[Intl_DxMedPhys] Out of Field Fetal Dose Calculations

[Rebecca Milman]

When I was a resident, I was told a story about Lou Wagner getting a phone
call once about a fetal dose estimate (either for fluoro or radiography).
His first (and I think only) question was whether or not the fetus was in
the imaging field of view. (I take no responsibility for the veracity of
this story...)

I may be the outlier here, but if the fetus isn't in the imaging field of
view, the dose will be lower than where there are any known effects. Fetal
dose estimate is important (saying this so people won't accuse me of hating
babies...) but whether it's 10 mGy or 0.36 mGy just doesn't matter and
won't have any effect on clinical decision-making. It is also worth
reporting any fetal dose estimate as a range since it's not known with much
accuracy.

Rebecca.

*Rebecca Milman, Ph.D.*
*University of Colorado Anschutz Medical Campus*

On Tue, Jun 3, 2025 at 12:06 PM Gary via Intl_dxmedphys_wd_osu_list <
intl_dxmedphys_wd_osu_list at lists.osu.edu> wrote:

> It is not modern, but the Felmlee CT fetal dose paper might be a start.
> It gave dose to a point near the conceptus but at n cm outside the scan
> range.  Your IR procedure would have a pretty different kV, but I would
> guess that an estimate based on CT would be an upper limit.
>
> From the paper, the dose fraction at 1 cm outside a 10 cm wide scan range
> is 0.2, while the dose fraction at the center of the same field would be
> 0.55 so that you could perhaps take the fetal dose to be 0.2 / 0.55 times
> whatever the dose is at depth in the middle of your IR field.  So if the
> dose to the tissue in field is 1 mGy, the fetal dose at 1 cm out of field
> should be pretty close to 0.36 mGy.
>
> ---
> Thanks,
> Gary Isenhower
>
>
> On Tue, 3 Jun 2025 11:43:05 -0500, Gretchen Raterman Bell via
> Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
> wrote:
>
> >Salutations!
> >
> >I am currently working on a fetal dose estimation for an IR neph tube
> >procedure where the docs did a great job of keeping the fetus out of
> >the FOV.  But when looking at a past radiograph with the tubes in
> >place (yes, this is a multi-step fetal dose calc), it appears that the
> >fetal anatomy would have to be right outside the FOV for the IR
> >procedure.  Currently, my only reference would be Wagner, Fig. A-6,
> >which caps out at 2.5 cm for the closest approach of the rad field.
> >While I do a literature search, I figured I'd ask the gurus here if
> >anyone happens to have a more modern paper for out of field fetal dose
> >calcs?  One that perhaps addresses ~ 1 cm or less outside FOV?
> >
> >Thank you, thank you, thank you, to anyone who has said  paper.
> >
> >Gretchen R. Bell, M.S., DABR
> >Diagnostic Imaging Physicist
> >Ochsner Medical Center
> >(504)842-8506
>
>
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