[Intl_DxMedPhys] Out of Field Fetal Dose Calculations

[Gary]

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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.  

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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