[Intl_DxMedPhys] Recent Tx Gain Variation on Siemens Sola 1.5T MRI

[Bob Kobistek]

Hi Steve:

I would contact Siemens and have the engineer run his tests. Don’t assume that he’ll run his test and say everything is fine. Let him run the tests.


Robert J. Kobistek, MS, FACR, DABR, MRSE(MRSC™)
Medical Physicist
RJK Medical Physics, Inc.
440-463-7879

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+bob=rjkmedphys.com at lists.osu.edu> On Behalf Of Steven Shea via Intl_dxmedphys_wd_osu_list
Sent: Friday, October 24, 2025 6:13 PM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: [Intl_DxMedPhys] Recent Tx Gain Variation on Siemens Sola 1.5T MRI

Hi list friends, I am reaching out regarding recent findings in the ACR Weekly QA on a Siemens Magnetom Sola 1. 5T MRI system at our institution. The recorded Tx Gain (found as reference amplitude on the Siemens system) started varying by +/-
Hi list friends,

I am reaching out regarding recent findings in the ACR Weekly QA on a Siemens Magnetom Sola 1.5T MRI system at our institution. The recorded Tx Gain (found as reference amplitude on the Siemens system) started varying by +/- 30 V since ~July. Previously, it had been rather stable within a ~+/- 5 range (may be a little higher). The graph below demonstrates:
[cid:image001.png at 01DC4723.168C4070]
I did annual testing in late August and did not identify any other issues with standard ACR phantom tests, homogeneity tests, or the head coil tests. I look for any service events that would explain this but could not find any. I decided not to flag it in my report and I waited a month or more to see if the variation would continue, which it has. I then went through the DICOM headers to see if any protocol parameters were changing. They were not; coil elements selected were also quite consistent (a potential issue on Siemens systems). I even managed to fish out the Reference Amplitude values from the Private Tag [0021, 1019]. They confirmed the same measurements that the technologist had been recording. I could even see that the reported Reference Amplitude was quite consistent between different sequences, which means that even if the tech recorded from different series, it would not have caused above:
[cid:image002.png at 01DC4723.168C4070]

I should also state that the phantom setup procedure is quite repeatable due to the Siemens provided holder and one technologist is running the 90% of the QA. This is a long way of saying I have come to the conclusion that this is real. (And, yes, I likely over-analyzed the issue.)

My main issue is concern on how I deal with Siemens service on this. If I send them above, I expect they will come out and run standard tests and tell me the system is fine. Have any of you ever run into this and know of causes? Or specific things to test/target? Anything else I or the tech could do? I would appreciate any insights.

Thanks, Steve

Steven Shea, PhD
Associate Professor, MR Scientist
Department of Radiology & Medical Imaging. Loyola Medicine

PS: I should mention that the system has a known, slow helium leak which is captured on the center frequency measurements. However, that predates this issue and has been present for more than +1 year. (It is scheduled to finally be addressed in the next month -- needless to say that has me at odds with local service.) I do not feel as though this is the source.

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