display test tolerances

[elizaGSTT]

is it possible to add a line of text after each output on hazen modules to display the tolerances for each test as this has been outlined in the magnet/acr guidance?

[YassineAzma]

Provisional tolerances

TEST	Pass	Warning	Fail
Geometric Accuracy	All measured lengths within +-2mm of true values		Any lengths differ more than +- 3mm. Possibly include some form of check for distortion correction being on
Spatial Resolution	This will require input from you as there is no guidance regarding MTF from the ACR I have code for the visual test in MATLAB which I can translate into Hazen at some point if there’s interest.
Slice Thickness Accuracy	Measured slice thickness should be 5.0 +- 0.7mm		Errors greater than +- 1.0mm fail
Slice Position Accuracy	Absolute bar length difference <= 5mm	Absolute bar length difference >5mm and <7mm  Potentially flag phantom set-up, table positioning and laser calibration	Absolute bar length > 7mm
Image Intensity Uniformity	Below 3T: >= 87.5%3T: >= 82%	Below 3T: >85% and <87.5%3T: >80% and <82%	Below 3T: <85T3T: <80% Possibly warn if the user has not enabled some form of filtering (i.e. pre-scan normalization)
Percent-Signal Ghosting	PSG <= 2.5%	PSG > 2.5% and < 3%	PSG > 3%
Signal to Noise Ratio	This will require input from you as there is no guidance regarding SNR from the ACR

[tomaroberts]

@elizaGSTT – please can you put the tolerances in here for each task associated with the MagNET phantom.

[elizaGSTT]

please find attached the tolerances for the MagNET phantom.

[YassineAzma]

Hi @elizaGSTT, I'm hoping to have this done next week. How do these examples this look to you?

Would you want it to be more explicit about what the pass and fail conditions are?

[elizaGSTT]

Hello,

It looks good but just a quick clarification. When you say below 3T does that mean this was data from a 1.5T scanner? This is the only confusing bit for me.

Also with other issues that I’m having with the code do you want me to add them all as separate issues for each module or all together?

Kind regards, Elizabeth

[YassineAzma]

It means that it was acquired below 3T. This could be 1.5T, 0.55T or whatever. The uniformity test tolerances are field strength specific, differing above 3T and when below.

I want to cover my bases as I know that you have a 0.55T scanner.

If there's not an existing issue that documents the problem, please make one. I'd rather they be module specific.

[sophie22]

What is the benefit of displaying the tolerances (as requested) or even interpreting the hazen calculation results (as in Yassine's example), if this is already included in the Excel template used to create the final report?

Is it to help determine whether the acquired images are suitable for analysis in the first place or need to make new acquisition?

[elizaGSTT]

Dear Sophie,

As we explained, we usually quickly check our results when on site so displaying the tolerances would help us save time when trying to evaluate whether something is within the expected limits on the fly without having to look at the spreadsheet. If a result is off then we might need to get a new acquisition.

Regards, Elizabeth