[Intl_DxMedPhys] [External] Re: rotation time artifact

Sun Jan 4 16:17:52 EST 2026

Dear Idris,

It could be either X-ray tube or detector DAS related, or something else. You may display the four images in the air window (WL=-1000 and e.g., WW=100~150) so that the artifacts will become very strong (and thus ugly) in the air area. As such, you may get more hints on the root cause or at least more evidence/proof to deal with the possible pushing back.

Best,

Xiangyang

Xiangyang Tang, PhD, DABR, FSPIE, FAAPM & FAIMBE-elected
Professor of Radiology and Imaging Sciences
PI, Translational Research in CT Lab
Director, Medical Physics Imaging Residency Program
Department of Radiology and Imaging Sciences
Emory University School of Medicine

The book entitled "Spectral Multi-Detector CT (sMDCT): Data Acquisition, Image Formation, Quality Assessment and Contrast Enhancement<https://urldefense.com/v3/__https://www.amazon.com/Spectral-Multi-Detector-Computed-Tomography-sMDCT/dp/0367137534?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=ATVPDKIKX0DER__;!!KGKeukY!xf6yY14-8cF8VzGLhZJox_cxFmWE-HbYQawtOx8kHOfAqMy1z-4m7qQrEdz3Ra_05UnRwQaxG_TEYwIvEXcsc2OVsTxu5UIJRX4KAv37Q4ewOkeVQA$ >"

Mail address:
Emory Clinic Building C Suite 5018
Atlanta, GA 30322

email: xiangyang.tang at emory.edu

________________________________
From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+xiangyang.tang=emory.edu at lists.osu.edu> on behalf of Chong, Sang hoon (LHMC - Radiology) via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Sent: Friday, January 2, 2026 4:44 PM
To: Cuddy-Walsh, Sarah (HC/SC) <sarah.cuddy-walsh at hc-sc.gc.ca>; Idris Elbakri <idris at canqap.co>; intl_dxmedphys_wd_osu_list at lists.osu.edu <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [External] Re: [Intl_DxMedPhys] rotation time artifact

Dear Idris, 0. 33s is pretty close to the minimum rotation time of the CT scanner (0. 27 s), and your artifact might have been caused by not enough sampling. Is this the first time seeing such an artifact from the particular protocol? I’d suggest
Dear Idris,

0.33s is pretty close to the minimum rotation time of the CT scanner (0.27 s), and your artifact might have been caused by not enough sampling. Is this the first time seeing such an artifact from the particular protocol?

I’d suggest increasing mAs, decreasing pitch, or using a different reconstruction algorithm, and see if that improves the artifact. Or to test, maybe try using a smaller phantom and see if the problem persists. I hope someone else can also chime in to confirm.

Best,

Sang Hoon

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

Sang Hoon (Bryan) Chong, Ph.D.

Diagnostic/Nuclear Medicine Medical Physicist

Department of Radiology

41 Mall Road P.O. Box 541 Burlington, MA 01805

T: 781-744-8177 | C: 267-218-5887

[cid:image002.png at 01DBF0F5.30004760]

This email may contain confidential information intended only for the recipient.

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+sanghoon.chong=lahey.org at lists.osu.edu> on behalf of Cuddy-Walsh, Sarah (HC/SC) via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Date: Friday, January 2, 2026 at 10:11 AM
To: Idris Elbakri <idris at canqap.co>, intl_dxmedphys_wd_osu_list at lists.osu.edu <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [External] Re: [Intl_DxMedPhys] rotation time artifact

Unclassified / Non classifié

I haven’t seen this before but am intrigued. Is the DAP the same for all protocols (i.e. does the dose rate increase as the rotation time decreases?). Have you tried checking the position of the detector/x-ray source in the header for each projection? What is the extent of the rotation (ex. 210 degrees)?

Happy New Year!

Sarah Cuddy-Walsh, Ph.D.

From: Idris Elbakri <idris at canqap.co>
Sent: 2025-12-31 7:27 AM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: [Intl_DxMedPhys] rotation time artifact

Dear colleagues, I am curious to see if anyone has encountered a CT artifact that appears when certain rotation times are used. This artifact started appearing a few weeks ago on our head protocol on a Philips Spectral 7500. I investigated a

Dear colleagues,

I am curious to see if anyone has encountered a CT artifact that appears when certain rotation times are used. This artifact started appearing a few weeks ago on our head protocol on a Philips Spectral 7500. I investigated a bit and found that the artifact appears when the rotation times are short (0.33 and 0.4 seconds) and disappears at 0.5 sec or higher. Is the fast rotation inducing some sort of vibration? Nothing in the protocol has changed from a few weeks ago when there was no artifact.

Upon further ingestigation I also think the artifact appears in other protocols, but is not as obvious, and its dependence on rotation time is not evident. I still suspect some sort of mechanical effect.

I suspect the vendor will push back and say that there is nothing wrong with the scanner as they have just completed a PM. I appreciate any insight you can provide if you have seen something like this and how you might have resolved it.

Cheers,

Idris Elbakri, PhD, MCCPM

PS. Figure from left to right: 0.33, 0.4, 0.5 and 0.75 sec rotation times.

[cid:image001.png at 01DC7BCF.326A0D50]

________________________________
PLEASE NOTE: This message is intended for the use of the person to whom it is addressed. It may contain information that is privileged, confidential and exempt from disclosure under applicable law. If you are not the intended recipient, your use of this message for any purpose is strictly prohibited. If you have received this communication in error, please delete the message and notify the sender so that we may correct our records. See our web page at https://urldefense.com/v3/__http://www.bilh.org__;!!KGKeukY!xf6yY14-8cF8VzGLhZJox_cxFmWE-HbYQawtOx8kHOfAqMy1z-4m7qQrEdz3Ra_05UnRwQaxG_TEYwIvEXcsc2OVsTxu5UIJRX4KAv37Q4egG8-XUA$ <https://urldefense.com/v3/__http://www.bilh.org__;!!KGKeukY!wnsetSjdc3-PQAH9_E4yeyMhSeJ13tSc5Ai3a7Hb4ZdLiLAQAerXjCM6GJRvAMYXRdYAmIRP7A6SzeuieeEu58q5SzV73alnInUceOb-gKlVlXU$> for a full directory of Beth Israel Lahey Health sites, staff, services and career opportunities.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.osu.edu/mailman/private/intl_dxmedphys_wd_osu_list/attachments/20260104/c80b0d2b/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 739753 bytes
Desc: image001.png
URL: <https://lists.osu.edu/mailman/private/intl_dxmedphys_wd_osu_list/attachments/20260104/c80b0d2b/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 74568 bytes
Desc: image002.png
URL: <https://lists.osu.edu/mailman/private/intl_dxmedphys_wd_osu_list/attachments/20260104/c80b0d2b/attachment-0001.png>