myQA iON - Parameters – IBA Dosimetry Service & Support

Under Settings, the users can define a series of parameters for independent dose analysis. Once these parameters are defined and saved, they will be applied to all further analyses in myQA iON. No analysis will start if the parameters are not defined.

Specific permissions for the user role must be granted to modify those parameters.

When using the SW for the first time as an administrator the global parameters must be defined. myQA iON will give a warning to the user when global parameters are missing.

Example: missing global parameters

If the parameters defined for a specific instance are different from the ones used for the global parameters, a PARAMETERS MODIFIED banner (1) is displayed on the top-right corner of the screen. To align the parameters of a specific analysis with the global parameters, the values of the parameters must be modified in the tool bar above the results (2).

Global parameters are set under Settings, but local parameters can be set by clicking on the calculation
tab for a specific analysis.
If parameters have been altered locally, click the Reset button (3) to return to the global parameter
value.
Individual values can be reset to the global value by clicking the Reset button (4) that appears next to
the updated value.

Note: Any modification of global MC parameters will only be applied to newly imported patient plans. If new calculations are needed on existing patients, please delete and re-import the patient plan.

Log Analysis

To define settings for the Irradiation Logs, click the Log Analysis tab on the settings page. This page includes:

Display Settings (PT only)
Warning Error Management (PT only)
Radiotherapy Log Analysis (RT only)

Display settings (PT only)

Display settings for the Log Analysis can be toggled ON or OFF depending on the user’s needs.

Click Save when the desired display settings have been selected.

Warning Error Management (PT only)

The user can define warning error parameters:

Click the + New warning/error threshold button.
In the dialog select Position or MU and enter the necessary information.
Warning error threshold dialog(s); Direction field is added when Position is selected
Click Save to create the new warning error.

Radiotherapy log analysis (RT only)

In the Radiotherapy log analysis tab, select the Log reconstruction type from the dropdown menu.
Click Save to confirm the selection.

Table 3.1. Description of log reconstruction type

Log reconstruction type	Description
Original sampling	The control point sampling of the reconstructed RT plan is equal to the control point sampling of the original RT plan. This is the default setting in myQA iON.
Smart sampling	400 control points are selected from the reconstructed RT plan.
Gantry sampling	From the reconstructed RT plan, 1 control point is sampled for each degree of the gantry rotation.
High resolution sampling	1 control point of the log-file is equal to 1 control point of the corresponding beam in the reconstructed RT plan.

MatriXX analysis (PT only)

2D Gamma

By default, the gamma calculation is global (relative to the maximum dose value in the reference image). The evaluated dataset is not resampled. For each pixel of the reference image, the dose search in the evaluated image is done using interpolation with a sample spacing that is 10 times smaller than the pixel spacing of the reference image.

Enter the information for the 2D Gamma parameters and click Save.

Table 3.2. Description of 2D gamma parameters

Item	Description
Reference Dose	Chosen by the user. Possible values: Measurement or TPS.
Tolerance on dose	Dose difference (DD) for the gamma analysis.
Distance to agreement	Distance to agreement value (DTA) for the gamma analysis.
Threshold	Percentage of the maximum value of the dose of the TPS image or the reconstructed image below which voxels are not considered for the gamma analysis. Please note, external contour is needed for applying maximum dose threshold of DVH plotting.
Warning percentile	Percentage of voxels that need to pass the gamma test. If the number of voxels that pass the test is above, then the test is passed. Otherwise, a "warning" is displayed in the results of the gamma analysis.
Error percentile	Percentage of voxels that need to pass the gamma test. If the number of voxels that pass the test is above, then the test is passed or in warning, depending on the results and the parameter above. Otherwise, an "error" is displayed in the results of the gamma analysis.

Water Phantoms

This section allows the user to define water phantoms that can be used during the MatriXX analysis

Add a water phantom by clicking New water phantom. Create a name and select a default view (Axial,
Coronal, Sagittal).
Click Save to add the new water phantom to the list

When a water phantom is created, three actions can be performed:

Import DICOM: Import CTs and Structure Set (External type ROI must be included) for this water
phantom.
Edit: Edit the name and default view for this water phantom.
Delete: Delete the water phantom from the SW.

Monte Carlo

The Independent Dose is a calculated separately from the prescription based on MC simulations. It is used to compare with the prescribed dose. myQA iON allows for independent dose calculation for both PT and RT.

