DICOM PS3.3 2020a - Information Object Definitions

C.8.8.25.9 Depth Dose Parameters Sequence Attributes (Current)
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##### C.8.8.25.9 Depth Dose Parameters Sequence Attributes

Some delivery systems determine the settings of the range shifter (or beam energy) and range modulators internally based upon clinical parameters.

The Attributes mentioned in this section represent those clinical parameters.

When the Depth Dose Parameters Sequence (300A,0505) is present, those specifications have precedence over the definitions of the Range Shifters defined in Range Shifter Settings Sequence (300A,0360) and the Range Modulator defined in Range Modulator Settings Sequence (300A,0380).

The following three figures explain the use of the Range Modulated Region Attributes.

Figure C.8.8.25.9-1 shows an example of those Attributes with the following values:

- Nominal Range Modulated Region Depths (300A,0504) = 147\298

- Reference Dose Definition (300A,0512) = CENTER

- Distal Depth (300A,0502) = 301

- Distal Depth Fraction (300A,0501) = 0.9

- Nominal Range Modulation Fractions (300A,0503) = 0.95\0.98

Figure C.8.8.25.9-1. Attributes specifying a depth dose distribution parameters in case of Reference Dose Definition (300A,0512) = CENTER

Figure C.8.8.25.9-2 is an expansion of the steep-gradient part of the depth dose curve for better readability of the parameters annotating this part.

Figure C.8.8.25.9-2. Attributes specifying a generic depth dose distribution. Abscissa expanded near distal edge of dose distribution.

Defined Terms for Reference Dose Definition (300A,0512):

HIGHEST

  The maximum dose for the highest energy of the non-range modulated component is used for determining the fractions.

MAXIMUM

  The maximum dose of the range modulated depth dose distribution is used for determining the fractions.

CENTER

  The dose measured at the center of the range modulated region of the depth dose distribution is used for determining the fractions.

Figure C.8.8.25.9-3 shows the usage of the Defined Terms of Reference Dose Definition (300A,0512).

In Figure C.8.8.25.9-3, the modulated region is defined the same as in Figure C.8.8.25.9-1:

- Nominal Range Modulated Region Depths (300A,0504) = (147\298)

In this example, the 100% reference level for the dose definition is determined for the Defined Terms specified in Reference Dose Definition (300A,0512) as follows:

HIGHEST

  The maximum dose for the highest energy of the non-range modulated component is located at 304 mm and used for determining the fractions.

MAXIMUM

  The maximum dose of the range modulated depth dose distribution is located at 300 mm and used for determining the fractions.

CENTER

  The dose measured at 220 mm depth at the center of the range modulated region of the depth dose distribution is used for determining the fractions.

Figure C.8.8.25.9-3. Representation of the different Reference Dose Definition (300A,0512) using the range modulated depth dose distribution or highest energy component depth dose distribution.

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DICOM PS3.3 2020a - Information Object Definitions