[Intl_DxMedPhys] [External] PET 3D Normalization and Well Counter Calibration impact on MPR processing speed

[Palmer, Matthew R. (BIDMC - Radiology)]

That is the craziest PET-WCC/Norm issue I've ever heard.

One suggestion though is that as part of trying to diagnose this, you or the techs could have set the prior Norm and WCC files to be active, perhaps one at a time, and then see if that solved the problem.  That functionality is in the Calibration Manager.

Another guess at what may have caused this is that perhaps the files occupied an area of the hard drive prone to errors.  Of course that doesn't explain why your phantom didn't exhibit the slow-down.  Maybe just luck?

Matt Palmer
BIDMC

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu> On Behalf Of Josh M Wilson via Intl_dxmedphys_wd_osu_list
Sent: Friday, January 9, 2026 1:07 PM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: [External] [Intl_DxMedPhys] PET 3D Normalization and Well Counter Calibration impact on MPR processing speed

Over the years I've done plenty of quarterly PET normalization and well counter calibrations without issue. Last quarter I did a routine 3D normalization and WCC on a GE Discovery MI. I did the extra reconstruction at the end to confirm the

Over the years I've done plenty of quarterly PET normalization and well counter calibrations without issue.

Last quarter I did a routine 3D normalization and WCC on a GE Discovery MI. I did the extra reconstruction at the end to confirm the quantification was as expected. Then I did a quarterly PET ACR phantom scan, did the 10 mm ACR reformats, confirmed SUV values, cleaned up and left. All without issue.

Starting the next day, the clinic reported that when they did clinical scans and did their routine MPRs, the slice reconstructions would crawl along (before it would take a couple of seconds to do the whole volume, now it was 2-3 slices per second!). Naturally, because I'd been in the night before, I was asked about what I'd done. I explained the process and couldn't guess at how a normalization and WCC, which would be applied at the time of image reconstruction (not again for MPRs to the best of my knowledge), could cause MPR processing to become extremely slow. I offered to redo the calibrations but also didn't want to further compound an issue in case it was coincidental and due to something else.

The manufacturer pulled system logs and found nothing. Eventually, they bought a new computer and did a load from cold. No change.
By now, the techs had acclimated to the slow pace, another quarter had passed, and I went out to repeat the 3D norm and WCC. You might be able to guess what happened: The following the day the MPRs were back to zipping along.

I feel it's clear that the norm and WCC I'd acquired previously "broke" the MPR processing, but I can't figure out how. At this point, I have only 1 guess. Considering that:

  1.  Images still reconstructed and were quantitatively accurate (i.e., unlikely that 0, NaN, undefined values had snuck in), and

  1.  For small volumes, like the ACR phantom I reformatted, there was no noticeable lag.
Did I somehow manage to generate an extremely "long", high-precision numerical value in the calibration files that caused intensive computation time and memory use for larger data volumes? Any other theories or does anyone else know what might have happened?

Best,
Josh M. Wilson, PhD

Radiation Physicist, Clinical Imaging Physics Group
Duke University Health System

Director, Duke Imaging Physics Residency Program
Assistant Professor, Department of Radiology
Duke University School of Medicine

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