[Intl_DxMedPhys] MUGA EF discrepancies?

Tue May 20 16:35:00 EDT 2025

Nima,

The EDbkgdC and ESbkgdC values cancel out only if the ED and ES ROI areas
are identical, which should not happen.

If you move the bkgd ROI around, it would not surprise me that the EF is
affected due to a change in the average bkgd count value (bkgd ROI total
counts / bkgd ROI area).

If you calculate both EDbkgdC and ESbkgdC (using Siemens displayed values
for average background count and ED and ES ROI areas), and then use them in
the formula as I have stated above, what do you obtain?

On Tue, May 20, 2025 at 2:04 PM Nima Kasraie <
Nima.Kasraie at utsouthwestern.edu> wrote:

> Thanks Bill.
>
>
>
> Assuming the same bkg (as you say) simplifies the formula to the green
> formula I put up earlier. (the bkg values in the numerator cancel out. No?)
>
>
>
> One thing is for sure: When I moved the BKG ROI inside the Siemens scanner
> workflow, the EF changed considerably. (I brought it down to 75%).
>
>
>
> I’ve ruled out other possible suspects:
>
>    - Temporal smoothing or interpolation. The TAC looks nice and curved,
>    not flat. And no noise.
>    - No gating issues
>    - No Arrhythmia.
>    - Patient had a strong squeeze
>
>
>
> That leaves count distortions due to detector saturation or patient size
> (attenuation effects), and poor ROI definitions as suspect.
>
>
>
> But I’m still not convinced. A 15% discrepancy is kinda high. (or is it?)
>
>
>
>
>
> *Nima Kasraie, PhD, MSc, DABR, DABSNM*
>
> Lead Physicist, Children’s Medical Center Dallas
> <https://urldefense.com/v3/__https://www.childrens.com/__;!!KGKeukY!1qdlEytVkuG1dFzpZhdnV_WDefNz0xR-ZpxclEzd3yZ62-efKTA19xJUon5iJas6KLwoaWd_NB7ziiH1JGVPDfuOZ6iGoXmkGVU1FUgk$ >
>
> Associate Professor, Department of Radiology, UT Southwestern
> <https://urldefense.com/v3/__https://profiles.utsouthwestern.edu/profile/187443/nima-kasraie.html__;!!KGKeukY!1qdlEytVkuG1dFzpZhdnV_WDefNz0xR-ZpxclEzd3yZ62-efKTA19xJUon5iJas6KLwoaWd_NB7ziiH1JGVPDfuOZ6iGoXmkGfSxipvY$ >
>
> Phone: 214-648-7978
>
>
>
> *From:* Bill Erwin <ervster57 at gmail.com>
> *Sent:* Tuesday, May 20, 2025 1:25 PM
> *To:* Nima Kasraie <Nima.Kasraie at UTSouthwestern.edu>
> *Cc:* intl_dxmedphys_wd_osu_list at lists.osu.edu
> *Subject:* Re: [Intl_DxMedPhys] MUGA EF discrepancies?
>
>
>
> Nima, The correct formula for planar NM MUGA EF is supposed to be: EF(%) =
> 100 x (EDC-EDbkgdC - ESC-ESbkdgC) / (EDC-EDbkgdC) EDbkgdC = bkgd ROI total
> count x ED ROI area / bkgd ROI area ESbkgdC = bkgd ROI total count x ES ROI
> area / bkgd ROI
>
> Nima,
>
>
>
> The correct formula for planar NM MUGA EF is supposed to be:
>
>
>
> EF(%) = 100 x (EDC-EDbkgdC - ESC-ESbkdgC) / (EDC-EDbkgdC)
>
>
>
> EDbkgdC = bkgd ROI total count x ED ROI area / bkgd ROI area
>
> ESbkgdC = bkgd ROI total count x ES ROI area / bkgd ROI area
>
>
>
> Where the background ROI is typically drawn near the LV in the end systole
> image (assuming that area represents the projection of extra-LV tissue
> "background" activity), and the same bkgd total counts from that ROI at ES
> used for both ED and ES bkgd correction.  That is how it is supposed to be
> drawn on Siemens (either automatically or manually).  Automated method
> results are illustrated in Fig. 18-23 in Bushberg 4th Ed and Fig. 18-12 in
> the study guide (for those who have either one of those).  The quantitative
> data needed for the calculation are in the figure (for anyone wanting to
> verify the calculation).
>
>
>
> I recommend comparing all the ROIs defined by the automated software with
> those defined manually.  Any substantial differences would certainly result
> in such a discrepancy.  (It would be a NM physician's call as to which ROIs
> are correct.)
>
>
>
> Regards,
>
> Bill
>
>
>
>
>
>
>
> On Tue, May 20, 2025 at 12:26 PM Nima Kasraie via
> Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
> wrote:
>
> Hello group, Need some collective wisdom from the hive: What are possible
> causes of the automated software overestimating EF, compared to manual EF
> calculation in MUGA studies? Does anyone have any experience with this? I
> have a case of discrepancy
>
> Hello group,
>
>
>
> Need some collective wisdom from the hive:
>
>
>
> What are possible causes of the automated software overestimating EF,
> compared to manual EF calculation in MUGA studies? Does anyone have any
> experience with this?
>
>
>
> I have a case of discrepancy between the automated EF value generated by
> the Siemens analysis software and a manual calculation of the EF, where the
> auto-generated EF value seems to be much higher than the manually
> calculated EF obtained using:
>
>
>
> Manual EF calculation formula used: EF = (EDC-ESC)/(EDC-bkg)
>
>
>
> Using this formula, EF is ~ 67.8%, which falls within normal range and
> correlates well with the patient's prior echocardiogram showing an LVEF of
> 67%. However, the software is giving an EF value of 82.7%, which seems high.
>
>
>
> Perhaps a software correction I’m not aware of?
>
>
>
>
>
> Nima
>
>
>
>
>
>
>
> P.S. : Interesting side note:
>
>
>
> ChatGPT responded saying a low background count can give elevated EF
> values:
>
>
>
> which is actually false: EF goes down with decreased bkg counts (as one
> can see from the green formula above). And he’s using the same formula.
>
>
>
> So there’s that. Ha!😊
>
>
>
> And btw, Perplexity said the exact opposite:
>
>
>
>
>
> Moral of the story: your model is only as good as the sources you train it
> with!
>
>
>
> *Nima Kasraie, PhD, MSc, DABR (D), DABSNM (I)*
>
> Associate Professor of Radiology
>
> Medical Physics Division
>
>
>
> Department of Radiology
>
> 5323 Harry Hines Blvd., Dallas, Texas 75390-9071
>
> Phone: 214-648-7978
>
> https://urldefense.com/v3/__http://www.utsouthwestern.edu/radiology__;!!KGKeukY!1qdlEytVkuG1dFzpZhdnV_WDefNz0xR-ZpxclEzd3yZ62-efKTA19xJUon5iJas6KLwoaWd_NB7ziiH1JGVPDfuOZ6iGoXmkGYoBNRja$ 
> <https://urldefense.com/v3/__http:/www.utsouthwestern.edu/radiology__;!!KGKeukY!25bfLAaxVTa-WLkAxQ_8HWNJaRXNj_RcF1yRTDrA0LM3YghSmtAuFFrteQA4M455_O0kbbCf9mCtlRJldwcg_FbJy8-vxMPGswuOyOiVdKzKtGzD2NBPJw$>
>
>
>
>
>
>
> ------------------------------
>
> *UT** Southwestern*
>
> Medical Center
>
> The future of medicine, today.
>
>
>
>
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