Hi,

thanks for sharing great information on this forum! Every time I find my way here, I learn something new.
Today, I would like to try doing that via a question to the users:

ASTM 2597-22 defines a measurement procedure for CSa and ISO-MTL. Given that the typically reported value is at 4s total integration time, these values are highly dependent on selected framerate, gain and also doserate. To display detector capability, surely a high framerate, low gain and highest possible dose is favorable to characterize a detector.

Is there a correction or calculation that can be done for a too weak source? A 200 W tube vs 2000 W tube would obviously result in different detector characterization, which is surely not the intent of the standard. One could argue to buy a more powerful tube, but what if I have a detector that needs a hypothetical 50kW tube to fully make use of the statement "such the detector is not saturated under the thinnest step" - is there a way to go about that?

Also, an interested party came up with the question if the standard sets a restriction to use the same focal spot for iSRb and CSa/ISO-MTL, if multiple are available? E.g. is it required to use a small spot for CSa/ISO-MTL if it was used for iSRb (to reach geometric mag requirement), or can the larger spot with more dose (or even a different tube) be used? To me the tube should not limit the detector characterization.

thank you,
Marcus

Hi Marcus,

you bring up an important topic. And you are right, the dose rate of the tube is also relevant when the time is limited. The best results will bring a detector with a high frame rate and/or a high capacity to capture as much dose as possible. In practical applications this is similar and you should look for the tube AND the DDA which fit best to your application. The spatial resolution is another parameter in the spidernet diagram and often high values here have to be paid with lower values in CSa and SMTR.

In E2597 the spatial resolution of the detector is nearly independent of the focal spot size of the tube as the duplex wire is in contact with the active surface of the detector.
Therefore you will get the best overall results when you use a powerful tube.

The idea of the correction for a lower dose is a good idea - a factor of ten less dose would decrease the values where noise is measured by a factor of square root of ten.