[Intl_DxMedPhys] TJC acquisition monitor requirements

Wed Sep 23 14:45:41 EDT 2026

Agreed. And I read my original message again, and I see that I left out a detail. When I said I measured the distances covered by some number of squares on a SMPTE pattern, I meant I measured them with a ruler – not the electronic caliper.

Robert J. Kobistek, MS, FACR, DABR, MRSE(MRSC™)
Medical Physicist
RJK Medical Physics, Inc.
440-463-7879

From: Douglas Pfeiffer <xraydoug at me.com>
Sent: Wednesday, September 23, 2026 11:48 AM
To: Januseski, Daniel <DJANUSESKI at virtua.org>
Cc: Bob Kobistek <bob at rjkmedphys.com>; DxMedPhys List <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: Re: [Intl_DxMedPhys] TJC acquisition monitor requirements

Yeah, that’s what I was calling caliper accuracy, which I believe is independent of the display device. Since this is specifically under the acquisition display, and because there is geometric/distance accuracy under the CT heading, they must be thinking of something different.
[cid:image001.png at 01DD4B6A.34AF6770]

Best regards,
Doug

Douglas Pfeiffer, MS, DABR FACR, FAAPM (he/him)
Medical Physicist, Radiation Safety Officer
Boulder Community Health
xraydoug at me.com<mailto:xraydoug at me.com>
303.415.7515

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The opinions expressed in this message are the product of the gray and white matter loitering in my cranium. I speak for myself and no one else, unless I say otherwise.

On Sep 23, 2026, at 8:37 AM, Januseski, Daniel <DJANUSESKI at virtua.org<mailto:DJANUSESKI at virtua.org>> wrote:

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I have been performing a test for years on CT where I measure a known object across the phantom with the on device distance tool and compare it to the real size of the object.  For the ACR phantom, the included 100 mm point objects in section 3 (uniformity) seems optimum for this test.  It is testing if the device’s display measuring tool is properly calibrated (footnote:  never had a failure!).

Yes, technically this is a software feature and is not purely display-dependent so maybe this is not what they are considering.  But considering display geometric accuracy as described by Bob is as he says dependent on aspect ratio and is not a factor in modern flat panel displays (it was a concern in CRTs due to EMF interference), this is my best guess at what JC wants.

Dan Januseski, MS, DABR
Voorhees, NJ

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 Bob Kobistek via Intl_dxmedphys_wd_osu_list
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Subject: [EXTERNAL] Re: [Intl_DxMedPhys] TJC acquisition monitor requirements

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I’d forgotten about that. A while back I used to check it by measuring the length of some number of squares on a SMPTE pattern in both vertically and horizontally. So it was more of an aspect ratio test, but that’s the only thing I could think
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I’d forgotten about that. A while back I used to check it by measuring the length of some number of squares on a SMPTE pattern in both vertically and horizontally. So it was more of an aspect ratio test, but that’s the only thing I could think
I’d forgotten about that. A while back I used to check it by measuring the length of some number of squares on a SMPTE pattern in both vertically and horizontally. So it was more of an aspect ratio test, but that’s the only thing I could think of that could be called spatial accuracy as it relates only to the monitor.

Robert J. Kobistek, MS, FACR, DABR, MRSE(MRSC™)
Medical Physicist
RJK Medical Physics, Inc.
440-463-7879

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 Douglas Pfeiffer via Intl_dxmedphys_wd_osu_list
Sent: Wednesday, September 23, 2026 8:31 AM
To: DxMedPhys List <intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>>
Subject: [Intl_DxMedPhys] TJC acquisition monitor requirements

Good morning! I just received a document to prepare us for upcoming TJC inspections. It includes the following: My question is about the last item - spatial accuracy. I’ve never measured spatial accuracy on an acquisition display, and I don’t
Good morning!

I just received a document to prepare us for upcoming TJC inspections. It includes the following:
<image001.png>

My question is about the last item - spatial accuracy. I’ve never measured spatial accuracy on an acquisition display, and I don’t remember anyone ever talking about it. The only time I could imagine it being an issue at all is during MR- and CT-guided biopsies, but that is accuracy of the system calipers and not a function of the display. What are folks doing with this one?

Best regards,
Doug

Douglas Pfeiffer, MS, DABR FACR, FAAPM (he/him)
Medical Physicist, Radiation Safety Officer
Boulder Community Health
xraydoug at me.com<mailto:xraydoug at me.com>
303.415.7515

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