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myQA Machines - End-to-End Tests for Imaging and Planning

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General Procedure

The general procedure for End-to-End (E2E) Tests for Imaging-and-Planning (I&P) is shown the the following workflow. Please note, this can vary according to the site's internal workflow for QA.

  • CT image acquisition of the myQA SRS Phantom with the I&P insert (see myQA SRS Instructions for Use for more information)
  • Import the acquired CT image into the TPS
  • In the TPS:
    • Contour the structures
    • Calculate an SRS or SBRT plan using the available structures
    • Calculate a QA Plan with the myQA SRS detector
  •  Measure the QA Plan at the LINAC with the myQA SRS detector
  • Setup the myQA SRS Phantom with the I&P insert at the LINAC to perform the alignment check

The CT scanning protocol shall be used the same as the one used for a specific treatment modality and anatomical site. The same CT slice thickness and a voxel size not exceeding 1.5 mm is recommended.

To support the myQA SRS Phantom E2E I&P insert tests, a predefined E2E general template has been created and can be found in the Protocol Templates folder in myQA Machines. This protocol structure is based on the several published sources about E2E tests in RT.

To meet the clinical needs of the user, these templates can be adapted, or the user can generate their own protocols.

E2E I&P insert internal structures; 1-5: cylinders, 6-9: spheres, 10-12: vertebrae, 13: spinal cord, 14-15: air cavities, 16: fiducials. For technical specifications, please see Chapter 5. Technical Specifications in myQA SRS Instructions for Use.

Note: The I&P insert contains non-hazardous materials for MR scanning. If an MR scan of the I&P insert                  should be acquired, the insert shall be used without myQA SRS Phantom. It is the customer’s                          responsibility to find the correct scanning protocol and sequence. For the full set of the MR Guided RT            QA tools, please use contact IBA dosimetry representative.

 

Test Setup: Create an E2E Test Protocol

The E2E protocol template contains a predefined name and description per protocol and task available. This template is defined by one task (E2E task) with a set of predefined tests with default values for references and tolerances which are related to the myQA SRS system. Please note, these values should be adapted by the user according to their clinical workflow and used protocols.

Inside this task nine tests are included which are the actual QA checks to be performed: eight of them are
numerical dosimetry tests and one is a Winston-Lutz test (see Section 8.2).

  • 01 E2E HU constancy
  • 02 E2E (Electron and / or Mass) density constancy
  • 03 E2E Contour and volume constancy
  • 04 E2E Dose and gamma constancy
  • 05 E2E Winston-Lutz
  • 06 – 09 Alignment checks (CBCT, kV and MV imaging, and optical system)

E2E general template

 

After setting up the machines and measurement devices (see Chapter 4, myQA Platform Instructions for
Use), a Protocol Template can be created:

  • In Test Setup, select Protocol Template in the Machines & Templates panel and click Edit on the ribbon.
  • Expand the E2E general template select E2E task (Constancy checks) to set the reoccurence of the task.For more information on creating Protocol Templates, see Section 2.1.2.
  • Expand the E2E task (Constancy checks) to see the available test templates. For each E2E test, update the necessary information in the Test template window. Check the Acceptance criteria: To update the acceptance criteria, select a value, click Edit, and edit the parameters in the popup dialog. Click Save to confirm the changes.
  • Click Save on the Test setup ribbon when all necessary changes have been made.
  • Create a Machine Protocol, see Section 2.1.3
  • Execute the E2E tests, see Section 2.1.4.

Information about each test can be found below.

 

IMPORTANT NOTICE: IMPORT THE AQUIRED CT INTO THE TPS BEFORE PERFORMING TESTS

Before executing any test from this template, please ensure that a CT scan of the myQA SRS Phantom with the I&P insert has been loaded into the TPS system. See Section 3.6 in myQA SRS Instructions for Use for more information.

IMPORTANT NOTICE: ANY PREDEFINED VALUES ARE ONLY EXAMPLES

The tolerances provided in the templates are examples and can be used as starting point, but the user should revise them and adapt these values to their used protocols and clinical workflow, as well as any other reference parameter such as HU, gamma acceptance criteria, etc.

 

01 E2E HU constancy (Dosimetry)

The I&P insert contains five cylinders of different materials. The materials and their HU reference values are shown under the Acceptance criteria section of the Test template window.

  • Import the acquired CT into the TPS, if not already done.
  • Check the HU values of the different cylinders in the TPS.
  • Enter the values and tolerances into the myQA test to compare the obtained HU values against the
    reference ones.
    Note: Predefined HU values are obtained with a scanning protocol 120 kV, 200 mA. The acceptance               criteria and tolerances provided for each test are starting values only. The user must revise these           values so they correspond to their used parameters and practice or modify them accordingly.

 

02 E2E Electron and Mass density constancy (Dosimetry)

The same cylinders used in test 01 can be used for this test.

