Having defined the Measurement Preferences, the next step is to define the Analysis Parameters as described below.
Very often you may want to display some important dosimetry parameters, for instance flatness and symmetry values for a profile, or depth of Dmax and Rp for depth doses. The parameters are available in the Numerical Analysis panel. Which parameters you want to display, and how they should be calculated, are configured as shown on the following pages.
Clicking on the right side to the tab Analysis Parameters, you will get the following list:
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Electron Depth Dose
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Photon Depth Dose
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Proton Depth Dose Bragg Peak
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Proton Depth Dose SOBP
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TPR/TMR
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Electron Profile
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Photon Profile
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Photon FFF Profile
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Isodoses
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General Tolerances
For all the protocol windows, following general handling rules are essential:
Default protocols cannot be edited. However, you can copy an existing protocol and thereafter modify different parameters.
Only the details activated with a checkmark will be included into the calculation of the analysis parameters.
By choosing any default protocol, you will see the details of the protocol on the right side but grayed out since they cannot be edited.
Create new button
Creates an empty protocol. Parameters need to be defined in the Details box.
Copy selected button
Creates a protocol by copying the selected one in the list.
By default, the new protocol name is called, Custom_n, where n is the nth time when a protocol is created. The user-created protocol is automatically saved in the software.
Delete selected or Delete all button
Delete the selected user-defined protocol or all user-defined protocols.
Export to file and Import from file buttons
The selected user-defined protocol can be exported and then imported to any myQA Accept application. This allows you to exchange the protocol with another myQA Accept computer.
Change name button
Select a protocol in the Selected protocol list, edit it in the Change name box, and then click the Change name button.
Protocol Tolerances… button
By clicking the Protocol Tolerances… button, the Edit Groups dialog opens. The expected values and their tolerance of the selected parameters in the current protocol for a group of measurements with the same energy, field size, and SSD are defined here.
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First, define the group measurement settings
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To add a new group, click the Add group or Clone button.
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To remove the group, click its Remove button.
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To edit a setting, double-click the cell and then edit the value.
See two examples below:
Example of the Expected values and tolerance groups dialog for a photon profile protocol. Only the profiles with the combination of Energy and Field Size, and SSD defined in the protocol will be evaluated -
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To edit the tolerance of a protocol parameter, click its Edit button to open the Edit tolerances dialog. Double-click the cell and then enter the value.
Example for Edit tolerances of a DIN profile protocol.
- Click Ok to confirm the change and close the dialog.
Field Width = measured field width / nominal field width * 100%,
Where nominal field width = Field Size * (SSD + Depth) / SAD.
Ideally, the measured field width is equal to the nominal field width. Therefore, the “Expected value” for the parameter “Field Width” is 100%.
Template Tables for Protocol Tolerances
For the following analysis protocols, the SW provides the protocol tolerance template tables:
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Photon profiles: Elekta_Profiles and Varian_TrueBeam_Profiles (see the left screenshot)
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Photon FFF profiles: Elekta_FFF_Profiles, Varian_Halcyon_Profiles, Varian_TrueBeam_FFF_Profiles(see the right screenshot), and SFPM_35_2019_FFF
For these protocols, by clicking the Protocol Tolerances… button for the first time, the Expected values and tolerance groups dialog will open containing the corresponding template table.
template tables must be inspected before use
The protocol tolerance template tables must be inspected carefully before use. If necessary, modify their contents accordingly.
If the tolerance table has been modified, the last modified table will be used the next time when the myQA Accept application is opened.
important remarks for using the template tables
The protocol tolerance template tables and their listed data are not meant to replace neither the recommendations of the national and international organizations that aim to provide a uniform platform for the QA procedures in radiation therapy (e.g., AAPM, IAEA), nor the clinical reference data already measured, evaluated for each treatment machine, and validated for the commissioning of the TPS.
The tables are intended to be used solely for the numerical analysis of PDD’s and profiles within myQA Accept / SMARTSCAN software products of IBA Dosimetry.
