MicroDose 2.2
From Detec-Rad.com
MicroDose 2.2 is a MS-Windows application for the acquisition and real time analysis of dosimetric data acquired with a Tissue Equivalent Proportional Counter (TEPC) interfaced with MCA cards which are installed in a personal computer.
The TEPC is the instrument of choice for providing dose equivalent in mixed radiation fields, such as those encountered in nuclear power plants, in high altitude flights and in the radiation environment of space. The dose equivalent is the absorbed dose multiplied by a weighting factor which depends of the radiobiological effectiveness, i.e. destructive power, of the radiation field. For X-rays and gamma rays, this weighting factor is 1 while it is 5 to 20 for neutrons, depending on their energies. The simultaneous measurement of the dose and the determination of the appropriate weighting factor is the function of the TEPC. The gathering of this data and its analysis and display in real time is the job of MicroDose.
MicroDose 2.2’s realtime data analysis
MicroDose has the look and feel of PC based multichannel analyzer (MCA) applications.
MicroDose 2.2 is targeted towards a dual MCA system based on two on-board MCA PC cards of 16k channels each. The use of a dual MCA system totalling 32k channels provides the sensitivity to a wide dynamic range in pulse heights required by the professional health physics specialist. Currently, the MCard series by Aptec Inc. is supported but the adaptation of MicroDose to other MCA models can be easily realized.
The main graphical window of MicroDose is shown on the figure on the right side. It presents the "event size spectrum ", familiar to microdosimetrists, and this display is updated in real time as new pulse height data is acquired. The vertical scale presents either number of events (d(y) display mode) or dose ( yd(y) display mode).
The framed parameters in the column on the right-hand side of the plot area displays various diagnostic and control parameters :
- Overlap info : diagnostic information on the overlap region of the two MCA spectra
- Display mode : vertical scale selection ; ‘Events’ d(y), or ‘Events x Energy’ yd(y)
- Gamma multiplier : factor used to fine tune the subtraction of the gamma component of the spectrum
- Analysis limits : lineal energy (or LET) limits inside which the dosimetric information is computed
Below the control parameters, one finds the result area. During data acquisition, a full analysis is performed every 5 seconds. The analysis makes use of important TEPC parameters such as the mean chord length and the mass of gas that it contains. The results include :
- Run LVT : current run live time in seconds
- QF (ICRP60) : mean quality factor of the radiation field according to ICRP60 standard
- H*(ICRP60) : dose equivalent at 1 cm depth (H*(10)) according to ICRP60. Units autorange from mSv to Sv
- dH*/dt, <dH*/dt> : instantaneous and average dose equivalent rates. Units autorange from mSv/hour to Sv/hour.
- <YF>, <YD> : first moments of d(y) and yd(y) plots
MicroDose 2.2 is especially well suited to interface with the new generation of multi-element TEPCs.
MicroDose’s offline gamma subtraction mode data analysis
Following the gathering of data in a mixed radiation field, MicroDose offers the possibility of subtracting from the current data, a previously saved event size spectrum. This is the " Gamma subtraction mode ". An example of the usefulness of this feature is shown on Figure 2. When in this mode, the results field is updated to provide the dosimetric information of the net data (blue curve). This allows the determination of the contributions of the different components of the radiation field to the total dosimetric quantities.
MicroDose's graphical interface features
- Automatic logarithmic scaling of incoming data
- Cursor positionning for precise result of selected point
- Multi-level area zooming around cursor position
