DICOM PS3.3 2020c - Information Object Definitions

C.8.8.26.2 Scan Spot Prescribed Indices (Current)
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##### C.8.8.26.2 Scan Spot Prescribed Indices

Scan Spot Prescribed Indices (300A,0391) are used to associate each delivered spot with its corresponding prescribed spot. If the ordering information is unknown, both Scan Spot Reordered (300A,0393) and Scan Spot Prescribed Indices (300A,0391) shall be absent.

There are various cases how the scan spots are delivered in comparison with the prescribed spot order.

Following are various examples specifying how the scan spot prescribed index shall be used.

###### C.8.8.26.2.1 Content of RT Ion Plan for following Use Cases

It is assumed that the RT Ion Plan contains the following spot positions in the Scan Spot Position Map (300A,0394) and related Scan Spot Meterset Weights (300A,0396).

The following table is a representation of the prescription where “w” represents the Scan Spot Meterset Weight.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047)
--- | ---
x0,y0 | w0
x1,y1 | w1
x2,y2 | w2
x3,y3 | w3
x4,y4 | w4

The prescription does not contain an explicit index for the scan spot order. The index is defined implicitly by the order of the spots within the prescribed map. The implicit index starts at 0.

The following examples specify some different cases of delivered scan spot order that can then be supported using the spot index in the RT Ion Beams Treatment Record.

###### C.8.8.26.2.2 Treatment Recording Use Cases

The following tables contain 3 columns as follows:

First column: The delivered Scan Spot Position in the Scan Spot Position Map (300A,0394). In this column the spot positions are annotated as they have been delivered. The index following the coordinate character refers to the index in the RT Ion Plan. If the index is appended, it shows that 2 or more delivered scan spots refer to the same Scan Spot Position in the RT Ion Plan.

Second column: The Scan Spot Meterset Delivered (3008,0047). The Meterset Delivered is indicated by 'm'.

Third column: The Scan Spot Prescribed Indices (300A,0391) referring to the position in the Scan Spot Meterset Weights (300A,0396) of the referenced RT Ion Plan are indicated as they are recorded in the RT Ion Beams Treatment Record.

###### C.8.8.26.2.3 Use Case 1: No pause, no spot reordering, no spot splitting, no repainting

This use case is an example where the spots are treated in the exact order as prescribed in the RT Ion Plan.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047)
--- | ---
x1,y1 | m1
x2,y2 | m2
x3,y3 | m3
x4,y4 | m4

Since there was no re-ordering, Scan Spot Reordered (300A,0393) is absent or NO and Scan Spot Prescribed Indices (300A,0391) shall be absent.

###### C.8.8.26.2.4 Use Case 2: Pause

This use case is an example of a spot broken up into two reported spots due to a pause in the middle of treatment.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047) | Scan Spot Prescribed Indices (300A,0391)
--- | --- | ---
x1,y1 | m1 | 1
x2,y2 | m2 | 2
x3a,y3a | m3a | 3
x3b,y3b | m3b | 3
x4,y4 | m4 | 4

The pause occurred during the delivery of the 3rd spot. When the delivery resumed, the spot was not located at the same position prior to the pause. The notations x3a,y3a represent the position of the spot prior to the pause. x3b,y3b represent the position of the resumed spot. Both spots refer to the same prescribed spot. The Meterset m3a represents the measured Meterset prior to the pause and m3b represents the measured Meterset after resumption.

###### C.8.8.26.2.5 Use Case 3: Tuning Spot

Some delivery systems use a tuning spot (aka pulse) to adjust the different beam parameters. This tuning spot can be delivered at the beginning of the beam or at any time during the beam. The tuning spot may not reach exactly the same position as a prescribed spot.

The suffix 't' indicates a tuning spot.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047) | Scan Spot Prescribed Indices (300A,0391)
--- | --- | ---
x4t,y4t | m4t | 4
x1,y1 | m1 | 1
x2,y2 | m2 | 2
x3,y3 | m3 | 3
x4,y4 | m4 | 4
x5,y5 | m5 | 5

A tuning spot was delivered at the beginning of a control point. The tuning spot will be present in the treatment record. As it is the first one being delivered for that control point, it will be the first one in the record.

