C.8.8.13 RT Fraction Scheme Module
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#### C.8.8.13 RT Fraction Scheme Module

The RT Fraction Scheme module contains attributes that describe a single or multiple scheme of dose descriptions. Each sequence item contains dose specification information, fractionation patterns, and either beam or brachytherapy application setup specifications. The design of the RT Fraction Scheme module allows a beam or brachytherapy application setup to be used in multiple fraction schemes.

Table C.8-49. RT Fraction Scheme Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Fraction Group Sequence | (300A,0070) | 1 | Sequence of Fraction Groups in current Fraction Scheme. One or more items shall be included in this sequence.
>Fraction Group Number | (300A,0071) | 1 | Identification number of the Fraction Group. The value of Fraction Group Number (300A,0071) shall be unique within the RT Plan in which it is created.
>Fraction Group Description | (300A,0072) | 3 | The user defined description for the fraction group.
>Referenced Dose Sequence | (300C,0080) | 3 | Related instances of RT Dose (for grids, isodose curves and named/unnamed point doses). One or more items are permitted in this sequence. See Note 1.
>>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>Referenced Dose Reference Sequence | (300C,0050) | 3 | Sequence of Dose References for the current Fraction Group. One or more items are permitted in this sequence.
>>Referenced Dose Reference Number | (300C,0051) | 1 | Uniquely identifies Dose Reference specified by Dose Reference Number (300A,0012) within Dose Reference Sequence (300A,0010) in RT Prescription Module.
>>Constraint Weight | (300A,0021) | 3 | Relative importance of satisfying constraint, where high values represent more important constraints.
>>Delivery Warning Dose | (300A,0022) | 3 | The dose (in Gy) that when reached or exceeded should cause some action to be taken.
>>Delivery Maximum Dose | (300A,0023) | 3 | The maximum dose (in Gy) that can be delivered to the dose reference.
>>Target Minimum Dose | (300A,0025) | 3 | Minimum permitted dose (in Gy) to Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is TARGET.
>>Target Prescription Dose | (300A,0026) | 3 | Prescribed dose (in Gy) to Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is TARGET.
>>Target Maximum Dose | (300A,0027) | 3 | Maximum permitted dose (in Gy) to Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is TARGET.
>>Target Underdose Volume Fraction | (300A,0028) | 3 | Maximum permitted fraction (in percent) of Target to receive less than the Target Prescription Dose (300A,0027) if Dose Reference Type (300A,0020) of referenced Dose Reference is TARGET and Dose Reference Structure Type (300A,0014) of referenced Dose Reference is VOLUME.
>>Organ at Risk Full-volume Dose | (300A,002A) | 3 | Maximum dose (in Gy) to entire Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is ORGAN_AT_RISK and Dose Reference Structure Type (300A,0014) of referenced Dose Reference is VOLUME.
>>Organ at Risk Limit Dose | (300A,002B) | 3 | Maximum permitted dose (in Gy) to any part of Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is ORGAN_AT_RISK and Dose Reference Structure Type (300A,0014) of referenced Dose Reference is VOLUME.
>>Organ at Risk Maximum Dose | (300A,002C) | 3 | Maximum dose (in Gy) to non-overdosed part of Dose Reference if Dose Reference Type (300A,0020) of referenced Dose Reference is ORGAN_AT_RISK and Dose Reference Structure Type (300A,0014) of referenced Dose Reference is VOLUME.
>>Organ at Risk Overdose Volume Fraction | (300A,002D) | 3 | Maximum permitted fraction (in percent) of Organ at Risk to receive more than the Organ at Risk Maximum Dose if Dose Reference Type (300A,0020) of referenced Dose Reference is ORGAN_AT_RISK and Dose Reference Structure Type (300A,0014) of referenced Dose Reference is VOLUME.
>Number of Fractions Planned | (300A,0078) | 2 | Total number of treatments (Fractions) prescribed for current Fraction Group.
>Number of Fraction Pattern Digits Per Day | (300A,0079) | 3 | Number of digits in Fraction Pattern (300A,007B) used to represent one day. See Note 2.
>Repeat Fraction Cycle Length | (300A,007A) | 3 | Number of weeks needed to describe treatment pattern. See Note 2.
>Fraction Pattern | (300A,007B) | 3 | String of 0's (no treatment) and 1's (treatment) describing treatment pattern. Length of string is 7 x Number of Fraction Pattern Digits Per Day x Repeat Fraction Cycle Length. Pattern shall start on a Monday. See Note 2.
