[Intl_DxMedPhys] Lu-177 Dose Calibrator Configuration for 20 mL Syringes

[Bill Erwin]

P. S. There should not be a substantial geometry dependence, but you should
nonetheless perform a test for your lab.  For example:
1. Assay an amount of Lu-177 in a 3-ml syringe (QS'ed up to the measurement
volume used for that syringe, which might be < 3 ml?)
2. Transfer "all" of the activity from the 3-ml syringe to a 20-ml syringe
and QS the 20-ml syringe to the measurement volume used for that syringe
(and e-QS the 3-ml syringe to its measurement volume used and re-assay to
measure the residual, which would be subtracted from 20-ml syringe reading)
3. Assay the 20-ml syringe using the same calibrator setting as that for
the 3-ml syringe (correcting for the residual left in the 3-ml syringe),
and calculate % difference.  A useful limit for not needing a calibration
setting change might be +/-2%.

When our institution began using Lu-177 back in 2013 (Lu-177 DOTATATE
clinical trial), I assayed an amount in 1-ml in the 30-ml vial, and then
added 1-ml increments, and measured up to 25-ml.  I observed essentially no
variation in the reading with the dose calibrator factory setting (and we
did not have to change the calibrator setting when we initially
cross-calibrated with the Lu-177 DOTATATE manufacturer, which was AAA at
the time).

On Wed, May 21, 2025 at 12:27 PM Bill Erwin <ervster57 at gmail.com> wrote:

> Troy,
>
> FYI: https://urldefense.com/v3/__https://jnm.snmjournals.org/content/60/supplement_1/2080__;!!KGKeukY!yRCnA-vIPPc7OlNO2pwH3CcBdWJFC7LzWGpCLsSEzOKekYlswBqE8oDGLZHKPXeLZfSegc6C90YMlKmgOlp3jVj0K3nyNcVkI8ASt6Tw$  (SNMMI
> abstract on Lu-177 assay in different sized syringes and glass vials)
>
> Regards,
> Bill
>
> On Wed, May 21, 2025 at 10:13 AM troyxzhou--- via
> Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
> wrote:
>
>> Dear list I hope you’re all doing well. I’m reaching out to gather your
>> experiences with measuring Lu-177 in a 20 mL syringe on dose calibrators.
>> To date, our acceptance testing using up to 3 mL syringes showed negligible
>> geometry
>>
>> Dear list
>>
>>
>>
>> I hope you’re all doing well. I’m reaching out to gather your experiences
>> with measuring Lu-177 in a 20 mL syringe on dose calibrators. To date, our
>> acceptance testing using up to 3 mL syringes showed negligible geometry
>> effects, but we haven’t evaluated larger volumes.
>>
>>
>>
>> Specifically:
>>
>>    - Have you observed any significant geometry variation when
>>    calibrating Lu-177 in 20 mL syringes?
>>    - If so, did you configure a separate channel for that volume, or
>>    were the existing settings sufficient?
>>
>>
>>
>> Any insights or recommendations would be greatly appreciated.
>>
>>
>>
>> Thank you in advance for your help.
>>
>>
>>
>> Best regards,
>>
>>
>>
>> Troy Zhou, PHD
>>
>> Diagnostic Radiation Physics Services
>>
>> 650-683-0918
>>
>
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