On the public record

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Researcher investigating the devices used in radiotherapy are often party to confidential information provided by the manufacturers of those devices.  As a general rule, it is impossible to breach a confidentiality agreement by reporting information which is already on the public record.  The following notes are provided in the interests of helping researchers to know what can be reported in the scientific literature, with impunity.

The Varian Clinac 21Ex, Monitor Chamber
from Popescu et al,

  • “The dose scoring regions are two slabs of air bordered vertically by three equidistant kapton windows and horizontally by the chamber wall, chamber gap and container wall. Furthermore, inside each air slab there are two kapton signal plates.”
  • “Only the dose accumulated in the top part of the chamber is used to terminate the radiation beam on Varian linacs after delivering the set number of MU. Moreover, only the inner compartment of the chamber is used for monitoring the beam output, while the outer compartments are used for monitoring the beam flatness and symmetry.”

Elekta SL linac, Target
From Mesbahi, Iran. J. Radiat. Res. 4(1): 7-14 (2006):

  • “The target comprised 3 mm thick tungsten (95%), nickel (3.75%) and iron (1.25%) alloy of density 18.0 g/cm3, attached to a 4.5 mm thick copper backing plate.”

Elekta linac, Multileaf collimator
From Haryanto et al, Strahlentherapie und Onkologie 1: 58 (2004):

  • “The Elekta multileaf collimator consists of 80 independent leaves which are divided into two banks. The material of the leaves is tungsten alloy with a density of 18.0g/cm3. The Elekta multileaf collimator has curved leaf ends and a stepped design for the leaf sides. The projection of the leaf pitch in the isocentric plane is 1.0cm, but the projection of an individual leaf is 1.1cm. The Elekta multileaf collimator is placed 29.8cm below the target and has a thickness of 7.5cm.”

From www.elekta.com:

  • The MLC has two sets of 40 tungsten leaves.

The Elekta iView GT a-Si EPID
From Parent et al, Phys. Med. Biol. 52: 3351 (2007):

  • “The active part of the detector consists of a [1mm] copper plate and a 133mg/cm2 terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) screen.”
  • The distance from source to surface to surface is 157cm.
  • The distance from source to sensitive layer is 160cm.

From Parent et al, Med. Phys. 33(12): 4529 (2006):

  • The layers contained in the Elekta EPID (from top to bottom) are:
    • Aluminium cover
    • 0.1cm copper plate
    • Graphite cover
    • Phosphor screen
    • Glass and a-Si photodiode array
    • Supporting material (carbon fibre, aluminium)
    • Printed circuit board
    • Aluminium cover

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