[Intl_DxMedPhys] EXT MSG Re: Siemens CT IQ level

Fri Jan 9 11:22:58 EST 2026

Thank you everyone for these responses!! Super helpful.
I am hearing pretty universally about how IQ level is supposed to work, but no one seems to know how image quality is measured or how well it actually works. Sounds like a super useful research paper, but would require access to a decent number of scanners. Reach out if you have a Somaris 10 scanner (PCCT or EID) and would be interested in working on this!

Stephanie

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu> On Behalf Of Allan Thomas via Intl_dxmedphys_wd_osu_list
Sent: Friday, January 9, 2026 10:47 AM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: Re: [Intl_DxMedPhys] EXT MSG Re: Siemens CT IQ level **EXTERNAL**

I think the responses so far have provided most of the basic information about IQ level. It is meant to be a more nuanced value that goes beyond a quality reference mAs. Because different Siemens scanners have different bore sizes, filtration,

I think the responses so far have provided most of the basic information about IQ level. It is meant to be a more nuanced value that goes beyond a quality reference mAs. Because different Siemens scanners have different bore sizes, filtration,
I think the responses so far have provided most of the basic information about IQ level. It is meant to be a more nuanced value that goes beyond a quality reference mAs. Because different Siemens scanners have different bore sizes, filtration, and dose vs image quality, IQ level is meant to make it easier to transition protocols across multiple scanner platforms. In principle, an IQ level of "X" for a given protocol on Scanner A (e.g. an Alpha Peak) will produce similar image quality on Scanner B (e.g. an X.Cite) using that same protocol. Historically, in order to achieve comparable image quality across two such scanners, a lot of effort would be required on the part of the medical physicist to understand differences in CTDIvol vs mAs, dose vs image quality, impact of bow tie filters, impact of CARE kV, etc.

IQ level is linear with CTDIvol just like mAs is. And each individual protocol, scanner, etc. will have its own relationships for mAs/IQ level. Steve Bache provided some of those specifics to this list for the Alpha Peak some time ago. I provide them again below and have added some data for adult head protocols as well. The data I provide below is for an Alpha Peak scanner on VB10 software. I don't believe CARE Dose4D settings will impact the data I include below because it all reflects information for the "reference size patient." But I can't ensure this is true.

Note that specifically for the Alpha, CARE keV also impacts the mAs/IQ level and eventual target CTDIvol in a given protocol. This is much like CARE kV on EID-CT scanners but also different in that it is tied globally to the protocol for all patients, not a given patient based on their size. If the protocol is set up for "soft tissue with contrast" for CARE keV, all patients will be scanned using the target dose and dose modulation associated with the 60 keV setting. This will not change based on patient size like CARE kV does.

I have not personally done any testing or experiments to see if the concept of IQ level actually achieves its goal: comparable image quality across scanner platforms when the same IQ level is set for a given protocol. But if you desire to know how IQ level relates to quality reference mAs and CTDIvol for any protocol on a Somaris 10 scanner, you can find that information by digging into the dose settings. The actual effective mAs tied to the IQ level that is set and the CTDIvol that is produced for the reference size patient can still be found.

I don't have much experience with Somaris 10 scanners that are EID, but I think the basic principles still apply. The IQ level will dictate a certain quality reference mAs and CTDIvol for the reference size patient, but this will likely change for body vs head, adult vs peds, and with variation in kV (CARE kV settings).

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----------------------------
Allan Thomas, PhD, DABR
Assistant Professor of Radiology
Mallinckrodt Institute of Radiology   |   Washington University School of Medicine
510 S. Kingshighway  |  St. Louis, MO  63110
•:501.529.8496  |  •: allant at wustl.edu<mailto:allant at wustl.edu>
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On Fri, Jan 9, 2026 at 8:39 AM Gauntt, David via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>> wrote:
Stephanie, We have a photon counting Siemens scanner, but if you learn anything about the IQ and dose let me (and the rest of the mailing list) know. I have yet to find anyone at Siemens who knows what affects dose (including the IQ setting). 
Stephanie,

We have a photon counting Siemens scanner, but if you learn anything about the IQ and dose let me (and the rest of the mailing list) know.  I have yet to find anyone at Siemens who knows what affects dose (including the IQ setting).

--
David M. Gauntt, Ph.D.
Associate Professor, Department of Radiology
University of Alabama at Birmingham Medical Center
davidgauntt at uabmc.edu<mailto:davidgauntt at uabmc.edu>

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From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+davidgauntt=uabmc.edu at lists.osu.edu<mailto:uabmc.edu at lists.osu.edu>> on behalf of DxMedPhys List <intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>>
Reply-To: "Stephanie M. Leon" <Stephanie.M.Leon at hitchcock.org<mailto:Stephanie.M.Leon at hitchcock.org>>
Date: Thursday, January 8, 2026 at 1:21 PM
To: "Stephanie M. Leon" <Stephanie.M.Leon at hitchcock.org<mailto:Stephanie.M.Leon at hitchcock.org>>, DxMedPhys List <intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>>
Subject: EXT MSG Re: [Intl_DxMedPhys] Siemens CT IQ level

Just to clarify, if it makes a difference, this is not a PCCT scanner. It’s a Pro. Pulse and I’m wondering about a traditional single-energy scan. From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces@ lists. osu. edu> On Behalf
Just to clarify, if it makes a difference, this is not a PCCT scanner. It’s a Pro.Pulse and I’m wondering about a traditional single-energy scan.

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu>> On Behalf Of Stephanie M. Leon via Intl_dxmedphys_wd_osu_list
Sent: Thursday, January 8, 2026 2:04 PM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [Intl_DxMedPhys] Siemens CT IQ level **EXTERNAL**

Hi all, Apparently the newer Siemens CT scanners have dispensed with reference mAs and now use IQ (image quality) Level. I’m having trouble finding any detail about IQ Level. Is there a way to directly relate it to the old reference mAs,
Hi all, Apparently the newer Siemens CT scanners have dispensed with reference mAs and now use IQ (image quality) Level. I’m having trouble finding any detail about IQ Level. Is there a way to directly relate it to the old reference mAs,
Hi all,

Apparently the newer Siemens CT scanners have dispensed with reference mAs and now use IQ (image quality) Level. I’m having trouble finding any detail about IQ Level. Is there a way to directly relate it to the old reference mAs, assuming a single-energy scan at the same kVp?

Thanks!

Stephanie Leon

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