IBA Dosimetry does not take any responsibility in the clinical use of these tables in corroboration with myQA Accept and SMARTSCAN or in any other context. Before relying on the results delivered based on these tables, the user must evaluate whether the data provided within them fits the purpose of the beam analysis of their treatment system. The configuration and the contents of the tables associated with this document and clinically used within myQA Accept / SMARTSCAN for procedures such as LINAC / TPS commissioning, Beam Data Collection or periodic QA is the sole responsibility of the customer.
For more information about the protocol tolerance template tables, please see About Template Tables for Protocol Tolerances.
Electron Depth Dose
For electron depth measurements analysis, a list of parameters can be selected by users . A set of parameters can be defined in a custom protocol or can be selected from one of the predefined protocols.
Photon Depth Dose
For photon depth measurements analysis, a list of parameters can be selected by the user. A set of parameters can be defined in a custom protocol or can be selected from one of the predefined protocols.
Proton Depth Dose Bragg Peak / SOBP
For proton depth measurements analyses (Bragg Peak or SOBP), a list of parameters can be selected by the user. A set of parameters can be defined in a custom protocol or can be selected from the predefined protocol.
TPR / TMR
For isocentric treatments, a list of parameters can be selected by the user. A set of parameters can be defined in a custom protocol or can be selected from one of the predefined protocols.
Electron Profile
Clicking Electron Profile in the Analysis parameters, you can choose one of the protocols. According to your selection, the measurement is going to be analyzed in the Numerical Analysis panel.
Photon Profile
After choosing Photon Profile in the Analysis parameters, you can choose one of the photon protocols (except for photon FFF beams, see the next section). According to your selection, the measurement is going to be analyzed in the Numerical Analysis panel.
Photon FFF Profile
In myQA Accept, two groups of predefined protocols are available. Group 1 profile analysis protocol are based on a recommendation of Varian, and Group 2 is based on a French protocol SFPM_35_2019_FFF. By clicking Photon FFF Profile in the Analysis parameters, a predefined protocol for FFF beams is available to be selected.
Default protocols cannot be edited, but
| Group 1 | Group 2 | |
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| Protocol name |
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| Parameter |
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The detailed parameter descriptions and protocol algorithms are described in Section 8.1.5, myQA Accept Reference Guide
It shows Varian recommended details for FFF beams using Point of Inflection and optionally the Off-Axis-Intensity parameters.
The parameters for Off-Axis-Intensity for the field sizes of 100 mm × 100 mm and 400 mm × 400 mm for the Varian LINAC are provide in the default protocol for FFF beams.
Users who have other conceptions of FFF profiles can create a new protocol as following:
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Click the Create new button. (Optionally) type in a desired name for the protocol in the text box of the Change name and then click the Change name button. The newly created protocol is listed and selected in the Selected protocol field:
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Click to select Point of Inflection.
The algorithm is described in Section 8.1.5, myQA Accept Reference Guide. The FFF profiles rescale point of inflection default value is 50%, which is reasonable for most of the cases. However, e.g., for small field sizes, you may need to adjust this value according to the resulting penumbra margins. See an example below; the value of 60% to renormalize at the point of inflection is a better choice.
If rescaling the point of inflection to 50% (see red labels), the upper limit of the penumbra margin, 80% is outside the profile. However, rescaling the point of inflection to a higher value, e.g., 60% (see blue labels), to calculate the penumbra will yield to a reasonable solution. Please note, this illustrates only one side of the profile. Note that for small fields (nominally smaller than 5 cm × 5 cm), based on the recommendation of the TRS 483, the field size is calculated at the FWHM of the profile at 50% of the Dmax.
Isodoses
Selecting Isodoses, you will get the following window with default Isodose Levels already defined. The default values cannot be deleted.
Clicking the New button will bring you to the following window, where you are able to define isodose levels according to your preferences.
In the Templates field appears the pre-defined name “Isodoses_0”, which can be edited of course.
Click on Level field to change the level value. Confirm the new value either by tapping the Enter key or by clicking a different Level field. After having defined all levels, you can uncheck any levels which you do not want to have displayed.
