[Intl_DxMedPhys] MUGA EF discrepancies?

[Bill Erwin]

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!z7B0__j4vmca44U8dF0rcwK9hblLR_CSqNL02i0tET1xHUYXS6FKwoNwzN7qFriuU6MT2MYulbWD-PILOjRuS3HWXH-sScYp_w03hgD2$ 
> <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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