Philips Azurion - 19.1.4 Dose Model

NOTE Other vendors might use other units to express the dose area product. This should be taken
in
to account when comparing dose values of dierent systems.
Detector Dose
The residual dose at the an-scaer grid on the detector aer the X-rays have passed the paent. The
system uses the detector dose as an input to regulate the amount of X-ray radiaon in order to obtain
the proper image quality.
Determinisc Eects
Determinisc eects of ionizing radiaon are related on a microbiological scale to cell destrucon
caused by high radiaon levels. Determinisc eects or ssue reacons may occur when the radiaon
dose has exceeded a certain threshold level, which may depend on the irradiated ssue or organ and
on the paent's sensivity to radiaon. When the threshold is exceeded, the severity of the ssue
reacons increases with increased radiaon dose.
The eects can be directly related to the radiaon exposure. On a microbiological scale, these eects
are related to cell destrucon caused by high radiaon levels. The threshold dose is typically 2 Gy for
transient skin erythema (redness of the skin) and 3 Gy for temporary hair loss.
The air kerma is a measure to esmate the determinisc eects of ionizing radiaon.
Stochasc Eects
Stochasc eects of ionizing radiaon are related on a microbiologial scale to cell mutaons due to
DNA damage caused by low radiaon levels. Such mutaons may be controlled and eliminated by the
human body or may develop into cancer on the long term (many years). It is dicult to show a direct
relaonship between radiaon exposure and cancer for individual cases. The Internaonal Commission
on Radiological Protecon assumes that the stochasc risk or probability of developing cancer is linear
with the total radiaon dose received, and that there is no threshold as with the determinisc risk.
Unlike the determinisc risk, the stochasc risk does not change if dose is spread over mulple parts of
the body.
The dose area product is a measure to esmate the stochasc eects of ionizing radiaon.
Paent Thickness
The depth of ssue irradiated, expressed in cm H
2
O or cm PMMA.
19.1.4 Dose Model
To determine the applied dose on various parts of the paent’s body and to assist in reducing the
determinisc eects of radiaon, a dose model is used.
In this model the human body is divided into four zones.
Glossary Denions
Azurion Release 1.2 Ins
trucons for Use 388 Philips Healthcare 4522 203 52421