C.8.8.3 RT Dose Module
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#### C.8.8.3 RT Dose Module

The RT Dose module is used to convey 2D or 3D radiation dose data generated from treatment planning systems or similar devices. The attributes defined within the module support dose for a single radiation beam (potentially comprised of multiple segments, as delivered in a dynamic treatment) or a group of beams comprising either a fraction group (see Section C.8.8.13) or a complete treatment plan (potentially the sum of multiple fraction groups).

The RT Dose module provides the mechanism to transmit a 3D array of dose data as a set of 2D dose planes that may or may not be related to CT or MR image planes. This mechanism works via the DICOM Multi-frame module that is required if multi-frame pixel data are sent.

Table C.8-39. RT Dose Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Samples per Pixel | (0028,0002) | 1C | Number of samples (planes) in this image. See Section C.8.8.3.4.1 for specialization. Required if Pixel Data (7FE0,0010) is present.
Photometric Interpretation | (0028,0004) | 1C | Specifies the intended interpretation of the pixel data. See Section C.8.8.3.4.2 for specialization. Required if Pixel Data (7FE0,0010) is present.
Bits Allocated | (0028,0100) | 1C | Number of bits allocated for each pixel sample. Each sample shall have the same number of bits allocated. See Section C.8.8.3.4.3 for specialization. Required Pixel Data (7FE0,0010) is present.
Bits Stored | (0028,0101) | 1C | Number of bits stored for each pixel sample. Each sample shall have the same number of bits stored. See Section C.8.8.3.4.4 for specialization. Required if Pixel Data (7FE0,0010) is present.
High Bit | (0028,0102) | 1C | Most significant bit for each pixel sample. Each sample shall have the same high bit. See Section C.8.8.3.4.5 for specialization. Required if Pixel Data (7FE0,0010) is present.
Pixel Representation | (0028,0103) | 1C | Data representation of the pixel samples. Each sample shall have the same pixel representation. See Section C.8.8.3.4.6 for specialization. Required Pixel Data (7FE0,0010) is present.
Dose Units | (3004,0002) | 1 | Units used to describe dose. Enumerated Values: GY Gray RELATIVE dose relative to implicit reference value
Dose Type | (3004,0004) | 1 | Type of dose. Defined Terms: PHYSICAL physical dose EFFECTIVE physical dose after correction for biological effect using user-defined modeling technique ERROR difference between desired and planned dose
Spatial Transform of Dose | (3004,0005) | 3 | The use of transformation in the calculation of the combined dose. Defined Terms: NONE No transformation. Calculated on the original image set RIGID Only Rigid transform used (see definition in Section C.20.2.1.2) NON_RIGID Any other transform used
Referenced Spatial Registration Sequence | (0070,0404) | 2C | A reference to a Spatial Registration SOP Instance or a Deformable Spatial Registration SOP Instance, which defines the transformation used to transform the dose. Required, if Spatial Transform of Dose (3004,0005) is provided and has a value of RIGID or NON_RIGID. Zero or more items shall be included in this sequence. See Section C.8.8.3.5
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
Instance Number | (0020,0013) | 3 | A number that identifies this object instance.
Dose Comment | (3004,0006) | 3 | User-defined comments for dose data.
Normalization Point | (3004,0008) | 3 | Coordinates (x, y, z) of normalization point in the patient based coordinate system described in Section C.7.6.2.1.1 (mm). See Section C.8.8.3.1.
Dose Summation Type | (3004,000A) | 1 | Type of dose summation. Defined Terms: PLAN dose calculated for entire delivery of all fraction groups of RT Plan MULTI_PLAN dose calculated for entire delivery of 2 or more RT Plans FRACTION dose calculated for entire delivery of a single Fraction Group within RT Plan BEAM dose calculated for entire delivery of one or more Beams within RT Plan BRACHY dose calculated for entire delivery of one or more Brachy Application Setups within RT Plan FRACTION_SESSION dose calculated for a single session ("fraction") of a single Fraction Group within RT Plan BEAM_SESSION dose calculated for a single session ("fraction") of one or more Beams within RT Plan BRACHY_SESSION dose calculated for a single session ("fraction") of one or more Brachy Application Setups within RT Plan CONTROL_POINT dose calculated for one or more Control Points within a Beam for a single fraction RECORD dose calculated for RT Beams Treatment Record
Referenced RT Plan Sequence | (300C,0002) | 1C | Sequence describing RT Plan associated with dose. Required if Dose Summation Type (3004,000A) is PLAN, MULTI_PLAN, FRACTION, BEAM, BRACHY, FRACTION_SESSION, BEAM_SESSION, BRACHY_SESSION or CONTROL_POINT. Only a single item shall be included in this sequence, unless Dose Summation Type (3004,000A) is MULTI_PLAN, in which case two or more items shall be included in this sequence. See Note 1.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>Referenced Fraction Group Sequence | (300C,0020) | 1C | Sequence of one Fraction Group containing beams or brachy application setups contributing to dose. Required if Dose Summation Type (3004,000A) is FRACTION, BEAM, BRACHY, FRACTION_SESSION, BEAM_SESSION, BRACHY_SESSION or CONTROL_POINT. Only a single item shall be included in this sequence. See Note 1.
>>Referenced Fraction Group Number | (300C,0022) | 1 | Uniquely identifies Fraction Group specified by Fraction Group Number (300A,0071) in Fraction Group Sequence of RT Fraction Scheme Module within RT Plan referenced in Referenced RT Plan Sequence (300C,0002).
