DICOM PS3.3 2019d - Information Object Definitions
C.8.8.25.7 Ion Control Point Sequence

The control point sequence for RT Ion Beams is defined using the same rule set as in the RT Beams Module (see Section C.8.8.14.5). Specifically, the following rules apply:

This definition allows unambiguous and explicit determination of those parameters changing while irradiation is occurring, as opposed to those parameters that change between irradiation segments. No assumptions are made about the behavior of machine parameters between specified control points, and communicating devices shall agree on this behavior outside the Standard.

The following example illustrates this rule (not all parameters are shown), in the case of a scanning beam with 2 segments and Total Cumulative Meterset of 70.

Control Point 0: All applicable treatment parameters defined, Cumulative Meterset Weight = 0 Nominal Energy: 200 Scan Spot Position Map: -40, -35, -40, -30 (Positions for 1st segment) Scan Spot Meterset Weight: 0.5, 0.3, 1.2, (Values add up to Meterset difference between Control Points 0 and 1)

Control Point 1: All applicable treatment parameters defined, Cumulative Meterset Weight = 30.0 Nominal Energy: 200 Scan Spot Position Map: -40, -35, -40, -30 (Positions for 1st segment) Scan Spot Meterset Weight:0.0, 0.0, 0.0, … (All values are 0.0, because Meterset Weight difference between Control Point 1 and 2 is 0.0)

Control Point 2: All applicable treatment parameters defined, Cumulative Meterset Weight = 30.0 Nominal Energy: 180 Scan Spot Position Map: -55, -40, -55, -35, (Positions for 2nd segment) Spot Meterset Weight: 0.7, 0.8, 1.5 (Values add up to Meterset difference between Control Points 2 and 3)

Control Point 3: All applicable treatment parameters defined, Cumulative Meterset Weight = 70.0 Nominal Energy: 180 Scan Spot Position Map: -55, -40, -55, -35, (Positions for 2nd segment) Spot Meterset Weight: 0.0, 0.0, 0.0, (All values are 0.0, because there is no following control point (end of sequence).

DICOM PS3.3 2019d - Information Object Definitions