[Intl_DxMedPhys] Thyroid Uptake Tests: discordance between 2 different probes

[Erin Niven]

Thanks everyone for your suggestions!  I rearranged my schedule so I could actually do some testing on both systems yesterday.  I compared all hardware and software options for geometry and ROI/protocol differences - there were none.  I decided it had to have something to do with the counting of the pill in the phantom, and that was it.  The odds of the experienced tech doing this were low, but he somehow managed to rotate the insert to the back for both patients on the old system, but have it in the front position for the new system.  It turned out to be a great learning experience for them - they didn't realize how attenuating the back position was compared to the front position.
Sincerely,Erin


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    On Tuesday, January 28, 2025 at 10:57:19 p.m. NST, Josh M Wilson via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu> wrote:  
 
 Erin, We encountered something similar when recently upgrading to a Captus 4000e. Without knowing what Atomlab settings were in place and the capsule workflow, the two parameters I'd double-check are: ROI Selections high and low peak (both forErin,
We encountered something similar when recently upgrading to a Captus 4000e. Without knowing what Atomlab settings were in place and the capsule workflow, the two parameters I'd double-check are:ROI Selections high and low peak (both for the clinical protocols and the QC, because if memory serves, out of the box, they're different)In the Protocol Set-up, in the Dose Administration, check which method is selected and that what the Capintec manual describes is being done is consistent with what the technologiststhink they're doing. 
Best,Josh M. Wilson, PhD
Radiation Physicist, Clinical Imaging Physics GroupDuke University Health System
Director, Duke Imaging Physics Residency ProgramAssistant Professor, Department of RadiologyDuke University School of MedicineFrom: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+joshua.wilson=duke.edu at lists.osu.edu> on behalf of Erin Niven via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Sent: Tuesday, January 28, 2025 11:28 AM
To: International Diagnostic Medical Physics List <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [Intl_DxMedPhys] Thyroid Uptake Tests: discordance between 2 different probes Good afternoon, We are in the process of switching from an Atomlab 960 to a Captus 4000e and noticed a significant difference between uptake measurements. The protocols are the same - just comparing the counts of the pill placed in the thyroidGood afternoon,
We are in the process of switching from an Atomlab 960 to a Captus 4000e and noticed a significant difference between uptake measurements.  The protocols are the same - just comparing the counts of the pill placed in the thyroid phantom to the counts from the patient's thyroid 24 hours apart.  The Atomlab is yielding much higher uptake measurements compared to the Captus (pills and patients were counted on both probes, one after the other).
I have a suspicion as to why this might be, but can't get around to doing some measurements today or tomorrow.  So I thought I would see if anyone else has run into this problem before, or if you have suggestions for me to test.
Sincerely,Erin Niven, PhD, CHP, RRPT, MCCPM


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