Depending on the density conversion curve used in the TPS, the user can perform this test using electron density (relative to water) or mass density (g/cm3).

  • Import the acquired CT into the TPS, if not already done.
  • Apply the relative electron density or mass density conversion curve and find the corresponding values.
  • Enter the values into the myQA test to compare the obtained values against the reference ones.

Note: IBA predefined density values are obtained from manufacturer datasheets. Please revise the values               accordingly.

 

03 E2E Contour and volume constancy (Dosimetry)

The I&P insert contains various structures of different sizes and shapes, such as spheres and air-cavities, which can be contoured in the TPS.

  • Import the acquired CT into the TPS, if not already done.
  • Contour each specific structure and calculate the volume, following the commonly used approach.
  • Enter the values into the myQA test to compare the volumes [mm3] against the reference values already predefined in this test.

Note: Please modify the acceptance criteria accordingly.

 

04 E2E Dose and gamma constancy (Dosimetry)

The I&P insert contains three fiducials that can be used to define the treatment planning isocenter (0,0,0).
The positions of the fiducials coincides with printed lines on the phantom and insert:

  • Right fiducial: (60, 0, 0) mm
  • Left fiducial: (-60, 0, 0) mm
  • Bottom fiducial: (0, -70, 0) mm

These coordinates are determined using the isocenter position where the three fiducials cross.
Some examples of the plans can include following:

  1. VMAT or IMRT plan for the standard or hypofractionated irradiation of the vertebra body with cord structure as OAR.
  2. VMAT or conformal arc plan for standard or hypofractionated treatment of the spherical structures with isocenter defined at the center of the fiducials.
  3. Multiple target VMAT plan using several spherical volumes as targets.

Due to the small volume of the structures, it is recommended to use a dose calculation grid size of 2 mm or lower and perform calculations with the dose calculation algorithm, taking into account tissue heterogeneities.

Criteria for the dose coverage or maximum doses in the sample plans are left to the clinic’s discretion (as well as energies, beam setups, etc.) to reflect typical conditions in the clinical treatments.

Delivered doses in the isocenter plane can be verified using the myQA SRS detector or, if relevant, by means of the film or chamber inserts.

The user can verify point doses in the specific structure volumes as well as overall 2D dose distributions using myQA SRS detector and myQA Patients software.

  • Import the acquired CT into the TPS, if not already done.
  • Contour the specific structures in the TPS.
  • Calculate a test plan on the insert CT.
  • Calculate the QA plan on the detector scan or virtual CT images.
  • Measure the plan with the detector positioned as the insert.
  • Perform the corresponding comparison between TPS and measured dose, i.e., point doses, 2D gamma analysis.
  • Enter the values into the myQA test to compare the results against the reference ones, defined based on your local QA Patient Verification Protocol.Note: Please modify the acceptance criteria accordingly.

If more than one plan is evaluated, a copy of the test in the myQA Machines - Test setup workspace can be created and pasted into the same E2E task with a new name.

  • In the Test-setup, right-click on a Test and click Copy.
  • Right-click the current Task and click Paste.
  • A copy of the test has been created in the task.

 

05 E2E Winston Lutz (Mechanical)

See Section 8.2 for performing the Winston Lutz test.

 

06-09 E2E Alignment checks

Test options:

06 E2E Alignment check: Cone beam CT (CBCT kV/MV) - Volumetric check
07 E2E Alignment check: kV imaging (CBCT kV/MV) - Planar check
08 E2E Alignment check: MV imaging (Planar MV (EPID))
09 E2E Alignment check: Optical system (other - SGRT systems)

The I&P insert can be used for positioning checks of CBCT, kV/MV imaging, and optical system by means of shifting the phantom a desired distance from the isocenter position and comparing calculated alignment from imaging system against reference image.

The reference image is defined as the CT image acquired with the myQA SRS Phantom and the insert together and placed at isocenter (0,0,0). Fiducials can be used for alignments in the TPS system. See 04 E2E Dose and gamma constancy (Dosimetry) for fiducial coordinates.

There are four alignment check tests (06 – 09), one per imaging system: CBCT, kV imaging, MV imaging, and optical system. The alignment checks shall be performed for the imaging system(s) commonly used in the clinical routine at the site.

  • Align the system (myQA SRS Phantom and insert) to the isocenter using the corresponding markers.
  • Apply a shift by moving the couch, for instance, of 10 mm in all three directions.
  • Acquire an image with the image system commonly used in the clinical routine.
  • Import the acquired CT (reference image) or DRRs (digitally reconstructed radiography) into the imaging system software.
  • Compute the distance between both images using the imaging system software and compare against the real applied shift.
  • Enter the values into the myQA test to compare them against the reference ones, already predefined in this test, e.g., 10 mm in all three directions.
    Note: The user must revise the acceptance criteria accordingly. The example given in this test applies             a shift of 10 mm in all three directions.