[Intl_DxMedPhys] Sanity Check Needed for Pb-212 HVL

[Gretchen Raterman Bell]

UPDATE:  I made a rookie error.  Dr. Reagan Dugan pointed out that the
Smith/Stabin table only provides HVL data for that isotope and not the
daughter products.

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



On Thu, Apr 16, 2026 at 2:59 PM Gretchen Raterman Bell <
gretchen.raterman at gmail.com> wrote:

> Thank you for pointing that out!  I'll update the group.  Someone else
> sent me a Canadian paper that states 11.2 for 1st HVL and 15.2 for 2nd.  So
> all this makes more sense!!
>
> Gretchen R. Bell, M.S., DABR
> Diagnostic Imaging Physicist
> Ochsner Medical Center
> (504)842-8506
>
>
>
> On Thu, Apr 16, 2026 at 2:55 PM Reagan Dugan <rdugan1102 at gmail.com> wrote:
>
>> Hi Gretchen,
>>
>> If I'm reading the Stabin paper correctly, they didn't combine emissions
>> from parent/daughter, so that HVL for Pb-212 would only be accounting for
>> the Pb-212 gamma emissions (238  keV mostly). If you scroll down the list a
>> bit to Tl-208, the HVL is 15.5 mm, which makes more sense to me given the
>> number of emissions and energies.
>>
>> I haven't had to do shielding designs for alpha emitters yet, but I'd
>> probably base the design off the Tl-208 data since those are the primary
>> gammas used for imaging. Trying to account for the entire decay chain will
>> probably require monte carlo simulations and another task group. I'd also
>> double check to make sure you use the correct half life for Tl-208 since
>> there's equilibrium issues at play.
>>
>> For our clinical trials here we've just been using one of our pluvicto
>> rooms in PET which were shielded for F18 before any of the theranostics
>> stuff took off. We haven't gone through the math yet, but I think we're
>> operating under the assumption that the workload for the trials is so low
>> that the existing shielding is fine. For newer rooms we've just been
>> assuming a full workload of Lu-177 therapies using the TG-313 archer
>> coefficients.
>>
>> If you end up working through the math for the alpha emitters, I'd love
>> to see what you come up with if you're willing to share.
>>
>> Good luck!
>>
>> *Reagan Dugan, PhD*
>>
>> Imaging Physics Resident
>>
>> Department of Radiology
>>
>> The University of Chicago Medicine
>>
>> 5841 S. Maryland Ave. | MC 2026 | Room M-529
>>
>> Chicago, Il 60637
>>
>> Office: 773-702-1220
>>
>>
>> On Thu, Apr 16, 2026 at 2:14 PM Gretchen Raterman Bell via
>> Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
>> wrote:
>>
>>> Greetings! I am dipping my toe into shielding requirements for
>>> theranostics.   One of the hot new isotopes of course is Pb-212.   I had
>>> looked at its decay chain a while back and saw a rather high-yield MeV
>>> emission from its daughter Tl-208 and
>>> Greetings!
>>>
>>> I am dipping my toe into shielding requirements for theranostics.  One
>>> of the hot new isotopes of course is Pb-212.  I had looked at its decay
>>> chain a while back and saw a rather high-yield MeV emission from its
>>> daughter Tl-208 and figured we could forget about a reasonable amount of
>>> lead.  We'd have to use time and distance.  HOWEVER today, I thought to
>>> look at the Smith and Stabin paper that lists 1000+ isotopes with their
>>> gamma rate factors and HVL, etc. data.  Pb-212 is listed as having an HVL
>>> of only 0.756 mm Pb, which is about 1/7th the HVL they list for F-18!  I
>>> understand that F-18 is almost 100% positron decay, but I still find this
>>> difference in HVL incredible.
>>>
>>> Before going down a wild rabbit hole, I figured I'd probe the list for
>>> any other insights into Pb-212.  We are starting a clinical trial soon
>>> using it, and I've been tasked with writing up a Radiation Safety SOP.  In
>>> addition, we are doing a reno of one of our NM departments, and they would
>>> like to add dedicated theranostic injection rooms... so trying to see what
>>> kind of lead to put in the walls.  (It's truly an impossible task, but I'm
>>> giving it my "college try.")
>>>
>>> Many, many thank yous in advance.
>>>
>>> Gretchen R. Bell, M.S., DABR
>>> Diagnostic Imaging Physicist
>>> Ochsner Medical Center
>>> (504)842-8506
>>>
>>>
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