Under the MC tab the user can set the parameters for MCSquare (PT only), Gate (Carbon only), SciMoCa (RT only), and 3D Gamma calculations.

Note: Depending of the configuration, MCSquare, SciMoCa, or Gate might not be visible.

Monte Carlo Algorithms

The myQA iON SW is provided with the MCSquare[2] (open-source) and SciMoCa[3] dose engines. The option to
install these dose engine is presented during installation. The dose engine versions bundled in myQA iON
might be different from the latest version available.

Please note, for Carbon customers, the Gate[4] dose engine must be acquired separately.

Commissioning of the MC engines is performed with the support of the IBA Dosimetry team following the
procedure in the installation manual[1].

MCSquare (PT only)

Enter the information for the MCSquare parameters and click Save.

Table 3.3. Description of MCSquare parameters

Item	Description
Dose Calculation Grid - Voxel Size (mm)	CT voxel spacing grid: Default setting. X, Y, Z fields cannot be edited. Custom dose grid: Presents the dose calculation grid voxel size in millimetres. Text boxes are provided for X, Y, and Z values. Acceptable minimum value is 0.500 mm and maximum value is 10.000 mm for each.
Number of particles	The number of primary protons to simulate. The number of protons used for the simulation is one of the two stopping criteria for the MC algorithm (entered by the user).
Uncertainty	Toggle on Compute uncertainty to activate the Uncertainty field. Maximum statistical uncertainty (in percent): The simulation stops after N protons (the number of particles) have been simulated. If the uncertainty parameter is used, 10 simulations are launched, each with N/10 protons. If necessary, more simulations are launched until the uncertainty criteria is met. The uncertainty is the second stopping criterion of the MC algorithm. The final result is the average of all the simulations. The statistical uncertainty on that average for each voxel is the standard deviation divided by the root of the number of simulations. It is reported in % of the local dose per voxel. The global uncertainty used as the stopping criteria is the average of the uncertainties of all the voxels receiving at least 50% of the max dose.
Energy Cut	Energy cut (MeV) below which heavy charged particles are locally absorbed.
Dist max	Maximum distance between two steps (cm).
Epsilon max	Maximum fractional energy loss (dE/T) per step.
Te min	Energy threshold (MeV) for the production of secondary electrons.
Simulations	Toggle ON the following parameters to include them in the calculation: Simulate Nuclear Interactions Simulate Secondary Protons Simulate Secondary Deuterons Simulate Secondary Alphas
Patient specific calculations	Toggle on the Apply patient specific Monte Carlo parameters for calculation of logs to apply local parameters to all subsequent logs being analyzed for all patients. To apply calculations to a single patient see Section 5.2.1.2.

Gate (Carbon only)

For independent dose calculation of carbon ion treatments the Gate[4] algorithm is available through the
connection of the IDEAL software to myQA iON. The Gate algorithm is based on the paper by Grevillot L, et
al.[5].

For carbon patients:

A specific user must be identified for sending results from IDEAL to myQA iON. No special rights are needed for the myQA iON user, but the credentials of the user must be the same between IDEAL and myQA iON. See Create a New user.
The C+ | PHYSICAL DOSE banner will be displayed at the top right corner of the screen of the application.

Select one of the two parameters (Number of particles or Compute uncertainty) and enter the necessary information. Click Save.
Please note, it is only possible to use one of the two available parameters, i.e., if Number of particles is used, Compute uncertainty is greyed out and not available.

Table 3.4. Description of Gate parameters

Item

Description

Number of
particles

Number of particles per beam. The number of primary particles to simulate. The number
of particles used for the simulation is one of the two stopping criteria for the MC algorithm
(entered by the user).

The simulation stops after N particles (the number of particles) have been simulated.

Uncertainty

Toggle on Compute uncertainty to activate the Uncertainty field. This value is the
maximum statistical uncertainty (in percent):

If the uncertainty parameter is used, 10 simulations are launched, each with N/10 particles. If necessary, more simulations are launched until the uncertainty criteria is met. The uncertainty is the second stopping criterion of the MC algorithm.
he final result is the average of all the simulations.
The statistical uncertainty on that average for each voxel is the standard deviation divided by the root of the number of simulations. It is reported in % of the local dose per voxel.

