In the Dosimetry QA Plugin, reference (baseline) measurements are carried out in the Test setup workspace
whereas QA measurements carried out in the Test setup workspace. Four Dosimetry QA test types are
provided:
- Energy Constancy
- Output Constancy
- Profile Constancy
- Wedge Constancy
Note: Currently only Profile Constancy test are available for the myQA SRS detector.
CAUTION: DESCRIBE TEST CONFIGURATIONS
User shall describe the configuration in test template and/or test definition.
CAUTION: THE SAME SETUP FOR BOTH TEST SETUP AND TEST RUN
For every test type, a setup containing reference measurements (baselines) and test acceptance criteria (tolerance value, tolerance band, etc.) will be defined first in the Test setup workspace. The QA tests can be then performed in the Test run workspace.
The measurement setup in test setup and test run must be the same. It is recommended to describe the test procedure and indicate the following parameters in the Description box of the Test Definition dialog:
- Field Size
- Energy
- Gantry Angle
- Detector type
- Detector orientation
- Detector build-up / depth
IMPORTANT NOTICE: ASSIGN TEST PARAMETERS
Only the person who is responsible for QA can define the parameters of the tests. The parameters given in the user manual are only examples.
IMPORTANT NOTICE: THE OUTPUT CALIBRATION SHOULD NOT BE OLDER THAN THREE MONTHS
If the output calibration is older than 3 months, the software will display a warning. It is recommended to perform the Output Calibration again.
About FFF beam analysis
In the current software version, the analysis method for the penumbra calculation for FFF beams (see
Section 4.2.3.7 myQA Accept Instructions for Use) is sensitive to the correctness of device positioning. In
addition, to ensure correct results, the field size is limited to 20 cm × 20 cm.
It is recommended to use any of the optimized analysis methods for analyzing the profiles of FFF beams,
i.e., FFF or SFPM_35_2019_FFF analysis methods. A warning sign appears next to the name of the analysis
method if a non-FFF analysis method is chosen for a FFF frame. Users should be cautious about results.
CAUTION: ANALYSIS METHODS FOR FFF BEAMS
For profile constancy tests, protocols specifically defined for FFF beams are not optimized for FF.
Such application may lead to erroneous QA results
CAUTION: ANALYSIS METHODS FOR FF BEAMS
For profile constancy tests, protocols specifically defined for FF beams are not optimized for FFF.
Such application may lead to erroneous QA results
IMPORTANT NOTICE: SLOPE VALUES FOR FIELDS SIZES < 10 CM × 10 CM FOR SFPM_35_2019_FFF PROTOCOL
Slope values for field sizes smaller than 10 cm × 10 cm for SFPM_35_2019_FFF protocol
are rather inconsistent, as the small fields lies in the broad profile peak that is rather
homogeneous^1
^1: Fogliata, A., et al. "Definition of parameters for quality assurance of flattening filter free (FFF) photon
beams in radiation therapy." Medical physics 39.10 (2012): 6455-6464.
About Small Fields
Standard protocols are defined for standard field sizes. For smaller field sizes, i.e., field sizes smaller than 5
cm × 5 cm, please refer to Small Fields protocol.
Note: Based on the recommendation of the TRS 483, for small fields (nominally smaller than 5 cm
× 5 cm), the field size is calculated as the FWHM of the profile at the 50% of the D_max.
Configure the Measurement Device in the Software
The definition and settings of the machine and detector in the software are defined in the myQA Platform > Equipment Setup. Please see Chapter 4, myQA Platform Instructions for Use.
Default settings
CAUTION: DEFAULT CALIBRATIONS / CORRECTIONS
Be default, the following calibrations / corrections are used automatically for
measurements:
- Latest factory calibration
- Latest created or copied output calibration of the same beam quality
- KTP correction for the active valid output calibration (if available)
- Latest user uniformity correction (if available)
Please ensure the latest calibrations / corrections match your measurement settings.
The copied calibration is used by default for a measurement if they contain the most recent measurement data.
