DICOM PS3.3 2021e - Information Object Definitions
C.36.2.2.13 Blocks Definition Macro

This Macro defines the geometric configuration elements which cannot vary during delivery.

Table C.36.2.2.13-1. Blocks Definition Macro Attributes

Attribute Name

Tag

Type

Attribute Description

Number of Blocks

(300A,00F0)

1C

Number of Blocks defined in the Block Definition Sequence (300A,066A).

Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) is FULL. May be present otherwise.

Block Definition Sequence

(300A,066A)

1C

Block definitions.

Required if Number of Blocks (300A,00F0) is present and has a non-zero value.

The number of Items included in this Sequence shall equal the value of Number of Blocks (300A,00F0).

Only one Item in this Sequence shall have (130123, DCM, "Aperture Block") as the code value of Device Type Code Sequence (3010,002E).

>Include Table C.36.2.2.3-1 “RT Accessory Device Identification Macro Attributes”.

DCID 9517 “Radiotherapy Block Device Types”.

The Device Alternate Identifier (3010,001B) Attribute of the RT Accessory Device Identification Macro shall not contain a value when the Number of Block Slab Items (300A,0440) is non-zero.

>Device Index

(3010,0039)

1

Index of the Device in this Sequence.

The value shall start at 1 and increase monotonically by 1.

>Referenced Defined Device Index

(300A,0602)

1C

Device Index value that links the device defined by this Sequence Item to the corresponding device in an RT Radiation Instance. The device identification of the two devices may or may not be the same.

The value is the index of a device in the Block Definition Sequence (300A,066A) within the single SOP Instance referenced by Referenced RT Instance Sequence (300A,0631).

Required if the Instance referenced in Referenced RT Instance Sequence (300A,0631) contains the device that corresponds to the device defined by this Sequence Item.

See Section C.36.2.2.8.1.5.

>Beam Modifier Orientation Angle

(300A,0645)

1

Angle in degrees of the Beam Modifier Coordinate System with respect to the Base Beam Modifier Coordinate System. The angle is a Continuous Rotation Angle, see Section C.36.1.1.5.

See Section C.36.1.1.9.

>Material ID

(300A,00E1)

2

User-defined identifier for material used to manufacture the Block.

>Block Divergence

(300A,00FA)

1C

Whether or not the block is shaped according to the beam geometrical divergence.

Enumerated Values:

PRESENT

Block edges are shaped for beam divergence.

ABSENT

Block edges are not shaped for beam divergence.

Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise.

>Block Orientation

(300A,066C)

1C

Specifies on which side of the block base the block extends.

Enumerated Values:

PATIENT_SIDE

The block extends from its base towards the patient.

SOURCE_SIDE

The block extends from its base towards the Radiation Source.

Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise.

>Radiation Beam Block Thickness

(300A,066D)

2C

Physical thickness of block in mm parallel to the central radiation beam axis.

Required if Material ID (300A,00E1) has a value. May be present otherwise.

>Block Edge Data Sequence

(300A,066F)

2

Block Edge Data streams.

The polygons represented by the Block Edge Data (300A,066B) data streams in all Items in this Sequence shall be non-overlapping.

Zero or more Items shall be included in this Sequence.

>>Block Edge Data

(300A,066B)

1

A data stream of coordinate pairs in mm representing a polygon which comprise the block edge.

The polygon is implicitly closed from the last pair to the origin pair and all edges shall be non-intersecting except at the vertices. Any given coordinate pair shall only occur once in the data stream.

Coordinates are projected on the Beam Modifier Definition Plane.

>Number of Block Slab Items

(300A,0440)

1C

Number of slabs composing the block if the block has been sliced parallel to the Beam Modifier Definition Plane. If the block has not been sliced the value shall be zero.

Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise.

>Block Slab Sequence

(300A,0441)

1C

Sequence of slab(s) that comprise the block.

Required if Number of Block Slab Items (300A,0440) is present and has a value greater than 1.

The number of Items included in this Sequence shall equal the value of Number of Block Slab Items (300A,0440).

>>Block Slab Number

(300A,0043)

1

Identification number of the Block Slab.

The value shall start at 1, and increase monotonically by 1.

The number indicates the order of the slabs with respect to the source, where Number 1 corresponds to the slab nearest to the source.

>>Radiation Beam Block Slab Thickness

(300A,066E)

3

Physical thickness of block slab in mm in a direction parallel to the radiation beam axis.

The sum of Radiation Beam Block Slab Thickness (300A,066E) values in all Items of this Sequence must equal the Radiation Beam Block Thickness (300A,066D) of the block.

>>Device Alternate Identifier

(3010,001B)

2

An identifier intended to be read by a device such as a bar code reader.

>>Device Alternate Identifier Type

(3010,001C)

1C

Defines the type of Device Alternate Identifier.

Required if Device Alternate Identifier (3010,001B) has a value.

Defined Terms:

BARCODE

RFID

>>Device Alternate Identifier Format

(3010,001D)

1C

Description of the format in which the Device Alternate Identifier (3010,001B) is issued.

Required if Device Alternate Identifier (3010,001B) has a value.

See Section 10.36.1.1.


DICOM PS3.3 2021e - Information Object Definitions