>Beam Dose Meaning | (300A,008B) | 3 | Indicates the meaning of Beam Dose (300A,0084). Enumerated Values: BEAM_LEVEL Beam Dose value is individually calculated for this Beam FRACTION_LEVEL Dose is calculated on the Fraction level, and the value of Beam Dose (300A,0084) is assigned to the Beam to carry a nominally distributed dose only.
>Number of Beams | (300A,0080) | 1 | Number of Beams in current Fraction Group. If Number of Beams is greater then zero, Number of Brachy Application Setups (300A,00A0) shall equal zero.
>Referenced Beam Sequence | (300C,0004) | 1C | Sequence of treatment beams in current Fraction Group. One or more items shall be included in this sequence. Required if Number of Beams (300A,0080) is greater than zero.
>>Referenced Beam Number | (300C,0006) | 1 | Uniquely identifies Beam specified by Beam Number (300A,00C0) within Beam Sequence (300A,00B0) in RT Beams Module.
>>Beam Dose Specification Point | (300A,0082) | 3 | Coordinates (x,y,z) of point at which Beam Dose is specified in the patient based coordinate system described in Section C.7.6.2.1.1 (mm). See Note 3.
>>Beam Dose | (300A,0084) | 3 | Dose (in Gy) at Beam Dose Specification Point (300A,0082) due to current Beam.
>>Beam Dose Verification Control Point Sequence | (300A,008C) | 3 | Sequence of Items containing Beam Dose Verification Control Points. Two or more items may be included in this sequence.
>>>Cumulative Meterset Weight | (300A,0134) | 1 | The cumulative Meterset weight value, at which the beam dose point geometrical parameters apply.
>>>Referenced Control Point Index | (300C,00F0) | 1C | Uniquely identifies the Control Point specified by Control Point Index (300A,0112) within Beam referenced by Referenced Beam Number (300C,0006). See Section C.8.8.13.1.1 Required, if the Referenced Cumulative Meterset corresponds to a Control Point in the Control Point Sequence (300A,0111).
>>>Average Beam Dose Point Depth | (300A,008D) | 2C | The average depth (in mm) in the patient along a ray from the source to the dose point specified by the Beam Dose Specification Point (300A,0082) from the current Beam Dose Verification Control Point to the next one. See Section C.8.8.13.1.2 Required for all but the last items in that sequence.
>>>Average Beam Dose Point Equivalent Depth | (300A,008E) | 2C | The average radiological depth in mm (water-equivalent depth, taking tissue heterogeneity into account) in the patient along a ray from the source to the dose point specified by the Beam Dose Specification Point (300A,0082) from the current Beam Dose Verification Control Point to the next one. See Section C.8.8.13.1.2 Required for all but the last items in that sequence.
>>>Average Beam Dose Point SSD | (300A,008F) | 2C | Average Source to patient surface distance in mm along a ray from the source to the dose point specified by the Beam Dose Specification Point (300A,0082) from the current Beam Dose Verification Control Point to the next one. See Section C.8.8.13.1.2 Required for all but the last items in that sequence.
>>Beam Meterset | (300A,0086) | 3 | Machine setting to be delivered for current Beam, specified in Monitor Units (MU) or minutes as defined by Primary Dosimeter Unit (300A,00B3) (in RT Beams Module) for referenced Beam. See Note 4.
>>Beam Delivery Duration Limit | (300A,00C5) | 3 | The expected maximum delivery time in sec. See Note 7.
>Number of Brachy Application Setups | (300A,00A0) | 1 | Number of Brachy Application Setups in current Fraction Group. If Number of Brachy Application Setups is greater then zero, Number of Beams (300A,0080) shall equal zero.
>Referenced Brachy Application Setup Sequence | (300C,000A) | 1C | Sequence of treatment Brachy Application Setups in current Fraction Group. Required if Number of Brachy Application Setups (300A,00A0) is greater than zero. 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) within Brachy Application Setup Sequence (300A,0230) in RT Brachy Application Setups Module.
>>Brachy Application Setup Dose Specification Point | (300A,00A2) | 3 | Coordinates (x,y,z) of point in the patient based coordinate system described in Section C.7.6.2.1.1 at which Brachy Application Setup Dose (300A,00A4) is specified (mm).
>>Brachy Application Setup Dose | (300A,00A4) | 3 | Dose (in Gy) at Brachy Application Setup Dose Specification Point (300A,00A2) due to current Brachy Application Setup.

