[Intl_DxMedPhys] Older Siemens EI question

[Douglas Pfeiffer]

Dear all,

I recently tested a 2009 Siemens Axiom Luminos TF and found that the reported EI (or EXI in Siemens parlance) was about 50% of from what it should be. The service engineer replied thusly:
In Siemens we calculate the EXI as the arithmetic mean of gray value of a central area (refer to the example picture below) under consideration of the actual collimation.
EXI value is not calculated for dull detector image.
 
For the Cannon detector in Luminos TF system, there is no adjustment for the EXI value. The maximum we can do is to calibrate the detector.

The IEC standard [62494-1 (2008)] is very specifically calibrated at RQA5 in a uniform field. Has anyone else been told anything like what this person is saying?

Best regards,
Doug



Douglas Pfeiffer, MS, DABR FACR, FAAPM (he/him)
Medical Physicist, Radiation Safety Officer
Boulder Community Health
xraydoug at me.com
303.415.7515

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The opinions expressed in this message are the product of the gray and white matter loitering in my cranium. I speak for myself and no one else, unless I say otherwise.

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