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SRS Prescription (Controlled Inhomogeneity)

Using SRS Prescription (Controlled Inhomogeneity) Mode

You can activate the SRS Prescription (controlled inhomogeneity) mode for the PTV or the PTV – boost in the Advanced menu.

SRS Prescription (controlled inhomogeneity) mode attempts to achieve both the coverage and desired dose constraint and thereby generates more inhomogeneous PTV dose distributions that are typically used in Stereotactic Radiosurgery.

Changes to the PTV – Boost and Boost Objects



No.ComponentDescription

Desired Dose Constraint

The Maximum Dose Constraint changes to Desired Dose Constraint.

When you select Calculate, the optimization algorithm tries to meet the desired dose constraint.

% IDLThe isodose line percentage specifies the inhomogeneity between the prescription dose and the maximum dose at fixed volumes. % IDL = prescription dose (Gy)/desired dose constraint (Gy) *100.

/SRSAs soon as the SRS Prescription (controlled inhomogeneity) mode is enabled, the software displays /SRS beside the prescription dose.

DVH for the PTV in SRS Prescription Mode



No.ComponentDescription

SRS Prescription (controlled inhomogeneity) “off”

When SRS Prescription (controlled inhomogeneity) is turned off, the optimizer attempts to meet the prescription point (triangle) for the PTV or PTV – boost. However, the optimizer has the freedom to choose a maximum dose. This results in a rather homogeneous dose distribution.

SRS Prescription (controlled inhomogeneity) “on”

When SRS Prescription (controlled inhomogeneity) is turned on, the optimizer attempts to meet both the prescription point (triangle) and the desired dose constraint for the PTV or PTV – boost. This results in a rather heterogeneous dose distribution.

Art-No. 60919-40EN

Utgivningsdatum: 2019-05-22