The Baseline Measurements page includes three mandatory steps,
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Background measurements,
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Dose rate measurement,
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CAX check measurements (see CAX Check),
and one optional step,
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Preliminary scans (see Preliminary Scans for myQA Accept).
The steps are listed under Summary on the left side of the page. For the first time running the baseline measurements, if one of these mandatory steps is aborted or failed, the baseline measurements need to be repeated from the beginning.
During the measurement, Summery shows the status of each step:
The status display (HV setup, background, and normalization) in the Controller view of myQA Accept core is sometimes not synchronized with the baseline measurement status in SMARTSCAN. In this case, please refer to the display in the SMARTSCAN wizard.
General Handling
User Interaction and Info/Status Display
During the measurements, elapsed time and remaining time, status (when a single measurement is done), and graphical scan display for CAX check and preliminary scans are displayed, e.g.,
For the steps that require operator’s interaction on the LINAC or equipment, the needed information is shown in an overlay that disappears automatically if the interaction is done.
Normalization
During the procedure of CAX check/preliminary scans, normalization is automatically performed first.
The detector position for normalization is at isocenter and reference depth of 100 mm for photons and 25 mm for electrons. The normalization status is informed via the measurement Status.
A normalization measurement is done automatically if one of the following parameters changes:
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Radiation type
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Energy
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Field detector
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Reference detector
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Field size
Re-Run Measurements
Once all first three steps have been successfully finished, the following options are available:
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Any step can be re-run by clicking the corresponding Run button under Summary
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Click the Measurements tab to open the Measurements page and start the measurements
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Click the preliminary scans Run to start preliminary scans (optional). Note that but once started, the results need to be accepted to go the Measurements page.
Background Measurements
The background measurements are carried out for all three electrometer sensitivity ranges:
High: 400+ fA – 400 pA (resolution: 0.5fA)
Medium: 250 pA – 40 nA (resolution: 5fA)
Low: 25 nA – 4 µA (resolution: 0.5pA)
A recommendation is shown in an overlay whenever a user interaction is needed (e.g., if the last background measurement was older than 2 hours).
Dose Rate Measurements
The dose rate measured here is used to calculate the estimated monitor units for the measurements in the following steps until a new dose rate measurement is required.
Measurement Settings
Once the background measurement is done, an overlay, Dose Rate Preparation, appears with the LINAC and field/reference detector information for the dose rate measurement.
Energy: Middle energy of all configured energies (e.g., 10 MV if 6, 10, 12, 15 MV are configured)
Field and reference detectors: Selected in the Confirmation page for field size: 100 mm × 100 mm
Once the beam for dose rate measurement is turned on, the measurement begins.
Dose rate measurement must be performed with the exact settings in the overlay. Please deliver the planned monitor units (250 MU for an FF beam or 500 MU for an FFF beam) exactly. This dose rate is used for estimating the minimum required monitor units for the later measurements. A wrong monitor unit delivery will lead to wrong estimations.
Please do not change the dose rate during the measurements without re-doing the baseline measurements.
Determination of the Electrometer Ranges
For dose rate measurements, the wizard sets the proper electrometer sensitivity ranges for the selected field and reference detectors.
A depth dose is measured between 1 cm and 6 cm with maximum speed. The electrometer range is selected where the current at the maximum of the depth dose is located (see Background Measurements above for the three ranges).
Dose Rate for FFF Beams
Starting from myQA Accept version 8.5, the SMARTSCAN application supports the Dose Rate measurement with FFF beams directly.
If the queue to be measured contained only FFF energies, the Dose Rate is measured directly with it the same as for FF energies.
If the queue to be measured contained a mix of FF and FFF energies, the queue optimization is carried out for FF energies first and then FFF energies:
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First, the FF energies are optimized, and the Dose Rate measurement is performed.
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Secondly, the FFF energies are optimized and when the queue items to be measured contain FFF energies, the wizard will guide through a new Dose Rate measurement.