Radcal PDC, Instruction Manual

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System description
Introduction
The PDC is designed to function as a stand-alone battery powered instrument. Its
application can be extended by connection to a PC computer running the optional
software package (see separate software user manual). A support stand is
provided to elevate the PDC above structures that might add scattered radiation
to a primary beam measurement.
The PDC has been designed for use with a patient equivalent phantom when
measuring entrance or image receptor doses. This is not included in the system
package.
Construction
The PDC consists of an ion chamber assembly, electronic printed circuit board
incorporating displays, a switch panel and battery.
The components are housed within a protective housing that incorporates a beam
alignment target.
Note
. There are no user accessible components within the housing.
The Ion chamber
The ion chamber is suspended within the protective housing to minimize
disturbance during positioning the PDC in the radiation beam. The chamber
consists of central and outer active areas. Dose measurement uses the central
area only whilst both areas are used for DAP measurement.
The radiation target
A target assembly is provided to assist with alignment to the radiation beam.
Attention
. When making dose measurements the radiation field size must exceed
the red 10cm diameter area.
Where a light field is not available a matrix of radio-opaque markers are provided
for alignment with a fluoroscopic image. The markers are placed at points of
major intercept on the target and are illustrated by red dots.
The Electronic system
The PDC uses a micro controller to manage and process instructions and
measurement data. A common high voltage generator is used to energize both
sections of the ion chamber. The system incorporates three independent
electrometers that are permanently coupled to collector plates of the ion chamber.
Their functions are:
1. Central area
2. Outer area, low sensitivity
3. Outer area, high sensitivity
The electrometer outputs are continuously sampled by the processor.
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