### Note

1. An RT Dose IOD referenced within the Referenced Dose Sequence (300C,0080) can be used for storing grid-based (pixel) data, isodose curves, and/or individual dose points (with optional dose point names) for the current Fraction Group.

2. The fractionation pattern does not indicate the actual start of treatment, or the order or timing of fraction delivery. If treatment does not commence as outlined in the pattern, it is the application's responsibility to make any necessary adjustments.

   Examples of Fractionation Pattern Schemes:

   1. 1 fraction group, 1 fraction per day (Monday to Friday):

      - Number of Fraction Pattern Digits per Day = 1, Repeat Fraction Cycle Length = 1, Fraction Pattern = 1111100

   2. 2 fraction groups, 1 fraction per day, first fraction group Monday, Wednesday, and Friday, second fraction group Tuesday and Thursday:

      - Fraction Group 1: Number of Fraction Pattern Digits Per Day = 1, Repeat Fraction Cycle Length = 1, Fraction Pattern = 1010100

      - Fraction Group 2: Number of Fraction Pattern Digits Per Day = 1, Repeat Fraction Cycle Length = 1, Fraction Pattern = 0101000

   3. 2 fraction groups, 1 fraction per day, alternating fraction groups every day of treatment (Monday to Friday):

      - Fraction Group 1: Number of Fraction Pattern Digits Per Day = 1, Repeat Fraction Cycle Length = 2, Fraction Pattern = 10101000101000

      - Fraction Group 2: Number of Fraction Pattern Digits Per Day = 1, Repeat Fraction Cycle Length = 2, Fraction Pattern = 01010001010100

   4. 1 fraction group, 2 fractions per day (Monday to Friday):

      - Fraction Group 1: Number of Fraction Pattern Digits Per Day = 2, Repeat Fraction Cycle Length = 1, Fraction Pattern = 11111111110000

   5. 2 fraction groups, 2 fractions per day, alternating fraction groups every treatment (Monday to Friday):

      - Fraction Group 1: Number of Fraction Pattern Digits Per Day = 1, Repeat Fraction Cycle Length = 1, Fraction Pattern = 1111100

      - Fraction Group 2: Number of Fraction Pattern Digits Per Day = 2, Repeat Fraction Cycle Length = 1, Fraction Pattern = 11111111110000

3. The Beam Dose Specification Point (300A,0082) and Brachy Application Setup Dose Specification Point (300A,00A2) contain the coordinates of the single point used for dose normalization. This point is distinct from the Referenced Dose Reference Sequence (300C,0050) in the RT Beams module and the Brachy Referenced Dose Reference Sequence (300C,0055) in the RT Brachy Application Setups module, which are used for plan evaluation and dose tracking.

4. The Meterset at a given Control Point (see RT Beams Module) is equal to Beam Meterset (300A,0086) multiplied by the Cumulative Meterset Weight (300A,0134) for the Control Point, divided by the Final Cumulative Meterset Weight (300A,010E).

5. Attribute Referenced Patient Setup Number (300C,006A) was previously defined. Its use in this Module is now retired (see PS3.3-2004).

6. Attributes Beam Dose Point Depth, Beam Dose Point Equivalent Depth and Beam Dose Point SSD were previously included in this Module as optional Attributes but have been retired. See PS3.3-2011.

7. The Beam Delivery Duration Limit (300A,00C5) is the maximum time span allowed to deliver a single fraction of a beam to prevent significant over-treatments. Treatment is expected to be terminated upon reaching the Beam Delivery Duration Limit independent of the meterset. This limit represents the expected time span including some increase by a factor greater than 1 to accommodate normal variations in delivery.

##### C.8.8.13.1 Beam Dose Verification Parameters

###### C.8.8.13.1.1 Referenced Control Point

The number of items in the Beam Dose Verification Control Point Sequence (300A,008B) 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 Item is the same it shall be referenced by the Referenced Control Point Index (300C,00F0).

###### C.8.8.13.1.2 Distance Parameters

The values given in Average Beam Dose Point Depth (300A,008D), Average Beam Dose Point Equivalent Depth (300A,008E) and Average Beam Dose Point SSD (300A,008F) shall always contain average values from the current Beam Dose Verification Control Point to the next. In case of e.g., an arc therapy, these values reflect the changing depth parameters. In case these distances do not change, e.g., for a static beam treatment, the average value equals the static value under the given geometric conditions.

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