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Hi, If it helps, I have attached a graph of the PB212 and daughter activities over 24hrs (using the WISE uranium website). So, t=0 is freshly produced Pb212. A transient equilibrium state is reached after about 8-9hrs, with all daughters appearing</div>
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Hi,</div>
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If it helps, I have attached a graph of the PB212 and daughter activities over 24hrs (using the WISE uranium website). So, t=0 is freshly produced Pb212. A transient equilibrium state is reached after about 8-9hrs, with all daughters appearing to 'decay' then
with the same half-life as Pb212. </div>
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<br>
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But the point to watch is that due to half-life ratios, the Bateman equations give the first daughter (Bi208) activity as 110% that of Pb212 , despite the decay value being 100%. This in turn leads to higher activities for Tl208 and Po212 of 40% and 71% respectively.</div>
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As noted , the main gamma emission of concern for shielding from Tl208 is the 2.6MeV gamma , in 100% of the Tl208 decays. Calculations of shielding might need the appropriate activity of Tl208 , in relation to the PB212 activity, so this might help. </div>
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Regards</div>
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Bill Thomson</div>
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<b>From:</b> Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+bill.thomson=nhs.net@lists.osu.edu> on behalf of Gretchen Raterman Bell via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list@lists.osu.edu><br>
<b>Sent:</b> 16 April 2026 21:02<br>
<b>To:</b> Gretchen Raterman Bell via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list@lists.osu.edu><br>
<b>Subject:</b> Re: [Intl_DxMedPhys] Sanity Check Needed for Pb-212 HVL</div>
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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</div>
<div style="direction: ltr;">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.</div>
<p style="direction: ltr; text-align: left; margin-top: 1em; margin-bottom: 1em;">
<span style="font-family: tahoma, sans-serif; font-size: 9.75pt;">Gretchen R. Bell, M.S., DABR</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Diagnostic Imaging Physicist</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Ochsner Medical Center</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">(504)842-8506</span></p>
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<div style="direction: ltr;">On Thu, Apr 16, 2026 at 2:59 PM Gretchen Raterman Bell <<a href="mailto:gretchen.raterman@gmail.com" id="OWA2a9cad30-2c62-edf7-59b9-de95cb9fe82d" class="OWAAutoLink">gretchen.raterman@gmail.com</a>> wrote:</div>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left: 1px solid rgb(204, 204, 204);">
<div style="direction: ltr;">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!!</div>
<p style="direction: ltr; text-align: left; margin-top: 1em; margin-bottom: 1em;">
<span style="font-family: tahoma, sans-serif; font-size: 9.75pt;">Gretchen R. Bell, M.S., DABR</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Diagnostic Imaging Physicist</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Ochsner Medical Center</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">(504)842-8506</span></p>
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<div style="direction: ltr;">On Thu, Apr 16, 2026 at 2:55 PM Reagan Dugan <<a href="mailto:rdugan1102@gmail.com" id="OWAfc428918-57ec-4321-490e-07ff72d4942b" class="OWAAutoLink">rdugan1102@gmail.com</a>> wrote:</div>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left: 1px solid rgb(204, 204, 204);">
<div style="direction: ltr;">Hi Gretchen, </div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">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.</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">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.</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">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. </div>
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</div>
<div style="direction: ltr;">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. </div>
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<div style="direction: ltr;">Good luck!</div>
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<p style="direction: ltr; text-align: left; text-indent: 0px; margin: 0in; font-family: Aptos, sans-serif;">
<span style="font-size: 13px; color: black;"><b>Reagan Dugan, PhD</b></span></p>
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<div style="direction: ltr;">On Thu, Apr 16, 2026 at 2:14 PM Gretchen Raterman Bell via Intl_dxmedphys_wd_osu_list <<a href="mailto:intl_dxmedphys_wd_osu_list@lists.osu.edu" id="OWAfac913ae-3d4c-81da-83e9-b6b1587203a1" class="OWAAutoLink">intl_dxmedphys_wd_osu_list@lists.osu.edu</a>>
wrote:</div>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left: 1px solid rgb(204, 204, 204);">
<div style="line-height: 1px; max-height: 0px; display: none; font-size: 1px; color: rgb(255, 255, 255);">
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</div>
<div style="direction: ltr;">Greetings!</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">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.</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">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.")</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">Many, many thank yous in advance.</div>
<p style="direction: ltr; text-align: left; margin-top: 1em; margin-bottom: 1em;">
<span style="font-family: tahoma, sans-serif; font-size: 9.75pt;">Gretchen R. Bell, M.S., DABR</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Diagnostic Imaging Physicist</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">Ochsner Medical Center</span><span style="font-family: tahoma, sans-serif;"><br>
</span><span style="font-family: tahoma, sans-serif; font-size: 13px;">(504)842-8506</span></p>
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