Users Manual Part 1

Clinical User’s Guide IBA | ix|
Volume 1 - Treatment Session
Essential Performances
The Essential Performances (EP) applicable to the Proteus PLUS for Pencil Beam
Scanning (PBS) are given below.
Terminology
Range: The Range (d
90
), or open beam range, is defined as the depth along the beam
central axis in water to the distal 90% point of the maximum dose value, achieved
without Beam Modifying Accessories (Range Compensator, Range Shifter).
Distal fall-off: The Distal Dose Fall-off is defined as the distance (in g/cm
2
) in which
the dose, measured in water along the beam central axis, decreases from 80 to 20%
of the maximum dose value.
Field Size: The Field Size is defined as the distance (in mm) between the 50% points
of the maximum dose value, measured along the line perpendicular to the beam
central axis, on the isocenter in air.
Spot size (beam sigma): The Beam Sigma is defined as one standard deviation of
the fluence distribution along a line orthogonal to the beam axis, on the isocenter in
air.
Monitor Units: Monitor Unit is defined as an arbitrary unit in which a quantity is
displayed and from which absorbed dose can be calculated.
EP Name Limit allowed for EP value
Dimensions of the Radiation Field
Field Size 30.0 cm * 40.0 cm or larger
Depth Max depth: 32 g/cm
2
Min Range (open beam range,
without accessories)
Dedicated Nozzle: =3.1 g/cm
2
(“extended minimum range” option) OR
4.1 g/cm
2
(without “extended minimum
range” option).
Universal Nozzle: =7.7 g/cm
2
(PBS)
Irradiation Time/Dose Rate
Irradiation Time/Dose Rate 2 min for 2 Gy in 1L or faster
Dose Gradient on the Edges of the Radiation Field
Spot size (sigma) 2.7 to 8.5 mm
Distal Dose Fall-Off 1 mm 20%-80% (on top of monoE
beam) or smaller (ICRU)
Reproducibility of 2D (Lateral) Dose Distribution in PBS
Spot Position Accuracy 1 mm or 10% of beam sigma or smaller