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myQA SRS - Setting up the myQA SRS Phantom

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CAUTION: USE A TROLLEY OR TWO PERSONS FOR CARRYING 
Due to its weight, it is recommended to use either a trolley or two persons to carry the myQA SRS Phantom. Furthermore, there is a possibility of overbalance when lifting or carrying the phantom. Do not use the device anymore if mechanical components are broken.

 

CAUTION: TRANSPORT BOX IS MR UNSAFE. 
The transport box of the myQA SRS Phantom2 is MR unsafe.
Do not bring the transport box in an MR treatment room.

 

IMPORTANT NOTICE: PHANTOM VARIATIONS 
There are some variations when setting up the different phantoms. Any differences in the setup of the phantoms will be explained below.

  • Open the myQA SRS Phantom transport case. Remove the foam pieces covering the phantom. 
    These foam pieces are essential for safe transport of the device. It is recommended to keep them in the transport case when the phantom is in use.
  • Depending on the phantom variety, the packing may vary. For example, the myQA SRS Phantom2 cylinder cap is permanently affixed to the main body of the phantom. When repacking phantoms, please repack the device in the same order it came packed.

    Packing for the myQA SRS Phantom Cyberknife in its transport case. 1: phantom (1a: main body; 1b: round cap); 2: base; 3: chamber and film inserts

      For the myQA SRS Phantom and Cyberknife Phantom only:

  • Fix the cap (1b) to the main (cylindrical) body of the phantom (1a). Rotate the cap until the screw holes for the cap and the cylinder are aligned, ensuring that there are no air-gaps between the two parts.
  • Secure the pieces with the three screws (1c).

      For all myQA SRS Phantom variants:

  • Before inserting the myQA SRS or any inserts, please ensure the phantom is in the upright (zero degree orientation). To aid in the orientation of the phantom body we have provided a “THIS SIDE UP” sticker (2) at the top of the phantom body.

  • Note: If the "THIS SIDE UP" sticker is missing, please contact IBA Dosimetry                    (Chapter 10).


    To ensure proper alignment of the SRS sensor with external marks for laser alignment, the insert slot is slightly asymmetric with respect to the x-axis of the main phantom body. It is important that the zero orientation is respected for QA measurement tasks, calibration procedure, and proper handling of the inserts. If the phantom is used in the wrong orientation, a slight deviation between laser marks and SRS sensor may occur, resulting in inaccurate measurements.

    CAUTION: ENSURE PROPER AND SAFE POSITIONING 
    Always ensure proper and safe positioning of the phantom (any variety) on the patient table, to prevent it from falling down. Be aware of the possibility of overbalance. Do not use the device anymore if mechanical components are broken.


Insert the detector (or insert) into the phantom

myQA SRS for Cyberknife The following instructions are only for the myQA SRS Cyberknife variant. If the normal myQA SRS system is being used, proceed to the next section. 

  • Before inserting the detector, the fiducial plate / filler plate must be attached to the detector. 
  • Using the alignment pins, affix the plate to the detector.
  • Ensure that there are no air gaps between the plate and detector.

Insert the Detector 

  • Insert the detector into the phantom until the sensor area is completely inside the phantom.
  • Rotate the phantom to the desired angle if needed.

CAUTION: DO NOT LIFT THE ASSEMBLY AT THE DETECTOR 
When the detector is inside the phantom, do not lift the assembly at the detector. Always use the handles for positioning and aligning.

CAUTION: ENSURE PROPER POSITIONING OF THE MYQA SRS DETECTOR OR INSERTS IN THE MYQA SRS PHANTOM 
Always ensure proper positioning of the myQA SRS detector or any other insets in the phantom being used (i.e., myQA SRS Phantom, myQA SRS Phantom2 , myQA SRS Cyberknife Phantom). Additional air gaps, off axis or off-center placement can lead to wrong measurements.

Phantom Inserts 

If using the myQA SRS Cyberknife variant, please ensure that the dummy plate has been correctly placed on top of the insert being used (see Section 3.2.2.2).

 

Chamber inserts

  • Gently slide the insert into the phantom until it is fully inserted.
  • Ensure the correct chamber adapter is in the insert.
  • Insert the corresponding chamber into the hole of the insert.

Film inserts 

  • Install the film in the insert. Ensure the film is correctly positioned in the insert.
  • With the insert in the upright position, gently slide the insert into the phantom until it is fully inserted.

Winston-Lutz insert 

An alignment marker (1) to shows when the insert is correctly oriented and fully inserted into the phantom: 

  • Ensure that the insert and the phantom body are oriented in the upright position.
  • Slide the insert into the phantom until it is fully inserted. 
  • If the insert is not placed properly, the alignment marker will stick out from the phantom.
     
    Alignment marker for the Winston Lutz Insert
The insert has been inserted correctly

 

 

 

 

The insert has not been inserted correctly


 

 

 

 

E2E I&P insert 

  • Ensure that the insert and the phantom body are oriented in the upright position.
  • Slide the insert into the phantom until it is fully inserted.

 

Alignment under a LINAC

  • Align the effective point of measurement as indicated by the markings on the sides of the device to the isocenter. Use the room-lasers, if available. 
  • Position the device in the center of the beam (1). Then align the effective point of measurement (2) as indicated by the markings on the sides of the device to the isocenter. Use the room-lasers, if available.

    A: Alignment to the isocenter; B: Offset alignment
  • Use the adjustment functions of the treatment or lifting table to position the detector assembly, aligning the sensor's crosshairs with the light field's crosshairs at the beam center.
  • Then, adjust so that the side cross markers on the detector assembly and the side-cross of room lasers are superimposed in the center of the beam.

If the myQA SRS detector is used alone, use side-alignment markers of the device (see Detector Sensors)

IMPORTANT NOTICE: USE THE SIDE MARKERS FOR POSITIONING 
Due to the higher uncertainty when positioning the device in the light field (diffuse penumbras and crosshair width), it is advisable to refer to the side markers that are engraved in the housing.

 

Device Warm-up and Pre-Irradiation

Warm-up: For reliable results, the device should be running for at least 30 minutes prior to the first measurements. 

Pre-irradiation: 121 mm × 141 mm; a small pre-irradiation dose equivalent to 1 Gy is recommended, which also allows a general check of functionality.

CAUTION: PRE-IRRADIATION FOR CYBERKNIFE VARIANT NOT MANDATORY 
Pre-irradiation is not mandatory for the myQA SRS Cyberknife variant, but can be performed as a quick functionality test. 
Please note, the normal 12 cm × 14 cm field size is not possible, instead it is advised to use the maximum field size if performing a pre-irradiation.