Output Calibration / Uniformity Correction
Output calibration and user uniformity correction files created in myQA Platform will be applied to
measurements in myQA machines. Procedures for creating these files are described in Section 4.3.2, myQA Platform Instructions for Use.
IMPORTANT NOTICE: CALIBRATE THE ABSOLUTE DOSE OUTPUT REGULARLY
Absolute drift of a device may be unnoticeable. Absolute dose calibration should be
repeated regularly.
IMPORTANT NOTICE: OUTPUT CALIBRATION SHOULD NOT BE OLDER THAN THREE MONTHS
If the output calibration is older than 3 months, the software will display a warning in
the Test Setup and Test Run. It is recommended to perform the output calibration
again.
Default active calibration / correction
The output calibration or user uniformity correction with the latest measurement time will be set to active
and used by default (including the copied output calibration).
Define a non-default active calibration / correction as the active one
If a non-default calibration or user uniformity correction should be used, it can be selected in the myQA
Platform > Equipment setup workspace:
IMPORTANT NOTICE: USING A NON-DEFAULT CALIBRATION
If the default calibration or user uniformity correction for the measurements is not used, it is user’s responsibility to ensure that the selected calibration delivers acceptable results.
General Steps for Dosimetry QA
Similar to a generic QA procedure, the general steps to run a fully integrated dosimetry QA are also
including:
1. Create a protocol template for dosimetry QA tests (see Section 3.3)
2. Create a protocol for a machine to be tested (see Section 3.4)
3. Perform the QA tests (see Section 3.5)
Create a Protocol Template for Dosimetry QA
- In the Test Setup, click Edit in the ribbon, select Protocol Templates in the Machines & Templates panel.
- Click New in the ribbon or context menu.
- Enter the name of the protocol, e.g., Dosimetry QA, and description if desired.
- With the Dosimetry QA protocol selected (if not, click to select it), click New in the ribbon, and enter the task template name, e.g., Dosimetry QA Task. Select the task execution interval in Recurrence. See Section 2.3.4, myQA Machines Reference Guide, for the detailed instruction.
- To create test templates, select the task where the tests should be located, click New in the ribbon,
select the appropriate Category and Result Type, and enter description, acceptance criteria, field size, and gantry angle. - Repeat the last step until all tests are created.
Example: Test Template for Wedge Constancy; here the user can indicate field size at isocenter.
Note: It is possible to add attachments to Protocol / Task / Tests Templates and Definitions as
described in Section 2.3.4, myQA Machines Reference Guide.
Profile Constancy
Note: Profile Constancy tests can now be performed on the myQA SRS device.
- To define a Test Template for Profile Constancy, two more parameters are required: profile directions (1) and the analysis method (2). These two parameters affect the acceptance criteria entries and cannot be edited in the Test Definition panel for a machine protocol.
Example: Test Template for Profile Constancy
CAUTION: USE SMALL FIELDS PROTOCOL FOR FIELD SIZES < 5 CM × 5 CM
For profile constancy tests with field sizes < 5 cm × 5 cm, the Small Fields protocol has to be used.
The use of a standard protocol, which is not specifically defined for small fields, may lead to erroneous QA results.
IMPORTANT NOTICE: USAGE OF THE MYQA SRS DEVICE WITH SFPM PROTOCOL
To increase the consistency of the measurements for the parameters assoicated with the SFPM protocol, it is recommended to use 500 MU or more for performing profile constancy analysis with this protocol - The available analysis methods are:
For the ANSM 28-02-2023 and SFPM_34_2019_FFF, the user must manually enter the position on the reference points.
See myQA Platform Reference Guide for information on predefined parameters for the analysis methods.
Note: Warning and Error Tolerances are given only for the analysis method based on the International Electrotechnical Commission Standard IEC-60976 (see screenshot below) in the software. The tolerances for other protocols can be taken, e.g., from the acceptance criteria of the machine vendor or clinical QA standards. The users need to enter these values manually.