>>Referenced Beam Sequence | (300C,0004) | 1C | Sequence of Beams in current Fraction Group contributing to dose. Required if Dose Summation Type (3004,000A) is BEAM, BEAM_SESSION or CONTROL_POINT. One or more items shall be included in this sequence.
>>>Referenced Beam Number | (300C,0006) | 1 | Uniquely identifies Beam specified by Beam Number (300A,00C0) in Beam Sequence of RT Beams Module within RT Plan referenced in Referenced RT Plan Sequence (300C,0002).
>>>Referenced Control Point Sequence | (300C,00F2) | 1C | Sequence defining the Control Points in current Beam contributing to dose. Required if Dose Summation Type (3004,000A) is CONTROL_POINT. Only a single item shall be included in this sequence.
>>>>Referenced Start Control Point Index | (300C,00F4) | 1 | Identifies Control Point specified by Control Point Index (300A,0112) within Beam referenced by Referenced Beam Number (300C,0006). This is the first of the two Control Points from which the Dose contribution to the Control Point can be calculated.
>>>>Referenced Stop Control Point Index | (300C,00F6) | 1 | Identifies Control Point specified by Control Point Index (300A,0112) within Beam referenced by Referenced Beam Number (300C,0006). This is the second of the two Control Points from which the Dose contribution to the Control Point can be calculated. The Control Point Index (300A,0112) referenced by Referenced Stop Control Point Index (300C,00F6) shall be the Control Point Index (300A,0112) immediately following the Control Point Index (300A,0112) referenced by Referenced Start Control Point Index (300C,00F4) within the Referenced Beam Number (300C,0006).
>>Referenced Brachy Application Setup Sequence | (300C,000A) | 1C | Sequence of Brachy Application Setups in current Fraction Group contributing to dose. Required if Dose Summation Type (3004,000A) is BRACHY or BRACHY_SESSION. One or more items shall be included in this sequence.
>>>Referenced Brachy Application Setup Number | (300C,000C) | 1 | Uniquely identifies Brachy Application Setup specified by Brachy Application Setup Number (300A,0234) in Brachy Application Setup Sequence (300A,0230) of RT Brachy Application Setups Module within RT Plan referenced in Referenced RT Plan Sequence (300C,0002).
Referenced Treatment Record Sequence | (3008,0030) | 1C | Sequence describing RT Beams Treatment Record associated with dose. One or more Items shall be included in this sequence. Required if Dose Summation Type (3004,000A) is RECORD.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>Referenced Beam Sequence | (300C,0004) | 1C | Sequence of Beams contributing to dose. One or more items shall be included in this sequence. Required, if the dose does not apply to the complete RT Beams Treatment Record referenced in the Referenced Treatment Record Sequence (3008,0030).
>>Referenced Beam Number | (300C,0006) | 1 | Uniquely identifies Beam specified by Beam Number (300A,00C0) in Beam Sequence of RT Beams Module within RT Beams Treatment Record referenced in the Referenced Treatment Record Sequence (3008,0030).
Grid Frame Offset Vector | (3004,000C) | 1C | An array that contains the dose image plane offsets (in mm) of the dose image frames in a multi-frame dose. Required if multi-frame pixel data are present and Frame Increment Pointer (0028,0009) points to Grid Frame Offset Vector (3004,000C). See Section C.8.8.3.2.
Dose Grid Scaling | (3004,000E) | 1C | Scaling factor that when multiplied by the dose grid data found in Pixel Data (7FE0,0010) attribute of the Image Pixel Module, yields grid doses in the dose units as specified by Dose Units (3004,0002). Required if Pixel Data (7FE0,0010) is present.
Tissue Heterogeneity Correction | (3004,0014) | 3 | Specifies a list of patient heterogeneity characteristics used for calculating dose. This Attribute shall be multi-valued if beams used to compute the dose have differing correction techniques. Enumerated Values: IMAGE image data ROI_OVERRIDE one or more ROI densities override image or water values where they exist WATER entire volume treated as water equivalent
Derivation Code Sequence | (0008,9215) | 3 | A coded description of how this dose was derived from other RT Dose and/or RT Plan objects. One or more Items are permitted in this Sequence. More than one Item indicates that successive derivation steps have been applied.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 7220 “RT Dose Derivation”.
Referenced Instance Sequence | (0008,114A) | 3 | The set of SOP Instances used to derive this RT Dose SOP instance. One or more Items are permitted in this Sequence.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>Purpose of Reference Code Sequence | (0040,A170) | 1 | Code describing the purpose of the reference to the Instance(s). Only a single Item is permitted in this Sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 7221 “RT Dose Purpose of Reference”.

### Note

In order to prevent misrepresentation of the dose summation:

1. If the Dose Summation Type (3004,000A) is PLAN, then only a single instance of RT Plan is referenced and the dose will be for the entire plan (i.e., it is not viable to combine only certain fraction groups of different plans).

2. If the Dose Summation Type (3004,000A) is MULTI_PLAN, then 2 or more instances of RT Plan may be referenced. As above, each reference will be for the entire plan.

3. If the Dose Summation Type (3004,000A) is FRACTION or FRACTION_SESSION, then only a single instance of RT PLAN and a single Fraction Group are referenced (i.e., component beams or brachy application setups are not referenced).

##### C.8.8.3.1 Normalization Point

Normalization Point (3004,0008) aids in the interpretation and subsequent use of the transmitted data. If used, it shall be a point receiving dose contributions from all referenced components of the dose summation.

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