The tuning spot in this example was targeting the 4th spot of the prescription. In the record the Scan Spot Prescribed Indices will refer to the 4th position. As the tuning spot may not match the prescribed position, it will have its own coordinates represented by the suffix 't'.

###### C.8.8.26.2.6 Use Case 4: Repainting

Use case demonstrating how re-paints of the spot map within the same control point can be represented.

The suffix 'p<n>' indicates a painting iteration.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047) | Scan Spot Prescribed Indices (300A,0391)
--- | --- | ---
x1p1,y1p1 | m1p1 | 1
x2p1,y2p1 | m2p1 | 2
x3p1,y3p1 | m3p1 | 3
x4p1,y4p1 | m4p1 | 4
x5p1,y5p1 | m5p1 | 5
x1p2,y1p2 | m1p2 | 1
x2p2,y2p2 | m2p2 | 2
x3p2,y3p2 | m3p2 | 3
x4p2,y4p2 | m4p2 | 4
x5p2,y5p2 | m5p2 | 5
x1p3,y1p3 | m1p3 | 1
x2p3,y2p3 | m2p3 | 2
x3p3,y3p3 | m3p3 | 3
x4p3,y4p3 | m4p3 | 4
x5p3,y5p3 | m5p3 | 5

When repainting is requested (Number of Paintings (300A,039A) is greater than 1), the record shall contain each of the delivered paintings.

In the example, painting was performed three times. Each repainted spot is described by the Scan Spot Position, the Delivered Metersets of the specific painting, and the Scan Spot Prescribed Indices.

###### C.8.8.26.2.7 Use Case 5: Spot Reordering

In this use case, the number of spots remains the same, but they are simply treated in a different order than planned.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047) | Scan Spot Prescribed Indices (300A,0391)
--- | --- | ---
x4,y4 | m4 | 4
x2,y2 | m2 | 2
x5,y5 | m5 | 5
x3,y3 | m3 | 3
x1,y1 | m1 | 1

When Scan Spot Re-Ordering is allowed, the spots are listed in the order of the delivery and reference the Scan Spot Prescribed Indices.

###### C.8.8.26.2.8 Use Case 6: Combination

This use case is a combination of all the above including tuning spots, repaints, and additional re-ordering.

The suffix 't' indicates a tuning spot.

The suffix 'p<n>' indicates a painting iteration.

The suffix '(r)' in Scan Spot Prescribed Indices (300A,0391) indicates that the spot has been re-ordered.

Scan Spot Position Map (300A,0394) | Scan Spot Metersets Delivered (3008,0047) | Scan Spot Prescribed Indices (300A,0391)
--- | --- | ---
x4t,y4t | m4t | 4
x2p1,y2p1 | m2p1 | 2 (r)
x5p1,y5p1 | m5p1 | 5 (r)
x1p1,y1p1 | m1p1 | 1 (r)
x4p1,y4p1 | m4p1 | 4
x3p1,y3p1 | m3p1 | 3 (r)
x3t,y3t | m3t | 3
x2p2,y2p2 | m2p2 | 2 (r)
x5p2,y5p2 | m5p2 | 5 (r)
x1p2,y1p2 | m1p2 | 1 (r)
x4p2,y4p2 | m4p2 | 4
x3p2,y3p2 | m3p2 | 3 (r)
x2p3,y2p3 | m2p3 | 2 (r)
x5p3,y5p3 | m5p3 | 5 (r)
x1p3,y1p3 | m1p3 | 1 (r)
x3p3,y3p3 | m3p3 | 3 (r)

The repainting is represented by recording the spot multiple times and referencing to the same scan spot prescribed index.

The tuning pulse is recorded for the first two paintings and references the scan spot prescribed index of the spot being used for tuning.

The order of the spots is the spot order actually delivered.

The third painting did not deliver all the prescribed spots because some of the spot Metersets were below the minimum deliverable Meterset of the machine.

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DICOM PS3.3 2020c - Information Object Definitions