Zeiss INTRABEAM, Инструкция по эксплуатации

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Operation INTRABEAM Water Phantom
Version 6.2
Page 64 G-30-1767-en
Centering of the XRS 4 with the applicator mounted on the measuring
window of the IC ionization chamber is not easy to perform, since the flat
dose distribution would not take into account any maximum value over the X-
Y surface of the applicator. It is therefore advisable to initially center the XRS
4 alone precisely and then fix this point before attaching the applicator and
performing the depth dose measurement. For information on precise posi-
tioning of the XRS 4 along the X-Y axes, refer to "Positioning the probe tip for
recording the depth dose curve", on page 35.
Note
The XRS 4 with attached applicator should approach the surface of the meas-
uring chamber with extreme caution in order to prevent damage to the meas-
uring chamber and/or to the applicator.
The minimum distance (offset) between the XRS 4 with applicator and the ref-
erence point of the ionization chamber can be calculated using the following
formula: (See "Distance between the probe tip and the IC ionization
chamber", on page 42).
r
1
= d
H
+ d
A
+ d
IC
Note
As was the case with the spherical applicators, the user must make a correc-
tion regarding the actual distance between the reference point of the ioniza-
tion chamber and the application surface by taking the offset described above
into consideration.
The XRS 4 with applicator is then moved upwards to perform the measure-
ments at different depths using the dosimeter and calculate the dose rate
along the central Z axis, and therefore the transfer function as well. As a
means of improving the statistics, it is advisable to set measuring points in 0.5
mm steps during the first 15 mm in order to collect as many measuring points
as possible along the steep part of the depth dose curve. This supports the
user in obtaining a more appropriate function for calculating the dose rate of
the surface applicator on its application surface (z = 0 mm).
Positioning the flat or surface applicator with the X-ray probe in the Z
axis
Note
As was the case with the spherical applicators, the user must make a correc-
tion regarding the actual distance between the reference point of the ioniza-
tion chamber and the applicator surface by taking the offset described above
into consideration.