Preconditions
Isodoses can be calculated based on an array. This can be calculated from a 2D measurement. To achieve good accuracy, a high number of curves in the 2D measurement are recommended.
General Tolerances
The General Tolerance tab defines the criteria of noise level, CAX check and scatter radiation level of a measurement. In addition, the parameters of the 1-D Gamma Analysis can be defined here. Each parameter value can be edited in the corresponding text box.
Noise Detection
Noise Detection is used for Peak Analysis in the Smoothing operation (see Smoothing) to prevent data over-processing.
A noise peak, NP, is defined as, if the three adjacent points do not increase or decrease monotonously,
NP = Pleft – Pright,
where Pleft/Pright is the magnitude of the two left/right points:
The software goes through every three adjacent points to search for the maximum peak, NPMAX. A noise threshold is defined using the percentage of the threshold noise peak (NPThreshold) relative to the maximum noise peak:
Noise Threshold = NT = (NPThreshold / NPMAX) ×100%
There are two criteria for Noise Detection:
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Spike Threshold (ST): It is failed if any noise peak exceeds this threshold. It is designed for searching for the spikes in the curve.
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Noise Peak Threshold (NT): it is used for evaluating the normal noise level of a curve. The algorithm calculates the number of peaks exceeding this threshold. The noise level is considered acceptable if the number of peaks does not exceed the threshold of Allowed peak number exceeding NT per 100 points.
If any one of these two thresholds is violated, it should be considered that the noise level is too high for smoothing and thus it is not recommended to perform the Smoothing function.
The text displayed in Peak analysis in the Smoothing dialog is in red if failed; otherwise, the text is in green color.
Central Axis Check
CAX Shift Warning/Error Level: Tolerances of CAX shift deviation relative to isocenter
CAX Angle Warning/Error Level: Tolerances of CAX angle deviation (Δθ) defined as illustrated below:
The above parameters are used in CAX Measurement in the and Show CAX Analysis (see CAX Check).
These parameters are also used in the SMARTSCAN wizard. The wizard performs a CAX check during the baseline measurements. In SMARTSCAN, the CAX shift and angle deviation tolerance are defined here for displaying the possible misalignments.
Scattered Radiation
The tolerances of scattered radiation is only used in SMARTSCAN. See for descriptions.
1D-Gamma
In the 1D-Gamma section, the parameters for the Gamma evaluation (See also Mathematics and Section 8.5, myQA Accept Reference Guide can be defined:
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Delta Dose: The dose difference criterion
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Delta Distance: The distance difference criterion
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Search Distance: The spatial range used to search for representative points in the evaluated curve. This parameter should be in the range of Delta Distance to 1.5×Delta Distance. E.g. if Delta Distance is set to 3.0 mm then the Search Distance should be between 3.0 mm to 4.5 mm.
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Gamma Threshold 1: This is a user-defined value. The percentage of the total number of points having the Gamma-Index value smaller or equal to this value will be displayed in the Threshold 1 column in the Numerical Analysis panel (see Section 6.1, myQA Accept Reference Guide). The value of the Gamma Threshold 1 can be set between zero and the value of the Gamma Threshold 2.
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Gamma Threshold 2: This is a user-defined Gamma-Index value threshold. The percentage of the total number of points having the Gamma-Index value larger than this value will be displayed in the Threshold 2 column in the Numerical Analysis panel (see Section 6.1, myQA Accept Reference Guide). The value of the Gamma Threshold 2 parameter must be larger than the Gamma Threshold 1.
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Gamma Error Level: This value is between 0 and 2 and is set to 1 by default. This value is used to change the Passed/Fail criteria from the implicit Gamma Index value of 1 to a different value (which is smaller or equal to 2).
Be aware that by changing the Gamma Error Level to a value larger than 1, the percentage of points passing the 1D-Gamma evaluation will increase.
Be aware that by using a too large Search Distance value in comparison to the Delta Distance value, the percentage of the points passing the Gamma evaluation may artificially increase.