Create a Machine Protocol for Dosimetry QA
In the case described below, the protocol is created using a protocol template selected in the From
Template dropdown list. It can also be created from New. The procedure is similar to Section 3.3.
- Select a machine in the Machines & Templates panel.
- Click From Template in the Test Setup ribbon and select a dosimetry QA protocol template (created in the previous section).
The Test Setup page (example – creating a protocol for a machine)
- Create baselines for the tests.
If no reference measurement is available, at least two measurements are needed to set the baselines for all test types. An additional reference needs to be acquired in case of wedges (StarTrack or MatriXX).
The baselines for dosimetry QA are generated in the Test Definition panel. See the following subsections for different dosimetry QA tests.
Note: For copying/pasting dosimetry QA tests, see myQA Machines Reference Guide.
Output Constancy baseline measurement
Example: Test Definition for Output Constancy
- Combo box for the available measurement devices. Select the one to be connected to the software.
- Connect / disconnect button:
/
- connects / disconnects the selected measurement device.
- Background Measurement button:
- click to start the background measurement. Measurement time is 20 s.
- Temperature / Pressure Offsets button:
- click it to set / adjust temperature and pressure.
- cGy box: for entering the default dose output value
- Set to all button: sets the value in the cGy box to all enabled energies in the Measured column.
- Enable column: the energy with checked box will be measured
- Energy column: lists the available energies of the machine defined in the myQA Platform > Equipment Setup. If the output calibration of this energy is older than 3 months, a warning sign (5) with tooltip appears:
- Output Calibration column: place the cursor over the info icon (6); the tooltip displays detailed
information of the output calibration.For the same beam quality, output calibration with the active icon in myQA Platform > Equipment setup > Calibrations box will be selected. The latest output calibration is set as active by default. However, if a different calibration should be used, it can be selected with the Edit button in the
Calibrations box. If no output calibration with the same beam quality is available, a warning sign (7) appears in the Action column. The tooltip displays the possible causes: - Actions column: contains the action buttons Start (8), Paste (9) and / or Reset (10).
- Paste button: in myQA FastTrack workspace, measured values can be copied to a clipboard (see
Section 2.1.1, myQA FastTrack Reference Guide) and pasted as expected values here with the Paste
button. When the Paste button is disabled, a tooltip shows the possible causes: - Measured column: The measured result can be directly entered, measured, or the average of several
measurements using the Calculator (11).
Baseline measurement
Prerequisite: the device is ready for measurement.
- Click the Connect button (2).
- Click the Background Measurement button (3). The default measurement time is 20s. It can be stopped by clicking the Stop button. However, the background measurement is invalid if stopped pre-maturely.
- Click Temperature / Pressure Offsets button (4) set / adjust temperature and pressure.
The Measured values (i) are the internal temperature and pressure given by the measurement device. The user can keep these values or adjust them according to an external measurement device for temperature and pressure. The external values are entered in the Actual fields (ii). The difference between the internal and external values are displayed in the Offset column (iii). - Check the Enabled box of the energy to be tested.
If the device is properly connected and a valid output calibration is available for the selected energy, the Measurement button (8) will appear in the Actions column. - Click the Measurement button and turn on the beam (e.g., 100 MU, 600cGy/min). Click the Stop button when the beam is off.
The results will be automatically generated in the Measured box. The button in the Action box is changed to the Reset button (9).
- If the measurement should be re-run, click the Reset button , the Measurement button (8) will
appear again, and the Measured will be empty. Now the measurement can be run again. - If the measured result should take the average of several measurements:
- If the measurement should be re-run, click the Reset button , the Measurement button (8) will
- Write down each measurement result.
- Click the Calculator button (11), enter all results.
- Enter all measured results.
- If temperature and pressure calibration should be applied, checkmark the KTp box, enter the temperature and pressure values measured by a reliable external device in the Temperature and Pressure boxes, respectively.
Note: Do not checkmark the KTp box if the entered values have already been corrected during their measurement! - Optionally if a user defined factor should be applied to the average, enter it in the Factor field.