The global uncertainty used as the stopping criteria is the average of the uncertainties of all the voxels receiving at least 50% of the max dose.

SciMoCa (RT only)

Enter the information for the SciMoCa parameters and click Save.

CAUTION: ENSURE CORRECT ROI NAME AND DENSITY VALUE
Ensure accurate spelling of ROIs and input values for densities. Density will not be overwritten if the entered name does not match an ROI in the structure set or if the entered density value falls outside the range of 0.0000 g/cm3 – 24.0000 g/cm3.

Table 3.5. Description of SciMoCa parameters

Item	Description
Custom Dose Grid (X, Y, Z)	The dose calculation grid voxel size values (X, Y, Z) are presented in mm. Acceptable minimum value is 0.500 mm; maximum value is 10.000 mm.
External Density Threshold	Allows the user to set a minimum external contour density threshold. Acceptable range of values is between 0 and 1 g/cm3. Toggle on or off as needed. When turned off, the dose calculator will not set a minimum density for an external contour. When turned on the treatment table will be included in the CT scan.
HU to density file	Select the HU to density file and click the eye icon to view the file contents. From here, the file can only be viewed, not edited.
Calibration type	Calibration options include Dose to medium or Dose to water for valid calibration values. Options can be selected from the drop-down menu.
Minimum Uncertainty	Uncertainty presents a list of calculation speeds: Extra Fast (4%), Fast (2%), Fine (1%), Extra Fine (0.5%), and Commissioning (0.25%).
CT Couch Removal	Dose calculations performed by the treatment planning system typically remove the CT couch from the CT scan. If the couch removal setting is selected, a structure with a density override may still be taken into account for the dose calculation. When to turn on Remove Couch: If there is no skin contour AND External Density Threshold is used AND the couch needs removing. If there is an indistinct calculation box around the patient that includes the couch.
Region of Interest (ROI) Override	Provides the ability to add any ROI to the calculation by clicking the + Add ROI button. Density values are expressed in units of g/cm3. Acceptable minimum value is 0.0000 g/cm3; maximum value is 24.0000 g/cm3. A density value of zero (0) ignores the ROI in the density grid. Note: It is not possible to add more than 4 digits after the decimal point. If more than 4 digits are entered, a validation error is displayed. Global settings allow for density overrides by ROI as in the structure set. ROI density overrides follow the order given by the structure set. The default ROI density value is obtained from the CT DICOM-RT structure set density value. This value can be overridden in SciMoCa and will be used for dose calculation. Priority check boxes allow for selection of a specific structure / area to focus on for the analysis.
Patient specific calculations	Toggle on the Apply patient specific Monte Carlo parameters for calculation of logs to apply local parameters to all subsequent logs being analyzed for all patients. To apply calculations to a single patient see Section 5.2.1.2.
Densities	Steel Density Range: The range of mass density values that are interpreted as steel in units of g/cm3. The default range 7.9 g/cm3 to 8.1 g/cm3 will be used
Densities	Titanium Density Range: The range of mass density values that are interpreted as titanium in units of g/cm3. The default range 4.44 g/cm3 to 4.6 g/cm3 will be used.
Beam Model Dictionary	Click the Beam Model Dictionary button to view the file contents. From here, the file can only be viewed, not edited.

3D Gamma

The 3D Gamma algorithm implemented in myQA iON is based on the paper by Mingli Chen, et al. (2009)[6].

The TPS dose is used as reference.
The distance to agreement (DTA) is handled the same in all directions (x, y, and z). The image resolution is handled by looking at voxels that are at a certain distance and the spacing between

Enter the information for the 3D Gamma parameters and click Save.

Table 3.6. Description of 3D Gamma parameters

Item	Description
Tolerance on dose	Dose difference (DD) for the gamma analysis.
Distance to agreement	DTA for the gamma analysis.
Threshold	Percentage of the maximum value of the dose of the TPS image or the reconstructed image below which voxels are not considered for the gamma analysis.
Warning percentile	Percentage of voxels that need to pass the gamma test. If the number of voxels that pass the test is above, then the test is passed. Otherwise, a "warning" is displayed in the results of the gamma analysis.
Error percentile	Percentage of voxels that need to pass the gamma test. If the number of voxels that pass the test is above, then the test is passed or on warning, as 2D Gamma. Otherwise, an "error" is displayed in the results of the gamma analysis.