[Intl_DxMedPhys] Out of Field Fetal Dose Calculations

[Gretchen Raterman Bell]

Dr. Milman, I do agree with you, also as a non baby hater.  However, this
brings me to another point of discussion, which is everyone's favorite!  At
what time intervals do we sum doses, if at all?  The patient in question
had several x-ray exposures over the past week that could *possibly* sum to
close to 100 mGy.  Should it be exposures within a couple hours?  Couple
days?  Not at all?

Gretchen R. Bell, M.S., DABR
Diagnostic Imaging Physicist
Ochsner Medical Center
(504)842-8506



On Tue, Jun 3, 2025 at 2:00 PM Rebecca Milman via
Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu> wrote:

> 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
> 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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