- Click the Apply Result button; it will be added to the Measurement box.
Energy Constancy baseline measurement
The baseline measurement is the same as for Output Constancy describe above.
Example: Test Definition for Energy Constancy
Profile Constancy baseline measurement
The expected values can be taken from a measurement by clicking the Measurement button (8) or from
an imported one by clicking the Import Measured Data button (12) or paste with the Paste button (10) if
the measurement has been copied from FastTrack (see Section 2.1.1, myQA FastTrack Reference Guide) or
manually enter them.
Example: Test Definition for Profile Constancy
CAUTION: ASSIGN THE CORRECT MEASURED DATA TO THE RADIATION DEVICE
Be aware that the imported data will be assigned to the selected radiation device and can only be used for this device in the myQA Machines workspace.
CAUTION: ENSURE CORRECT WARM-UP PROCEDURE FOR ALL DEVICES
Please ensure the device has had an adequate warm-up period before taking measurements. A background measurement is necessary for correct readings.
For information on Profile Constancy measurements with the myQA SRS, see Using the myQA SRS device
below.
After a measurement is done, the reference detector type will be shown.
Beside the parameters / features for other Dosimetry QA Test Definition, the profile constancy has more
functionality:
Chart View button (13):
If there is measurement data available, click this button and the profiles can be viewed graphically (13a). The intensities at the cursor position are displayed (13b).
Context menu of the expected and tolerance values
- Right-click the select a value in the table, the context menu opens.
- Cut: deletes the selected value.
- Copy: copies the selected value to the
clipboard. - Paste: pastes the value in the clipboard to the
cell where it was clicked.
Import Measured Data button (12):
Click this button, a table appears containing the data imported into myQA and in myQA Machines > Test
Repository which has the same measurement settings (machine, energy, field sizes, and gantry angle)
and can be imported into the current test. For the gantry angle value, a tolerance of +/- 1° is accepted.
Examples: measured data available to be imported as profile baselines
IMPORTANT NOTICE: ASSIGN MEASURED DATA TO MACHINE
Be aware that the data imported in the myQA Platform workspace will be assigned to the selected machine and can be used only for this machine in the myQA Machines workspace.
- Select a measurement (row), its properties are shown on the right panel.
- Click Ok, the data is imported into Test Definition panel.
Beam Quality combo box (14):
- Select the desired beam quality.
If there is a valid output calibration for the selected beam quality, the Measurement button is available. If at least one expected value is inserted, the Beam Quality box will be inactivated. The energy can be changed after all expected values are deleted (the Beam Quality combo box becomes activated again).
Using the myQA SRS device
When using the myQA SRS device for measurements in myQA Machines, please be aware of the following:
CAUTION: DOSE RATE CALIBRATION NOT APPLIED
For the myQA SRS device, dose rate calibration is not applied in myQA Machines measurements. This also applies to data imported from other workspaces.
To avoid erroneous measurements, the same dose rate shall be used for Test Setup (baseline) and Test Run (measurement).
IMPORTANT NOTICE: MANUALLY ENTER THE DOSE RATE
Before starting the measurement, ensure that the correct Dose rate has been entered.
Wedge Constancy baseline measurement
For a Wedge Constancy baseline, two measurements, with and without wedge, are required. They can be
measured or imported. The measurement for the open field is automatically shared for all wedge angles,
thus it must be performed only once. Measurements can only be imported if the measurement settings
(machine, energy, gantry angle, field sizes, and wedge angle) match. They can be viewed graphically by
clicking the Chart View button in the last column.
In the Wedge Direction column, the inline profiles are automatically indicated as direction “In / Out” or
“Out / In” whereas the crossline profiles are automatically indicated as the wedge direction “Right to Left”
or “Left to Right”.
- Click Save in the ribbon when all test templates are created. This template can be used for so many machines as desired.
