulative Meterset Weight of a Control Point Sequence (300A,008C) Item is the same it shall be referenced by the​ Referenced Control Point Index (300C,00F0).​

C.8.8.15 RT Brachy Application Setups Module​

The RT Brachy Application Setups Module describes the application of a brachytherapy radiotherapy treatment. It contains one or​ moresources,eachassociatedwithoneormoreChannels.AChannelisadevicebywhichasourceisplacedinitsintendedtreatment​ position or positions. A Channel may consist of a Source Applicator plus a Transfer Tube, a Source Applicator alone, a rigid or flexible​ linear source, or a seed. A number of Channels (for example applicators, sources or seeds) are generally arranged in an Application​ Setup, which may be considered a "logical" device. It is important not to confuse Application Setup with Applicator. The model used​

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here has been primarily built around the concept of remote afterloading, but extended to support other brachytherapy applications​ such as manual applicators and molds, seeds, and sources. Additional devices that are not Channels are described as Brachy Ac-​ cessory Devices. Examples of Accessory Devices include shields that modify the dose distribution from all sources in the treatment.​ However, Channel shields modify the dose only for the source(s) in that Channel.​

Table C.8-51. RT Brachy Application Setups Module Attributes​

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Enumerated Values:​

AIR_KERMA_RATE​AirKermaRateifSourceisGammaemitting​ Isotope.​

DOSE_RATE_WATER​Dose Rate in Water if Source is Beta​ emitting Isotope.​

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>>IncludeTable10-11“SOPInstanceReferenceMacroAttributes”​

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