Falcon3 counting mode

Submitted by s.wu on Tue, 2017-06-20 19:21

Forums

FindDQE

I ran FindDQE on a beamstop image taken by Falcon3 counting mode (dose rate = 0.92e/p/s, total dose = 55e). The DQE goes above 1. The output is attached. Is there anything abnormal?

niko Tue, 2017-06-20 21:25

A DQE above 1 suggests that the total exposure was higher than what you entered. Please make sure you have the total exposure correct. Some software may alter the counts by some factor and this can then lead to incorrect assumed exposure values.

Crick_user Mon, 2017-10-02 10:13

Hey s.wu,

I am wondering whether you found a way out. We are experiencing the same issue right now. We triple checked the dose right before acquisition. Images were acquired in electron counting mode at dose rate of 0.6 e/px/s (total dose per pixel 40), as measured with EPU (1.9.1) and the Falcon Reference Image Manager. We still get a DQE well above 1.0.

Have you sorted it out?

NeCEN Wed, 2017-11-22 03:38

Dear all,

we are encountering the same issue: DQE of 1.5 for Falcon3 (counting, dose rate = 0.6e/p/s, total dose = 50e, Krios, 300kV).

Best,
Chris

niko Wed, 2017-11-22 11:47

Could you please provide the value for "Gain conversion factor (counts/e)" that is calculated by FindDQE? It should be close to 1 for a counting detector.

tarek Tue, 2020-05-05 02:35

I recently made a series of DQE measurements at varying electron flux (0.5-0.8 e/px*s).
The FindDQE results are puzzling me since they are completely contratry to my expectations. The higher the dose rate the "better" DQE is suggested?
However, the Gain conversion factor is consistently ~ 80.

I am happy to share the results if niko wants to have a look what is going on.

niko Tue, 2020-05-05 10:26

We have looked a little more into DQE measurements of counting detectors, and it turns to be more complicated than traditionally described in publications. Especially the measurement of the MTF is not straight forward because it seems to depend on the exposure rate. Traditionally, the MTF is assumed to be independent of the exposure rate. It is not clear at the moment how to include a variable MTF in DQE measurements, and therefore the FindDQE results obtained with the current version of the software are not reliable.