After the machine protocol is set up, select the protocol in the Protocol Tree View panel, and click Set Active in the Test Setup ribbon. Finally click Save in the Test Setup ribbon to exit the Edit mode. The protocol is now ready to be run in the Test Run page.
Note: When measuring wedge constancy with Dolphin in combination with an accelerator where the direction of the wedge is changed by rotating the collimator, only one wedge direction must be measured.
Perform Dosimetry QA Tests – Test Run
After the protocol is setup, performing the QA tests is straight forward.
- Click the Test Run navigation button under myQA Machines.
- Click Clinics in the ribbon to select the clinic where the machine is located.
- Select the machine and then an active task in the Agenda panel (left panel).
- Select a test in the Task View panel (middle panel).
The buttons / icons have the same functions as in the Test Definition panel described in Section 3.3.4. - Prepare the measurement device by selecting the device (1), connect it to the software (2), measure the background (3) and set the temperature / pressure correction (4).
Note: The temperature and pressure values entered for a dosimetry test are automatically taken for the other dosimetry tests of the same session. - Perform all the required measurements.
After a measurement is done, the status (Pass / Warning / Failed) is immediately updated in the State column. - After all measurements are done, click the Finish button in the lower-right corner of the test block to finalize the test.
- After all tests are done, click the Finish icon in the ribbon to finalize the task.
Share Measurements
By selecting this box, the measurement(s) will be populated to other tests that have the same parameters
including the same machine, energy, inline and crossline field sizes, gantry angle; for Wedge Constancy tests: with / without wedge and wedge direction (i.e., left-to-right or right-to-left), whichever is applicabl. In this way, the number of measurements can be minimized.
Note: Pressing the Reset button in the Action column resets only the measurement in the current test. It does not affect the measurements that has been already populated to other applicable tests.
Note: If Share Measurement is activated, please ensure that the correct number of MU are irradiated in case the output constancy test is one of the tests to be shared.
Import of Profiles into the Compare Page
Upon finishing the profile constancy test (by clicking the Finish button), four profile import icons, for
importing profiles of inline, crossline, and two diagonals, respectively, will appear on the top of the table.
The measured and expected profiles of one direction can be selected for analysis and graphical display in
Compare.
By clicking one of the icons, e.g., Inline profiles, the inline profiles will be added to the Compare page. The
software performs the following actions automatically:
- The Compare page opens, displaying the measured (measured in Test Setup) and expected profiles (measured in Test Run) of the selected direction. They are also listed in Data Import.
- The expected profile is set as reference.
- If a new direction is selected in myQA Machines, the previous profiles will be deleted from Compare and Data Import.
Applying kTp Correction in Dosimetry Plugin
When performing measurements with dosimetry Plugins, the user has the possibility to apply the
temperature and pressure correction (kTp) within the Machines workspace. The workflow is independent
whether the measurements are performed in Test Setup for baseline definition or in Test Run.
In the following, the workflow is described using an example in Test Run.
Single measurement with a connected device
If the measurements are performed directly in the software, the temperature / pressure correction is applied after the measurement device has been connected and the background measurement has been
performed.
- Click the Temperature / Pressure Offsets button (1) to open the dialog.
The Measured values (i) are the internal temperature and pressure given by the measurement device. The user can keep these values or adjust them according to an external measurement device for temperature and pressure. The external values are entered in the Actual fields (ii). The difference between the internal and external values are displayed in the Offset column (iii). - To start the measurement, click the Measurement button (2). The results are automatically temperature / pressure corrected.
Note: The temperature and pressure values entered for a dosimetry test are automatically applied to the other dosimetry tests of the same session.
Average of several measurements
The user can perform more than one measurement and use the average value as test result.
- Click the Calculator button (3) to open the dialog.
- Enter the results of the single measurements in the Measurement fields (4).
- If the single measurements were performed without KTp correction, checkmark the KTp box and enter the temperature and pressure values (5)
- Click Apply Result.
Note: Do not checkmark the KTp box if the entered values have already been corrected during
their measurement! Otherwise, the correction will be applied twice.