DICOM PS3.3 2018e - Information Object Definitions

C.8.8.8 RT ROI Observations Module

The RT ROI Observations Module specifies the identification and interpretation of an ROI specified in the Structure Set Module and ROI Contour Module.

Table C.8-44. RT ROI Observations Module Attributes

Attribute Name

Tag

Type

Attribute Description

RT ROI Observations Sequence

(3006,0080)

1

Sequence of observations related to ROIs defined in the ROI Module.

One or more Items shall be included in this Sequence.

>Observation Number

(3006,0082)

1

Identification number of the Observation. The value of Observation Number (3006,0082) shall be unique within the RT ROI Observations Sequence (3006,0080).

>Referenced ROI Number

(3006,0084)

1

Uniquely identifies the referenced ROI described in the Structure Set ROI Sequence (3006,0020).

>ROI Observation Label

(3006,0085)

3

User-defined label for ROI Observation.

>ROI Observation Description

(3006,0088)

3

User-defined description for ROI Observation.

>RT Related ROI Sequence

(3006,0030)

3

Sequence of significantly related ROIs, e.g., CTVs contained within a PTV.

One or more Items are permitted in this Sequence.

>>Referenced ROI Number

(3006,0084)

1

Uniquely identifies the related ROI described in the Structure Set ROI Sequence (3006,0020).

>>RT ROI Relationship

(3006,0033)

3

Relationship of referenced ROI with respect to referencing ROI.

Defined Terms:

SAME

ROIs represent the same entity

ENCLOSED

referenced ROI completely encloses referencing ROI

ENCLOSING

referencing ROI completely encloses referenced ROI

>Segmented Property Category Code Sequence

(0062,0003)

3

Sequence defining the general category of the property this ROI represents.

Only a single Item is permitted in this Sequence.

See Note 1.

>>Include Table 8.8-1 “Code Sequence Macro Attributes”

No Baseline CID is defined.

>RT ROI Identification Code Sequence

(3006,0086)

3

Sequence containing Code used to identify ROI.

Only a single Item is permitted in this Sequence.

See Note 2.

>>Include Table 8.8-1 “Code Sequence Macro Attributes”

For dose measurement devices Baseline CID 7026 “Radiotherapeutic Dose Measurement Devices”.

No Baseline CID is defined otherwise.

>>Segmented Property Type Modifier Code Sequence

(0062,0011)

3

Sequence defining the modifier of the property type of this segment.

One or more Items are permitted in this Sequence.

>>>Include Table 8.8-1 “Code Sequence Macro Attributes”

DCID 244 “Laterality”.

>Related RT ROI Observations Sequence

(3006,00A0)

3

Sequence of related ROI Observations.

One or more Items are permitted in this Sequence.

>>Observation Number

(3006,0082)

1

Uniquely identifies a related ROI Observation.

>RT ROI Interpreted Type

(3006,00A4)

2

Type of ROI. See Section C.8.8.8.1.

Defined Terms:

EXTERNAL

external patient contour

PTV

Planning Target Volume (as defined in [ICRU Report 50])

CTV

Clinical Target Volume (as defined in [ICRU Report 50])

GTV

Gross Tumor Volume (as defined in [ICRU Report 50])

TREATED_VOLUME

Treated Volume (as defined in [ICRU Report 50])

IRRAD_VOLUME

Irradiated Volume (as defined in [ICRU Report 50])

BOLUS

patient bolus to be used for external beam therapy

AVOIDANCE

region in which dose is to be minimized

ORGAN

patient organ

MARKER

patient marker or marker on a localizer

REGISTRATION

registration ROI

ISOCENTER

treatment isocenter to be used for external beam therapy

CONTRAST_AGENT

volume into which a contrast agent has been injected

CAVITY

patient anatomical cavity

BRACHY_CHANNEL

brachytherapy channel

BRACHY_ACCESSORY

brachytherapy accessory device

BRACHY_SRC_APP

brachytherapy source applicator

BRACHY_CHNL_SHLD

brachytherapy channel shield

SUPPORT

external patient support device

FIXATION

external patient fixation or immobilization device

DOSE_REGION

ROI to be used as a dose reference

CONTROL

ROI to be used in control of dose optimization and calculation

DOSE_MEASUREMENT

ROI representing a dose measurement device, such as a chamber or TLD

>ROI Interpreter

(3006,00A6)

2

Name of person performing the interpretation.

>Material ID

(300A,00E1)

3

User-supplied identifier for ROI material.

>ROI Physical Properties Sequence

(3006,00B0)

3

Sequence describing physical properties associated with current ROI interpretation.

One or more Items are permitted in this Sequence.

>>ROI Physical Property

(3006,00B2)

1

Physical property specified by ROI Physical Property Value (3006,00B4).

Defined Terms:

REL_MASS_DENSITY

mass density relative to water

REL_ELEC_DENSITY

electron density relative to water

EFFECTIVE_Z

effective atomic number

EFF_Z_PER_A

ratio of effective atomic number to mass (AMU-1)

REL_STOP_RATIO

ratio of linear stopping power of material relative to linear stopping power of water

ELEM_FRACTION

elemental composition of the material

MEAN_EXCI_ENERGY

Mean Excitation Energy of the material (eV)

>>ROI Elemental Composition Sequence

(3006,00B6)

1C

The elemental composition of the ROI and the atomic mass fraction of the elements in the ROI.

Required if ROI Physical Property (3006,00B2) equals ELEM_FRACTION.

One or more Items shall be included in this Sequence.

>>>ROI Elemental Composition Atomic Number

(3006,00B7)

1

The atomic number of the element for which the ROI Elemental Composition Sequence (3006,00B6) is present.

>>>ROI Elemental Composition Atomic Mass Fraction

(3006,00B8)

1

The fractional weight of the element for which the ROI Elemental Composition Sequence (3006,00B6) is present.

The sum of all ROI Elemental Composition Atomic Mass Fractions (3006,00B8) within the ROI Elemental Composition Sequence (3006,00B6) shall equal 1.0 within acceptable limits of floating point precision.

>>ROI Physical Property Value

(3006,00B4)

1

User-assigned value for physical property.

Note

The value has no meaning when ROI Physical Property (3006,00B2) has the value ELEM_FRACTION. Therefore this Attribute may contain any value and receivers may ignore that value.


Note

  1. This Attribute allows preserving information by copying the content of Segmented Property Category Code Sequence (0062,0003) in case a Segmentation object is re-encoded as an RT Structure Set or vice-versa.

  2. In case of re-encoding a Segmentation object as an RT Structure Set or vice-versa it is suggested, that the Segmented Property Type Code Sequence (0062,000F) is mapped to RT ROI Identification Code Sequence (3006,0086).

C.8.8.8.1 RT ROI Interpreted Type

RT ROI Interpreted Type (3006,00A4) shall describe the class of ROI (e.g., CTV, PTV). Individual instances of each class of structure (e.g., CTV1, CTV2) can be distinguished using ROI Observation Label (3006,0085).

DICOM PS3.3 2018e - Information Object Definitions