7T PIQT

Instructions on how to run a PIQT (Periodic Image Quality Test) on the 7T.

Setup

Switch the scanner to Classic. Remove the 32-channel receive coil insert. From the gray cupboard in the back of the scanner room (right-hand side of the magnet, in the corner near the technical room) grab the PIQT phantom holder (a) and the PIQT phantom itself (b). There is a similar-yet-not-identical pair of PIQT and holder at the 3T, so make sure to check that the labels on the phantom are as shown below, as otherwise the test results will seem to indicate that the geometry correction fails.

Put the phantom in its holder as shown in Figure c. Make sure that the marker ‘T’ is at the top of the phantom, and faces the foot-end of the scanner.

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Position the phantom in the coil and move to isocentre.

Run the PIQT

Start the application software (without patch). Without registering a patient, go to System -> ‘SPT…’ to open the System Performance Tool.

In the bottom half of the window (in the BatchView tab), select: Batch Files -> TEST-IQT -> vtrmtxpiqt_qa1_qa2_qa3 Right-click it and select ‘Run Batch’. (NOTE: although it sounds intuitive, do not use PIQT -> piqt!)

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While the batch file runs, you will have to press OK or Continue a few times, but this should all be straight-forward. The script may tell you that the phantom is not correctly placed inside the bore, and to move the table a few cm’s into/out of the bore. If this is the case, adjust the table accordingly and try again.

Process the results

After the batch file completes successfully, go to the ‘ImageView’ tab (at the bottom of the System Performance Tool). Find the patient ‘PIQT’. If you sort by Exam Start Date, it should be in the first row. Right click it, and click ‘Analyze’:

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This should only take a few seconds to complete (although if previous PIQT data are still in the database, it will analyse those as well and it may take a little bit longer). When it’s done, right-click again but now select ‘Generate Reports’.

In the window that opens, choose the settings as below and click ‘Ok’. (NOTE: WithSpec is currently not available on the 7T, but might be added later).

This should generate the desired report, which looks as follows:

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You can save this report through ‘Page’ -> ‘Save As…’, or using any other method you like.

Done!

Depending on what you’re looking for, you can find a whole set of different measurements in this document. In terms of spatial linearity, two important values would be ‘size_hor’ and ‘size_ver’, which should be close to 150 mm and not deviate by more than 1 mm.

For comparison, representative PIQT reports from september 2024 can be downloaded: File:SPT report 240905.pdf and File:SPT report 240930.pdf. A geometric reference ADNI phantom (from VUmc) was scanned using the same (7T Classic) setup between the acquisition of PIQT data for those two reports, confirming good geometrical accuracy (all tests passed) at that timepoint - indicating that the september 2024 PIQT reports can serve as additional reference for future PIQT comparisons.