[Intl_DxMedPhys] [External] Re: MUGA EF discrepancies?

Tue May 20 17:04:27 EDT 2025

I agree with Bill's explanations. The background activity subtracted from an ROI is the average background count times the area of that ROI. The example I use when teaching our residents uses a background ROI over the spleen to illustrate over subtraction of background counts, artifactually raising the EF.

[cid:9583f866-7bf9-4de8-9229-1f5f0e1eb2e4]

James R. Galt, Ph.D.
Director of Nuclear Medicine Physics
Professor, Department of Radiology and Imaging Sciences
Emory University School of Medicine
1364 Clifton Road
Atlanta, Georgia 30322
Phone: 404.712.7896
Fax: 404.712.7435
email: James.Galt at emory.edu<https://urldefense.com/v3/__https://ehcowa.emory.edu/owa/redir.aspx?C=2f26e93561f14cc098e285704b863f52&URL=mailto*3aJames_Galt*40emoryhealthcare.org__;JSU!!KGKeukY!3iiy9_CLNCr0sRrlRaWjB_cDzDf36M8DOIjgSh9snNud_yLirjV38Oy5StiC0L5i6rs8pSnn9Szc6nd7NMx6Tv8DCM5R1W8r6w64qA$ >
________________________________
From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+jgalt=emory.edu at lists.osu.edu> on behalf of Nima Kasraie via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Sent: Tuesday, May 20, 2025 3:04 PM
To: Bill Erwin <ervster57 at gmail.com>
Cc: intl_dxmedphys_wd_osu_list at lists.osu.edu <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [External] Re: [Intl_DxMedPhys] MUGA EF discrepancies?

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?)

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Nima Kasraie, PhD, MSc, DABR, DABSNM

Lead Physicist, Children’s Medical Center Dallas<https://urldefense.com/v3/__https://www.childrens.com/__;!!KGKeukY!3pCvelw6tZtcyeLAG6hgRJNhD2JASp4fOZ2x6gaz4a6WNLgJZuq92mu5TvK193Ge-uw2122pnWEmLD4R8zXTXqg6b92iO0qsWbkWTBxlHB5M48IkkJbJjw$>

Associate Professor, Department of Radiology, UT Southwestern<https://urldefense.com/v3/__https://profiles.utsouthwestern.edu/profile/187443/nima-kasraie.html__;!!KGKeukY!3pCvelw6tZtcyeLAG6hgRJNhD2JASp4fOZ2x6gaz4a6WNLgJZuq92mu5TvK193Ge-uw2122pnWEmLD4R8zXTXqg6b92iO0qsWbkWTBxlHB5M48LNPBEO6w$>

Phone: 214-648-7978

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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<mailto: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:

[cid:image003.png at 01DBC98F.3CA0A970]

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:

[cid:image004.png at 01DBC98F.3CA0A970]

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!3iiy9_CLNCr0sRrlRaWjB_cDzDf36M8DOIjgSh9snNud_yLirjV38Oy5StiC0L5i6rs8pSnn9Szc6nd7NMx6Tv8DCM5R1W8jfPaxpw$ <https://urldefense.com/v3/__http:/www.utsouthwestern.edu/radiology__;!!KGKeukY!25bfLAaxVTa-WLkAxQ_8HWNJaRXNj_RcF1yRTDrA0LM3YghSmtAuFFrteQA4M455_O0kbbCf9mCtlRJldwcg_FbJy8-vxMPGswuOyOiVdKzKtGzD2NBPJw$>

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________________________________

UT Southwestern

Medical Center

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