Zeiss INTRABEAM, Инструкция по эксплуатации

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Version 6.2
G-30-1767-en
Page 63
INTRABEAM Water Phantom Operation
This procedure may, however, prove to be very cumbersome for the user,
since the measuring chamber of the water phantom is permanently installed.
This means that, every time the XRS 4 with the attached applicator is moved
upwards (in the -z direction) in the front view of the chamber, the user has to
add water until the surface of the applicator is reached (which would be very
time-consuming for measurements in 0.5 mm steps).
However, measurements have shown that the depth dose curve of the appli-
cators can be measured in a fully immersed state (see illustration below), but
cannot be measured at an air/water interface which, as previously described,
is more difficult to implement. A comparison of the applicator values recorded
with the ionization chamber has shown that the difference between measure-
ment with an air/water interface and measurement with full immersion in
water is less than 1%, i.e. is still within the measuring tolerances. This is due
to the fact that the XRS 4 is completely embedded in the shaft of the cylin-
drical applicator. Therefore, no radiation can escape from the shaft laterally
and, e.g. as scatter radiation, influence the actual radiation field below the ap-
plicator (i.e. in the Z axis). For this reason, the measured depth dose curve is
not influenced either.
XRS 4 with flat/surface applicator, fully immersed in water