[Intl_DxMedPhys] Paediatric CT phantoms - Image quality

Fri Jun 27 07:59:50 EDT 2025

They have more noise for same dose at 80 cm collimation (I think you mean they asked you to use 4 cm in stead of 8) like a 2x change in noise if you use 8 vs 4. Joe, measure a phantom with AEC on and off at 8 and 4 and you will see what I mean. We just spoke with them on this.  Told them for peds we like to use 1.5 pitches and 8 cm helical… obviously for motion freezing. We took such measurements ourselves to see. The Apex didn’t have this behavior. We also compared helical artifacts to see if canon was trading noise for artifacts but I thought the artifact level was the same between them. We decided to just not schedule peds there unless our other wide axial scanner was broken.

Regarding minimum scan ranges, we decided at Wisconsin to use helical modes, not volume modes, because the switching from axial to helical when you need larger scan ranges is tricky to implement clinically. In other words, like if you need to go more than 16, but you don’t need 32 cm… Using all helical makes this easier to implement workflow wise (we think).

-stick

Timothy P. Szczykutowicz, Ph.D., DABR
Associate Professor
Departments of Radiology, Medical Physics and BME
University of Wisconsin Madison
Cell# 1-716-560-7751<tel:(716)%20560-7751>
Office# 1-608-263-5729
he/him/his

From: Meier, Joseph <Joseph.Meier at cchmc.org>
Sent: Thursday, June 26, 2025 5:41 PM
To: Szczykutowicz, Timothy P <TSzczykutowicz at uwhealth.org>; Baxter, Patricia [ISLH] <Patricia.Baxter at islandhealth.ca>; 'intl_dxmedphys_wd_osu_list at lists.osu.edu' <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: RE: Paediatric CT phantoms - Image quality

Speaking of scanning “fast” in the peds world, I have two questions for the community about Canon.  We recently purchased the Canon Insight scanner.

  1.  Our applications specialists strongly recommended we not use 4 cm collimation on our Canon scanners, and rather stick with 2 cm collimation.  Does anyone know why this is?  Currently we use 4 cm collimation on our Rev APEX and do not have any problems.  Increasing the collimation from 2 cm to 4 cm would cut the scan time down by half.

  1.  The Canon Insight is capable of a table speed of 450 mm/s, but we decided not to use it because the minimum scan range possible is 254 cm, which is too long in many cases, especially repeat scans.

-Joe Meier

Joseph Meier, PhD DABR
Diagnostic Imaging Medical Physicist, Cincinnati Children’s Hospital
Assistant Professor, University of Cincinnati
3333 Burnet Ave, MLC 5031
Cincinnati, OH 45229-3026
(713) 422-3597 (O)
(513) 636-7775 (Administrative Assistant)

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From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+joseph.meier=cchmc.org at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list-bounces+joseph.meier=cchmc.org at lists.osu.edu>> On Behalf Of Szczykutowicz, Timothy P via Intl_dxmedphys_wd_osu_list
Sent: Thursday, June 26, 2025 6:23 PM
To: Baxter, Patricia [ISLH] <Patricia.Baxter at islandhealth.ca<mailto:Patricia.Baxter at islandhealth.ca>>; 'intl_dxmedphys_wd_osu_list at lists.osu.edu' <intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>>
Subject: Re: [Intl_DxMedPhys] Paediatric CT phantoms - Image quality

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For a newborn, a typical Nalgene filled with water is good. The typical vendor water phantom is too big, same for the smallest module of the mercury phantom. I would just focus on noise, dose, and scan speed for peds. (so a water phantom is
For a newborn, a typical Nalgene filled with water is good. The typical vendor water phantom is too big, same for the smallest module of the mercury phantom.

I would just focus on noise, dose, and scan speed for peds. (so a water phantom is fine)

I don’t think you need to put in a contrast object or high resolution module. The kernel will decide the resolution, you can just copy that from protocols your rads already like. Mainly you are just looking to measure noise and make sure your tube can deliver enough dose at the fastest scan speed. You are going to likely be using 70-80 kV for newborns anyway (I am guessing, based on fact acr and vendor phantoms were too big for you, those are all good for larger size peds), so that part is easy. But you get into trouble quick with dose output at these low voltages when you program the protocols to scan fast (fastest rotation time and widest collimation and highest pitch your rads will tolerate (usually about 1.5)).

This is Nalgene trick is what I did when we got the mercury phantom and evaluated it for gammex (whitepaper is in my textbook on that and on the sun nuclear website). Of course I didn’t mention this in the whitepaper for them though 😉

-stick

Timothy P. Szczykutowicz, Ph.D., DABR
Associate Professor
Departments of Radiology, Medical Physics and BME
University of Wisconsin Madison
Cell# 1-716-560-7751<tel:(716)%20560-7751>
Office# 1-608-263-5729
he/him/his

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu>> On Behalf Of Baxter, Patricia [ISLH] via Intl_dxmedphys_wd_osu_list
Sent: Thursday, June 26, 2025 4:03 PM
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Subject: [Intl_DxMedPhys] Paediatric CT phantoms - Image quality

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Hi ListServ: I have the paediatric CTDI phantom, but only ACR and the vendor phantoms for image quality. What do you use to determine image quality when evaluating paediatric CT protocol changes? Pat Patricia Baxter, MSc, MCCPM (she/her) Island
Hi ListServ:

I have the paediatric CTDI phantom, but only ACR and the vendor phantoms for image quality.
What do you use to determine image quality when evaluating paediatric CT protocol changes?

Pat

Patricia Baxter, MSc, MCCPM (she/her)
Island Health: Leader, Radiation Safety, Imaging Physics and Quality Control
Diagnostic Imaging Physicist
Cell: 250.361.7261
E-mail: patricia.baxter at islandhealth.ca<mailto:patricia.baxter at islandhealth.ca>

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I am privileged to live, learn and work on the unceded traditional lands of the lək̓ʷəŋən languaged peoples, the Songhees and Esquimalt First Nations.

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